Land Use Based Distribution Pattern, Fractionation forms and Health Risk Assessment of Heavy Metals in Mining-affected Soils of Western Ghat of Goa, India

Abstract

Goa is a biodiversity hotspot and a major iron ore producer state in India. The study investigated heavy metal (HM) distribution pattern, fractionation forms under different land use types near an iron mining including health risks associated with different exposure pathways. Georeferenced 38 soil surface samples, 8 soil profile samples and 6 plant samples were collected from three land use types- agriculture cropland, fallow land and natural vegetation. Collected samples were analyzed for HM contamination in inductively coupled plasma atomic emission spectrophotometer (ICPAES). The mean total HM concentration in surface soil exceeded the background value. Weak acid soluble fraction % of metals posed no to medium risk values. Fallow land had higher metal content in surface soil. Principal component (PC) analysis showed Pb, Cd and Cr metals were more associated with mining activity. Vertical distribution pattern of HM accumulation in soil profiles showed a drastic reduction in HM concentration below plough layer in fallow land indicating anthropogenic sources of origin. Hazard index (HI) in the descending order were Cd> Cr >Pb. Non-carcinogenic HI value were considerably higher than safe level. Higher organic carbon (OC) and clay content in soil had a tendency to accumulate ample HM in unavailable form due to chelation effect. Soils had higher pool of unavailable residual HM as compared to available. Overall the land uses are in medium risk category and site specific management is requisite of the time to maintain the balance of this fragile ecosystem with anthropogenic activities in long run.