Quantifying the effect of traffic on lead accumulation in soil: a case study in Iran

Road transport is a ubiquitous source of lead contamination in the soil near highways with direct and indirect impacts on human health. Accumulation of traffic-induced lead in the soils depends on gasoline lead content, traffic volume, as well as meteorological conditions. To evaluate the effect of traffic on soil lead concentration, ۱۱۳ samples from the topsoil (۰-۱۵ cm) were collected in a regularly spaced grid (۷۰ x ۷۰ m) in the vicinity of a busy highway (Tehran-Karaj) ;the west of Tehran. Total lead (Pb) concentration in soil samples was extracted by ۴ M HNO۳. Three different kriging techniques (ordinary, universal and indicator kriging) were applied to investigate the spatial distribution of Pb. According to the measured values, the average concentration of Pb (۴۸ mg kg -۱) was very close to the upper limit of the Swiss guide value of ۵۰ mg kg-۱ with the maximum value (۷۵ mg kg-۱) exceeding this limit. The result also showed an accumulation of ۵ to ۲۵ mg kg-۱ Pb in the soil based on the distance from the highway. The average concentration of Pb decreased exponentially with distance from the highway up to ۲۰۰ m becoming relatively constant thereafter. The trend of spatial continuity of Pb concentration was in agreement with major wind direction. Comparing different kriging techniques indicated that UK was superior due to smaller error of estimation. The probability map of Pd concentration exceeding the Swiss guide value clearly shows the traffic to be the main cause of soil Pb contamination.   REFERENCES  Al –Chalabi, A. and Hawker, D. (۲۰۰۰) Distribution of vehicular lead in roadside soils of major roads of Brisbane, Australia. Water, Air, and Soil Pollut. ۱۱۸, ۲۹۹-۳۱۰. Amini, M., Afyuni, M., Khademi, H., Abbaspour, K.C. and Schulin, R. (۲۰۰۵) Mapping risk of cadmium and lead contamination to human health in soils of Central Iran. Sci. Total Environ. ۳۴۷, ۶۴-۷۷. 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کلیدواژه ها:

Lead accumulation ، Traffic ، Universal kriging ، Highway pollution ، Iran