| The Safety of water source area is an important guarantee to survival and physical healthy, which should be taken care of seriously and protected strictly. Guanting Reservoir in northwestern Beijing as an alternate water source of the capital has an important ecological significance; its upstream area consists of Guishui watershed and Yeyahu wetlands. This paper researched on watershed and wetlands, water samples, sediment samples from watershed and soil samples from wetland were collected, within analysis and detection of common heavy metals Fe, Mn, Ti, Zn, Cu, Pb, Ni, V, Cr, and Cd, in their total content and speciation. Comparison between the occurrence status and variation of heavy metals in the two environments, the findings concludes:(1) The total amount of water to10heavy metal enrichment is not uniform, with the highest enrichment of Cr, the lowest enrichment of Fe; Mn evolved in the adsorption-release patterns of other heavy metals. Total wetland soil heavy metals are to meet national standards Class Ⅰ (i.e. national natural reserve requirements). Correlation of the metal elements:Fe, Cr, Cu, Ni and V having a high correlation (>0.8); the chemical properties of the Ti stay stable therefore its distribution changes little; Zn, Pb and Cd lack of correlation to other elements. According to the results of cluster analysis,10elements of soil and sediment can be divided into six groups:{Ni, Cr, Cu,Fe, and V};{Pb};{Zn};{Cd};{Mn};{Ti}.(2) The process changing from soil to sediments found that Fe-Mn oxide adsorption capacity with Cr, Cu, Ni and V dropped in sediments, where Mn is due to the strong reduction of the deposition phase to promote the reduction of Mn4+to Mn2+with stronger activity and solubility, enhancing the release to water while reducing the amount deposited.(3) Heavy metals speciation suggests:In addition to the elements Mn, the remaining8elements main in the residue form, staying more stable. Comparison to other elements, Ni and Cr’s speciation distributed more evenly. And from soil to sediments certain metals were increased chemically active and effective form. For example, oxidizable Cu increased significantly and accompanied by a little of reducible Cu; reducible V increased double by the ratio in soil; speciation of Zn differs in the distribution, according to the trend of effective form, the sediment content increases2to3times compare to the soil; reducible Cd rose to half of the effective form within little in the soil; as an element with the highest proportion of effective state (>50%), reducible and acid-extractable Mn has higher proportion level, mainly related to the water environment to promote the release of the underlying surface Mn transformed and improved their activity.(4) The source of heavy metals in water source area showed:At present, most water source region has not been affected by human interference, its sediments and soils were as a result of earth soil-formation under natural conditions. Distribution and occurrence state of heavy metals close to local environmental background values can be used as a reference. But total Cr exceeding the background value and Mn’s higher proportion of a variety of effective forms were worthy of further discussion and more focus on. The development and utilization of this area in the future will be deeper in size; heavy metals will inevitably increase in the total amount of pollution hazards and effective forms, which require the relevant departments to prepare land use design and prevention of pollution, and to reinforce the monitoring of fragile ecologically areas. |
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