engleski

Deposition of sulphur and nitrogen in the forest area (Highlands District) of Croatia

Highland District (Gorski kotar) is a forested part of Croatia situated north of Rijeka, a Northern Adriatic port. In spite being next to Mediterranean Sea, due to the high mountains rising from the coast (up to 1500 m) the penetration of maritime air masses deeper into the mainland is prevented. Therefore, this area is characterized with continental climate, with cold winter and mild summer, both accompanied with high precipitation amounts. Although acid rains were claimed to be responsible for forest decline observed during the eighties, the first analyses of precipitation in this area started only in 1995, at two locations: a settlement (Site 1) approx 40 km east, and a hunting resort (Site 2), approx 25 km north-east from Rijeka. As this latter location is inaccessible during the winter time due to high snow level, the precipitation analyses were extended in 2004 to another Site 3, 8 km away and downhill from the Site 2. The results of the 14-years long survey led to several conclusions: • Precipitation weighted average (PWA) concentrations of sulphates and nitrogen species (nitrate and ammonium) at the remote island Site 4, at the entrance of the Kvarner Bay, and the mountainous Site 1 are practically equal, meaning there is hardly any influence of the Rijeka acid gases emissions to the rainwater acidity in this mountainous area ; • Similar depositions of S-SO42- and tot-N (NO3-+NH4+) in the city of Rijeka (Site 5) and Site 1 are due to different reasons: higher PWA concentrations of sulphates and nitrogen species in the urban site due to the local washout of the atmosphere, and higher precipitation depth in the mountainous site ; • Deposition of sulphur and nitrogen in the forest Sites is similar and within the respective critical loads. In conclusion, acid deposition is not likely to be the principal cause for the forest decline in the Highland District area. Further studies are required to identify the main cause/es.

bulk deposition; sulphates; nitrates; ammonium; critical loads

nije evidentirano