Seasonal Changes in As, Bi, Cd, Mo and halogen elements recorded in Greenland EastGRIP snow pit

Abstract

On July 2017, a series of 38 snow samples were collected from 1.9 m deep snow pit at the Greenland EastGRIP deep ice core drilling camp in 5 cm interval. We determined As, Ba, Bi, Cd, Mo and halogen elements together with water stable isotope ratios (δ18O) and ion species such as Na+, Ca2+, MSA (methylsulfonic acid), and SO42- from these samples. Well defined δ18O record indicates that the 1.9m deep snow pit samples cover 4.5 years from 2012 winter to 2017 summer. The concentration records of Ca2+ Na+, SO42- and Ba generally show peaks during spring seasons. This implies the large increases of atmospheric input of crust dust and sea salt for that season as well as other Greenland snow and icecore records. However, nss-SO42- also showed large peak from 2014 fall to 2015 spring. This is most likely due to the eruption of Holuhraun volcanoe, Iceland. As, Bi, Cd and Mo are known to be largely contributed by volcanic eruption. However, in our samples, no significant enrichment of these elements were found for the period of 2014~2015. Only Cd showed 2~3 times increase of crust enrichment factor (EFc). Considering the high EFc values of As, Bi, Cd and Mo over all samples, these elements seem to be significantly enriched by anthropogenic emissions, and thus the volcanic contributions were relatively small. In additions, Holuhraun eruption was known to be gas rich and ash poor. This also well supports the little influence of that volcanic eruption on the atmospheric input of the trace metals. Halogen elements such as Br and I reveal the seasonal change of these elements are characterized by summer peak. This represents that the atmospheric input of Br and I are related to bio-activities in polar region which is maximized during summer season.