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| writing:phytoremediation [2026/03/15 01:59] – [General details which might be useful] JacobCoffinWrites | writing:phytoremediation [2026/03/20 11:37] (current) – JacobCoffinWrites |
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| ===== Phytoremediation - and other techniques for using life to remediate contaminated sites ===== | ====== Phytoremediation, Bioremediation, and Mycoremediation - using life to remediate contaminated sites ====== |
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| | In the last few hundred years, humans have discovered and created a wide range of dangerous substances. And through industry, accidents, and poor waste management, we've contaminated land and water all over the earth with them. Cleaning up these sites is challenging and expensive, involving chemical washes, tremendous heat, or eternal storage of contaminated material in a landfill. And for the contaminated habitats, the cure is often almost as bad as the disease, with huge swaths of land clearcut, the soil excavated and replaced, and the old growth forests replaced with fields of fresh seedlings. But there is a surprisingly-recent field of study around using certain plants, fungi, and microorganisms with special capabilities to extract, contain, or even destroy the contaminants without otherwise disturbing the habitat. When this works, it's not just easier on the land but cheaper too. This is a quite new field, with new breakthroughs every year, and there's a sense that many otherwise-familiar organisms have special abilities we just haven't discovered yet. But the gist is already pretty clear: phytoremediation, bioremediation, and mycoremediation are powerful toolkits for eliminating some of the worst poisons humanity has ever produced. Most of what we need to remediate these contaminants already exists - in the right circumstances plants, bacteria, and fungi can eliminate things we've already written off as forever chemicals in a matter of weeks. Learning how to work with them, what species to match with what job and how to produce those right circumstances seems to be the work ahead of us. |
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| Cleaning up these sites is challenging and expensive. | This page is an attempt to gather up a broad strokes introduction to a quite new and technical field. The info here should introduce the contaminants, the present-day standards for remediation, the various bioremediation methods, and my own system for narrowing down your options and finding a plant/fungus/bacteria that fits your setting and situation. |
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| I also want to note up-front that though I've done my best to get this information correct, I'm in no ways an expert on phytoremediation, bioremediation, environmental restoration, chemistry, botany, or biology. The topics covered here involve a wide range of hazardous substances and practices for cleaning them up, but done incorrectly this stuff can kill you fast or slow! Please do not treat this research as real-life cleanup advice without vetting it with someone who actually knows what they're talking about. | Unfortunately, while I'd absolutely love to put together a catalogue of all known/potential phytoremediation/bioremediation/mycoremediation species, the contaminants they help with (and how they do it), and their ranges and invasive status, the scope of that project would be worthy of its own full time academic research. That said, the guide towards the end has helped me with my own research while trying to find options that fit my region, so perhaps it'll help you too! |
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| ==== What is Phytoremediation ==== | One last thing: I want to note up-front that though I've done my best to get this information correct, I'm in no ways an expert on phytoremediation, bioremediation, mycoremediation, environmental restoration, chemistry, botany, or biology. The topics covered here involve a wide range of hazardous substances and practices for cleaning them up, and done incorrectly this stuff can kill you fast or slow! Please do not treat this writing research as real-life cleanup advice without vetting it with someone who actually knows what they're talking about. Don't die because you got your bioremediaton advice from a guy who's highest mark in biology was a 'C' in high school. |
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| Phytoremediation is the practice of using living plants to clean soil, air and water by absorbing or breaking down hazardous contaminants. | ===== Contaminants ===== |
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| | ==== Defining Contaminated Sites ==== |
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| | Contaminated sites are places where the soil, water, air, plants, or some combination contain a hazardous substance at a level considered harmful to humans or the wider ecosystem. |
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| Plants can help clean up many types of contaminants including heavy metals, pesticides, explosives, and oil. However, they work best where contaminant levels are low because high concentrations may limit plant growth and take too long to clean up. Plants can also help prevent wind, rain, and groundwater flow from carrying contaminants away from the site to surrounding areas or deeper underground. | Sites can be contaminated intentionally/negligently, through accidents like truck wrecks, or through natural disasters such as hurricanes or floods. Sources of contaminants include manufacturing, transportation, mining, agriculture, waste management, energy production, military activities, and they even occur naturally (after all, lead, arsenic and asbestos are all mined from the ground). Many contaminants are harmful at a certain level, and some (like certain metals) are beneficial or even necessary at a low dose. Others are bad at any level because they're so harmful, because they accumulate in the body, or both. |
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| At its core principle, phytoremediation focuses on the ability of some plants to uniquely tolerate environmental pollutants. | === Exposure Pathways === |
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| ==== Defining Contaminated Sites ==== | [[https://www.epa.gov/ecobox/epa-ecobox-tools-exposure-pathways-exposure-pathways-era]] |
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| | One consideration which is included in assessing sites today is what will be harmed and how. In some countries, a pathway to human harm is part of the legal definition of a contaminated site. An exposure pathway defines the process by which a contaminant may come in contact with receptors (such as people, animals, farmland, fish, or the general environment but definitions vary). A pathway could be people eating contaminated food, or chemicals in the soil entering the groundwater and poisoning nearby wells. This could even include the risk posed by people riding dirt bikes in a former lead mine and kicking up dust, or children playing on heavy-metal-rich slag heaps in a factory town. |
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| | Some contaminated sites are considered lower priority because they pose little risk to human health and the environment because the level of contamination is low or the chance of exposure to toxics is low. |
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| | Other contaminated sites can pose greater risks to human health and the environment because the chemicals at these sites may exist in the environment for long periods of time or move easily through the environment. These sites must be carefully managed through containment, institutional controls such as access restriction, and/or cleanup to prevent harm to humans, wildlife, or the surrounding environment both on- and offsite. |
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| Contaminated sites are places where the soil, water, air, plants, or some combination have | Specifics are obviously going to vary based on where your story is set - different legal systems, unions, nations, provinces, states, even municipalities will have their own lists of which contaminants they track, the levels they consider concerning vs safe, and proper response procedures. |
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| | Its possible that a solarpunk society would track and remediate far more contaminants than our current societies do, or would have stricter standards on acceptable levels. They might also be less human-centric in their risk assessments, tracking and remediating harm to the environment and species we share our world with, even if no human appears to be endangered by a particular site. |
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| Specifics are obviously going to vary based on where your story is set - different legal systems, unions, nations, provinces, states, even municipalities will have their own lists of which contaminants they track, the levels they consider concerning vs safe, and proper response procedures. | [[https://www.epa.gov/superfund/contaminants-superfund-sites]] |
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| https://www.epa.gov/superfund/contaminants-superfund-sites | |
| ==== Types of Contaminants and Where They Come From ==== | ==== Types of Contaminants and Where They Come From ==== |
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| Nonetheless, and with the confidence of the layman, I've attempted to break the most common and dangerous contaminants into the following broad categories: | Nonetheless, and with the confidence of the layman, I've attempted to break the most common and dangerous contaminants into the following broad categories: |
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| ===Heavy Metals / Toxic Metals=== | === Heavy Metals / Toxic Metals === |
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| A heavy metal is a metal-like element noted for its potential toxicity, such as cadmium, lead, and mercury. While trying to find a full list of heavy metals for this page, I learned that there's some disagreement on the terminology around 'heavy metals' as being misleading or meaningless (not all heavy metals are toxic and some toxic metals are not elementally heavy), and that some people prefer 'toxic metals' which probably does the job better. That said, I've been reading papers on phytoremediation and environmental restoration for two years now without noticing the dispute, so 'heavy metal' still seems to be a good search term in this context. | A heavy metal is a metal-like element noted for its potential toxicity, such as cadmium, lead, and mercury. While trying to find a full list of heavy metals for this page, I learned that there's some disagreement on the terminology around 'heavy metals' as being misleading or meaningless (not all heavy metals are toxic and some toxic metals are not elementally heavy), and that some people prefer 'toxic metals' which probably does the job better. That said, I've been reading papers on phytoremediation and environmental restoration for two years now without noticing the dispute, so 'heavy metal' still seems to be a good search term in this context. |
