This report is the second edition of the U.S. Environmental Protection Agency's (US EPA's) 2005 report and provides a high level summary of information on the applicability of existing and emerging noncombustion technologies for the remediation of persistent organic pollutants (POPs) in soil.
Valence state: The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.
free product: A NAPL found in the subsurface in sufficient quantity that it can be partially recovered by pumping or gravity drain.
aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)).
Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced.
Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
anaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may be cultivated. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor.
Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal.
Quoted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
architecture: "Architecture" refers to the physical distribution of the contaminant in the subsurface. Residuals that take the form of long thin ganglia or small dispersed globules provide a larger surface area that will dissolve much faster than if the same amount of liquid were concentrated in a competent pool.
Sources: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
source zone: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
focal ulceration: The process or fact of a localized area being eroded away.
metaplasia of the glandular stomach: A change of cells to a form that does not normally occur in the tissue in which it is found.
hyperplasia of the glandular stomach: A condition in which there is an increase in the number of normal cells in a tissue or organ.
histiocytic: Degenerative.
duodenum: First part of the small intestine.
microcytic: Any abnormally small cell.
squamous cell papillomas: A small solid benign tumor with a clear-cut border that projects above the surrounding tissue.
squamous cell carcinomas: Cancer that begins in squamous cells-thin, flat cells that look under the microscope like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of hollow organs of the body, and the passages of the respiratory and digestive tracts. Squamous cell carcinomas may arise in any of these tissues.
jejunum: The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.
ileum: The distal and narrowest portion of the small intestine.
squamous: Flat cells that look like fish scales.
metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.
ossification: The process of creating bone, that is of transforming cartilage (or fibrous tissue) into bone.
clastogenesis: Any process resulting in the breakage of chromosomes.
neoplastic: Abnormal and uncontrolled growth of cells.
ulceration: The process or fact of being eroded away.
leucocytosis: An elevation of the total number of white cells in blood.
neutrophils: A type of white blood cell.
chromodulin: A small protein that binds four trivalent chromium ions.
biomagnification: The increased accumulation and concentration of a contaminant at higher levels of the food chain; organisms higher on the food chain will have larger amounts of contaminants than those lower on the food chain, because the contaminants are not eliminated or broken down into other chemicals within the organisms.
exencephaly: Cerebral tissue herniation through a congenital or acquired defect in the skull.
everted viscera: Rotated body organs in the chest cavity.
To Be Considered: Documents, such as federal or state guidances, that are not legally binding but may be relevant to the topic in question.
gaining: A gaining surface water body is one where groundwater flows into it.
losing: A surface water body is losing when there is a permeable sediment bed that is not in contact with the groundwater allowing the surface water to seep through it.
fluvial: Of or pertaining to flow in rivers and streams.
lacustrine: Of or pertaining to a lake as in lacustrine sediments—sediments at the bottom of a lake.
lipid: Any class of fats that are insoluble in water.
lipophilic: Able to dissolve in lipids—in this case fatty tissue.
organelles: A part of a cell such as mitochondrion, vacuole, or chloroplast that plays a specific role in how the cell functions and membranes.
RfD: The RfD is an estimate of a daily exposure of the human population (including sensitive sub-groups) to a substance that is likely to be without "the appreciable risk of deleterious effects during a lifetime." An RfD is expressed in units of mg/kg-day.
autonomic: That part of the nervous system that controls non-conscious actions such as heart rate, perspiration and digestion.
ataxia: Lack of muscle coordination.
funnel-and-gate configuration: A system where low-permeability walls (the funnel) placed in the saturated zone direct contaminated ground-water toward a permeable treatment zone (the gate)
Hekster, F.M., R.W.P.M. Laane, and P. de Voogt. 2003. Environmental and toxicity effects of perfluoroalkylated substances. Reviews of Environmental Contamination and Toxicology 179:99-121.
Higgins, C. and R. Luthy. 2006. Sorption of perfluorinated surfactants on sediments. Environmental Science & Technology 40(23):7251-7256.
Kaiser, M.A., B.S. Larsen, C-P.C. Kao, and R.C. Buck. 2005. Vapor pressures of perfluorooctanoic, -nonanoic, -decanoic, -undecanoic, and -dodecanoic acids. Journal of Chemical and Engineering Data 50(6):1841-1843.
Kauck, E.A. and A.R. Diesslin. 1951. Some properties of perfluorocarboxylic acids. Industrial and Engineering Chemical Research 43(10):2332-2334.
