Environmental Pollution of Potentially Toxic Elements (PTEs) and its Human Health Risk Assessment in Delhi Urban Environs, India

Environmental pollution of potentially toxic elements (PTEs) in urban wetlands is a serious concern due to their toxic, persisting nature and potential to bioaccumulate in aquatic food chain. A total of 34 samples (23 surface water, 8 surface sediment and 3 sediment cores) were analyzed for PTE concentrations in Okhla Bird Sanctuary. The surface waters are alkaline with pH ranging from 7.2 to 8.5, electrical conductivity ranging from 454 to 1557 mu S cm(-1). Hydrogeochemically, these are Na+-SO(4)(2- )type in summer and Ca2+-Mg2+- SO42- type in winter season as per Piper classification. These show low compliance with recommended quality guidelines for Pb in winter (33%), and no compliance for Cd and Pb in summer season. As per heavy metal pollution index (HPI), high pollution in winter and critical pollution in summer season is observed. A sharp seasonal decline in the water quality indicates concentration of pollution load in summer. The surface sediments of Okhla Bird Sanctuary show severe PTE pollution as per nemerow pollution index (NPI). As per geoaccumulation index (Igeo), sediments are moderately to strongly contaminated for Pb. As per enrichment factor (EF), the sediments show moderately severe enrichment for Pb. On an average, the sediments show low-medium toxicity as per mean ERM quotient (MERM-Q) and moderate ecological risk as per potential ecological risk index (RI). As per hazard index (HI), in winter season, waters from the riverine and middle part show toxicity, whereas in summer, all the waters show toxicity for adults and children. Similarly, the surface sediments also show non-carcinogenic toxicity for children.