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| It's also worth noting that some of these metals are nutritionally essential for animal or plant life but are considered toxic in high doses or other forms. | It's also worth noting that some of these metals are nutritionally essential for animal or plant life but are considered toxic in high doses or other forms. |
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| Entries with * are from the EPA Clean Water Act's [[https://www.epa.gov/sites/default/files/2015-09/documents/priority-pollutant-list-epa.pdf|list of Priority Pollutants]]. Entries with a ^ are RCRA-8 ([[https://www.epa.gov/sites/default/files/2016-01/documents/hw-char.pdf|Resource Conservation and Recovery Act]]) metals. | Entries with * are from the EPA Clean Water Act's [[https://www.epa.gov/sites/default/files/2015-09/documents/priority-pollutant-list-epa.pdf|list of Priority Pollutants]]. Entries with a ^ are RCRA-8 ([[https://www.epa.gov/sites/default/files/2016-01/documents/hw-char.pdf|Resource Conservation and Recovery Act]]) metals. |
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| * **Aluminum (Al)** - Aluminum is the second most-produced metal after iron. It is used in vehicles, packaging, building and construction, in conductor alloys, motors, and generators, transformers, capacitors, and in a variety of household items. Aluminium is generally used because of its corrosion resistance, non-pyrophoricity, and mechanical strength. High levels of aluminium occur near mining sites; small amounts of aluminium are released to the environment at coal-fired power plants or incinerators. In water, aluminium acts as a toxic agent on gill-breathing animals such as fish when the water is acidic, in which aluminium may precipitate on gills, which causes loss of plasma- and hemolymph ions leading to osmoregulatory failure. Aluminium is primary among the factors that reduce plant growth on acidic soils. Although it is generally harmless to plant growth in pH-neutral soils, in acid soils the concentration of toxic Al3+ cations increases and disturbs root growth and function. | * **Aluminum (Al)** - Aluminum is the second most-produced metal after iron. It is used in vehicles, packaging, building and construction, in conductor alloys, motors, and generators, transformers, capacitors, and in a variety of household items. Aluminium is generally used because of its corrosion resistance, non-pyrophoricity, and mechanical strength. High levels of aluminium occur near mining sites; small amounts of aluminium are released to the environment at coal-fired power plants or incinerators. In water, aluminium acts as a toxic agent on gill-breathing animals such as fish when the water is acidic, in which aluminium may precipitate on gills, which causes loss of plasma- and hemolymph ions leading to osmoregulatory failure. Aluminium is primary among the factors that reduce plant growth on acidic soils. Although it is generally harmless to plant growth in pH-neutral soils, in acid soils the concentration of toxic Al3+ cations increases and disturbs root growth and function. |
| * **Zinc (Zn)** * - Zinc is most commonly used as an anti-corrosion agent, and galvanization (coating of iron or steel) is its most familiar form. It also plays an important role in batteries and various alloys, in varistors and photocopying products, as a white pigment in paints and as a catalyst in the manufacture of rubber to disperse heat. Zinc chloride is often added to lumber as a fire retardant and sometimes as a wood preservative. Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints. Although Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for both prenatal and postnatal development, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption and the free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. Zinc in excess of 500 ppm in soil interferes with the plant absorption of other essential metals, such as iron and manganese | * **Zinc (Zn)** * - Zinc is most commonly used as an anti-corrosion agent, and galvanization (coating of iron or steel) is its most familiar form. It also plays an important role in batteries and various alloys, in varistors and photocopying products, as a white pigment in paints and as a catalyst in the manufacture of rubber to disperse heat. Zinc chloride is often added to lumber as a fire retardant and sometimes as a wood preservative. Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints. Although Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for both prenatal and postnatal development, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption and the free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. Zinc in excess of 500 ppm in soil interferes with the plant absorption of other essential metals, such as iron and manganese |
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| | === Persistent Organic Pollutants (POPs) === |
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| | [[https://en.wikipedia.org/wiki/Persistent_organic_pollutant|POPs]] are a broad category of organic compounds that are toxic, adversely affecting human health or the environment. They are persistent in the environment and able to last for years before breaking down. They're both very able to spread far from their source, and to bioaccumulate in fatty tissue in humans and other animals. |
| ===Persistent Organic Pollutants (POPs)=== | |
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| [[https://en.wikipedia.org/wiki/Persistent_organic_pollutant|POPs]] are a broad category of organic compounds that are toxic, adversely affecting human health or the environment. They are persistent in the environment and able to last for years before breaking down. They're both very able to spread far from their source, and to bioaccumulate in fatty tissue in humans and other animals. | |
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| You can find a good deal of information on them at [[https://www.epa.gov/international-cooperation/persistent-organic-pollutants-global-issue-global-response|this page]] which is (at time of writing, Feb 2026) still maintained by the EPA. This [[https://www.unep.org/cep/persistent-organic-pollutants-pops-and-pesticides|similar writeup by the UN]] provides more information on the Caribbean. | You can find a good deal of information on them at [[https://www.epa.gov/international-cooperation/persistent-organic-pollutants-global-issue-global-response|this page]] which is (at time of writing, Feb 2026) still maintained by the EPA. This [[https://www.unep.org/cep/persistent-organic-pollutants-pops-and-pesticides|similar writeup by the UN]] provides more information on the Caribbean. |
| * **Tetrabromodiphenyl ether (tetraBDE) and pentabromodiphenyl ether (pentaBDE)** - these are industrial chemicals and the main components of commercial pentabromodiphenyl ether (pentaBDE). This pair of molecules have been detected in humans in all regions of the world. | * **Tetrabromodiphenyl ether (tetraBDE) and pentabromodiphenyl ether (pentaBDE)** - these are industrial chemicals and the main components of commercial pentabromodiphenyl ether (pentaBDE). This pair of molecules have been detected in humans in all regions of the world. |
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| ===PFAS (Per- and poly-fluoroalkyl substances)=== | === PFAS (Per- and poly-fluoroalkyl substances) === |
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| PFAS are another broad category of manufactured chemicals that have been used in industry and consumer products since the 1940s. I often see them mentioned separately from POPs but many of them (such as PFOS and PFOA) are also persistent organic pollutants. There are thousands of different PFAS, some of which have been more widely used and studied than others. PFAS have been used in a wide variety of products including waterproof fabrics, nonstick pans, athletic clothing, carpets, shampoo, mobile phones, paint, furniture, adhesives, food packaging, firefighting foam, electrical insulation, and cosmetics. | PFAS are another broad category of manufactured chemicals that have been used in industry and consumer products since the 1940s. I often see them mentioned separately from POPs but many of them (such as PFOS and PFOA) are also persistent organic pollutants. There are thousands of different PFAS, some of which have been more widely used and studied than others. PFAS have been used in a wide variety of products including waterproof fabrics, nonstick pans, athletic clothing, carpets, shampoo, mobile phones, paint, furniture, adhesives, food packaging, firefighting foam, electrical insulation, and cosmetics. |
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| Often called "forever chemicals", PFAS move through soils and bioaccumulate in fish and wildlife, which are then eaten by humans. Residues are now commonly found in soil, rain, drinking water, and wastewater. Due to the large number of PFAS, it is challenging to assess the potential human health and environmental risks but some are known to be carcinogens or endocrine disruptors, and exposure to them has been linked to diseases and health conditions including cancers, ulcerative colitis, thyroid disease, suboptimal antibody response or decreased immunit. | Often called "forever chemicals", PFAS move through soils and bioaccumulate in fish and wildlife, which are then eaten by humans. Residues are now commonly found in soil, rain, drinking water, and wastewater. Due to the large number of PFAS, it is challenging to assess the potential human health and environmental risks but some are known to be carcinogens or endocrine disruptors, and exposure to them has been linked to diseases and health conditions including cancers, ulcerative colitis, thyroid disease, suboptimal antibody response or decreased immunit. |
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| [[https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas|This page]] by the EPA is still an excellent resource at time of writing. The [[https://en.wikipedia.org/wiki/PFAS|wikipedia page]] is also quite useful. | [[https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas|This page]] by the EPA is still an excellent resource at time of writing. The [[https://en.wikipedia.org/wiki/PFAS|wikipedia page]] is also quite useful. |
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| ===Organophosphate Esters (OPEs)=== | === Organophosphate Esters (OPEs) === |
