Contaminants in arctic snow collected over northwest Alaskan sea ice

Abstract

Snow cores were collected over sea ice from four northwest Alaskan Arctic estuaries that represented the annual snowfallfrom the 1995–1996 season. Dissolved trace metals, major cationsand anions, total mercury, and organochlorine compounds weredetermined and compared to concentrations in previous arctic studies. Traces (<4 nanograms per liter, ng L-1) of cis- and trans-chlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, dieldrin, endosulfan II, andPCBs were detected in some samples, with endosulfan I consistently present. High chlorpyrifos concentrations (70–80 ng L-1) also were estimated at three sites. The snow washighly enriched in sulfates (69–394 mg L-1), with highproportions of nonsea salt sulfates at three of five sites (9 of 15 samples), thus indicating possible contamination throughlong-distance transport and deposition of sulfate-rich atmospheric aerosols. Mercury, cadmium, chromium, molybdenum, and uranium were typically higher in the marine snow (n = 15) in relation to snow from arctic terrestrial studies, whereas cations associated with terrigenous sources, such as aluminum,frequently were lower over the sea ice. One Kasegaluk Lagoon site (Chukchi Sea) had especially high concentrations of totalmercury (mean = 214 ng L-1, standard deviation = 5 ng L-1), but no methyl mercury was detected above the method detection limit (0.036 ng L-1) at any of the sites. Elevated concentrations of sulfate, mercury, and certain heavymetals might indicate mechanisms of contaminant loss from the arctic atmosphere over marine water not previously reported overland areas. Scavenging by snow, fog, or riming processes and thehigh content of deposited halides might facilitate the loss of such contaminants from the atmosphere. Both the mercury and chlorpyrifos concentrations merit further investigation in view of their toxicity to aquatic organisms at low concentrations.