Persistent organic pollutants (POPs) are toxic chemicals that originate from man-made sources associated with the production, use, and disposal of certain organic chemicals. Many of the chemicals were produced commercially for pest and disease control, crop production and industrial use. Some of the POPs such as pesticides and polychlorinated biphenyls (PCBs) are intentionally produced, while others such as dixion and furans are unintentional by-products of industrial processes or result from the combustion of organic chemicals.
Under the Stockholm Convention on POPs (Stockholm Convention), which was adopted in 2001 and enacted in 2004, parties committed to reduce or eliminate the production, use, and release of the 12 POPs of greatest concern to the global community. In October 2008, the Stockholm Convention’s subsidiary body – the POPs Review Committee (POPRC) held its fourth meeting (POPRC-4) and an outcome of that meeting was that it recommended to the Conference of the Parties (COP) that nine (9) additional chemicals be added to the Stockholm Convention. In October 2009 at POPRC-5 meeting, several chemicals underwent a review process by the Committee.
The 24 POPs currently within the scope of the Stockholm Convention (or under review) include 14 pesticides and 10 industrial chemicals or by-products.
The 14 pesticides targeted by the Stockholm Convention were produced intentionally and used on agricultural crops or for public health vector control.; Over time, significant human health and environmental impacts were identified for these pesticides.; By the late 1970s, these pesticides had been banned or subjected to severe use restrictions in many countries.; However, some of these 14 pesticides are still used in parts of the world where they are considered essential for protecting public health.
The 10 industrial chemicals and by-product POPs within the scope of the Stockholm Convention include PCBs, dioxins, furans, brominated flame retardants (BFRs), perfluorooctane sulfonate (PFOS), and pentachlorobenzene. PCBs were produced intentionally but typically have been released into the environment unintentionally. Most countries stopped producing PCBs in the 1980s; for example, equipment manufactured in the US after 1979 usually does not contain PCBs.; However, older equipment containing PCBs is still in use. Dioxins and furans are usually produced and released unintentionally. They may be generated by industrial processes or by combustion, including fuel burning in vehicles, municipal and medical waste incineration, open burning of trash, and forest fires.
Another treaty regulating POPs internationally is the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal (Basel Convention). In response to Stockholm Convention provisions requiring coordination with the Basel Convention on POPs waste issues, the Basel convention developed guidance on the environmentally sound management of POPs waste. In 2004, the Basel Convention invited signatories of the Stockholm Convention to consider its recommendations on environmentally sound management for POPs wastes. The US is a signatory to the Basel Convention on POPs – but has not yet ratified the Convention.
In addition to the Stockholm Convention, the Convention on Long-Range Transboundary Air Pollution (LRTAP), a regional international treaty addresses environmental issues of the United Nations Economic Commission for Europe (UNECE) with a primary focus on air emissions. The LRTAP Convention has been extended by eight (8) Protocols that include specific requirements for countries to reduce air pollution including long-range air pollution. In 1998, the LRTAP Convention adopted a Protocol on POPs to regulate the production and use of 16 chemicals that were singled out according to agreed risk criteria. The table below lists all of the 26 chemicals identified under the Stockholm Convention on POPs and the LRTAP’s Protocol on POPs - both currently listed and under review.
POPs Identified by the Stockholm Convention and Long-Range Transboundary Air Pollution Convention
POP
Stockholm Convention
Long-Range Transboundary Air Pollution Convention
Currently Listed
Under Review (2009)
Pesticides
Aldrin
√
√
Alpha-hexachlorocyclohexane
√
√
Beta-hexachlorocyclohexane
√
√
Chlordane
√
√
Chlordecone
√
√
Dichlorodiphenyltrichloroethane (DDT)
√
√
Dieldrin
√
√
Endosulfan
√
Endrin
√
√
Heptachlor
√
√
Hexachlorobenzene (HCB)
√
√
Lindane
√
√
Mirex
√
√
Toxaphene
√
√
Industrial Chemicals or By-Products
Dioxins
√
√
Furans
√
√
Hexabromobiphenyl
√
√
Hexabromocyclododecane (HBCDD)
√
√
Hexachlorobutadiene (HCBD)
√
Octabromodiphenyl ether
√
√
Pentabromodiphenyl ether (penta-BDE)
√
√
Pentachlorobenzene
√
√
Perfluorooctane sulfonate (PFOS)
√
√
Polychlorinated biphenyls (PCB)
√
√
Polychlorinated naphthalenes (PCN)
√
Short-chained chlorinated paraffins (SCCP)
√
√
Note: Nine additional chemicals that were recently listed by the Stockholm Convention in May 2009 are shown in bold.