Comparison of two pretreatment methods for mercury stable isotope analysis in Antarctic moss

摘要

Mercury(Hg) stable isotope analysis can provide new insight for understanding the biogeochemistry and sources of Hg in the polar regions. To completely extract the low contents of Hg in polar samples and to avoid isotopic fractionation during the sample preparation stage, an effective and reliable pretreatment method is needed. In this work, two different pretreatment methods were compared for measuring Hg stable isotopes in Antarctic moss samples. One method was acid digestion(HNO_3︰H_2O_2=5︰3, v/v) and the second was a combustion-trapping treatment with a trapping solution(HNO_3:HCl=2:1, v/v). There were no significant differences in the analytical results obtained with the two methods. The overall mean values and uncertainties of total Hg(THg) and the isotopic compositions of Hg in the referenced materials were all in good agreement with the certified and reported values, indicating that both methods were accurate and applicable. Acid digestion is highly efficient, while the combustion-trapping method can be used to treat samples with low Hg content. The proposed methods were successfully used to determine the Hg isotopic compositions in moss samples collected from the Antarctic.