WU Jinnan, LONG Jian, LIU Lingfei, WU Qiusheng, HUANG Bocong, ZHANG Jumei
(Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China)

Abstract: Soils from three regions, Smelting Zone(A), Production Zone(B), and Reservation Zone(C), surrounding the typical lead-zinc mineralization area of the Zhahai Town, Huize County, Yunnan Province, were selected as research objects, and physicochemical properties of soil including pH, total carbon(TC), total nitrogen(TN), total phosphorus(TP) and contents of 5 heavy metals (Hg, Cd, Pb, Zn, Cu) in forest lands (LD) and cultivated lands (GD) were determined and investigated. The Canonical Correspondence Analysis (CCA) was used to explore relationships between soil physicochemical properties and heavy metal contents in soils of different land use patterns. An improved gray clustering evaluation method based on the entropy value and biological toxicity of heavy metals was performed to assess the pollution degree of heavy metals in soils of the study area. The results showed that, the heavy metal concentrations in all zones (A, B and C) exceeded the soil background value of Yunnan, and the heavy metal contents in different regions showed an order of A>B>C, the average contents of Hg, Cd, Pb, Zn and Cu in all soil samples were 7.24, 1.53, 1794, 2892 and 210 mg/kg, respectively. Generally, the contents of heavy metals in LD were higher than those in GD. Additionally, most soils in the study area were slightly acidic except ones in Zone A which were slightly alkaline. TC, TN and C/N in soils of LD were higher than those of GD, but TP content was significantly lower in LD than in GD (P<0.05). The CCA analysis showed that soil pH values of LD and GD had a negative correlation with contents of Cd and Cu, and had a positive correlation with contents of Zn and Pb, and soil pH showed the greatest effect on the difference of heavy metal contents. TC, TP and contents of Cd, Cu exhibited opposite correlations, positive in LD soils but negative in GD soils. The improved grey clustering evaluation showed that the degree of heavy metal contamination in LD was much greater than that in GD. The soils in Zone A had the most serious pollution level, followed by soils in Zone B and then soils in Zone C, which were contaminated slightly. Compared to conventional methods, the improved gray clustering evaluation method established in this study showed advantages in both accuracy and sensitivity.

Keywords: lead-zinc mineralization area; different types of land use; physicochemical properties; Heavy metals; improved gray clustering evaluation method

EARTH AND ENVIRONMENT Vol.46, No.6, Tot No.326, 2018, Page 561-570