Risk Assessment Based on TCLP Extrated Heavy Metals in Soil at Farmlands Near Molybdenum Mining Area

  Objective  Heavy metals and molybdenum (Mo) in the soil at farmlands around a Mo-mining area in Fujian were determined to assess the environmental pollution and health risk.

  Method  Soil samples at depth of 0-20 cm were collected for analysis at the farms close to a Mo-mine in August 2018.The total, as well as the TCLP (Toxicity Characteristic Leaching Procedure) extracted, Cd, Pb, Zn, Cr, Ni, Cu and Mo were determined for the assessment.

  Result  All of the Cd, Cu, Cr, Ni, Pb, Zn and Mo contents in the soil samples exceeded the provincial environmental limits. The total Cd, Zn and Cu contents in soil at 10 of the sampling lots exceeded the thresholds for agricultural land use, according to the Environmental Quality Standard for Soil. The Mo contents at all sites were higher than the safety limit. Data on the TCLP-extracted Cd, Pb and Mo indicated that these elements were of major risk concerns. The Nemerow comprehensive pollution index on soil showed that 60% of the sites were moderately polluted and that the farther away from the mine, the lower the degree of contamination of the land.

  Conclusion  Pollution by heavy metals in the soil was evident at the surveyed areas. Relatively, Cd, Pb and Mo posed a greater health risk than other heavy metals for the farmlands nearby the Mo-mine. The soil pollution tended to be more severe at the farms closer to the mine.