Environmental impact of vehicular emissions at Guwahati a case study with respect to the impact on roadside soil

Abstract

Title: ENVIRONMENTAL IMPACT OF VEHICULAR EMISSIONS AT GUWAHATI: A CASE STUDY WITH RESPECT TO THE IMPACT ON ROADSIDE SOIL Vehicle emission is a major contributor to air pollution. Vehicles release the pollutants at ground level and contaminate the gross environment. The roadside soil and the shrubs near the roads are very good receptors of the atmospheric pollutants. Some of the pollutants get deposited directly on the roadside soil and others come to soil from the atmosphere through dry and wet precipitation processes. The roadside soil in the urban areas having a high density of vehicles on the roads has therefore a very large thrust of pollutants. Vehicular emission consists of suspended particulate matter, carbon dioxide, carbon monoxide, hydrocarbons and oxides of nitrogen and sulphur. The particulate matter may contain unburnt hydrocarbons including polycyclic aromatic hydrocarbons and trace metals like Pb, Cd, Zn, Fe, Mn, Cu, Cr, etc. A diesel engine emits much more SPM whereas a gasoline engine emits toxic Pb, if leaded gasoline is used. The leaded gasoline contains 0.27 to 0.44 g Pb per liter from the added TEL (Tetraethyl lead). A car, using this fuel, gives off about 2.5 kg of Pb per year through exhaust emission, which results in a build-up of Pb concentration in road dust of upto 20 g/kg in urban areas. The highway soil is thus contaminated with Pb, Zn and Mn. The roadside soil has a large input of contaminants from vehicle-associated components, exhaust emission, transmission, lubricant losses, tyre wear, corrosion products, fuel loss, and road spillage. These components constitute nearly 70% of the contaminant input to roadside soil, the rest of the input being from surface binders used in road construction, dust fall and precipitation, road surface erosion, animal waste and vegetable debris, etc. Some of the input is lost through processes like road maintenance practices, road washings, and atmospheric loss due to wind, evaporation, splash and spray. While various reports are found relating the...