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| [[https://en.wikipedia.org/wiki/Organophosphate|OPEs]] are a functional group of similar chemicals found in Pesticides, Flame retardants, Plasticisers, Metal extractants, Surfactants, Nerve agents, Hydraulic fluids and lubricant additives. These compounds are highly toxic, show environmental persistence and accumulation, and contribute to numerous cases of poisoning and death each year. Like PFAS and phthalates, human exposure to OPEs appears widespread, originating from numerous products, the environment, and food. Their environmental persistence and toxicity raise serious concerns and their wide-scale dissemination as agricultural products has led to environmental accumulation and toxification of soil and water across the globe. They have been detected in the air as far away as Antarctica. | [[https://en.wikipedia.org/wiki/Organophosphate|OPEs]] are a functional group of similar chemicals found in Pesticides, Flame retardants, Plasticisers, Metal extractants, Surfactants, Nerve agents, Hydraulic fluids and lubricant additives. These compounds are highly toxic, show environmental persistence and accumulation, and contribute to numerous cases of poisoning and death each year. Like PFAS and phthalates, human exposure to OPEs appears widespread, originating from numerous products, the environment, and food. Their environmental persistence and toxicity raise serious concerns and their wide-scale dissemination as agricultural products has led to environmental accumulation and toxification of soil and water across the globe. They have been detected in the air as far away as Antarctica. |
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| Depending on the nature of the exposure and the specific compound in question, OPEs have been linked to potentially adverse impacts on multiple human organ systems, including the respiratory, gastrointestinal, central nervous system, cardiovascular, and renal systems. | Depending on the nature of the exposure and the specific compound in question, OPEs have been linked to potentially adverse impacts on multiple human organ systems, including the respiratory, gastrointestinal, central nervous system, cardiovascular, and renal systems. |
| This category may overlap with some of the above, I'm not sure. At one time OPEs were considered to be a good alternative for the widely used polybrominated diphenyl ethers (PBDEs), which were listed as persistent organic pollutants (POPs) by the Stockholm Convention. | This category may overlap with some of the above, I'm not sure. At one time OPEs were considered to be a good alternative for the widely used polybrominated diphenyl ethers (PBDEs), which were listed as persistent organic pollutants (POPs) by the Stockholm Convention. |
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| ===Volatile Organic Compounds (VOCs)=== | === Volatile Organic Compounds (VOCs) === |
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| Many VOCs are human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. VOCs typically are industrial solvents, such as trichloroethylene; fuel oxygenates, such as methyl tert-butyl ether (MTBE); or by-products produced by chlorination in water treatment, such as chloroform. VOCs are often components of petroleum fuels, hydraulic fluids, paint thinners, and dry cleaning agents. VOCs are common ground-water contaminants. | Many VOCs are human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. VOCs typically are industrial solvents, such as trichloroethylene; fuel oxygenates, such as methyl tert-butyl ether (MTBE); or by-products produced by chlorination in water treatment, such as chloroform. VOCs are often components of petroleum fuels, hydraulic fluids, paint thinners, and dry cleaning agents. VOCs are common ground-water contaminants. |
| Health effects include eye, nose, and throat irritation; headaches, loss of coordination, nausea, hearing disorders and damage to the liver, kidney, and central nervous system. Some VOCs are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, vomiting, nose bleeding, fatigue, dizziness. | Health effects include eye, nose, and throat irritation; headaches, loss of coordination, nausea, hearing disorders and damage to the liver, kidney, and central nervous system. Some VOCs are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, vomiting, nose bleeding, fatigue, dizziness. |
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| | === Asbestos === |
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| | Asbestos is a group of naturally occurring, toxic and carcinogenic, fibrous silicate minerals, used for thousands of years for their fire-resistant and insulating properties. The visible fibers are themselves each composed of millions of microscopic "fibrils" that can be released by abrasion and other processes. Sometimes called the Miracle Mineral, Asbestos' ability to form a fireproof fabric made it useful in a variety of applications. These included thousands of materials in the construction industry such as fire-retardant coatings, concrete, bricks, pipes and fireplace cement, heat-, fire-, and acid-resistant gaskets, pipe insulation, ceiling insulation, fireproof drywall, flooring, roofing, sprayed coatings, pipe insulation, and Asbestos Insulating Board (AIB), and drywall joint compound. It also saw use in friction products such as automobile clutch, brake, and transmission parts. As well as general use in heat-resistant fabrics, packaging, gaskets, and coatings, even lawn furniture. |
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| ===Asbestos=== | Some applications are considered to be more dangerous than others due to the amount of asbestos in the product and the material's friable nature. |
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| Asbestos is a group of naturally occurring, toxic and carcinogenic, fibrous silicate minerals, used for thousands of years for their fire-resistant and insulating properties. The visible fibers are themselves each composed of millions of microscopic "fibrils" that can be released by abrasion and other processes. Sometimes called the Miracle Mineral, Asbestos' ability to form a fireproof fabric made it useful in a variety of applications. These included thousands of materials in the construction industry such as fire-retardant coatings, concrete, bricks, pipes and fireplace cement, heat-, fire-, and acid-resistant gaskets, pipe insulation, ceiling insulation, fireproof drywall, flooring, roofing, sprayed coatings, pipe insulation, and Asbestos Insulating Board (AIB), and drywall joint compound. It also saw use in friction products such as automobile clutch, brake, and transmission parts. As well as general use in heat-resistant fabrics, packaging, gaskets, and coatings, even lawn furniture. | |
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| Some applications are considered to be more dangerous than others due to the amount of asbestos in the product and the material's friable nature. | |
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| Exposure to asbestos increases your risk of developing lung disease, such as lung cancer, mesothelioma, a rare form of cancer that is found in the thin lining of the lung, chest and the abdomen and heart, and asbestosis, a serious progressive, long-term, non-cancer disease of the lungs. | Exposure to asbestos increases your risk of developing lung disease, such as lung cancer, mesothelioma, a rare form of cancer that is found in the thin lining of the lung, chest and the abdomen and heart, and asbestosis, a serious progressive, long-term, non-cancer disease of the lungs. |
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| Compared to the impact on humans, the environmental pollution potential of asbestos products is often overlooked. Asbestos fibers are diverse in their physicochemical properties, and this diversity has a significant influence on their behavior in the environment. Recent research has confirmed that asbestos can be transported by water and spread to other parts of the environment. | Compared to the impact on humans, the environmental pollution potential of asbestos products is often overlooked. Asbestos fibers are diverse in their physicochemical properties, and this diversity has a significant influence on their behavior in the environment. Recent research has confirmed that asbestos can be transported by water and spread to other parts of the environment. |
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| ===Radioactive Contamination=== | |
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| Humans have been tinkering with radioactive substances for over a hundred years, often following insufficient safety practices. Sites can and have been contaminated through the mining, transportation, and refinement of materials for nuclear power, by the production of nuclear weapons, by the disposal of medical equipment and treatment solutions, and even by civilian factories which used radioactive materials, including radium and tritium, in manufacturing commercial products. Depending on the type of facility and the type of radiation released, contamination could be found in air, soil, liquids, or on equipment. | === Radioactive Contamination === |
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| The following US EPA resource is still quite helpful if you need more information: https://www.epa.gov/radtown/radioactively-contaminated-sites | Humans have been tinkering with radioactive substances for over a hundred years, often following insufficient safety practices. Sites can and have been contaminated through the mining, transportation, and refinement of materials for nuclear power, by the production of nuclear weapons, by the disposal of medical equipment and treatment solutions, and even by civilian factories which used radioactive materials, including radium and tritium, in manufacturing commercial products. Depending on the type of facility and the type of radiation released, contamination could be found in air, soil, liquids, or on equipment. |
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| | The following US EPA resource is still quite helpful if you need more information: [[https://www.epa.gov/radtown/radioactively-contaminated-sites]] |
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| ==== Existing Site Remediation Procedures ==== | ==== Existing Site Remediation Procedures ==== |
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| When it comes to cleaning up contaminated sites, phytoremediation is one of several options, each with its own advantages and disadvantages. Many of these practices are more invasive and expensive, but they're likely not going away, even if phytoremediation continues to improve. For sites which are badly contaminated, or which have multiple co-contaminants in one place, or where the cleanup is urgent to prevent further spread or to protect human communities, the most straightforward solution is going to remain digging out it out and remediating it elsewhere, under controlled conditions. | When it comes to cleaning up contaminated sites, phytoremediation is one of several options, each with its own advantages and disadvantages. Many of these practices are more invasive and expensive, but they're likely not going away, even if phytoremediation continues to improve. For sites which are badly contaminated, or which have multiple co-contaminants in one place, or where the cleanup is urgent to prevent further spread or to protect human communities, the most straightforward solution is going to remain digging out it out and remediating it elsewhere, under controlled conditions. |
