Zinc isotope systematics in snow and ice accretions in Central European mountains

Abstract

Zinc (Zn) pollution negatively affects human and ecosystem health. We quantified atmospheric Zn inputs at six remote mountain-top locations in the Czech Republic (Central Europe), and used δ66Zn isotope ratios to identify Zn from different pollution sources. The study sites were located at an elevation of approximately 1000m near the state borders with Germany and Poland. During two winter seasons (2009–2010), over 400 samples of vertical deposition (snow) and horizontal deposition (ice accretions) were collected. Zinc pollution levels were generally low. Zinc concentrations in snow and ice accretions were less than twice as high in the east, compared to the west. Across the sites, over 90% of Zn was present in a weak-acid soluble form. Zinc concentrations were 5 times higher in ice accretions, which formed from small droplets originating in the basal cloud layer, rich in pollutants, than in snow. In contrast, droplets resulting in snow formation were larger and scavenged less pollution due to their smaller surface area. δ66Zn of Pribram sphalerite (west) and smelter-derived fly ash (west) were low, −0.23 and −0.47‰, respectively. Olkusz sphalerite (east) had a higher δ66Zn of 0.02‰. δ66Zn of snow ranged from −0.60 to 0.68‰. Ice accretions had δ66Zn between −0.67 and 0.14‰. At the three eastern sites, δ66Zn of ice accretions was lower than δ66Zn of snow, suggesting the presence of volatilized smelter-derived or coal-burning derived Zn. δ66Zn of ice accretions at two of the three western sites was higher than δ66Zn of snow. Different δ66Zn values of snow and ice accretions from the same site reflected different pollution sources, which may have been situated at different distances from the receptor site. δ66Zn of the soluble Zn fraction was higher than δ66Zn of the insoluble Zn fraction, possibly also indicating a different origin of these two Zn fractions. Zinc isotope heterogeneity in the atmosphere of remote areas indicates that δ66Zn can be a useful tool in pollution provenance studies.