![]() Most Cr(III) compounds are only sparingly soluble at the normal range of groundwater pH (5.5-8.0) while some Cr(VI) compounds can be very soluble. Chromium metal is not naturally occurring and the presence of Cr(VI) can generally be attributed to industrial activity. Cr(III) compounds are the most stable form. The most commonly occurring states in chromium compounds are +2, +3, and +6 with the +2 being unstable and readily oxidized to +3. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA).#pdfsmall# Office of Water, EPA 822-R-16-005, 103 pp Chromium vi chemistry and behaviorĮlemental chromium (CAS ) is a transition group metal that can have oxidation states ranging from -2 to +6. Proposal to List Pentadecafluorooctanoic Acid (CAS No: 335-67-1, PFOA, Perfluorooctanoic Acid), Its Salts and PFOA-Related Compounds in Annexes A, B and/or C to the Stockholm Convention on Persistent Organic Pollutants. UNEP (United Nations Environmental Program). Sax's Dangerous Properties of Industrial Materials. Industrial and Engineering Chemical Research 43(10):2332-2334. Some properties of perfluorocarboxylic acids. Journal of Chemical and Engineering Data 50(6):1841-1843. Vapor pressures of perfluorooctanoic, -nonanoic, -decanoic, -undecanoic, and -dodecanoic acids. Sorption of perfluorinated surfactants on sediments. Reviews of Environmental Contamination and Toxicology 179:99-121. Environmental and toxicity effects of perfluoroalkylated substances. Opinion of the scientific panel on contaminants in the food chain on perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and their salts. 574 pp.ĮFSA (European Food Safety Authority). Draft Toxicological Profile for Perfluoroalkyls. References: ATSDR (Agency for Toxic Substances and Disease Registry). EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. Cometabolic dechlorination does not appear to produce energy for the organism. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. ![]() In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor. Depending on the contaminant of concern, a subset of these activities may be cultivated. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated SitesĪnaerobic: 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. 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. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. 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)).Īerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. 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. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor.
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