广东大宝山地区重金属污染水田土壤的Cu Pb Zn Cd全量与DTPA浸提态含量的相互关系研究

Relationships Between Total and DTPA Extractable Contents of Cu, Pb, Zn, Cd in Trace Metal-Contaminated Paddy Soils of Dabaoshan, Guangdong

通过现场采样及室内测试,分析了广东大宝山地区酸性金属矿长期污染水稻田的土壤特性,研究了重金属Cu、Pb、Zn、Cd的全量与DTPA浸提态含量的相互关系。结果表明,除Pb外,Cu、Zn和Cd的全量不同程度超标,而4种重金属的DTPA浸提态含量均较高,Pb和Cu的DTPA浸提率高于Zn和Cd。金属全量及其DTPA浸提量之间极显著相关。土壤酸性和有机质对金属Pb、Zn、Cd的DTPA浸出率表现出显著的促进作用,而与Cu的浸出率相关不显著。DTPA态金属可以作为测定该类水稻土壤金属有效态含量的简便指标。金属的全量、种类,土壤pH、有机质等属性,以及农业耕作等因素影响金属的DTPA态含量及有效性。

samples were collected from long- term trace metal- contaminated rice field in the north of Guangdong, China, resulted from irrigation with acid mine drainage. Soil properties, total contents and DTPA extractable fractions of Cu, Pb, Zn, Cd were analyzed to characterize availability of trace metals and their effect factors under acid soil condition. The results showed that contamination level exceeded national and EU soil environmental standards, based on total Cu, Zn and Cd, except for total Pb. DTPA contents of all four metals were considerably high, and percentages of DTPA Pb and Cu in total contents were higher than those of DTPA Zn and Cd. There were significant correlations between total and DTPA contents of four trace metals. It indicated that DTPA extractable metals might be considered as simple indictors of available contents in the studied paddy soils. Moreover, close associations among soil pH and trace metals showed that such acid contaminants originated from same pollution sources and long- term irrigation of acid mine drainage was one of causes leading to soil acidification. In addition, soil acidity, total nitrogen and organic carbon presented significant and positive correlations with percentage of DTPA extractable Pb, Zn, Cd in their total contents. While pH and organic carbon were not significantly correlated, and total nitrogen was negatively associated with percentage of DTPA Cu. It may be attributed to solubilization of acid and week sorption of organic matter for Pb, Zn, Cd, and specific fixation of organic acid for Cu. It may be suggested that DTPA contents and availability of metals depend on combined effects of total contents and types of metals, soil pH and organic matter, and agricultural managements in the studied paddy soil.