水源地周边土壤重金属分布特征及潜在风险-以深圳市为例

以深圳市水源地周边三种不同类型土壤(赤红壤?红壤?水稻田土)为研究对象,选择具有较高环境含量且毒性较强的Zn?Pb?As为目标,探究其在三种土壤剖面淋溶层?淀积层和母质层(A、B和C层)中的分布特征及赋存形态,同时分析重金属含量?赋存形态与土壤理化性质的相关性,并利用潜在生态危害指数法和潜在迁移指数法从重金属全量和赋存形态两个角度对土壤重金属的生态风险水平进行评估.结果表明:土壤重金属Zn?Pb?As在三类土壤各层中含量较高,但均低于当地土壤环境质量背景值,重金属含量受当地土壤成岩母质影响较大.形态分析表明三种重金属在三类土壤中均以残渣态为主,但红壤中可还原态Pb含量较高,在低pH时易转化为弱酸可溶态,而后释放并迁移.相关性分析表明Zn?Pb的全量与有机质含量呈极显著正相关,可还原态Zn与pH呈显著正相关,Pb和As的弱酸可溶态与可还原态显著正相关,黏粒和粉粒含量对Pb和As的形态分布造成不同程度的影响.三种重金属潜在生态危害级别均为轻微,对水源地安全潜在生态风险影响较小;重金属迁移能力大小在不同土类中依次为红壤土>赤红壤>水稻田土,元素本身迁移能力强弱依次为Zn>As>Pb;赤红壤和水稻田土A层Zn迁移能力最强,B层As最强,C层Zn?Pb?As均较弱;红壤中A层迁移能力Zn最强,B层Zn?Pb?As均较强,C层Zn?Pb?As均较弱.

Distribution characteristics and potential risk of heavy metals in soil around water source:A case study of Shenzhen city

Zn?Pb?As in three different types of soils (lato-red soil, red soil, and paddy soil) around the water sources in Shenzhen were selected as the research object. Their content and toxicity in the environment were high. And this study aims were exploring their distribution characteristics and existing species in the leaching layer, sedimentary layer and parent material layer (layers A, B and C) in these three soil profiles, analyzing the correlation between the content of heavy metals, the existing species and the physical and chemical properties of the soil. And based on them, we used the potential ecological hazard index and the potential migration index to evaluate the ecological risk of the heavy metals. The results showed:Zn, Pb, As had a higher content in each layer of the three types of soil, but they were all fewer than the background content of the local soil environmental quality, and the content of heavy metals was greatly affected by the local soil diagenetic parent material. The heavy metals were mainly in the residual state in the three types of soils. Relatively, the reducible Pb content in red soil was higher, and it was easy to transform into a weak acid soluable state at low pH, so it was easily release from soil and migrate to the water. Correlation analysis showed that the total amount of Zn and Pb was extremely significantly positively correlated with the organic matter content. The reducible state of Zn was significantly positively correlated with pH, and the weak acid soluable state of Pb and As was significantly positively correlated with the reducible state. The content of clay and powder particles affected the morphological distribution of lead and arsenic. The potential ecological hazards of the three heavy metals were all minor, which had little impact on the potential ecological risks of water source safety. The migration capacity of heavy metals in different soil types was red loam> latosolic red soil> paddy soil. The migration ability of the element in the soil was Zn>As>Pb; In latosolic red soil and paddy soil, the migration ability of Zn in layer A was the strongest, in layer B As was the strongest, and in layer C Zn, Pb, As were all weak. In red soil, Zn in layer A had the strongest migration ability, in layer B Zn, Pb, As were all strong, and Zn, Pb, As were all weak in layer C.