Comparison of vertical and horizontal atmospheric deposition of nitrate at Central European mountain-top sites during three consecutive winters
Abstrakt
Nitrogen (N) deposition, a key process of atmospheric self-cleaning, represents an important pathway for nutrients and pollutants to ecosystems. Enhanced N deposition flux contributes to acidification, eutrophication and loss of biodiversity.
N-NO3- concentrations in rime and snow were measured at 10 Czech plots situated in borderline mountains in 2009-2011 winters. The results were put in context with data-driven geostatistical modelling results of annual wet vertical and horizontal deposition.
Our hypotheses were that: (i) rime and snow would be more polluted in the highly industrialized north than in the south, (ii) the N-NO3- concentrations would differ in the three winters studied, and (iii), that N-NO3- rime deposition is not negligible in Central European mountain ranges. Our results indicated that winter N-NO3- concentrations were significantly higher in rime than in snow and that there were much larger between-site differences in N-NO3- concentrations for rime than for snow.
Relatively large differences were found between individual years. Atmospheric input of N-NO3- in winter was dominated by vertical deposition, i.e., snow.
Modelled results showed that mean winter rime deposition corresponded to about 6-25 %, and mean winter snow deposition made up 25-72.5 % of mean annual N-NO3- wet-only deposition. Model N-NO3-occult deposition estimated from throughfall and total (wet and dry) deposition is highly uncertain, however: N throughfall is not a relevant proxy for estimation of realistic total N deposition due to N exchange between the tree canopy and atmosphere.