| Popis: |
Precipitation samples were collected in three-week periods at two sites (site I, Slapy Reservoir and site II, Rimov Reservoir) in the Czech Republic from 1979 to 1994. Chemical composition with an emphasis on concentrations and deposition rates of nutrients were evaluated on seasonal, annual, and long-term basis. Long-range transport dominated the atmospheric deposition at site I, whereas local sources were relatively more important at site II. The average annual bulk deposition rates were 10 and 14 kg ha−1 for total nitrogen (TN), 0.15 and 0.24 kg ha−1 for total phosphorus (TP), and 17 and 20 kg ha−1 fororganic carbon at sites I and II, respectively. NH4N was the major component of TN ( > 40%), NO3N represented ∼ 35%, and organic nitrogen contributed by ∼ 23% to the TN deposition. Concentrations and deposition rates of nutrients showed pronounced annual cycles; concentrations reached the maximum values in late winter and early spring, deposition rates from April to August. These cycles are explained by the seasonality of both precipitation and nutrient sources (agriculture, residential heating sources, pollen, soil dust). The concentrations and/or deposition rates of NH4N and N03N doubled and more than tripled, respectively, in the Czech Republic between 1958 and the mid- 1980s. The concentrations and deposition rates of sulphate decreased at site I already in the 1980s, probably as a result of the general trend of decreasing sulphur emission in Europe, while this trend was surpassed by local sources at site II. However, a sharp decline in both N and S concentrations and deposition rates occurred in the early 1990s, due to the reduced emissions of ammonia NOx and SO2 in Central European post-communist countries after the the 1989 political and economical changes. |
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