Key points are not available for this paper at this time.
Estimates of atmospheric inputs of reactive nitrogen (N r ) into ecosystems are often based on vertical deposition. We investigated to what extent horizontal deposition affects total atmospheric deposition of N r in two sparsely populated mountain regions near the Czech–German–Polish borders in an era of easing pollution. Among three scenarios of horizontal-water contribution to rainfall (additional 5, 10 and 20%), the 10% scenario was considered the most realistic. Between 2023 and 2025, wet horizontal deposition of NH 4 + -N plus NO 3 - -N constituted as much as 66-77% of total wet inorganic N r deposition. This estimateBecause condensation of rain and fog droplets occurs at different altitudes, we hypothesized that the N r -source mix in horizontal and vertical deposition would differ. N-isotope analyses and Bayesian modeling indicated larger dominance (up to 75%) of vehicle-exhaust derived NH 4 + -N in fog than in rain. In contrast, the mix of NO 3 - -N sources for fog and rain was nearly identical, with average contributions of six sources making up 9-24% each. Remote large NO x sources originating in coal-burning powerplants and natural-gas burning industries played similarly weak roles as more local and/or diffuse sources related to residential coal and wood burning, traffic and biogenic/soil emissions. • Horizontal deposition adds 66-77% to vertical deposition of reactive nitrogen (N r ) • Such high atmospheric N r inputs via fog should not be neglected in ecosystem studies • δ 15 N values and SIMMR modeling revealed a major role of traffic NH 3 -N in all samples • Nitrate-N from six sources was well homogenized, with no dominant single polluter • N-source contributions were similar in fog and rain, despite de-coupled condensation
Novak et al. (Fri,) studied this question.