The characterization of atmospheric trace metals input recorded in East GRIP snow pit

Abstract

On July 2017, a series of 38 snow samples were collected from the 1.9 m deep snow pit at the Greenland East GRIP deep ice core drilling camp in 5 cm interval. These samples were analyzed for As, Bi, Cd, Cu, Mo, Pb, Sc and Zn in order to characterize the relative contributions from anthropogenic and natural sources to the fallout of these elements in northeast Greenland. Also, for the age dating, we measured water stable isotope ratios and ions such as Na+, Ca2+ and SO42-. The typical seasonal changes in water stable isotope ratios, Na+ and Ca2+ of the snow pit samples indicate that these samples covered the period from spring of 2013 to summer of 2017. On the other hand, nss-SO42- calculated with SO42- and Na+ showed a large peak from 2014 fall to 2015 summer. This period corresponded to the Holuhraun volcanic eruption (31 August 2014) at Iceland, and thus it can be inferred that the large increase of nss-SO42- for that period was most likely due to the input of volcanogenic SO42-. A volcanic eruption is also well known for an important natural source for atmospheric trace metals. The high crustal enrichment factors (EFc) of As, Bi, Cd, Cu, Mo, Pb and Zn in the Greenland East GRIP snow pit implies the large contributions from additional sources other than wind born crust dust. However, differently from the remarkable peak of nss-SO42- corresponding to the Holuhraun eruption, High concentrations and EFc values of trace metals were found every year especially during fall and winter. This represents no particular contributions from that the Holuhraun eruption. This also well meets the gas rich-ash poor eruption of Holuhraun volcanoes. Considering this, the seasonal enrichments of trace metals in East GRIP seem to be significantly contributed by anthropogenic emissions.