Contribution of rime to atmospheric sulphur deposition in Central Europe: A combined empirical and modelling approach

Abstract

Rime is an under-researched pathway of atmospheric deposition of ecological and environmental relevance, in particular in mountain regions. We present data on sulphur (S) deposition via rime and snow collected at 10 mountaintop sites in the Czech Republic (CR) during three consecutive winters (2009–2011). The mean S concentrations in rime ranged between 3.35 mg L−1 [site Tetrevec (TET) in the north] and 0.78 mg L−1 [site Kamena Loucka (LOU) in the south]. The most S-polluted site thus had S concentrations in rime that were approximately four times higher than the least S-polluted site. Across the sites, S concentrations in rime were 5–10 times higher than in snow. TET, identified as the most S-polluted site, received as much as 60% S from rime and only 40% S from snow. Our results indicated a substantial decline in S rime deposition since the 1990s, following the introduction of desulphurisation measures in the CR. The results of direct measurements of winter-time S deposition via rime are discussed in the context of annual occult deposition, including both rime and fog, obtained from a data-driven geostatistical model. According to our model, occult S deposition ranged between 0 and 1.5 g m−2 year−1 over 99.7% of the forested area of the CR, and generally increased with altitude. At nine sites, the winter-time deposition of S via rime corresponded to 5–13% of annual wet-only S deposition, while it reached 25% at the most S-polluted TET site. In environmental studies, the S deposition pathway via rime should not be neglected, as it might substantially contribute to the total S deposition flux even in mountains of medium elevation.