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Analysis of snow-cap pollution for air quality assessment in the vicinity of an oil refinery

Snow-cap can be used as a simple and effective indicator of industrial air pollution. In this study snow-cap samples were collected from 11 sites located in the vicinity of an oil refinery in Mažeikiai, a region in the north-west of Lithuania, in the winter of 2011. Analysis of snowmelt water and snow-dust was used to determine anthropogenic pollutants such as: sulphates and chlorides, nitrites, nitrates, ammonium nitrogen, total carbon, total nitrogen; heavy metals: lead (Pb), copper (Cu), chromium (Cr), cadmium (Cd). Concentrations of heavy metals in snow-dust were detected thousands of times higher than those in the snowmelt water. In this study, analysis of heavy metal concentration was conducted considering different distances and the wind direction within the impact zone of the oil refinery. The sequence of heavy metals according to their mean concentrations in the snow-dust samples was the following: Pb>Cr>Cu>Cd. Heavy metals highly correlated among each other. The load of snow-dust was evaluated to determine the pollution level in the study area. The highest daily load of snow-dust was 45.81±12.35 mg/m2 in the north-western direction from the oil refinery. According to classification of the daily load of snow-dust a lower than medium-risk level of pollution was determined in the vicinity of the oil refinery.