Spatial and Seasonal Variations of Hexachlorocyclohexanes (HCHs) and Hexachlorobenzene (HCB) in the Arctic Atmosphere

Abstract

Weekly high-volume air samples were collected between 2000 and 2003 at six Arctic sites, i.e., Alert, Kinngait, and Little Fox Lake (LFL) in Canada, Point Barrow in Alaska, Valkarkai in Russia, and Zeppelin in Norway. Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were quantified in all samples. Comparison showed that alpha-HCH and HCB were homogeneously distributed in the circumpolar atmosphere and uniform throughout the seasons. However, significantly higher atmospheric concentrations of alpha-HCH and HCB and strongertemperature dependence of alpha-HCH and gamma-HCH were found at LFL in Yukon (YK), which is unique among the sites by virtue of its high altitude and low latitude, resulting in higher precipitation rates and summer temperatures. Strong temperature dependence of alpha- and gamma-HCH at this location suggests that secondary emissions, i.e., re-evaporation from surfaces, were more important at this site than others. It is hypothesized that a higher precipitation rate at LFL facilitated the transfer of alpha-HCH from the atmosphere to surface media when technical HCH was still in use worldwide. On the other hand, higher temperature at LFL enhanced reevaporation to the atmosphere after the global ban of technical HCH. In contrast to alpha-HCH and HCB, larger spatial and seasonal differences were seen for gamma-HCH (a currently used pesticide), which likely reflect the influence of different primary contaminant sources on different Arctic locations. Fugacity ratios suggest a net deposition potential of HCB from air to seawater, whereas seawater/air exchange direction of alpha-HCH varies in the circumpolar environment.

Environmental fate and behavior of persistent organic pollutants in Shergyla Mountain, southeast of the Tibetan Plateau of China

“…In this study, the concentration of hexachlorobenzene (HCB) was quite constant, with a variation coefficient value of 36%, which was consistent with the results in other studies Su et al, 2006). Previous work has pointed out that compared to other POPs, HCB is very resistant to attack by photo-oxidants (Brubaker and Hites, 1998) and has relatively high volatility (vapor pressure: 1.80E-05 mm Hg) to avoid efficient dry particle and wet deposition, thus has an exceptionally long atmospheric residence time in excess of one year.…”

“…So it has been used as a reference compound to obtain a series of sampler-specific constant sampling rates R based on its constant amount in a certain region, further to convert the PAS-based amounts into volumetric air concentrations . In this study, an average air concentration value of 56 pg m À3 for HCB was assumed to prevail in the air of the Shergyla Mountain throughout the sampling year Su et al, 2006), which is also consistent with those in rural/ background sites in Western China (Cheng et al, 2007) and the representative value of HCB air level in Northern hemispheric background conditions (Barber et al, 2005;Su et al, 2006). The average sampler specific sampling rates R calculated in present study was 2.71 AE 0.77 m 3 day À1 and close to the R-values determined previously in the Tibetan Plateau Wang et al, 2010).…”

Three years (2008–2010) of measurements of atmospheric concentrations of organochlorine pesticides (OCPs) at Station Nord, North-East Greenland

“…23 A seasonal pattern of endosulfan I in the atmosphere, characterized by elevated concentrations in October-November and to a lesser extent in April-May, has been observed at Alert and Kinngait. 24,25 A similar pattern was observed in the present study, where concentrations peaked in April-May and rose again in September-October ( Fig. 1 ESI †).…”

“…Concentrations of heptachlor are usually below the detection limit in the Arctic atmosphere, since heptachlor is rapidly transformed to heptachlor epoxide. 25 However, heptachlor was detected in 30 out of 32 samples in the present study. The average annual concentration of trans-nonachlor was 0.39 pg m À3 , while cis-nonachlor concentrations were mostly close to the detection limit.…”

“…14 HCB concentrations showed a weak seasonality at Station Nord, with slightly higher concentrations in summer. Su et al 17 observed that HCB concentrations at ve Arctic stations were not inu-enced by variation of ambient temperature. Kallenborn et al 18 suggested that the expected high evaporation rates of HCB in the summer months are counterbalanced by increased photochemical degradation.…”