hrvatski

NITRATI U PRIVATNIM ZDENCIMA BJELOVARSKO- BILOGORSKE ŽUPANIJE

Introduction - Due to inadequate development of public water supply in the Bjelovar- Bilogorje County, 58, 5% of the population is using water from their own wells which are in most cases poorly built, shallow and unprotected from surface-contamination. This paper includes retrospective and field study. In this area were found wells built out of bricks or concrete, as well as drilled artesian and subartesian wells. The aim of this paper was to interprets collected data on the concentration of nitrates obtained from drinking water samples from individual wells and field studies in order to gain an insight into the concentration of nitrates in underground waters in the area of the Bjelovar-Bilogorje County. The following had to be established: does the way the wells are built and the material used have any influence on the pollution of the water with nitrates according to these categories: dug (excavated) wells built with bricks or concrete, and distance of shallow wells from septic tanks, liquid-manure pits or from agricultural sources of contamination. Results - According to the obtained results it can be confirmed that the chemical contamination of underground waters with nitrates in the Bjelovar-Bilogorje County is present in shallow water-bearing strata. The values of the nitrates varied from 0, 00 to 808, 00 mg NO3/I. A total of 974 dug wells and 81 artesian wells were studied from 2006 until 2010. The results show that the building methods and the distance from any source of contaminating influences the chemical contamination with nitrates, while the depth of the wells in the shallow water-bearing strata do not have any effect on the contamination with nitrates. Due to its porosity, dug wells built with bricks are the most dangerous, where 42% have contaminated samples and 58% are non-contaminated. Wells built out of concrete are far less porous giving thus 86% of non-contaminated and only 14% of contaminated samples. Of course, wells nearer to some sources of contamination have a bigger probability to be contaminated. Supporting this are results showing that 40% of contaminated samples which were taken from such wells built in concrete, while 99% of non-contaminated samples were taken from concrete-built wells whose sources of contamination are more than 20m away. An encouraging fact is that underground waters of deep water-bearing strata are still free of anthropogenic influence of chemical contamination with nitrates. Out of 81 studied wells not one was contaminated. This is shown by the very low concentration of nitrate ranging from 0, 00 – 9.75 mg/l in the studied period without annual increase trend. Conclusion - During the 5-year period of the study, a total of 974 wells were studied and the results have shown that the chemical contamination of underground waters with nitrate in the Bjelovar-Bilogorje County is present only in the shallow water-bearing strate (anthropogenic contamination) while in the artesian wells not one samples was found to have a concentration of nitrate over MDK.

nitrati; kopani zdenci; arteški zdenci; Bjelovarsko-bilogorska županija

nije evidentirano