Geochemical composition of snow samples from Antarctica, Greenland and northeast Canada

In this paper, we present new detailed data on the trace metal content of more than 200 shallow polar snow samples collected at various depths in numerous locations mainly in Antarctica and Greenland. The samples were collected in ultraclean plexiglass or teflon tubes from the walls of hand dug pits, using stringent contamination free techniques controlled by severe blank tests. They were then analysed for Na, Mg, K, Ca, Fe, Al, Mn, Pb, Cd, Cu, Zn and Ag in clean room conditions by flameless atomic absorption, after a preconcentration step (by non boiling evaporation in teflon bulbs) which includes dissolving any solid particles by concentrated nitric and hydrofluoric acids. The overall precision on the measured concentrations is of the order of 10 % for all the metals except Pb (20 %) and Cd (35 %), using 95 % confidence limits. The data obtained are compared with those published previously in the literature. Part of these previous data are shown to be erroneously too high, probably because of con-tamination problems both during field collection and analysis.本研究报道了一套全新的高精度数据集，涵盖200余份极地浅层雪样的痕量金属含量信息。该批雪样采自以南极洲与格陵兰岛为主的众多点位，按不同深度分层采集。 所有雪样均通过严格的无沾染采样流程获取：从人工挖掘的雪坑壁采集样品，使用超净有机玻璃（ultraclean plexiglass）或特氟龙（teflon）采样管盛装，所有操作均通过严苛的空白测试进行质量管控。 随后，样品在洁净室（clean room）环境下通过无火焰原子吸收光谱法（flameless atomic absorption）完成元素分析，检测指标包括钠（Na）、镁（Mg）、钾（K）、钙（Ca）、铁（Fe）、铝（Al）、锰（Mn）、铅（Pb）、镉（Cd）、铜（Cu）、锌（Zn）与银（Ag）。分析前需先完成预富集流程：采用浓硝酸与氢氟酸消解所有固体颗粒后，在特氟龙蒸发瓶中进行非沸腾蒸发以实现元素富集。 以95%置信限计算，除铅（20%）与镉（35%）外，其余所有金属元素的浓度测量总精密度均约为10%。 将本研究获取的数据集与既往文献发表的同类数据进行对比后发现，部分既往数据存在明显偏高的误差，推测其原因为野外采样与实验室分析阶段均出现了沾染问题。