Surface dispersal, emission source and human health risk assessment of heavy metal(loid)s in an active gas field, Southern Iran

Abstract

The presence of heavy metal(loid)s in soils from anthropogenic sources such as activities related to fossil fuel processing area could pose serious threat to the ecosystem and human health. However, risk factors depend on the source, distribution and human interaction with these contaminants and therefore case specific study is needed. In this study, using a geological information system (GIS) and 63 surface soil samples, we fully assessed 190 km2 area of a developing gas region in southern Iran. Mean concentration of manganese (Mn), zinc (Zn), copper (Cu), lead (Pb), total chromium (Cr), cobalt (Co), arsenic (As) and Cadmium (Cd) was 341.24, 129.40, 32.90, 26.85, 16.56, 7.52, 0.67 and 0.63 mg kg− 1, respectively, while As, Pb, Zn and Cd surpassed the local background level. Moreover, soil pollution was also assessed by the contamination factor (CF), geoaccumulation index (Igeo) and ecological risk factor (Er). Accordingly, these soils were classified as moderate to heavily polluted with As and Cd and un-polluted to slightly polluted by Cu, Zn, Pb, Mn, Cr and Co. The GIS and soil collection point tracing showed that the natural gas processing and residential activities were both significant pollution sources where ingestion was the main contributor to heavy metal(loid)s uptake. Overall, the hazardous index for noncarcinogenic health impact was < 1 indicating no risk; however, children were at greater risk than the adult. Total carcinogenic risk (TCR) index from As exceeded the maximum tolerable level (1.0E-04) for children and adults. Chromium Co, Cd and Pb exposure were within the acceptable limit in the adult group (TCR < 1.0E-06), but the Pb and Cr health-hazardous indices were higher than guideline value indicating the potential of cancer risk in children. Therefore, remedial actions are required to eliminate or reduce the toxicity of As, Cr and Pb attributed to the impacted soil.