Atmospheric transport and air-water exchange of organochlorine pesticides (OCPs) were investigated in temperate North America and the Arctic. OCPs studied were hexachlorocyclohexanes (HCHs, a-, b- and g-isomers), components of technical chlordane (trans- and cis-chlordane, trans-nonachlor), dieldrin, heptachlor exo-epoxide and toxaphene. Air and water samples were taken on cruises in the Great Lakes and Arctic to determine concentrations and gas exchange flux direction and magnitude. The Henry’s law constant, which describes the equilibrium distribution of a chemical between air and water, was determined for several OCPs as a function of temperature and used to assess the net direction of air-water exchange. Air samples were collected in Alabama to investigate southern U.S. sources of OCPs. Chemical markers (isomers, and enantiomers of chiral OCPs) were employed to infer sources and trace gas exchange. Elevated air concentrations of toxaphene and chlordanes were found in Alabama relative to the Great Lakes, indicating a southern U.S. source. Profiles of toxaphene compounds in air were similar to those in soil by being depleted in easily degraded species, suggesting that soil emissions control air concentrations. Gas exchange fluxes in the Great Lakes indicated near-equilibrium between air and water with excursions to net volatilization or deposition. Net volatilization of a-HCH from the Arctic Ocean was traced by evasion of non-racemic a-HCH into the atmosphere.

Atmospheric transport and air-water exchange of organochlorine pesticides (OCPs) were investigated in temperate North America and the Arctic. OCPs studied were hexachlorocyclohexanes (HCHs, a-, b- and g-isomers), components of technical chlordane (trans- and cis-chlordane, trans-nonachlor), dieldrin, heptachlor exo-epoxide and toxaphene. Air and water samples were taken on cruises in the Great Lakes and Arctic to determine concentrations and gas exchange flux direction and magnitude. The Henry’s law constant, which describes the equilibrium distribution of a chemical between air and water, was determined for several OCPs as a function of temperature and used to assess the net direction of air-water exchange. Air samples were collected in Alabama to investigate southern U.S. sources of OCPs. Chemical markers (isomers, and enantiomers of chiral OCPs) were employed to infer sources and trace gas exchange. Elevated air concentrations of toxaphene and chlordanes were found in Alabama relative to the Great Lakes, indicating a southern U.S. source. Profiles of toxaphene compounds in air were similar to those in soil by being depleted in easily degraded species, suggesting that soil emissions control air concentrations. Gas exchange fluxes in the Great Lakes indicated near-equilibrium between air and water with excursions to net volatilization or deposition. Net volatilization of a-HCH from the Arctic Ocean was traced by evasion of non-racemic a-HCH into the atmosphere.

Nearly 250,000 sites with past and present potentially polluting activities need urgent remediation within Europe. Major pollutants include organochlorines (OCls), e.g. chlorinated ethenes (CEs) and hexachlorocyclohexanes (HCHs), mainly used as industrial solvents and pesticides, respectively. Due to improper handling and disposal, OCls contaminants are present in the soil or groundwater surrounding sites, where they have been produced or used. CEs and HCHs can undergo degradation by microorganisms indigenous to the soil or groundwater. Therefore natural attenuation (NA), relying on the in situ biodegradation of pollutants, is considered as a cost effective remediation strategy, yet it requires accurate monitoring methods. Compound specific isotope analysis (CSIA) is a powerful tool to provide information on the extent of degradation and, when combining two isotope systems (2D-CSIA), such as carbon (δ13C) and chlorine (δ37Cl), on reaction mechanisms. The diagnostic reaction-specific isotope enrichment factors (εC and εCl) were determined in laboratory experiments for the anaerobic degradation of PCE, TCE (Paper II) and α-HCH (Paper III) by mixed bacterial cultures enriched from CEs and HCHs contaminated sites, respectively. The related mechanism-specific εCl/εC ratios were calculated as 0.35 ± 0.11 (PCE), 0.37 ± 0.11 (TCE) and 0.52 ± 0.23 (α-HCH). These values are smaller than previously reported values for pure cultures. This is explained by the microbial community composition changes observed during degradation of PCE and α-HCH, which also reflect the variability of the microbial community at the field level. Furthermore, εCl/εC ratio might be bacteria specific. These values allowed the estimation of the extent of contaminant degradation at the respective study sites (Paper III and IV). Application of both isotope systems (δ13C and δ37Cl) led to comparable estimates. However the choice of representative ε values is crucial for an accurate assessment. These studies show that CSIA is useful to quantify in situ degradation of OCls contaminants and identify reaction pathways, by combining δ13C and δ37Cl. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.</p>