[Characteristics and influencing factors of microbial function in soils around a typical mining smelter]. / å ¸åž‹çŸ¿å†¶åŒºå‘¨è¾¹åœŸå£¤å¾®ç”Ÿç‰©åŠŸèƒ½ç‰¹å¾åŠå½±å“å› ç´ .

Soil microorganisms were sensitive to heavy metal pollution, whose ecological effect on soil microbial community was impacted by the interaction of contaminated stresses and environmental factors. To explore the dominant factors governing those effects in heavy metal contaminated soil, field investigation was conducted for soil from different land use types in an area surrounding a typical mining smelter in Hunan Province. Soil microbial function parameters including microbial biomass carbon (MBC), basal respiration (BR), substrate-induced respiration (SIR) and nitrification potential (PNR) were used as measure endpoints for ecological effect to reflect soil carbon and nitrogen cycling. The results showed that the effect of land use on MBC, BR, and SIR was insignificant. The dominant impacting factors on microbial functions included CaCl2 extracted Pb (CaCl2-Pb) and soil organic matter (SOM) content. Results of multiple regression analysis showed that soil CaCl2-Pb and SOM together explained 39.8%-58.3% of the total variations of BR, SIR and PNR in soil, when CaCl2-Pb and SOM ranged in 0.004-13.14 mg·kg-1 and 0.24%-4.34%, respectively. Significantly quantitative exposure-effect equations were developed between the responses of soil BR, SIR and PNR and soil CaCl2-Pb and SOM when soil samples with medium contents (namely, SOM 1.70%～2.36% and CaCl2-Pb 0.004-12.98 mg·kg-1), which meant they could be used to quantitatively assess the ecological effect of heavy metals on microbial community function as measure endpoints.

[Security Risk and Influencing Factors of Agro-Products in Farmland Soil Around a Typical Mining Smelter].

The security risks of heavy metal pollution in agro-products are becoming increasingly serious. This paper investigated the heavy metal contamination of farmland soils and agro-products around a typical mining smelter in Hunan province, and explored the influencing factors based on principal component and correlation analyses. The results showed that the soils were significantly contaminated by heavy metals, with a mean concentrations of Cd, Cu, Pb, and Zn of 9.12, 358, 303, and 185 mg·kg-1, respectively, pH range from 4.67 to 7.22. All the sites included were under strict control. With regards to the agro-products, the concentration of heavy metal elements were different, and the order of heavy metal concentrations was Zn>Cu>Pb>Cd, with an order of biological enrichment factor(BCF) of Cd>Zn>Cu>Pb. Over-the-standard elements in agro-products included Pb and Cd at 78% and 41%, respectively, which indicated a higher security risk from these products. The accumulation of the same heavy metals in leaf vegetables were generally higher than sweet potatoes and solanaceous vegetables. The heavy metal concentrations in soils corresponded to the first principal component(P<0.01), with the variance reaching 88.0%, which dominated the sources of Cd, Cu, Pb, and Zn in agro-products. The enrichment characteristics were mainly affected by the type of crops, and was also regulated by the soil pH, cation exchange capacity, and soil organic matter(the correlation coefficients of r were -0.407- -0.641, P<0.05). In conclusion, there was a combined heavy metal pollution and high risk in soils and agro-products. Therefore, the planting of crops in the study area should be avoided, and soil remediation measures should be implemented to reduce security risks.