engleski

Anthropogenic contaminants in water and sediments of the Plitvice Lakes - implications for environmental protection and water management

The Plitvice Lakes, located in a pristine and sparsely populated area of the northwestern Dinarides, central Croatia, represent a unique hydrological system, which consists of 16 karst lakes interconnected by numerous cascades and waterfalls, formed by travertine barriers. Owing to their natural amenities, the Lakes were proclaimed a National Park in 1949, and since 1979, they are included on the UNESCO World Natural and Cultural Heritage List. In the last hundred years, the area around the Plitvice Lakes experienced significant changes with respect to predominant anthropogenic activities, which represented a major challenge for the environmental protection and water management. Before the Lakes were put under protection as a National Park, the area was characterised by intensive timber cutting and sawmill activities, while the main national road, connecting the North and South of Croatia, vent along the Lake’ s shore. The last few decades were characterised by a fast expansion of tourism, so that the number of visitors in the late 1980s reached 1 million per year, while all other activities, including road traffic near the Lakes, were significantly restricted. It should be stressed that the pressure from intensive tourism ceased for 5 years during the 1991-1995 war in Croatia, however, possible negative effects from war activities and lack of systematic protection measures in that period cannot be completely ruled out. In this study, water and dated recent sediments (0-30 cm) were analysed, using highly specific methods, for different anthropogenic contaminants, including heavy metals and specific organic chemicals, in order to assess possible influence of anthropogenic activities on that protected ecosystem. The special emphasis was on the two largest lakes, Lake Prosce and Lake Kozjak, which significantly differ from each other with respect to their exposure to modern anthropogenic sources. The upper Lake Prosce is situated in an area away from the major roads and tourist routes, while the lower Lake Kozjak is exposed to more intensive tourist traffic. The concentrations of typical anthropogenic contaminants (heavy metals, hydrocarbons, synthetic surfactants) in the water column of the Plitvice Lakes are generally low, however some contaminants, such as cadmium, indicated slightly enhanced levels, which might be indicative of some, still unrecognized, contamination inputs into the Lakes. The distribution of anthropogenic contaminants in the recent lake sediments was found to be highly indicative of characteristic historic phases of anthropogenic activities in the area. The most useful indicators of specific contamination sources were aliphatic and polycyclic aromatic hydrocarbons, anionic surfactants and some heavy metals, such as lead, chromium and cadmium. The profiles of the contaminants, related to road traffic, revealed that the maximum concentration was observed in the deeper layers of the sediment cores, which indicated that the strict protection measures in the area of the National Park, including the new regulation of the road traffic during 1960s, were efficient in reducing contaminant input to the Lakes. However, the maximum concentration of detergent-derived chemicals was observed in the uppermost layers, indicating increasing usage of synthetic surfactants in the last decades, especially by the hotels situated on the shore of the Lake Kozjak, which released their untreated wastewaters into the lake. While distribution of polycyclic aromatic hydrocarbons indicated that measures undertaken during the last 30 years were efficient in reducing hydrocarbon pollution, the occurrence of synthetic surfactants in concentrations, which are relatively high for a pristine area, suggest that wastewaters significantly contributed to the input of detergent-derived xenobiotic chemicals and, very probably, enhanced eutrophication.

Plitvica lakes ; anthropogenic contaminants

978-953-96071-2-6 (CD)