20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean.

The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air-water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water-air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air-surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

The trans-continental distributions of pentachlorophenol and pentachloroanisole in pine needles indicate separate origins.

The production and use of pentachlorophenol (PCP) was recently prohibited/restricted by the Stockholm Convention on persistent organic pollutants (POPs), but environmental data are few and of varying quality. We here present the first extensive dataset of the continent-wide (Eurasia and Canada) occurrence of PCP and its methylation product pentachloroanisole (PCA) in the environment, specifically in pine needles. The highest concentrations of PCP were found close to expected point sources, while PCA chiefly shows a northern and/or coastal distribution not correlating with PCP distribution. Although long-range transport and environmental methylation of PCP or formation from other precursors cannot be excluded, the distribution patterns suggest that such processes may not be the only source of PCA to remote regions and unknown sources should be sought. We suggest that natural sources, e.g., chlorination of organic matter in Boreal forest soils enhanced by chloride deposition from marine sources, should be investigated as a possible partial explanation of the observed distributions. The results show that neither PCA nor total PCP (ΣPCP = PCP + PCA) should be used to approximate the concentrations of PCP; PCP and PCA must be determined and quantified separately to understand their occurrence and fate in the environment. The background work shows that the accumulation of airborne POPs in plants is a complex process. The variations in life cycles and physiological adaptations have to be taken into account when using plants to evaluate the concentrations of POPs in remote areas.

Distribution of some organochlorine compounds in pine needles from Central and Northern Europe.

Levels of selected organochlorine compounds in pine needles were measured in two sampling series. The first series collected in 1989 covered Southern Germany to Northern Scandinavia, and the second collected in 1990 covered Czechoslovakia to Estonia. The levels of alpha-hexachlorocyclohexane (alpha-HCH) and hexachlorobenzene (HCB) were relatively uniform throughout Europe, while the levels of gamma-hexachlorocyclohexane (gamma-HCH) and the DDT group show higher levels in the southern parts of the investigated area. The deposition patterns of all compounds except alpha-HCH indicate a dependence on fresh release from diffuse or point sources rather than global fractionation. The analytes accumulate in the needles until senescence starts and, generally, the oldest needles have the highest concentrations. The accumulation rate of the analytes in mountain pine needles is about half that of Scots pine needles indicating the importance of species differences.

Toxaphene deposition to Lake Ontario via precipitation, 1994-1998.

Precipitation samples collected continuously at Point Petre on Lake Ontario from November 1994 through December 1998 were analyzed for total toxaphene (=sum of hexa-, hepta-, octa-, and nonachloro bornanes) and chlorobornane congeners (1997-98 only). Composite triplicate samples were collected during 4-week intervals throughoutthe 4-year study using heated wet-only samplers. These results represent the first detailed data for toxaphene in Great Lakes precipitation. Seasonal volume-weighted mean concentrations for total toxaphene in precipitation ranged from 0.25 to 1.5 ng/L. Highest concentrations were found during the four spring (March-May) periods at roughly twice the annual means. The pattern for hexathrough nona-homologues over the 4 years did not vary appreciably with average ratios (relative to hepta-) of 0.08: 1.0:1.3:0.2. The volume-weighted mean concentrations for individual chlorobornane congeners were consistent in their season pattern with maximums seen in the spring. The major chlorobornane in precipitation, B8-2229 (Parlar 44), which was present at concentrations ranging from 0.016 to 0.079 ng/L, constituted 28 and 29% of the congener sum for 1997 and 1998, respectively. Lakewide loadings of toxaphene for Lake Ontario via precipitation were estimated to be 12, 17, 12, and 13 kg/year for 1995-1998, respectively. Previous toxaphene loading estimates were calculated for the individual Great Lakes on the basis of the only concentration data available, a single precipitation estimate of 0.2 ng/L from early work in northwestern Ontario. The loading estimates in this study indicate that precipitation inputs of toxaphene are 3-4 times higher than previously reported for Lake Ontario. The 1998 estimates of Lake Ontario wet deposition flux are 50% of the estimated gas deposition flux. However, wet flux values from this study exceed the net gas-phase mass transfer of toxaphene across the air-water interface.

A mass balance model describing multiyear fate of organochlorine compounds in a high Arctic lake.

Data collected over a 3-year study of a high arctic watershed and lake are used to understand the fate of organochlorine compounds (OCs) and form the basis of a mass balance contaminant fate model. The model uses the fugacity/aquivalence approach to describe OC dynamics between air, stream inflows and outflow, the water column, and surficial sediments. The steady-state model results indicate that stream inflows contributed from 96 to >99% of total chemical loadings, but 57-98% of total loadings were lost from the lake via the outlet, the percentage of which is controlled by the hydrologic regime of the high arctic lake. Conversely, only 0.4-3.4% of loadings were retained within the sediments due to the high export rate, minimal scavenging from the water column and low organic carbon fraction of the sediments. Using the unsteady-state model, which includes year-round processes, degradation was estimated to account for losses of 7-32% for the more persistent OCs and 42-50% for the less persistent OCs (alpha-HCH, gamma-HCH, and endosulfan I). If loadings were eliminated, water column concentrations would decline with half-lives <1 year for less persistent OCs and 1-2 years for the more persistent OCs, whereas the half-lives for OCs in sediment are 8-25 years.