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| **Physical Methods:** | **Physical Methods:** |
| * **Disposal in a regulated landfill **Once the soil has been removed, it may be transported to a per-arranged site. This long term storage will usually involve dumping it into a lined and capped pit. Essentially we seal the dangerous stuff in giant tupperware and leave it there. | * **Disposal in a regulated landfill **Once the soil has been removed, it may be transported to a per-arranged site. This long term storage will usually involve dumping it into a lined and capped pit. Essentially we seal the dangerous stuff in giant tupperware and leave it there. |
| * **Soil washing** Alternatively, after the soil is removed, it may instead be transported to a facility where it is mixed with a solvent or surfactant to remove contaminants, which are then separated from the soil. This can be more complex but reduces the amount of 'waste' the project needs to store. | * **Soil washing** Alternatively, after the soil is removed, it may instead be transported to a facility where it is mixed with a solvent or surfactant to remove contaminants, which are then separated from the soil. This can be more complex but reduces the amount of 'waste' the project needs to store. |
| * **Soil thermal treatment**: Similar to soil washing, heat is applied to the soil to volatilize or destroy contaminants. | * **Soil thermal treatment**: Similar to soil washing, heat is applied to the soil to volatilize or destroy contaminants. |
| * **Soil vapor extraction (SVE):** This method is used to remove volatile organic compounds (VOCs) from the soil by drawing them into the atmosphere. | * **Soil vapor extraction (SVE):** This method is used to remove volatile organic compounds (VOCs) from the soil by drawing them into the atmosphere. |
| * This would be useful on newer sites, or ones that have been previously capped in some way blocking volitlisation. | * This would be useful on newer sites, or ones that have been previously capped in some way blocking volitlisation. |
| Safety note: It's important to remember that working on contaminated sites is dangerous and requires appropriate precautions. Depending on the contamination and state of the site, just walking around can be dangerous, and the remediations outlined above generally involve disturbing the site by digging up soil, which will lead to airborne dust and other increased risks of exposure. Dust control, PPE such as masks, even hazmat suits and self-contained air supplies can be necessary onsite. | Safety note: It's important to remember that working on contaminated sites is dangerous and requires appropriate precautions. Depending on the contamination and state of the site, just walking around can be dangerous, and the remediations outlined above generally involve disturbing the site by digging up soil, which will lead to airborne dust and other increased risks of exposure. Dust control, PPE such as masks, even hazmat suits and self-contained air supplies can be necessary onsite. |
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| | ===== Phytoremediation ===== |
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| | Phytoremediation is the practice of using living plants to clean soil, air and water by absorbing, containing, or breaking down hazardous substances (including heavy metals and organic compounds like pesticides, explosives, and oil). Many plants have an ability to tolerate one or more environmental pollutant(s) - and the mechanisms they use to protect themselves can be very useful with trapping or even destroying that contaminant. Sometimes this ability is easily mapped to their origin (if their native range has high natural soil concentrations of a certain heavy metal for example) sometimes it's less obvious. |
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| | We'll go into these mechanisms in more detail in the next section, but at its core, phytoremediation is about identifying plants with a suitable ability and matching them to a site or circumstance. |
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| | There are a few advantages here: |
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| | * Phytoremediation tends to be cheaper than traditional environmental restoration techniques. Compared to logging the site, excavating soil, cleaning that soil with heat or chemical washes etc or else landfilling it, purchasing new clean fill, and replanting the site, planting some trees and monitoring their health long-term can be appealing. |
| | * Phytoremediation is generally easier on the existing habitat. Some contaminated sites look fine to the naked eye, as the toxins are less harmful to shorter-lived animals or the existing plants than they are to humans. Phytoremediation (and myco- and bioremediation) tend to be much lower-impact than traditional alternatives. |
| | |
| | There are also some disadvantages: |
| | |
| | * Phytoremediation isn't as fast as 'traditional' environmental restoration techniques. If the site in your story is badly contaminated with high concentrations of the pollutant, or multiple contaminants of concern, or if the cleanup is otherwise urgent (perhaps it's near a major human settlement, near a freshwater aquifer, reservoir, etc), then physically digging out the poison and remediating it elsewhere might make the most sense. Phytoremediation etc may still be a good fit for the long-term 'polish' stage of the cleanup which will follow. |
| | * Even with well-adapted plants, high concentrations of a contaminant may limit plant growth or even kill the phytoremediation plants. Similarly, a site which is contaminated with one hazardous material is often contaminated with others (particularly industrial sites and dumping grounds). These co-contaminants can stunt or prevent plant growth, as even plants which are adapted to one poison may be harmed by others. |
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| | Other things to note: |
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| | * Plants can also help prevent wind, rain, and groundwater flow from carrying contaminants away from the site to surrounding areas or deeper underground. |
| | * These solutions can be implemented in combination - some sites have seen excellent success combining phyto- and bioremediation by inoculating trees with symbiotic bacteria. |
| | |
| | One theme I've noticed is that if you want to remediate heavy metals, microbes //might// be able to oxidize them down into a less harmful state but generally, plants seem to be your best option for containment and removal. (Organic compounds like POPs seem to be more of an even split between plants, fungi, and microbes, leaning towards fungi and microbes.) |
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| ==== Types of Phytoremediation ==== | ==== Types of Phytoremediation ==== |
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| === Phytoaccumulation/Phytoextraction=== | === Phytoaccumulation/Phytoextraction === |
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| | [[https://en.wikipedia.org/wiki/Phytoremediation#Phytoextraction|Phytoaccumulation]] involves the absorption of contaminants by plant roots followed by translocation of absorbed contaminants to shoots and deposition at vacuole, cell wall, cell membrane, and other metabolically inactive parts in plant tissues. Over time, these plants tend to concentrate higher amounts of contaminant in their tissues than exist in the ground/water. |
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| | The ideal Phytoaccumulation plants are known as [[https://en.wikipedia.org/wiki/Hyperaccumulator|Hyperaccumulators]]. These plants extract contaminants from the soil at a higher rate, transfer it more quickly to their shoots, and store large amounts in leaves and roots. In most papers I've read, the focus in phytoaccumulation/hyperaccumulation research is in the remediation of heavy metals, but plants can also bioaccumulate other substances, like PFAS. (This can be a good or bad thing - if the plants are part of a phytoremediation project, it's a benefit, otherwise this process might transfer the contamination to your local herbivors and up the food chain from there. Bioaccumulation of PFAS in agricultural plants is a particular concern). |
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| | Generally the goal here is to introduce plants which accumulate the contaminant of concern in harvestable plant biomass, such as shoots or leaves, but with some crops (such as sunflowers, hemp, or mustard plants) this could mean pulling the entire plant, roots and all. Because the plants are generally trapping this stuff to protect themselves from it, the highest concentrations are often in the roots. |
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| | In some ways this is one of the more intuitive ways to clean up a site. Why dig out all the contaminated soil, transport it, and extract the contaminant, when you can grow plants that will extract the contaminant and then simply remove part or all of the plant? |
| |
| In some ways this is one of the more intuitive ways to clean up a site. Why dig out all the contaminated soil, transport it, and clean it, when you can grow plants that will extract the contaminant and then simply remove the plant. | [[https://en.wikipedia.org/wiki/List_of_hyperaccumulators|Wikipedia's list of known hyperaccumulators]] can be a great starting point, but just know it's incomplete and you may be able to find a better fit for your region/contaminant looking through academic papers. |
| |
| === Phytomining === | === Phytomining === |
| [[https://en.wikipedia.org/wiki/Phytomining|Phytomining]], also known as Agromining, is another quite new field, looking to obtain various metals for industrial purposes using plants. It is currently the subject of several research studies and startups, including ones attempting to genetically modify more effective plants, and it seems like its overall viability is still undetermined at this time. | [[https://en.wikipedia.org/wiki/Phytomining|Phytomining]], also known as Agromining, is another quite new field, looking to obtain various metals for industrial purposes using plants. It is currently the subject of several research studies and startups, including ones attempting to genetically modify more effective plants, and it seems like its overall viability is still undetermined at this time. |
