Geochemistry and risk assessment of potentially toxic elements in surface river sediments (Chirchik-Akhangaran basin, Uzbekistan).

Abstract

The geochemistry of river sediments depends on several factors, namely the nature of exposed lithologies, weathering, different grain-size and sorting due to hydraulic phenomena, and anthropogenic inputs. Potentially toxic elements (PTEs) in river sediments may result in potential health risks due to overexposure when riverfronts are used for recreational activities. In the present study, sediments were collected from 17 sites in the Chirchik-Akhangaran River basin in the Tashkent Province (Uzbekistan, Central Asia) during baseflow conditions. The concentration of PTEs was determined in the < 2 mm (bulk) and < 63 µm (fine) grain-size fractions. The assessment of contamination using environmental indices highlighted low to moderate contamination for Li, Be, Co, Ni, Sb, V, and Cr in Chirchik and Akhangaran sediments and from moderate to high contamination for Cu, Zn, Mo, Cd, Tl, Pb, and As in some of the Akhangaran sites. The potential ecological risk indices suggest that risk ranges from low to moderate in most stations from the Chirchik and Akhangaran River catchments; high risk is restricted to few Akhangaran sites. Risk assessment carried out for the Chirchik River, where waterfront recreational use is popular, indicates that the non-carcinogenic risk is acceptable for all contaminants and all pathways for an outdoor recreational setting. The cumulative Hazard Index (HI) resulted to be lower than the acceptance threshold (HI < 1) for both children and adults (0.795 and 9.27 × 10^-2, respectively). In the case of carcinogenic effects, the risk is unacceptable for As through the ingestion pathway. The calculated screening level for As is 2.86 mg/kg.