Ultra-trace analysis of Hg in alkaline lavas and regolith from James Ross Island

Abstract

AbstractPolar regions represent a unique environment for the study of mercury cycling in the global ecosystem. Our research was focused on the assessment of the origin and mobility of mercury in the geochemical cycle in Maritime Antarctic (James Ross Island) by means of atomic absorption spectrometry. Mercury content in a set of extrusive (subaerial, subaqueous) and intrusive (dyke) alkaline basalts ranged between 1.6 µg kg-1 (for samples without xenoliths) and 8 µg kg-1 (for samples containing crustal xenoliths). The mercury content in alkaline basalts indicates a very low concentration of mercury in peridotitic mantle sources. Samples of regolith from James Ross Island were subjected to a comprehensive analytical procedure proposed for ultra-trace mercury concentrations involving fractionation and thermal analysis. Total mercury contents in regolith (2.7–11.3 µg kg-1) did not deviate from the natural background in this part of Antarctica. Additionally, the obtained results are about two orders of magnitude smaller than values formerly assumed for primary mercury contents in basaltic lavas. Our results from Antarctica were compared with mercury contents in basaltic rocks from Greenland and the findings were confirmed. It seems that the input of mercury of geological origin into the polar ecosystem is apparently lower than expected.