Levels of atrazine and simazine in waters in the rural and urban areas of north-west Croatia

The triazine herbicides atrazine and simazine were measured in samples of surface, ground, drinking and rain/snow waters collected in the 1992-2001 period in rural areas north-west of Zagreb city and in the city area. Atrazine was detected in 367 and simazine in 40 out of the 477 water samples analysed. The highest atrazine concentrations (up to 8.28 mug L-1) were measured in surface waters from the rural area in the 1992-1995 period. In the later sampling period (2001) a decreasing trend in atrazine concentrations was observed in surface and ground waters collected from privately owned wells. However, there were no great variations in levels of atrazine in drinking waters in either the rural or the urban area. The atrazine concentration exceeded 0.1 mug L-1 in 29% of drinking water samples, reflecting the contamination of ground waters serving as drinking water supplies. The sorption intensity of atrazine and simazine was tested in soil and aquifer sediments collected close to the wells used for the public water supply systems. The values of Freundlich K-f sorption coefficients indicated more efficient retention of compounds in the surface soil and in the aquitard layer than within the three aquifer porous ground water layers of more or less balanced gravel, sand, and silt content and with 0.99-1.5% of organic matter. The incidence and concentrations (<0.01-0.18 mug L-1) in rain/snow samples collected in the Zagreb city and at a rural site about 20 km north-west of the city centre indicated that atmospheric transport was also involved in atrazine environmental distribution.