Heavy metal concentration in urban snow as indicator of air pollution

By air pollution we mean the presence of certain substances in the atmosphere that are different from the normal composition of air and depending on their concentration and time of action lead to human health disorders, affect the flora and fauna, or alter the human living environment. An amount of pollutants discharged into the atmosphere is subjected to a dispersion process that lowers the concentration of pollutants as a function of distance from the source. Concentrations of heavy metals in the snow can be an indicator of air pollution in urban areas, also giving us indications on the origin of pollution. We compared the concentrations of heavy metals in the snow with the background levels to find out if they could be used as an effective indicator of urban air pollution. Samplings were carried out at road intersections in the center and peripheral areas of Bucharest to determine the influence of road traffic and industrial areas on the air pollution levels. Concentrations of copper, lead and cadmium were determined during sessions of sampling in various locations with low or high traffic density and at different distances from sources of industrial pollution. The concentrations of heavy metals in the snow in peripheral areas were clearly higher as compared with the concentrations in the inner city, as they were influenced by local pollution due to the industrial areas nearby the city, as well as due to the influence of wind on the dispersion of pollutants. The concentrations of copper were generally higher at road intersections with high traffic density as compared with sites of low traffic. This could be due to different driving style, especially braking, as the cars brakes are a major source of pollution with copper. In contrast, the cadmium and lead concentrations remained almost constant regardless of traffic intensity. For cadmium there were found relatively high concentrations even at the road intersections of low traffic. This indicates that, beside the traffic, there may be other important sources of pollution with cadmium. Thus we can conclude that the concentrations of heavy metals in the snow are a reliable guide for the degree of air pollution and can be used as a simple and effective indicator of urban air pollution.