Atmospheric deposition of current use pesticides in the Arctic: Snow core records from the Devon Island Ice Cap, Nunavut, Canada

Abstract

Current use pesticides (CUPs) have been detected in the Arctic, even though there are no direct sources and their long range atmospheric transport potential is generally lower than that of legacy pesticides. Data on the deposition of CUPs in the Arctic are required to assess the impact of their global usage and emission. In this study, selected CUPs were measured in the layers of a snow pit sampled on the Devon Ice Cap, Nunavut, Canada. The oldest sampled layers correspond to deposition from the early 1990s. Dacthal and endosulfan sulfate were most frequently detected, with peak deposition fluxes of 1.0 and 0.4 pg cm(-2) per year. While endosulfan sulfate was more abundant than its parent compounds in most years, endosulfan (sum of α and β isomers) was predominant in 2003 and 2006, which together with air mass backward trajectories suggests a possible origin from ongoing use in Eurasia. The interannual variation in CUP deposition fluxes could not be explained with annual variations in the extent of air mass origin over agricultural lands, suggesting that other factors, such as the interannual variation in pesticide use, play a role in affecting the long range transport of CUPs to the Arctic. The very high variability in the concentrations of CUPs in the horizontal layers of Arctic ice caps is most plausibly explained by the highly episodic nature of long range atmospheric transport and deposition. While this strong influence of rare events limits the suitability of ice caps as reliable records of historical trends in Arctic contaminant deposition with annual resolution, the presence of concentration peaks in the ice record is proof of the possibility of such transport and deposition.

Spatial Distributions and Seasonal Changes of Current‐Use Pesticides from the North Pacific to the Arctic Oceans

“…Dacthal concentrations in the North Pacific Ocean was comparable with or slightly higher than those in melt-ponds and seawater in the Canadian Arctic (Pućko et al, 2016) where the former play a key role in concentrating CUPs. Except for the low frequency of detection, dacthal is consistent with the range of concentrations in ice-core samples from the Devon Island Ice Cap, Nunavut, Canada (Zhang et al, 2013). Simazine and methoxychlor concentrations were in the ranges <MDL-0.76 ng/L (mean 0.13±0.14 ng/L) and <MDL-0.54 ng/L (mean 0.13±0.13 ng/L), respectively.…”

“…Alachlor concentrations were in the range 0.01–2.2 ng/L (mean 0.49±0.55 ng/L). In contrast to the North Pacific Ocean, dacthal was not detected in the Chukchi Sea, even though it has been widely reported in high altitude Arctic environments where LRAT had a significant influence (Bidleman et al, ; Hermanson et al, ; Hoferkamp et al, ; Morris et al, ; Pućko et al, ; Ruggirello et al, ; Vorkamp & Rigét, ; Yao et al, ; Zhang et al, ; Zhong, Xie, Cai, et al, ). The distribution in the present study indicates a short half‐life and rapid degradation of dacthal in the ocean, and varying degrees of LRAT in different environmental conditions of the Arctic (Gouin, Cousins, et al, ; Gouin, Mackay, et al, ; van Pul et al, ).…”

Current‐use pesticides in seawater and their bioaccumulation in polar bear–ringed seal food chains of the Canadian Arctic

“…For example, the isomerization of β‐endosulfan to α‐endosulfan in aquatic conditions occurs at approximately 3 times the rate of the reverse reaction, which is the most likely reason for the small representation of β‐endosulfan in both phases of seawater . Endosulfan sulfate is less volatile than the parent isomers, is equally as soluble in water as β‐endosulfan, and is formed via the oxidation of both isomers , resulting in a prominent presence in the dissolved phase of seawater and the Devon Island ice cap . Endosulfan sulfate has low sorption to particles in relation to its abundance in the dissolved phase because of its small log K OW value (3.2; Supplemental Data, Table S2), which resulted in low detection frequencies and concentrations in the particle phase (Figure and Supplemental Data, Table S11).…”

“…Endosulfan sulfate and dacthal were the most consistently detected CUPs with the greatest seawater concentrations. They were also the most frequently detected CUPs in the Devon Island ice cap (Nunavut), along with chlorothalonil, trifluralin, PCNB, metribuzin, and the endosulfan isomers [6]. Approximately 30% of the technical mixture of endosulfan is b-endosulfan; and b-endosulfan was a prominent component of Sendosulfan in the Devon Island ice cap (greater than or equal to a-endosulfan in some layers of the ice cores) [6].…”

Clinical Aspects of the Poisoning by the Pesticide Endosulfan

“…While endosulfan sulfate was more abundant than its parent compounds in most years, endosulfan (sum of α and β isomers) was predominant in 2003 and 2006 which, together with air mass backward trajectories, suggests a possible origin from ongoing use in Eurasia. 48 Potter et al 49 measured endosulfan wet deposition in precipitation over a 4-year period within an area of high agricultural use in Southern Florida (USA) and in nearby Biscayne and Everglades National Parks. Endosulfan's two isomers and endosulfan sulfate were detected at high frequency with the order of detection and concentration being: Endosulfan in soil can be degraded by some soil bacteria, as demonstrated by the findings of recently discovered endosulfan--degrading bacterial strain Alcaligenes faecalis JBW4 which was isolated from activated sludge.…”