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| It is included in this list because the harvested hyperaccumulators need to be sent somewhere for containment, and it's possible that any industrial experience gleaned in commercial phytomining work will be useful in separating the contaminants from the plant matter. This would be ideal because reducing the mass of organic matter needing long-term storage will reduce both waste and cost. It may even be able to turn a waste product into a useful input in industry as many heavy metals have manufacturing uses. | It is included in this list because the harvested hyperaccumulators need to be sent somewhere for containment, and it's possible that any industrial experience gleaned in commercial phytomining work will be useful in separating the contaminants from the plant matter. This would be ideal because reducing the mass of organic matter needing long-term storage will reduce both waste and cost. It may even be able to turn a waste product into a useful input in industry as many heavy metals have manufacturing uses. This could mean that in a solarpunk setting, phytomining operations receive some of all of their inputs from partner organizations doing site remediation and environmental restoration. |
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| === Phytovolatilization === | === Phytovolatilization === |
| |
| Some plants take up contaminants from the soil and release them into the atmosphere - this is known as [[https://pubs.acs.org/doi/10.1021/acs.est.5b04113|Phytovolatilization]]. This can be a good thing, such as [[https://repository.lib.ncsu.edu/server/api/core/bitstreams/58fa0ea2-71dd-4b3d-9892-9f355c24e670/content|when the contaminant is something like Dioxane which can be photodegraded and has a half-life measured in hours to days when exposed to sunlight]] but it can also be a problem, like [[https://pmc.ncbi.nlm.nih.gov/articles/PMC7967564/#sec3-ijerph-18-02435|when the contaminant is a heavy metal]]. Aerosolized mercury may be enough of a hazard to rule out some phytoremediation candidates. So far it seems like most of the time when I see phytovolatilization mentioned in a phytoremediation paper the authors are treating a low phytovolatilization rate as being a good thing but it definitely varies by contaminant. | Some plants take up contaminants from the soil and release them into the atmosphere - this is known as [[https://pubs.acs.org/doi/10.1021/acs.est.5b04113|Phytovolatilization]]. This can be a good thing, such as [[https://repository.lib.ncsu.edu/server/api/core/bitstreams/58fa0ea2-71dd-4b3d-9892-9f355c24e670/content|when the contaminant is something like Dioxane which can be photodegraded and has a half-life measured in hours to days when exposed to sunlight]] but it can also be a problem, like [[https://pmc.ncbi.nlm.nih.gov/articles/PMC7967564/#sec3-ijerph-18-02435|when the contaminant is a heavy metal]]. Aerosolized mercury or PFAS may be enough of a hazard to rule out some phytoremediation candidates if they're known for phytovolatilizing contaminants along with transpirated water. So far it seems like most of the time when I see phytovolatilization mentioned in a phytoremediation paper the authors are treating a low phytovolatilization rate as being a good thing but it definitely varies by contaminant. |
| |
| | === Rhizofiltration === |
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| | Rhizofiltration is a form of phytoremediation that involves filtering contaminated groundwater, surface water and wastewater through a mass of roots to remove toxic substances or excess nutrients. The contaminant is stored in the root tissues or adsorbed onto the root surface. |
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| | It seems like this encompasses both plants grown in soil and in water (including dedicated wastewater treatment systems with plants growing in a substrate, in which case the plants are harvested and replaced with new ones once their roots are saturated with toxins). |
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| | From what I've seen, the focus here seems to be on heavy metal contamination - a few resources have stated that rhizofiltration is effective for treating large volumes of water with low concentrations of metals, such as the runoff from e-waste sites. |
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| | === Phytodegradation === |
| |
| === Rhizofiltration === | Out of all these options, this is probably the closest fit to "remediation" in "phytoremediation." [[https://en.wikipedia.org/wiki/Phytoremediation#Phytodegradation|Phytodegradation]] is a process where plants absorb organic pollutants and break them down into less harmful substances through metabolic processes or by releasing enzymes. It's not possible for every contaminant (for example, most? all? heavy metals) but for organic ones like Dioxins or VOCs, it can be a pretty miraculous. We'll talk more about bioremediation through fungus and bacteria in the next sections, it seems like they may be even better for this work. |
| | |
| Rhizofiltration is a form of phytoremediation that involves filtering contaminated groundwater, surface water and wastewater through a mass of roots to remove toxic substances or excess nutrients. | |
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| === Rhizodegradation === | === Rhizodegradation === |
| |
| rhizodegradation refers to the degradation of contaminants into other forms within the rhizosphere. This microorganism-rich soil zone around the roots plays a crucial role in degrading synthetic organic contaminants by releasing enzymes such as laccases, peroxidases, cytochrome P450, dehalogenases, and monooxygenases, contributing to soil decontamination | Rhizodegradation refers to the degradation of contaminants into other forms within the rhizosphere. This microorganism-rich soil zone around the roots plays a crucial role in degrading synthetic organic contaminants by releasing enzymes such as laccases, peroxidases, cytochrome P450, dehalogenases, and monooxygenases, contributing to soil decontamination. |
| | |
| | This seems more focused on organic compounds and seems to involve bioremediation and mycoremediation all working together. I've noticed a pretty consistent theme that most of these organisms work better as a team than alone - whether that's bacterial strains working more efficiently when part of a larger group, or trees and fungi or bacteria working symbiotically to remediate contamination. |
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| === Phytostabilization === | === Phytostabilization === |
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| | This title seems to encompass two different processes with similar results. The first is when plants change the soil's physical and chemical properties, making it less suitable for contaminant leaching. This might be the biological equivalent to adding a chemical binding/fixing agent to the soil. The second is when the plants take up contaminants but trap them in their roots to protect themselves. This has overlap with phytoaccumulation but in the case of trees, it would make it challenging to remove the contaminated plant matter from the site. Just the same, it does have the effect of stopping the contaminant from spreading or migrating underground. |
| |
| This title seems to encompass two different processes with similar results. The first is when plants change the soil's physical and chemical properties, making it less suitable for contaminant leaching. The second is when the plants take up contaminants but trap them in their roots to protect themselves. Obviously this would make it challenging to remove the contaminated plant matter from the site as you would with hyperaccumulators, but it does have the effect of stopping the contaminant from spreading or migrating underground. | === Hydraulic Control === |
| |
| | There are other ways to utilize plants in environmental remediation. One of the big challenges of restoring contaminated land is managing the flow of groundwater below (and out of) the site - many contaminants are quite stable underground, meaning they'll persist and remain dangerous for a very long time, and they can often spread and migrate with the groundwater flow. This plume can eventually contaminate wells and underground aquifers people rely on for drinking water and emerge from springs into surface water bodies. |
| |
| ===Phytodegradation/bioremediation === | Certain plants, such as poplar trees, can be used as natural water pumps, operating so well during their growing season that they can actually [[https://www.cluin.org/download/studentpapers/vandenbos.pdf|reverse the flow of groundwater]]. |
| |
| Out of all these options, this is probably the closest fit to "remediation" in "phytoremediation." [[https://en.wikipedia.org/wiki/Phytoremediation#Phytodegradation|Phytodegradation]] is a process where plants absorb organic pollutants and break them down into less harmful substances through metabolic processes or by releasing enzymes. It's not possible for every contaminant (for example, most? all? heavy metals) but for organic ones like Dioxins or VOCs, it can be a pretty miraculous. We'll talk more about bioremediation through fungus and bacteria in the next sections, it seems like they may be even better for this work. For example, liginolytic fungi evolved to digest tree lignin, one of the complex, tough organic polymers used by trees to make strong wood. Lignin is unusually hard to break down, and the chain of tools some of the fungis developed is so powerful it is general purpose, enabling them to break down many organic chemicals (like dioxins). | This was used to interesting effect in [[https://www.wsp.com/en-us/projects/leveraging-nature-to-help-solve-the-pfas-puzzle-in-groundwater|this project]], which used biochar to trap PFAS in groundwater, and used poplar trees to draw groundwater into that 'trap'. |
| |
| | It's important to note that the efficacy of these projects varies by site and it can be hard to tell why the trees seem serve as an excellent barrier in one case, and have minimal impact in others. |
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| | ===== Mycoremediation ===== |
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| ===Hydraulic Control === | [[https://en.wikipedia.org/wiki/Mycoremediation|Mycoremediation]] is a set of remediation methods which use fungi to decontaminate the environment. The linked wikipedia article is honestly very good and covers this topic in more depth than I'll probably be able to. |
| |
| There are other ways to utilize plants in environmental remediation. One of the big challenges of restoring contaminated land is managing the flow of groundwater below the site - many contaminants are quite stable underground, meaning they'll persist and remain dangerous for a very long time, and they can often spread and migrate with the groundwater flow. This plume can eventually contaminate wells and underground aquifers people rely on for drinking water and emerge from springs into surface water bodies. | The short version is that fungi are an effective way to remove a wide array of contaminants from damaged environments or wastewater. They can bioaccumulate heavy metals in their fruiting bodies for harvest and removal and break down organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals, personal care products, pesticides, herbicides, X-ray contrast agents, and even explosives such as 2,4,6-trinitrotoluene. |
