Environmental Risk Assessment of Heavy Metal Pollution in Watershed near At the Abandoned/Closed Metal Mine.

Heavy metals released from abandoned metal mines can be introduced into adjacent watershed after severe rainfall and cause serious environmental problems. Numerous studies have been reported for addressing adverse effect of heavy metals on ecological system but few studies were available for assessing ecological risk of heavy metal pollution in the environment. Therefore, aims of this research were i) to monitor heavy metal concentration in the environment including soil, surface water, sediment, and plants of the watershed ii) to calculate pollution index based on heavy metal concentration and varied environmental parameters iii) to predict spatial distribution of heavy metals with geological information system (GIS). Total of seven clusters were defined to measure heavy metal concentration in soil and 18 sampling sites were selected for surface water, sediment, and plants samples along with watershed near at the abandoned mine. The highest heavy metal concentration in soil was observed at cluster A where is the closest cluster to adit with 1,199.46 mg kg^-1 for As, 123.96 mg kg^-1 for Cu, and 2,373.08 mg kg^-1 for Pb. In case of Cd, the highest concentration, 13.09 mg kg^-1, was measured in cluster D. Calculated pollution index of heavy metals in each environmental compartment was ordered as sediment (1.86) > soil (0.92) > surface water (0.57). This result might indicate that introduced heavy metals in the environment have tendency to sorb solid phase rather than to dissolve in aqueous phase. In conclusion, risk assessment of heavy metals is necessary to minimize its adverse effect on ecology system and human health. Furthermore, calculating pollution index can be adapted for comprehensive understanding of hazardous pollutants in the environment.