摘要
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Summary
We intensively investigated the composition and distribution of several major ions and stable isotopes (未2H, 未18O) in precipitation in 2008 and 2009 at three sites in the Shiyang River Basin of northwestern China. The goal was to provide basic data that would help us to understand the geochemical evolution and recharge sources of groundwater in the basin鈥檚 Quaternary aquifer. The 未2H and 未18O values for 75 precipitation samples ranged from +35.7鈥?to 鈭?70.9鈥?and from +4.6鈥?to 鈭?3.3鈥? respectively. The relationship between 未2H and 未18O defined a well-constrained local meteoric line, which was nearly identical to the meteoric water line for northern China. The evaporation process in this dry region of northwestern China obviously altered the original relationship between rainfall 未2H and 未18O, resulting in d-excess values < 8鈥? as has been previously reported in many arid regions. The relationship between local temperature and precipitation 未18O was statistically significant based on monthly average 未18O values and air temperatures. Mean annual concentrations of , , Cl鈭?/sup>, , Ca2+, Mg2+, Na+, and K+ in mountain and desert areas were lower than those in most of China鈥檚 cities. The majority of the rainfall samples had a Cl鈭?/sup> concentration of 1.5-2.5 mg L鈭?, and the excess of Na+ over Cl鈭?/sup>, combined with a strong excess of non-marine and the overall precipitation chemistry, indicates that some solutes were contributed from terrestrial sources during the air mass trajectory over land. These values will provide reliable rainfall input information that can be used in future groundwater recharge calculations in the study area.