| |
| Certain plants, such as poplar trees, can be used as natural water pumps, operating so well during their growing season that they can actually [[https://www.cluin.org/download/studentpapers/vandenbos.pdf|reverse the flow of groundwater]]. | Wikipedia states that the byproducts of this remediation can be valuable materials themselves, such as enzymes (like laccase), or edible or medicinal mushrooms but the bioaccumulation factor means that this option will definitely vary by site/contaminant, and it may be //very// important to keep people and animals away from these mushrooms. For example, oyster mushrooms are effective at breaking down all kinds of stuff (we'll get into specifics in the next section), including PFAS - but they also bioacumulate PFAS in their tissues. This means a mycoremediation crew could accelerate the removal of PFAS from a contaminated site by harvesting the mushrooms and sending them for safe destruction, but if they're eaten by animals, the PFAS would accumulate in their tissues and move up the food chain (if those animals get eaten by predators) or otherwise persist in the environment. |
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| This was used to interesting effect in [[https://www.wsp.com/en-us/projects/leveraging-nature-to-help-solve-the-pfas-puzzle-in-groundwater|this project]], which used biochar to trap PFAS in groundwater, and used poplar trees to draw groundwater into that 'trap'. | === So how do they work? === |
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| It's important to note that the efficacy of these projects varies by site and it can be hard to tell why the trees seem serve as an excellent barrier in one case, and have minimal impact in others. | **Chemical Breakdown** |
| | |
| |
| ==== Other Types of Bioremediation ==== | Fungi play an important role in decomposing almost everything else, and they've developed some incredibly effective, non-specific extracellular enzymes to do that work. |
| |
| === Fungal === | For example, liginolytic fungi evolved to digest tree lignin, one of the complex, tough organic polymers used by trees to make strong wood. Lignin is a long-chain organic (carbon-based) compound and unusually hard to break down, and the chain of tools some of the fungi developed is so powerful it is general purpose, enabling them to break down many structurally similar organic pollutants (like dioxins). |
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| Due to their demonstrated ability to biodegrade complex pollutants, including synthetic dyes, hydrocarbons, and explosives such as 2,4,6-trinitrotoluene | It's worth noting that mushrooms may be a precursor to subsequent microbial activity rather than individually effective in the removal of pollutants. All of these things work together, see also: [[https://en.wikipedia.org/wiki/Arbuscular_mycorrhiza#Phytoremediation|arbuscular mycorrhizal fungi]] |
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| arbuscular mycorrhizal fungi https://en.wikipedia.org/wiki/Arbuscular_mycorrhiza#Phytoremediation | **Metal Absorption** |
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| === Bacterial === | Many fungi are hyperaccumulators, therefore they are able to concentrate toxins in their fruiting bodies for later removal. This is usually true for populations that have been exposed to contaminants for a long time, and have developed a high tolerance. Hyperaccumulation occurs via biosorption on the cellular surface, where the metals enter the mycelium passively with very little intracellular uptake. A variety of fungi, such as //Pleurotus//, //Aspergillus//, and //Trichoderma//, have proven to be effective in the removal of lead, cadmium, nickel, chromium, mercury, arsenic, copper, boron, iron and zinc in marine environments, wastewater and on land. |
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| The term Bioremediation seems to apply both to the general practice of using living things to clean up contaminated sites, and specifically to using microorganisms to break down contaminants into less harmful substances. In fact, from what I've seen so far, it seems the second use-case is more common. At the very least "bioremediation <contaminant name>" has been a very useful search when I need to find research on cleaning a particular poison using bacteria. | In some overlap with our page on [[landfill_mining|Landfill Mining]], it seems they've also been used to recover precious metals from ewaste. |
| |
| This is an entire massive field of study with some remarkable successes to its credit. It probably deserves its own page at some point, but for now we're going to consolidate it here. | A few resources mention that their hyperacumulation traits are more distinct in fungi which have been exposed to a contaminated site for a long time, so transferring a contaminant-adapted strain of a native fungi to an new site might speed up the remediation process. |
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| Bioremediation can be done in situ or ex situ. It seems like bioremediation is often used in situations where liquid medium has been contaminated, such as with industrial oil spills or other organic pollutants, or where a contaminant plume is spreading through groundwater. | ===== Bioremediation ===== |
| |
| As with plants, these microorganisms exist in and thrive in complex network of symbiosis we don't fully understand, and their performance in a given cleanup will depend strongly on whether they have the right tools to do their job. Some are provided by other bacteria, others can be provided as chemical inputs, added via the same liquid medium the bacteria is introduced through. | The term Bioremediation seems to apply both to the general practice of using living things to clean up contaminated sites, and specifically to using microorganisms to break down contaminants into less harmful substances. But from what I've seen so far, it seems the second use-case is more common. At the very least "bioremediation <contaminant name>" has been a very useful search when I need to find research on cleaning a particular poison using bacteria. |
| |
| | This is an entire massive field of study with some remarkable successes to its credit. It probably deserves its own page at some point, but for now we're going to consolidate it here. |
| |
| | Bioremediation can be done in situ or ex situ. It seems like bioremediation is often used in situations where liquid medium has been contaminated, such as with industrial oil spills or other organic pollutants, or where a contaminant plume is spreading through groundwater. |
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| Bacterial bioremediation can also be used in combination with phytoextraction, such as in [[https://spinoff.nasa.gov/NASA-Enlists-Trees-Bacteria-to-Clean-Up-Earth|this example]] where poplar trees were used almost like biological pumps to draw in groundwater and transpirate it into the atmosphere. The trees had been inoculated with specific strains of symbiotic bacteria, known as endophytes, that would eliminate the TCE the trees absorbed from the soil and would help protect them from the toxin while doing so. The bacteria thrive on eating TCE and similar compounds, consuming the molecule’s carbon backbone and exuding chloride ions that end up as a harmless by-product in adjacent soil. The trees were soaked in a solution containing the endophyte bacterial inoculum as bare root cuttings, before being brought onsite and planted. | As with plants, these microorganisms exist in and thrive in complex network of symbiosis we don't fully understand, and their performance in a given cleanup will depend strongly on whether they have the right tools to do their job. Some are provided by other bacteria, others can be provided as chemical inputs, added via the same liquid medium the bacteria is introduced through. |
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| | From what I've found, bioremediation seems to be an excellent option if you're looking for a way to clean up organic compounds like POPs, fuels, especially when the contaminant is in groundwater. |
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| Microbes play pivotal roles in enhancing plant tolerance to heavy metal stress through metal solubilization, immobilization, and detoxification. Specific groups of microbes, including plant growth-promoting rhizobacteria (PGPR), mycorrhizal fungi, and metal-resistant bacteria, are discussed for their beneficial effects in remediation processes. | If you're planning to write about bioremediation, there's two terms which are good to know: |
| https://link.springer.com/chapter/10.1007/978-981-96-4253-3_11 | |
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| https://www.sciencedirect.com/science/article/pii/S0301479724038970 | **Biostimulation** |
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| ==== Finding Phytoremediation Options That Fit Your Story and Setting ==== | As an in-situ bioremediation technology, biostimulation involves implanting nutrients in the subsurface that stimulate the microorganisms in the reduction of the contaminant of concern. There's a lot of chemistry in figuring out the right substrate to use to provide whatever normally-scarce resources the bioremediation bacteria need to thrive, such as electron donors. Basically you periodically give the bacteria the tools they need to do their job and let them get on with it. |
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| Bioremediation/Phytoremediation are very new fields, with tons of ongoing research. Unless you go in with very specific requirements already in mind, you'll likely notice that there's an almost overwhelming number of options and variables to consider - there are hundreds of contaminants of concern, far more species that may work on them, and complex relationships where some species work on some contaminants but will be poisoned by others, or work best when supported by other species. Add to that concerns about accidentally importing invasive species and it can become quite a tangle. This isn't helped by the density of academic research language and the fact that these reports are often short on the sort of details which help when planning/writing depictions of remediation work in the field. | **Bioaugmentation** |
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| === My workflow for finding suitable plants while not going insane === | Depending on the contaminant of concern, the presence of suitable native microorganisms capable of breaking it down may not be guaranteed. Or their levels may be so low as to be insufficient if biostimulation is used alone. In these situations, bioaugmentation can be considered as a possible option, either as a means of initiation or as a backup. Pre-grown bioremediation microorganisms are added to contaminated sites in order to improve their ability to degrade contaminants. I've found examples of these added bacteria being tilled into contaminated soil or added to aquifers or contaminated groundwater via injection wells. |
