Mobility and ecological risk assessment of heavy metals in soils impacted by hazardous smelting waste

Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China

E-mail: banerjeeenvsc@gmail.com

Manuscript received online 12 October 2020, revised and accepted 29 November 2020

The present study was carried out in a metals smelting area to identify the phase associations of metals in solid matrix with the application of mBCR procedure of sequential extraction and to assess the elemental mobility, probable bioavailability and their ecological risks in relation to soil contamination levels. pH (5.73–6.85) of the studied soil is acidic to neutral in nature and showed some effects on the distribution pattern related to extent of contamination. The study revealed that the mean Pb (790±112 mg/kg), Cd (21.02±3.26 mg/kg) and As (60.33±6.30 mg/kg) exhibited the high concentration due to the severe impact of smelting activities, which is with high impact than the level III standard of soil quality prescribed in Mainland China (GB15618-1995). The overall percentage of metal content in different fractions is in the sequence of Residual > Oxidixable > Reducible > Exchangeable fraction. Though, an appreciable amount of Pb is fastened in the reducible fraction, Cu and As are tied in the oxidizable fraction and lastly, Cd is in exchangeable fraction. Under changing environmental conditions these non-residual metals may be released back to the surrounding soil environment by various processes of remobilization. The percentage of metal in the exchangeable and carbonate fractions (% F1 for BCR) can be measured by Risk assessment code (RAC), which is used to assess the environmental risks and the potential risk levels of heavy metals like As, Pb, Cd and Cu ranged 4.09–11.52, 10.05–15.26, 29.54–42.08 and 8.50–16.54 and respectively. According to soil pollution indices and risk assessment criteria the metals had the following order: Cd > Pb > Cu > As. The results indicate a high environmental mobility for heavy metals in the studied region which represents high degree of potential risk in ecology.