Annual cycles of organochlorine pesticide enantiomers in Arctic air suggest changing sources and pathways

Abstract

Abstract. Air samples collected during 1994–2000 at the Canadian Arctic air monitoring station Alert (82°30' N, 62°20' W) were analysed by enantiospecific gas chromatography–mass spectrometry for α-hexachlorocyclohexane (α-HCH), trans-chlordane (TC) and cis-chlordane (CC). Results were expressed as enantiomer fractions (EF = peak areas of (+)/[(+) + (−)] enantiomers), where EFs = 0.5, < 0.5 and > 0.5 indicate racemic composition, and preferential depletion of (+) and (−) enantiomers, respectively. Long-term average EFs were close to racemic values for α -HCH (0.504 ± 0.004, n = 197) and CC (0.505 ± 0.004, n = 162), and deviated farther from racemic for TC (0.470 ± 0.013, n = 165). Digital filtration analysis revealed annual cycles of lower α-HCH EFs in summer–fall and higher EFs in winter–spring. These cycles suggest volatilization of partially degraded α-HCH with EF < 0.5 from open water and advection to Alert during the warm season, and background transport of α-HCH with EF > 0.5 during the cold season. The contribution of sea-volatilized α-HCH was only 11% at Alert, vs. 32% at Resolute Bay (74.68° N, 94.90° W) in 1999. EFs of TC also followed annual cycles of lower and higher values in the warm and cold seasons. These were in phase with low and high cycles of the TC/CC ratio (expressed as FTC = TC/(TC+CC)), which suggests greater contribution of microbially "weathered" TC in summer–fall versus winter–spring. CC was closer to racemic than TC and displayed seasonal cycles only in 1997–1998. EF profiles are likely to change with rising contribution of secondary emission sources, weathering of residues in the environment, and loss of ice cover in the Arctic. Enantiomer-specific analysis could provide added forensic capability to air monitoring programs.

Year-Round Monitoring of Contaminants in Neal and Rogers Creeks, Hood River Basin, Oregon, 2011-12, and Assessment of Risks to Salmonids

“…Other contaminant transport pathways also exist; chlordane is commonly transported through atmospheric deposition [ 56 ] and PCP leaches from fungicide-treated lumber utility poles [ 57 ]. These chlorinated pesticides were widely used in the basin for agricultural, home, and public health pest control or as wood preservatives during the early- and mid-twentieth century, but most approved uses were banned during the 1970s and 1980s.…”

Concentration and chiral signature of chlordane in soils and sediments of the Central Tibetan Plateau, China: Transformation in the surficial process

“…In addition to transformation, the re-volatilization might also influence the F TC of the residual chlordane in the soils. CC shares slightly greater enthalpies of vaporization and octanol-air partitioning than TC (Su et al, 2008;Bidleman et al, 2015). Thus, CC showed a greater preference for adsorption onto SOC than TC during soil-air exchange.…”

“…Technical chlordane was used worldwide as a pesticide for farmlands, home lawns and gardens and as a termiticide for housing foundations (Li et al, 2007), but it was phased out commercially in Europe and the U.S. in 1997. Nevertheless, chlordane is still detected worldwide (Wong et al, 2009;Ulrich et al, 2009;Bidleman et al, 2015). To implement the Stockholm Convention, China banned chlordane production for all purposes in 2009.…”

“…Enantiomer signatures have been used to trace chlordane sources and pathways (Bidleman et al, 1998(Bidleman et al, , 2015Leone et al, 2001) and even the fate of chlordane in surficial processes (Fish et al, 2001;Bidleman et al, 2012). Meanwhile, the ratio of TC to CC has been used to indicate the degree of "weathering" in the environment (Bidleman et al, 2015).…”

“…Recently, much interest has been paid to chlordane and other organochlorine pesticides (OCPs) in background regions such as the Arctic (Ma et al, 2011;Becker et al, 2012;Bidleman et al, 2015), which help in understanding their global fate. As a unique background region, the Tibetan Plateau (TP), covering over 2.5 million km 2 and at an average elevation of more than 4000 m, has been regarded as one of the most remote and isolated regions in the world.…”