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| Start with the contaminant of concern. Pick your poison, then look up which plants can be used to remediate, accumulate, or stabilize it. | [[https://www.sciencedirect.com/science/article/pii/S2666821122001193|This paper]] provides a detailed description and diagrams of the process of introducing bioremediation bacteria to contaminated aquifers. It includes details on the arrangement of wells for testing and remediation. The paper is about dechlorinators but it seems likely that other groundwater bioremediation projects might follow similar steps. |
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| [[https://en.wikipedia.org/wiki/List_of_hyperaccumulators|Wikipedia's list of known hyperaccumulators]] can be a start but it may also be incomplete or out of date and it focuses mostly on heavy metals. For each contaminant you can often find [[https://pmc.ncbi.nlm.nih.gov/articles/PMC7967564/#sec3-ijerph-18-02435|a review paper such as this one]] which will provide lists of phytoremediation species which have been tested for suitability in other studies. | [[https://clu-in.org/techfocus/default.focus/sec/bioremediation/cat/Aerobic_Bioremediation_(Direct)/|This site]] provides some similar hands-on details for bioaugmentation in aquifers using injected oxygen [[https://pubs.acs.org/doi/10.1021/acsestwater.3c00182|or other gases]] to enable aerobic bacteria in what would otherwise be an anerobic environment. |
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| You don't need to read up on how these plants work yet - some contaminants have dozens or hundreds of suitable plants so you need to narrow it down. First check each one to see if they’re native or naturalized in the region where your story is set (or decide if they’re an invasive that’s already present that might also be tolerated as part of the cleanup). Introducing an invasive or potentially-invasive species is generally a really bad idea, which makes it a hard sell in an environmental justice related story. (If your list is especially short or you really need a particular plant, consider whether its range may have moved with climate change.) | So an example bioremediation project might look like this: |
| |
| The academic papers will generally use the plants scientific name so just search for that in your search engine of choice with the word 'range' tacked on the end. Wikipedia or a plant database like [[https://powo.science.kew.org/|Plants of the World Online]] will generally have a listing complete with a map. If it's listed as 'introduced' in my story's setting, I like to then search "<plant name> invasive" and see if it has a listing in my relevant invasive species databases (in my case [[https://www.naisn.org/]] and [[https://www.invasiveplantatlas.org]]). | - Test the groundwater to determine the level of contamination and extent of the plume |
| | - Test for the presence of suitable bioremediation bacteria (and the symbiotic bacteria which enable them). Using native bacteria already present in the groundwater is much preferred. Bacteria can also be invasive. |
| | * If they are present, test to determine what, if any, chemical nutrients/additives/remediation would help them to thrive and work quickly |
| | * Biostimulation - pump the necessary solution into the aquifer |
| | - If the concentration of contaminants is too high, or the right mix of bacteria aren’t present, they would try bioaugmentation - injecting pre-grown cultures along with the necessary substrate. |
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| Make a shortlist of any relevant plants that seem to be effective in some way, and are native/naturalized in your region, then look more into how they work, and use that to shape the scene/setting in your story. This is a good time to look into specific scientific studies on phytoremediation with that one plant and to try to parse them as best you can. | [[https://www.epa.gov/sites/default/files/2015-04/documents/engappinsitbio.pdf|This older report]] provides some similar information. |
| |
| Some plants are hyperaccumulators, meaning they take up an outsized portion of the poison into their tissues and trap it there. This is great in the short term, but they’re not destroying it, just extracting/containing it, so humans will need to remove the plants at some point. For small plants this might mean pulling them up stem and root and bagging them, while for bigger trees it could mean collecting the leaves that fall annually or even cutting them down or pollarding/coppicing them routinely to capture and remove some of the contaminant they’ve contained. It will depend on the type of plant and how they store the contaminant. | Bacterial bioremediation can also be used in combination with phytoextraction, such as in [[https://spinoff.nasa.gov/NASA-Enlists-Trees-Bacteria-to-Clean-Up-Earth|this example]] where poplar trees were used almost like biological pumps to draw in groundwater and transpirate it into the atmosphere. The trees had been inoculated with specific strains of symbiotic bacteria, known as endophytes, that would eliminate the TCE the trees absorbed from the soil and would help protect them from the toxin while doing so. The bacteria thrive on eating TCE and similar compounds, consuming the molecule’s carbon backbone and exuding chloride ions that end up as a harmless by-product in adjacent soil. The trees were soaked in a solution containing the endophyte bacterial inoculum as bare root cuttings, before being brought onsite and planted. |
| |
| Other plants actually remediate the poison by breaking it down, or by expiating it into the air where it is exposed to sunlight and broken down, or through other biochemical processes. These are more of a set-it-and-forget-it solution. | Microbes [[https://link.springer.com/chapter/10.1007/978-981-96-4253-3_11|play pivotal roles]] in enhancing plant tolerance to heavy metal stress through metal solubilization, immobilization, and detoxification. Specific groups of microbes, including plant growth-promoting rhizobacteria (PGPR), mycorrhizal fungi, and metal-resistant bacteria, are discussed for their beneficial effects in remediation processes. |
| |
| Still others only stabilize it, holding it in place inside their roots or causing it to bind chemically to other elements and become less bioavailable. This doesn’t remove it exactly, but it might keep it contained or stop a plume of contaminant spreading underground. There are also plants like poplars which both accumulate a range of contaminants, but also drink up so much water that they can actually redirect groundwater movement. | Some other relevant articles: |
| |
| There are so many plants, contaminants of concerns, and varying ways the two interact that it really does need some review | * [[https://www.sciencedirect.com/science/article/pii/S0301479724038970]] |
| | * [[https://www.tandfonline.com/doi/full/10.1080/15226514.2025.2539429#d1e304]] |
| | * [[https://www.sciencedirect.com/science/article/pii/S2352186423002067#sec3]] |
| | * [[https://biosearchambiente.it/en/portfolio/ethylene-glycol/#1455640520643-eb3f1774-23c2]] |
| | * [[https://www.atsdr.cdc.gov/toxprofiles/tp96-c6.pdf]] |
| | * [[https://www.sciencedirect.com/science/article/pii/S2666821122001193]] |
| |
| | ===== Finding Phytoremediation Options That Fit Your Story and Setting ===== |
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| | Bioremediation/Phytoremediation are very new fields, with tons of ongoing research. Unless you go in with very specific requirements already in mind, you'll likely notice that there's an almost overwhelming number of options and variables to consider - there are thousands of contaminants of concern, far more species that may work on them, and complex relationships where some species work on some contaminants but will be poisoned by others, or work best when supported by other species. Add to that concerns about accidentally importing invasive species and it can become quite a tangle. This isn't helped by the density of academic research language and the fact that these reports are often short on the sort of details which help when planning/writing depictions of remediation work in the field. |
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| ==== General details which might be useful ==== | === My workflow for finding suitable plants while not going insane: === |
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| **Bioremediation** - [[https://www.sciencedirect.com/science/article/pii/S2666821122001193|This paper]] provides a detailed description and diagrams of the process of introducing bioremediation bacteria to contaminated aquifers. It includes details on the arrangement of wells for testing and remediation. The paper is about dechlorinators but it seems likely that other groundwater bioremediation projects might follow similar steps. [[https://clu-in.org/techfocus/default.focus/sec/bioremediation/cat/Aerobic_Bioremediation_(Direct)/|This site]] provides some similar hands-on details. | (This should also work for bacteria and fungi - if anything these seem to be a little easier as they seem to have larger native ranges.) |
| - Test the groundwater to determine the level of contamination and extent of the plume | |
| - Test for the presence of suitable bioremediation bacteria (and the symbiotic bacteria which enable them). Using native bacteria already present in the groundwater is preferred. Bacteria can also be invasive. | |
| * If they are present, test to determine what, if any, chemical nutrients/additives/remediation would help them to thrive and work quickly | |
| * Biostimulation - pump the necessary solution into the aquifer | |
| - If the concentration of contaminants is too high, or the right mix of dechlorinators aren’t present, they would try bioaugmentation - injecting pre-grown dechlorinator cultures along with the necessary substrate. | |
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| [[https://www.epa.gov/sites/default/files/2015-04/documents/engappinsitbio.pdf|This older report]] provides some similar information. | Start with the contaminant of concern. Pick your poison, then look up which plants etc can be used to remediate, accumulate, or stabilize it. |
| ====Resources ==== | |
| | [[https://en.wikipedia.org/wiki/List_of_hyperaccumulators|Wikipedia's list of known hyperaccumulators]] can be a start but it may also be incomplete or out of date and it focuses on heavy metals. For each contaminant you can often find [[https://pmc.ncbi.nlm.nih.gov/articles/PMC7967564/#sec3-ijerph-18-02435|a review paper such as this one]] which will provide lists of phytoremediation species which have been tested for suitability in other studies. |
