Reductive dechlorination of hexachlorocyclohexane (HCH) isomers in soil under anaerobic conditions.
The biological anaerobic reductive dechlorination of beta-hexachlorocyclohexane under methanogenic conditions was tested in a number of contaminated soil samples from two locations in the Netherlands. Soils from a heavily polluted location showed rapid dechlorination of beta-hexachlorocyclohexane to benzene and chlorobenzene with lactate as electron donor. Soils from an adjacent slightly polluted location did not show substantial dechlorination of beta-hexachlorocyclohexane within 4 months. A heavily polluted sample was selected to optimise the dechlorination. All tested hexachlorocyclohexane isomers (alpha-, beta-, gamma-, and delta-), either added separately or simultaneously, were dechlorinated in this soil sample. The most rapid dechlorination was observed at a temperature of 30 degrees C. Dechlorination of beta-hexachlorocyclohexane was observed with acetate, propionate, lactate, methanol, H2, yeast extract and landfill leachate as electron donors. In a soil percolation column, packed with a selected heavily polluted soil sample, the presence of 10 mM sulphate in the influent led to simultaneous dechlorination of beta-hexachlorocyclohexane and sulphate reduction. When the column was fed with 10 mM nitrate instead of sulphate, dechlorination ceased immediately. After omitting nitrate from the influent, dechlorination activity recovered in about 1 month. Also in a separate column, the addition of nitrate from the start of the experiment did not result in dechlorination of beta-HCH. The significance of these experiments for in situ bioremediation of polluted soils is discussed.
Middeldorp
Peter J M
PJ
TNO Environment, Energy and Process innovation, PO Box 342, 7300 AH Apeldoorn, The Netherlands. p.middeldorp@mep.tno.nl
van Doesburg
Wim
W
Schraa
Gosse
G
Stams
Alfons J M
AJ
D001673:Biodegradation, Environmental; D002713:Chlorine / Q000737:chemistry; D004579:Electron Transport; D001556:Hexachlorocyclohexane / Q000737:chemistry / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics; D009426:Netherlands; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D013696:Temperature
D012989:Soil Pollutants; D002713:Chlorine; D001556:Hexachlorocyclohexane