[Spatial and temporal distribution of trace elements in surface water in the Xilin River Basin].

In order to better understand the hydrological process in Xilin River Basin, 248 water samples were collected in 13 sections (10 were at the mainstream and 3 were at the three tributaries) over the Xilin River during 2006-2008 and thereafter analyzed by high resolution inductively coupled plasma mass spectrometry (ICP-MS) for 20 trace elements. The temporal and spatial distribution characteristics of trace elements were obtained. The results showed that the average concentration values of trace elements were 0. 1-10 microg x L(-1). Most of those values were at the concentration ranges of precipitation and groundwater and very close to the values of groundwater, indicating that the surface water was recharged by precipitation and groundwater especially by groundwater. The variation of concentration of trace elements in surface water was not strong at the temporal scale. Usually, the concentration values of trace elements were higher in April and May than those in July and August while those values were a bit lower in 2007 than in 2006 and 2008. Most of the trace element concentrations showed a upward trend from upstream to downstream. The enrichment of trace elements was contributed to the recharge of tributaries and groundwater, the evaporation of the stream water.