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| | You don't need to read up on how these plants work yet - some contaminants have dozens or hundreds of suitable plants so you need to narrow it down. First check each one to see if they’re native or naturalized in the region where your story is set (or decide if they’re an invasive that’s already present that might also be tolerated as part of the cleanup). Introducing an invasive or potentially-invasive species is generally a really bad idea, which makes it a hard sell in an environmental justice related story. (If your list is especially short or you really need a particular plant, consider whether its range may have moved with climate change.) |
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| | The academic papers will generally use the plants scientific name so just search for that in your search engine of choice with the word 'range' tacked on the end. Wikipedia or a plant database like [[https://powo.science.kew.org/|Plants of the World Online]] will generally have a listing complete with a map. If it's listed as 'introduced' in my story's location, I like to then search "<plant name> invasive" and see if it has a listing in my relevant invasive species databases (in my case [[https://www.naisn.org/]] and [[https://www.invasiveplantatlas.org]]). |
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| | Make a shortlist of any relevant plants that seem to be effective in some way, and are native/naturalized in your region, then look more into how they work, and use that to shape the scene/setting in your story. This is a good time to look into specific scientific studies on phytoremediation with that one plant and to try to parse them as best you can. |
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| | Some plants are hyperaccumulators, meaning they take up an outsized portion of the poison into their tissues and trap it there. This is great in the short term, but they’re not destroying it, just extracting/containing it, so humans will need to remove the plants at some point. For small plants this might mean pulling them up stem and root and bagging them, while for bigger trees it could mean collecting the leaves that fall annually or even cutting them down or pollarding/coppicing them routinely to capture and remove some of the contaminant they’ve contained. It will depend on the type of plant and how they store the contaminant. |
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| | Other plants actually remediate the poison by breaking it down, or by transpirating it into the air where it is exposed to sunlight and broken down, or through other biochemical processes. These are more of a set-it-and-forget-it solution. |
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| | Still others only stabilize it, holding it in place inside their roots or causing it to bind chemically to other elements and become less bioavailable. This doesn’t remove it exactly, but it might keep it contained or stop a plume of contaminant spreading underground. There are also plants like poplars which both accumulate a range of contaminants, but also drink up so much water that they can actually redirect groundwater movement. |
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| | ===== Other Resources ===== |
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| | ==== Useful Links ==== |
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| * [[https://en.wikipedia.org/wiki/List_of_hyperaccumulators|Wikipedia's list of known hyperaccumulators]] | * [[https://en.wikipedia.org/wiki/List_of_hyperaccumulators|Wikipedia's list of known hyperaccumulators]] |
| * [[https://docs.google.com/document/d/1vsbsZKa3q9bUwm9PnnEayDuQGLFi-HKIqSYYv8J7cy8/edit?usp=sharing|This document]] is an open source attempt to collect options for the bioremediation of dioxin, vinyl chloride and related toxins. | * [[https://docs.google.com/document/d/1vsbsZKa3q9bUwm9PnnEayDuQGLFi-HKIqSYYv8J7cy8/edit?usp=sharing|This document]] is an open source attempt to collect options for the bioremediation of dioxin, vinyl chloride and related toxins. |
| * The following documents provide decent lists of likely contaminants produced by internal combustion engine automobiles (such as you might find in a scrapyard, salvage operation, or car graveyard). | * The following documents provide decent lists of likely contaminants produced by internal combustion engine automobiles (such as you might find in a scrapyard, salvage operation, or car graveyard). |
| * https://www.epa.gov/sites/default/files/2015-10/documents/sector_m_autosalvage.pdf | * [[https://www.epa.gov/sites/default/files/2015-10/documents/sector_m_autosalvage.pdf]] |
| * https://web.archive.org/web/20230309211038/https://eeuroparts.com/blog/how-toxic-are-the-chemicals-in-your-car/ | * [[https://web.archive.org/web/20230309211038/https://eeuroparts.com/blog/how-toxic-are-the-chemicals-in-your-car/]] |
| * [[https://nepis.epa.gov/Exe/ZyNET.exe/940082TP.txt?ZyActionD=ZyDocument&Client=EPA&Index=1995%20Thru%201999&Docs=&Query=%28%28deep%20rooting%29%20or%20%28deep%20rooting%29%29%20OR%20FNAME%3D%22940082TP.txt%22%20AND%20FNAME%3D%22940082TP.txt%22&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5CZYFILES%5CINDEX%20DATA%5C95THRU99%5CTXT%5C00000042%5C940082TP.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=34&SeekPage=f|This paper]] has some details on deep rooting poplar trees. | * [[https://nepis.epa.gov/Exe/ZyNET.exe/940082TP.txt?ZyActionD=ZyDocument&Client=EPA&Index=1995%20Thru%201999&Docs=&Query=%28%28deep%20rooting%29%20or%20%28deep%20rooting%29%29%20OR%20FNAME%3D%22940082TP.txt%22%20AND%20FNAME%3D%22940082TP.txt%22&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5CZYFILES%5CINDEX%20DATA%5C95THRU99%5CTXT%5C00000042%5C940082TP.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=34&SeekPage=f|This paper]] has some details on deep rooting poplar trees. |
| * A decent list of candidates for zinc https://www.sciencedirect.com/science/article/pii/S2352554121001777#sec3 | * A decent list of candidates for zinc [[https://www.sciencedirect.com/science/article/pii/S2352554121001777#sec3]] |
| * Some options for bioremediation of PFAS https://www.sciencedirect.com/science/article/pii/S2949919424000694#sec1 https://www.nature.com/articles/s41467-022-31881-5 https://stud.epsilon.slu.se/9787/1/gobelius_l_161108.pdf | * Some options for bioremediation of PFAS [[https://www.sciencedirect.com/science/article/pii/S2949919424000694#sec1]] [[https://www.nature.com/articles/s41467-022-31881-5]] [[https://stud.epsilon.slu.se/9787/1/gobelius_l_161108.pdf]] |
| * A summary of current progress in bioremediation of 1,4-Dioxane https://www.researchgate.net/publication/380607199_Advances_in_Remediation_Solutions_New_Developments_and_Opportunities_in_14-Dioxane_Biological_Treatment#pfc | * A summary of current progress in bioremediation of 1,4-Dioxane [[https://www.researchgate.net/publication/380607199_Advances_in_Remediation_Solutions_New_Developments_and_Opportunities_in_14-Dioxane_Biological_Treatment#pfc]] |
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| ==== Other concerns ==== | ==== Other concerns ==== |
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| Many invasive species are strong phytoremediators since they can tolerate and take in nonessential metals, as well as handle poor growing medium and climate conditions. Therefore extensive knowledge of the plant selected within the site-climate must be known | Many invasive species are strong phytoremediators since they can tolerate and take in nonessential metals, as well as handle poor growing medium and climate conditions. |
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| ==== Related concepts ==== | ==== Related concepts ==== |
| [[https://www.sciencedirect.com/science/article/pii/S004896972107306X#s0055|This paper]] suggests using biofuel crops to slowly extract some amount of heavy metals from a site, until bioavailable metals in the soil are low enough for a second phase. The idea is that even if these crops don't qualify as hyperaccumulators, as long as they take up some amount of the contaminant of concern, their commercial use would make the effort profitable enough to be worth continuing. One of the main challenges with remediation efforts in the real world is cost - there's usually no profit in remediating contaminated sites for anyone other than contractor companies doing the digging and transportation. Phytoremediation is often cheaper than the alternative, but it may still require ongoing labor such as soil and water testing, site assessments, or the harvesting of contaminated plant material. This may be of less concern in a solarpunk society where this work is better prioritized, or even where basic needs are met through systems like universal basic income, and people are more free to pursue their callings, including cleaning up damaged sites. | [[https://www.sciencedirect.com/science/article/pii/S004896972107306X#s0055|This paper]] suggests using biofuel crops to slowly extract some amount of heavy metals from a site, until bioavailable metals in the soil are low enough for a second phase. The idea is that even if these crops don't qualify as hyperaccumulators, as long as they take up some amount of the contaminant of concern, their commercial use would make the effort profitable enough to be worth continuing. One of the main challenges with remediation efforts in the real world is cost - there's usually no profit in remediating contaminated sites for anyone other than contractor companies doing the digging and transportation. Phytoremediation is often cheaper than the alternative, but it may still require ongoing labor such as soil and water testing, site assessments, or the harvesting of contaminated plant material. This may be of less concern in a solarpunk society where this work is better prioritized, or even where basic needs are met through systems like universal basic income, and people are more free to pursue their callings, including cleaning up damaged sites. |
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| | === Detection Dogs === |
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| | We've covered plants, fungi, and microbes, but what about animals? Dogs have an amazing ability to detect scents and can be very effective partners in finding contamination. |
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| Detection Dogs: | [[https://www.washington.edu/boundless/conservation-canines/]] |
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| https://www.washington.edu/boundless/conservation-canines/ | [[https://aegisenvironmentalinc.com/commercial/site-investigation-scent-dog/]] |
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| https://aegisenvironmentalinc.com/commercial/site-investigation-scent-dog/ | [[https://www.wsp.com/en-us/insights/meet-louie-wsps-newest-four-legged-pollution-detective#:~:text=They%20are%20trained%20to%20identify,glues%2C%20and%20dry%20cleaning%20applications]] |
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| https://www.wsp.com/en-us/insights/meet-louie-wsps-newest-four-legged-pollution-detective#:~:text=They%20are%20trained%20to%20identify,glues%2C%20and%20dry%20cleaning%20applications | |
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