黄河口盐地碱蓬湿地土壤-植物系统重金属污染评价

以黄河口盐地碱蓬湿地为例,评价了淹水和非淹水区湿地表层土壤As、Cd、Cu、Cr、Pb和Zn 6种重金属的污染程度及其在土壤-植物系统中的迁移、富集特征,分析了不同积水深度和土壤理化性质对研究区土壤重金属含量的影响.研究结果表明,与土壤或沉积物质量标准相比,黄河口盐地碱蓬湿地土壤受As和Cd污染最严重,而其它重金属污染较轻；非淹水土壤Cd、Cr和Zn含量高于淹水湿地,而As、Cu和Pb则较低；而且淹水土壤As含量随积水深度增加而呈下降趋势,但积水深度对其他重金属含量的影响不明显.相关性分析结果表明,按照受土壤关键影响因子的不同重金属(除As外)可以分为两类:第一类为Cd、Cr和Zn,这些重金属含量受土壤pH值和盐分影响较大,且相互间存在显著正相关关系,表明它们可能有相同的来源；第二类为Pb和Cu,它们受土壤pH值、盐分和有机质的影响,且Pb和Cu之间存在显著正相关关系.除Cr、Cu和Zn外,重金属在盐地碱蓬的根系内一般不发生显著富集,但绝大多数重金属都表现出地上部分的含量比根系更高的现象.

Assessment of heavy metal contamination in the soil-plant system of the Suaeda salsa wetland in the Yellow River Estuary

The contamination levels of heavy metals (i.e., As, Cd, Cr, Cu, Pb, and Zn) and their transport and accumulation in the soil-plant system were assessed for wetland surface soils of the Suaeda salsa wetland in the Yellow River Estuary, and the influences of water depth and soil physico-chemical properties on heavy metal concentrations were also investigated. Our results showed that both As and Cd contamination was more serious according to the guideline values of various soil and sediment quality standards, whereas the soil in this region was slightly contaminated by other heavy metals. The concentrations of Cd, Cr and Zn were higher in non-flooding wetland than those in flooding wetland, whereas the concentrations of As, Cu and Pb were lower. Moreover, As concentration increased with increasing stand water depth in the flooding wetland, while weak influences of stand water depth on other heavy metals were observed. The relationships between metal concentrations and soil properties were identified using correlation analysis. Significant positive correlations were observed among the concentrations of Cd, Cr and Zn, indicating these three metals might come from similar sources. Moreover, these three metals were significantly positively correlated with soil salinity but negatively correlated with soil pH values. This was probably because ions in sea water affected the concentrations of Cd, Cr, and Zn. On the other hand, Pb and Cu were differently from these three metals, but similarly to each other. The concentration of Cu was negatively correlated with soil salinity and positively pH, while Pb concentration was significantly correlated with that of organic matter. Generally, these metals were not accumulated in the roots of Suaeda salsa, but its accumulation ability was still greater compared to another wetland species (Spartina alterniflora). Cu and Zn had the highest enrichment factors compared to other metals. There was medium Cu and Zn accumulation in flooding wetland, and great Cu accumulation in non-flooding wetland. The translocation factor indicated that Suaeda salsa had the strongest translocation ability for As and Cu. In general, the aboveground parts of the plant had higher metal concentrations than underground parts. Flooding could influence metal accumulation in plant organs, and it greatly decreased the enrichment factor of Cu and the translocation factor of Cr, whereas greatly increased the translocation factor of As.