Study On Trace Elements In Waters In The Xilin River Basin

The chemical components of natural water are the consequences of long-term interaction between water and the surrounding environment. As a result, the chemical composition of water records, to a certain extent, the history of water formation and movement. To a large extent, the composition of trace elements in water body characterizes the water environmental quality, the chemical signatures of regional environment, the rules of the distribution, migration and transmission of water elements. The studies on the features of trace elements have the significance both for understanding the relationship between surface water and precipitation or groundwater in a basin scale, and for ion composition and ion source in the river.Xilin Gol prairie is the most typical temperate grassland all over the world. In recent years, the sharply degeneration of regional environment has extensivly attracts academic and governmental attention. As we have known, the degeneration of environment of arid and semi-arid region is directly related to overutilization of water resources. However, because of the rare studies on the regional hydrology in Xilin river basin, it brings a bit more difficulties for the restoration of the ecological environment.This paper is based on the firsthand chemical data information by the field work and sample (24sampling points,471samples) in Xilin river basin from2006to2008and use relatively analytical tools, like PCA, cluster analysis, etc. It analyzes roundly the spatial and temporal distribution characteristic of trace element that tries to be given a certain explanation of the forming reason, and states the transforming relationship of water in this basin. Above all, the main results and preliminary conclusions as follows:(1)Compared with SongHua River, Yangtze River and sea, the average concentrations of most of trace elements is in between0.1～10μg·L-1in Xilin River, which indicates the trace element composition is closely related to geography location. In addition, according to the average concentrations of trace elements in local groundwater and meteoric waters, it indicates that surface water depends on meteoric waters and groundwater at the same time, principally groundwater.(2)There is little annual and interannual change of trace element in Xilin River basin. And the changed trend of most elements of surface water and ground water is similar, the record of annual change of concentration is that the concentration is higher in April and May and lower in July and August. Because the trace element enriches in snow in winter, and the element concentration is diluted with runoff increased. However, the change of concentration of a part of element is different, which may be influenced by absorption or other recharge sources. In2007, mainly due to the drought, the precipitation amount decreased and precipitation leaching effect reduced. At the same time, in drought years the main supply source of shallow groundwater is deep groundwater, and the deep groundwater concentration is obviously lower than the of shallow groundwater. Most elements concentration in the surface water and groundwater is slightly smaller than other years, the surface water and groundwater both show a lower concentration in2007.(3)The concentration of most of the trace elements and macroelements of surface water is on the rise from upstream to downstream, which is related to supply and evaporation from groundwater. To varying degrees, each element increases in the point location S7-S8for the effects of human behaviors and the supply of the side runoff. Each element for groundwater reaches to peak at the point location G4from upstream to downstream, which is closely related to water-rock interaction occurring on the different lithologic structure at south bank and human behaviors. Moreover, perpendicular to the direction of Xilin River, from south to north element concentration changes obviously at the point location G9, this because there is the supply of bedrock fissure water. In addition, the point locations G5and G8are deep phreatic water, whose element concentrations are lower than other point locations.(4)Using PCA can classify correlation and main component of element, and we can preliminary judge the change rule of elements to confirm the results of each element’s time distribution at chapter four, which show that most elements are relative, and the elements like TDS、HCO3-、Cl-、SO42-、Na+、Mg2+、Ca2+、Sr、B、Li are high correlation and their changed trends are similar. As a result of PCA, the change of element is influenced by rock-eluviation, soil-eluviation, mining, human behaviors and meteoric waters.(5)24point locations are classified the convergence and divergence zone by clustering analysis. The point locations like S1～S12, G1～G3, G5and G8are polymerized first, regarded as the same supply recharge source, which is influenced by rock-weathering and evaporative crystallization and less from outside. Then a secondary polymerization occurs between the first polymer and rainfall, which shows rainfall is affected by other supply of far moisture. The third polymerization occurs between the second polymer and G4, G6, G7and S13, which shows influence from outside is strong. Otherwise, the polymer stragglings with G9and G10, because bedrock fissure water from coteau supplies G9, and farther water source may supply G10, which is consistent with the result of each element’s time distribution at chapter four.