| With the urbanization process in China, shortage and pollution of water resource within cities are turning worse. Urban landscape water quality deteriorates, especially the eutrophication phenomenon caused by the outbreak of algae, making the living environmental quality of urban residents continue to decline. For eutrophication control, previous studies have focused on nitrogen and phosphorus, and the rule of their effects on the growth of algae. But effects of other nutrients in water, in particular, the direct and indirect effects of trace elements on the growth and reproduction of algae, are less studied.Supported by the National major water special project “Study of the impact of nitrogen, phosphorus and trace elements on the urban water quality†of the 12 th Five-Year Plan, this study focuses on three different typical landscape waters. They are the Dishui Lake in Shanghai, the Hancheng Lake in Xi’an, and the Cui Lake in Kunming respectively. The sources and break-even analysis of trace elements Fe, Mn, Zn, Cu, Mo in the water bodies of the three different urban landscape waters are carried out. Also the space-time distribution and seasonal variation of trace elements are studied. With chlorophyll a as a representative indicator of the eutrophication of the water, the correlation relationship between the trace elements and eutrophication of water bodies is studiedThe results show that:(1) The sources of the trace elements in urban landscape water body mainly include tributary water, dry wet deposition and rainwater runoff. The tributarywater is the most important input way of trace elements, and the concentration changes of trace elements in water is mainly affected by changes of tributary waters.(2) The distributions of trace elements in landscape water and in sediment are obviously different, mainly embodied in: among the three representative waters, the concentrations of trace elements in waters vary widely, but vary a little in sediments.(3) In landscape water bodies, the concentrations of Fe, Mn, Zn are relatively higher, and change obviously with the seasons: they are significantly higher in summer and autumn than in winter and spring. The concentrations of Cu, Mo are lower and they do not change much with the seasons.(4) The correlation of trace elements and chlorophyll-a depends mainly on the concentration range of chlorophyll a. At low concentrations, trace elements, especially Fe, Mn, Zn, have good correlations with chlorophyll a. At high concentrations, only Fe maintains a good correlation with chlorophyll a. This phenomenon indicates that the promoting effect of trace elements on the growth of algae occurs mainly when the water is in low eutrophication level or non- eutrophication stage. |
