Transport and fate of hexachlorocyclohexanes in the oceanic air and surface seawater

Abstract

Abstract. Hexachlorocyclohexanes (HCHs) are ubiquitous organic pollutants derived from pesticide application. They are subject to long-range transport, persistent in the environment, and capable of accumulation in biota. Shipboard measurements of HCH isomers (α-, γ -and β-HCH) in surface seawater and boundary layer atmospheric samples were conducted in the Atlantic and the Southern Ocean in October to December of 2008.HCHs concentrations (the sum of α-, γ -and β-HCH) in the lower atmosphere ranged from 12 to 37 pg m −3 (mean: 27 ± 11 pg m −3 ) in the Northern Hemisphere (NH), and from 1.5 to 4.0 pg m −3 (mean: 2.8 ± 1.1 pg m −3 ) in the Southern Hemisphere (SH), respectively. Water concentrations were: α-HCH 0.33-47 pg l −1 , γ -HCH 0.02-33 pg l −1 and β-HCH 0.11-9.5 pg l −1 . Dissolved HCH concentrations decreased from the North Atlantic to the Southern Ocean, indicating historical use of HCHs in the NH. Spatial distribution showed increasing concentrations from the equator towards North and South latitudes illustrating the concept of cold trapping in high latitudes and less interhemispheric mixing process. In comparison to concentrations measured in 1987-1999/2000, gaseous HCHs were slightly lower, while dissolved HCHs decreased by factor of 2-3 orders of magnitude. Air-water exchange gradients suggested net deposition for α-HCH (mean: 3800 pg m −2 day −1 ) and γ -HCH (mean: 2000 pg m −2 day −1 ), whereas β-HCH varied between equilibrium (volatilization: <0-12 pg m −2 day −1 ) and net deposition (range: 6-690 pg m −2 day −1 ). Climate change may significantly accelerate the release of "old" HCHs from continental storage (e.g. soil, vegetation and high mountains)Correspondence to: Z. Xie (zhiyong.xie@hzg.de) and drive long-range transport from sources to deposition in the open oceans. Biological productivities may interfere with the air-water exchange process as well. Consequently, further investigation is necessary to elucidate the long term trends and the biogeochemical turnover of HCHs in the oceanic environment.

Selected current‐use and historic‐use pesticides in air and seawater of the Bohai and Yellow Seas, China

“…Xie et al . [] summarized that the air‐water exchange of α‐HCH in the North Atlantic changed from net deposition in 1990 to equilibrium in 1999, and a new equilibrium had established at lower seawater concentrations in 2008. Cai et al .…”

“…γ‐HCH was also close to equilibrium in the Bohai Sea, but mainly underwent net deposition in the Yellow Sea as a result of the lower dissolved concentrations. Air‐water exchange direction for γ‐HCH has been dominated by net deposition in most studies [ Xie et al ., ], and this is consistent with the fact that lindane has been globally banned for agricultural use just recently. However, atmospheric concentrations of γ‐HCH might also show greater seasonality and net volatilization could happen in seasons with much lower gaseous concentrations [ Zhong et al ., ].…”

Dissolved organic matter in sea spray: a transfer study from marine surface water to aerosols

“…An oceanic air and surface water transfer study of pollutants with hexachlorocyclohexanes Xie et al(2011) already demonstrated the presence of deposition and volatilization processes. Here, we focus on chemical structural changes, depletions and enrichments in the process of primary marine aerosol formation via the bubble bursting process.…”

Distribution and air–sea exchange of organochlorine pesticides in the North Pacific and the Arctic

“…Extraction, clean‐up, and analysis of the samples were performed according to the method described elsewhere [ Zhong et al , 2012; Xie et al , 2011]. Briefly, each sample was spiked with the surrogate standard d 6 ‐HCH prior to extraction, then extracted using dichloromethane with MX extractor and purified on a 10% water‐deactivated silica gel column.…”