Atmospheric-borne Pb, Zn, and Cd from a Zinc Smelter in Southwestern China and Effect on Soil Quality.

  Dust emission from smelters is regarded as one major contributor to heavy metal contamination in soils and could severely influence soil quality. In this study, downwind surface soils within 1.5 km of a zinc smelter in Maguzhen, Guizhou, China, active ca. 10 y but ceased in 2000, were investigated. Reference soils, at a downwind distance of 10 km. from the smelter were included. Soils within 1.5 km of the zinc smelter accumulated high levels of Zn (508 mg kg^-1), Pb (95.6mg kg^-1), and Cd (5.98mg kg^-1) with lower ratios of Zn/Cd (59.1-115) and Pb/Cd (12.4-23.4). Composite pollution indices (CPIs) of surface soils (2.52-15.2) were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. Saturation degree of metals (SDM) in soils within 1.5 km of the smelter (averaging 1.25) was six times higher than reference soils (0.209). A smaller soil microbial biomass was found in metal accumulated soils (85.1-438µgC g^-1) than in reference soils (497 µgC g^-1), and a negative correlation (P < 0.01) of soil microbial biomass carbon to organic carbon ratio (C_mic/C_org) with SDM was observed. Microbial consumption of carbon sources in contaminated soils was quicker than in reference soils, and a shift in substrate utilization pattern was apparent and was negatively correlated with SDM (R= -0.773, P < 0.01). Apparently, dust-deposited Pb, Zn, and Cd in soils from zinc smelting are readily mobilized, and affect soil quality, particularly microbial biomass.

 Key Words:  Zinc smelter; Saturation degree of metal; Sequential extraction; Microbial biomass; Soil quality.