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Volatile Short-chain Chlorinated Hydrocarbons in the Groundwater of the City of Zagreb
M. Marijanović-Rajčić
A. Senta
Sažetak
The aim of the study was to assess the quality of the groundwater sampled from private wells and the public water-supply system in terms of estimating the contamination caused by short-chain chlorinated hydrocarbons, as well as to estimate the exposure of the citizens dwelling in different suburbs to these pollutants of their drinking water (Fig. 1). The aim of the study was also to determine which suburb is supplied through the public water-supply system with water originating from the Sašnak spring that is contaminated with volatile chlorinated short-chain hydrocarbons.
Drinking water samples were taken from 3 private wells and 1 public water-supply system situated in 3 Zagreb suburbs - Pešćenica, Trnje, and Trešnjevka. The sampling was carried out during 2003 and was undertaken on a seasonal basis. Short-chain chlorinated hydrocarbons - 1,1,1-trichloroethane, carbon tetrachloride, 1,1,2-trichloroethene and 1,1,2,2-tetrachloroethene - were determined by gas chromatography, following "liquid-liquid extraction" in pentane. For that purpose, we applied the gas chromatograph equipped with an electron-capture detector, thermo-programmable operations, and a suitable capillary column. The technique applied was that of split-injection.
The groundwater of the City of Zagreb was found to be contaminated with volatile chlorinated hydrocarbons. The concentration level of 1,1,1-trichloroethane, determined in most of the samples, was found to be low (Fig. 2). On the other hand, 1,1,2-trichloroethene was present in all samples in concentrations of about 1 µg l-1 (Fig. 3). Only the drinking water samples taken from private wells in the suburb of Trnje contained somewhat higher mass concentrations of 1,1,1-trichloroethane, with the peak value of 19.03 µg l-1, measured in the winter season. In the samples taken from private wells in Trnje, the mass concentrations of 1,1,2,2-tetrachloroethene ranged from 15.30 µg l-1 to 18.65 µg l-1, as measured in autumn (Fig. 4). In most of the water samples analysed, carbon tetrachloride was not detected at all, while in some of them it was present in low concentrations of about µg l-1, or less.
The drinking water taken from the private wells in Trnje, was more pronouncedly contaminated with short-chain chlorinated hydrocarbons than was the water taken from private wells in the other two suburbs. The same goes for the water sampled from the public water-supply system providing drinking water to Pešćenica.
The mass concentrations of carbon tetrachloride, detected in all examined samples, were below the maximum limit value specified in the Croatian standard (CS) for drinking water, and the value recommended by the World Health Organization (WHO), which is 2 µg l-1. The same goes for the mass concentration of 1,1,2-trichloroethene, which was determined in all samples in low concentrations, falling below the CS-recommended value of 30 µg l-1 and the WHO-recommended value of 70 µg l-1 (provisional). The determined concentrations of 1,1,1-trichloroethane also fell below the CS-recommended value of 50 µg l-1 and the WHO-recommended value of 2000 µg l-1 (provisional). Only the mass concentrations of 1,1,2,2 tetrachloroethene, determined in the examined water samples from the wells in Trnje, exceeded the CS-recommended value of 10 µg l-1, but were still below the WHO-recommended value of 40 µg l-1, as measured in autumn.
The results of this analysis are in harmony with the previous results obtained for carbon tetrachloride. Contamination of the groundwater, caused by 1,1,1-trichloroethane, was evident in Trnje, although there had been no previous publications to point that out. 1,1,2 trichloroethene was present in the groundwater of the City of Zagreb, but in low concentrations. 1,1,2,2-tetrachloroethene was determined in all samples, which is in harmony with the previously obtained results.
The groundwater of the City of Zagreb is contaminated with short-chain chlorinated hydrocarbons, especially 1,1,2,2-tetrachloroethene and 1,1,1-trichloroethane. The highest level of contamination was found in the water taken from private wells in the suburb of Trnje, while the lowest was found to be that of private wells in Trešnjevka. A somewhat higher level of contamination with the targeted compounds was evident in the water samples taken from the public water-supply system providing drinking water to the suburb of Pešćenica. Therefore, the citizens of Pešćenica were exposed more to the toxic impact of the examined compounds, and they were the ones supplied with the water from the Sašnak spring. Households using water from private wells in Trnje are more exposed to the water pollutants in question than are those in the Pešćenica and Trešnjevka areas.
Ključne riječi
Volatile Short-chain Chlorinated Hydrocarbons; groundwater; contamination; private wells
Hrčak ID:
19427
URI
Datum izdavanja:
11.1.2008.
Posjeta: 2.778 *