莲花山钨矿区土壤重金属污染与理化特征

Characterization of Heavy Metals Contamination and Physicochemical Properties of Soils in Lianhuashan Tungsten Mine Area of Guangdong Province

以莲花山钨矿区废弃地及周边农田土壤为研究对象,研究了矿区土壤理化特性、重金属含量、营养元素状况及土壤酶活性的空间分异特性,为该矿区环境污染治理和生态恢复提供科学依据。结果表明,矿区废弃地土壤电导率、总酸度和交换性酸度显著高于背景土壤,受矿区酸性废水的长期影响,矿区下游土壤出现了酸化和盐化,影响随离矿区距离有所减弱。矿区废弃地土壤Zn、Cu、Mn、Pb、Cd和As均高于背景值,其中主要污染元素为Cd和As,它们分别超过背景值的24、169倍,并导致矿区废弃地下游农田土壤Cd和As污染。采矿废弃地土壤有机质、全N及碱解N含量低于背景土壤。废弃地的总钾和总磷基本一致,但是钾和磷有效性显著降低。与土壤背景值相比,采矿废弃地、选矿废弃地及矿区农田土壤过氧化氢酶和磷酸酶显著下降,选矿废弃地土壤的尿酶和蔗糖酶显著降低。土壤尿酶活性可表征土壤退化,可有效地反映土壤酸化、高电导率及As和Cd污染。

The physical and chemical properties, heavy metal and nutrient contents, and enzyme activities in soils were investigated for understanding the heavy metal contamination and soil degradation at abandoned tungsten mine area. The results showed that total acidity, exchangeable acidity and electric conductivity in the mine wasteland were significantly higher than those in the background soil. Higher pH value and electric conductivity were observed in the downstream soils of the mining sites, which were attributed to the acid mine effluents. The metal concentrations of Zn, Cu, Mn, Pb, Cd and As in the soils from the abandoned mine area were higher than those from the background area. Meanwhile, the As and Cd concentrations in the wasteland were 169 and 24 times higher than the background value, respectively, resulting in As and Cd pollution in the downstream paddy soils of the mine area. The organic matter, total and alkali-hydrolyzable nitrogen were lower than those in the background soil. No significant difference for total K and total P between different soils was observed, however available P and available K in the wasteland soil significantly decreased. Compared to the background soil, the catalase and phosphatase activities significantly decreased in both the mine wasteland and the polluted paddy soil, but the urease and sucrase activities decreased significantly only in the wasteland impacted by ore processing. The urease activity significantly related with acidity, electric conductivity, and As and Cd pollution, it could be used as a helpful bio-indicator for evaluation of soil degradation.