engleski

Bulk Deposition of Nitrogen within Kvarner Bay Area (Croatia), 1984-2003

Trends in nitrogen deposition (N-NO3- and N-NH4+) at 3 sites are presented: the urban Site 1 (Rijeka), the remote Site 2 (island of Cres), and an inland Site 3 (Delnice). The deposition of N-NO3- varies mostly between 200 and 500 eq ha-1 y-1 at urban Site 1 and inland Site 3, while lower deposition rates between 100 and 300 eq ha-1 y-1 are found at the remote Site 2. Similarly, results obtained since 1996 indicate higher deposition of N-NH4+ at Site 1 and 3 (500-900 eq ha-1y-1) comparative to Site 2 (~300eq ha-1y-1). The same is valid for total N deposition that is found to be 900-1300 eq ha-1y-1 at Sites 1 and 3, while ~ 500 eq ha-1y-1 at Site 2. Higher deposition of N (and S) observed in 2002. are due to higher frequency of Saharan sand episodes, with high load of these ions. If these data were excluded, all sites exhibit a declining trend in deposition of nitrogen (except N-NO3- at Site 3). The decline in N-NO3- at Site 1 is following the reduction in ambient NO2 concentrations. The PWA concentrations of nitrate and ammonium (and sulphate, as well) are higher only in the samples from urban Site 1, thus confirming the local washout of the atmosphere, while at Sites 2 and 3 these values are similar. Higher deposition of N (and S) at Site 3 is due to higher precipitation depth. The deposition of total N (and S-SO42-) at Site 3 is bellow the critical loads calculated for the most sensitive soil-vegetation forest type for this mountainous region (with exception of 2002. data).

precipitation chemistry; trend; nitrate; ammonium

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