Study On Distribution Characteristics Of Trace Metals In Typical Landscape Water Body And Its Effects On Algae Growth

Landscape water plays an important role in the construction of ecological environment in cities, howerer, the eutrophication is easily happened and eventually lose the ornamental value of the water bodies because of its low depth and flow rate.Under normal circumstances, eutrophication is mainly caused by the excessive content of nitrogen and phosphorus. Nevertheless, some researches have indicated that low concentrations of trace elements in water also are important nutrients for algae growth.And in the early stages of the eutrophication in which the algae density is below a certain level, the change of trace elements has an important influence on the growth of algae, and even becomes the main factor. Therefore, it is urgent to study the influence of trace elements on the growth of algae in the point of eutrophication. On the other hand,with the advancement of urbanization, the content of trace elements which is represented by the heavy metals is gradually increasing, and affects the health of the water environment. So it is necessary to study the distribution characteristics of trace elements in landscape water to provide the basis for revealing the characteristics that the influence of trace elements on the growth of algae based on the investigation.This paper was supported by “Urban water of nitrogen, phosphorus and trace elements on the quality of the water environmental impact study”. Feature element such as Fe, Mn, Zn, Cu, Mo and Ce were determined by the investigation on typical landscape water bodies in Xi’an. And then Hancheng lake, Nan lake, Xingqing lake and Guangyun lake were selected to monitor the above elements continuously and research the distribution characteristics and source of trace metals in water and sediments.Finally, trace metals such as Fe, Mn, Zn, Cu, Mo that strongly influence algae growthwere selected based on the above results. And then Microcystis Aeruginosa, usually appearing in eutrophication water, was determined to study to reveal the growth characteristics influenced by trace metals, and proposed schemes to control eutrophication. The main results are as follows:(1)The concentration of 11 trace metal of 11 landscape waters in Xi ’ an was measured,and then feature element that strongly influence algae growth such as Fe, Mn,Zn,Cu,Mo and Ce were determined to study based on the standard the concentration of trace metals is less than 1 mg/L, afterwards, Hancheng lake, Nan lake, Xingqing lake and Guangyun lake were selected to monitor the above elements continuously.(2)The concentration of Fe and Zn were higher than other elements in urban landscape waters, followed by Mn, Cu and Mo; particularly, the concentration of Ce was extremely less than other elements. The average concentration of Fe, Mn, Zn and Mo in Guangyun lake were highest and Cu concentration of Hancheng Lake was highest.(3)In Xi’an typical landscape water body, Fe, Mn mainly came from rock weathering and natural sedimentation, Zn and Cu mainly came from traffic exhaust, life sewage and garbage pile settlement, Mo mainly came from human activities and atmospheric precipitation. However, Fe, Mn, Zn, Cu in sediments of Xi’an typical landscape water body was mainly composed with the compounds of industrial pollution,traffic pollution and natural soures, Mo and Ce have similar geochemical behavior,mainly came from the composed of natural source and fire coal use.(4)Fe, Mn, Zn, Cu, Mo was selected in experimental and the Microcystis aeruginosa algae was the experimental algae. Algal density, total soluble sugars, the growth rate of algae were measured to evaluate the growth of algae. We carried out the impact of different elements concentration on algae growth experiments. The results showed that trace elements affect the growth of algae which showed that low concentration promote the growth of algae however the high concentration inhibite its growth, when the concentration range of Fe, Mn, Zn, Cu, Mo were 5 ~ 500, 1~ 70,1 ~100,1 ~ 10, 1 ~ 50 ug / L respectively, the growth of algae was the fastest.(5)By fitting the numerical relations between Fe, Mn, Zn, Cu, Mo mass concentration and the algae growth rate,the regression equation with the correlationcoefficient of 0.985, 0.923, 0.811, 0.897, 0.925, respectively, were determined,which can be used to analyze the coefficient between the concentration of trace metals and algae growth.