| Yeyahu wetland is the important wetlands in Beijing. This paper mainly studies the element As and Hg in water and sediment, content of surface soil, distribution, chemical composition and form of Yeyahu wetland area in order to explore the influence factors of sediment, elemental Hg accumulation of As in soil.The determination analysis result of the As and Hg elements content shows that:The average concentration of As and Hg is1.28ug/L and0.16ug/L in water, respectively. The values of the87.5%of samples are higher than the surface water standard in our country. The average concentration of As and Hg is10.07mg/kg and0.0887mg/kg in surface soil,94%of the As samples are higher than the soil background values of Beijing, while100%of the Hg samples. The average concentration of As and Hg is7.17mg/kg and0.034mg/kg in the surface sediment.53.5%of As and73.4%of Hg are higher than the sediment background value of Beijing. The content of As increased in a little range with the increase of the profile depth in the sediment, while the content of Hg is significantly lower.The determination analysis result of the chemical form of As and Hg elements shows that:As is existed in the form of residue and organic combination forms, accounts for about46%and27%of the total in the soil, respectively, while in the form of iron manganese oxide combining form and residual form, two of them account for70%of the total in the sediment. Hg is existed in soil and sediment organic combination form as the main form, the second is the residue. As is distributed in9cm-33cm in the profile sediment, residue content is significantly higher than the upper and the lower, elemental Hg proportion accounted for about40%of the total, and is added with the increase of depth.The result of the enrichment conditions of As and Hg in the surface sediments shows that: The enrichment factors of As in the samples are under1000, except the sample1, which is2700, while the samples are all under800for Hg. The enrichment factor of As exceeds Hg except the sample4,5and14. The correlation analysis of As, Hg in the soil and other heavy metals shows that:pH, soil organic carbon,REDOX potential and the As and Hg were not significant correlation. As is significantly related with Fe, Mn, Cu and V, however, Hg is not relevant with pH, other elements and organic carbon content. This conclusion suggests that:The contents of Fe and Mn are important to affect the accumulation of the distribution of As in the soil, and these factors are hard to effect the content of Hg. The correlation analysis of form of As, Hg and TOC, pH, amount of As and Hg shows that:pH is positively correlated with As carbonate form relations, while is negative correlated with the total of Hg, Hg organic combination form. TOC and As and As exchangeable form, the organic combination form, residue was significantly positive correlation, which illustrates pH, organic carbon in the form of Hg and As content made a certain degree of influence. And the negative correlation between exchangeable form of Hg and carbonate combination state of As shows that there is Influence between As and Hg.The assessment results of potential ecological risk of As and Hg in Yeyahu wetland is as follows:(1) The result by accumulate index method shows that:The sediments and soil were not be polluted by As and Hg. The Igeo index of samples are in a clean level except the sample S18, which is slightly polluted.(2) The result by potential ecological risk index shoes that:The pollution is slightly for As from the point of view of potential ecological risk index. The pollution is slightly for Hg for most samples except individual samples, and there are a strong, moderate, slight risk several risk levels for the potential ecological risk in the sediments. Most of As in soil is in moderate pollution and the potential ecological risk is low, most potential ecological risk of Hg is in a high level state, which indicates that the potential ecological risk of Hg is higher, therefore, some measures should be adopted to control and manage the pollution of Hg.(3)The result by ecological risk coding method shows that:The potential ecological risk of As and Hg are both at a lower level in soil, and As in surface sediment samples is in a medium degree of potential risks, while most of Hg is not at risk, except some samples, which are at low level. |
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