Accumulation of Some Heavy Metals in Roadside Soil along the National Highway-8 in Rajasthan (India)

Environmental pollution by heavy metals from automobiles has attained much attention in the recent past. The present research was conducted to study Pb and Cd level concentrations in soil along a major highway with high traffic density. Soil samples along highway were collected from 10 sites on the National Highway -8 between Kishangarh Toll to Bagru Toll in Ajmer and analysed for two heavy metals (lead and cadmium) using flame atomic absorption spectrophotometer (AAS). Physicochemical factors, believed to affect the mobility of metals in the soil of the study area, were examined such as pH, TOM, electrical conductivity, organic carbon, etc. The general decrease in concentrations of these metals with distance from the highway indicates their relation to traffic. Higher accumulations of metals have been observed in soil samples near to the highway (0-5 m) than in soil samples from sites a little farther away (5-10 m, 10-15 m). This is attributed mainly to aerial deposition of the metal particulates from motor vehicles. The values of heavy metals were compared with the results found by other investigators in various countries worldwide.