干旱区生态环境知识资源中心

The distribution of stable isotopes and ions in precipitation in the Shule River Basin, northwestern China, were investigated to understand the regional water cycle and precipitation input to groundwater recharge. The study found that the mean annual concentrations of Ca2+, Na+, SO4 (2-), Cl-, Mg2+, NO3 (-), and K+ in the basin were lower than those in other arid areas of northwestern China. The average concentrations of ions in the lower reaches of the Shule River were higher than those in the upper reaches. The results showed that the main ionic concentrations decreased with the increase of precipitation amount, indicating that heavy precipitation cannot only wash crustal aerosols out of the atmosphere, but also create a dilution effect. Cl- and Na+ in precipitation had a strong and positive correlation, suggesting a common origin for the two ions. However, the excess of Na+, combined with non-marine SO4 (2-) and NO3 (-), indicated that some ions were contributed by terrestrial origins. In the extremely arid regions of northwestern China, the evaporation process obviously changes the original relationship between delta H-2 and delta O-18 in precipitation, and leads to dexcess values < 8aEuro degrees. delta O-18 and temperature were significantly correlated, suggested that temperature strongly affected the characteristics of isotopes in the study area. The delta O-18 value indicates a dominant effect of westerly air masses and southwest monsoon in warm months, and the integrated influence of westerly and Siberian-Mongolian polar air masses in cold months. The d-excess values were generally lower in warm months than those in cold months, indicating that post-condensation processes played a significant role in the water cycle. The results provide reliable precipitation input information that can be used in future groundwater recharge calculations in the study area.