矿冶区周边水稻对不同来源重金属污染的指示作用

有色金属开采与冶炼可对周边环境造成严重的重金属污染,查明重金属污染来源对于矿冶周边重金属污染管理与控制具有重要意义.为探索利用矿冶周边水稻对As、Cd、Pb、Zn和Cu的富集与水稻体内元素的含量平衡特征指示重金属污染来源的可行性,选择了我国著名的水口山Pb-Zn矿山开采与冶炼周边区,根据重金属污染排放和迁移扩散特征,结合当地气象和地貌条件,确定了3个典型采样区,其中两个采样区分别邻近冶炼厂和尾砂库,另一处为位于两者之间的过渡区.采用蛇形采样法在稻田内采集33个成熟水稻及土壤样品,分析水稻不同部位(包括根、茎叶、籽粒)及土壤中As、Cd、Pb、Zn、Cu5种重金属和其他16种元素的含量.结果表明,3个采样区之间土壤中的As、Cd、Pb、Zn和Cu含量均存在显著性差异;各采样区水稻中除根际和籽粒中Cd含量外,各部位重金属含量也均有显著差异.靠近冶炼厂的水稻茎叶中As、Pb含量高于离冶炼厂较远的采样区水稻茎叶.尽管As、Pb在靠近尾砂库采样区土壤中含量最高,但在该区水稻茎叶中的含量却最低;在除As、Cd、Pb、Zn、Cu5种重金属以外的其他16种元素中,水稻根部仅有5种元素含量在各采样区之间存在差异,指示相同的土地利用类型及土壤母质条件;而在茎叶和籽粒中则分别有多达11和10种元素含量出现采样区差异,指示重金属污染来源影响水稻茎叶及籽粒中元素的含量平衡.多元统计分析结果显示,3个采样区水稻茎叶中元素含量平衡存在显著的分异,显示出明显的采样区属性.结合采样区域空间位置、污染物来源、水稻对重金属的富集与转运特征分析,3个采样区重金属主要污染特征可分别确定为水-气混合来源型、大气来源型和尾砂来源型.论文结果证明利用水稻茎叶指示矿冶周边重金属污染来源是可行的.

Using Rice as Bio-Indicator for Heavy Metal Contamination, a Study in the Pb-Zn Mining and Smelting Area at Shuikoushan, Hunan Province, China

Nonferrous metal mining and smelting activities have caused serious heavy metal contamination.It is highly desired to identify the sources of heavy metal contamination in order to control the heavy metal contamination effectively.The objective of this study was to explore the feasibility of using rice as bio-indicator for tracing heavy metal contamination sources in the area with intensive mining and smelting activities at Shuikoushan,Hunan province,China.According to the emission and transportation characteristics of heavy metals,as well as the local weather and topography conditions,three typical sampling sites were selected.Two of them were nearby the smelting and the tailing dams,respectively,while the other one was located at the transition zone between the former two.Thirty-three mature rice samples and their corresponding paddy soil samples were collected using the snaking sampling method.Arsenic,Pb,Cd,Zn,Cu and other 16 mineral elements were measured.The concentration of As,Pb,Cd,Zn and Cu in the soils and rice(rice roots,rice shoots,rice grain)were significant different between the three sampling sites,except Cd in the rice roots and rice grain.Multivariate statistical analysis showed a clear difference in elements correlation in the rice shoots between the three sampling sites,indicating heavy metal accumulation in rice had a significant effect on the uptake of mineral elements.The lower levels of As,Pb,Zn,Cu in soils,whereas higher concentrations and translocation factor values of these heavy metal elements in rice shoots and grains suggested that rice shoots could probably absorb extra heavy metals from atmospheric deposition.Based on the integrated analysis on spatial location,contamination sources as well as the accumulation and translocation factor values of the rice,the three sampling sites could be characterized as contaminated from wastewater-gas combined,atmospheric and tailing sources.The correlation of elements characterized in rice shoots using CA and PCA methods could be used to differentiate heavy metal contamination around the Pb-Zn mining and smelting areas at Shuikoushan.The results demonstrated rice growing in mining and smelting areas can be used to trace heavy metal contamination.