Computing Parametric Pollution, Geo-Accumulation and Ecological Risk Indices for Selected Heavy Metals of a Multiple use Site : A Case Study of Charsadda Road, Peshawar (P-0804) (MFN 5507)

Abstract

Charsadda Road is one of the busiest roads in Peshawar with a diverse surrounding environment involving residential, industrial, commercial and agricultural zones along with heavy traffic which contribute to heavy metal pollution on the road. For the assessment of heavy metal pollution level roadside dust and two common vegetation species namely Cyperus esculentus and Cynodon dactylon, were collected from ten sites along the entire road. The samples were analyzed for three heavy metals using AAS (atomic absorption spectrometry). The average concentration values for Cadmium (Cd), Chromium (Cr) and Lead (Pb) were 0.25544, 1.257375 and 5.0063 μg/ml respectively in case of Cyperus esculentus. The average concentration values for Cadmium, Chromium and Lead were 0.302, 0.706 and 6.8867 μg/ml respectively in case of Cynodon dactylon. The average concentration values for Cadmium, Chromium and Lead were 0.4494, 1.0237 and 47.918 μg/ml respectively in case of roadside dust. In all two sample types i.e. vegetation and roadside dust, Cd concentrations are found to be higher than the background values. Cr and Pb on the other hand were fairly within the background concentrations. The pollution level was estimated using different statistical models. Average values of pollution index (IPI) for Cr, Cd and Pb in case of Cyperus esculentus are 0.01579, 3.0772 and 0.2503 respectively while those in case of Cynodon dactylon are 0.0089, 4.0266 and 0.3849 respectively. In case of roadside dust, average pollution index values (IPI) for Cr, Cd and Pb are 0.014, 5.9919 and 2.3958 respectively. Average value of pollution load index (PLI) for Cyperus esculentus was found to be 0.476325 and for Cynodon dactylon, it was 0.5174 and for dust it was 0.52306. Average values for geo-accumulation index of roadside dust for Chromium, Cadmium and Lead were found to be -6.8336, 1.8324 and -0.8222 respectively. Ecological risk due to roadside dust was evaluated using potential ecological risk index (RI), the average value for which was 191.7655. Out of all the calculated indices for the metals under consideration, Cd was found to be of major concern than Cr or Pb which correspond to middle or low level of pollution. The pollution level is expected to increase due to rapid urbanization of the area. Some protective measures have therefore been proposed.