资源环境科技发展态势分析平台

To analyse the environmental significance and zonal characteristics of stable isotopes of precipitation in Arid Central Asia systematically, this study took the Pan-Hexi region as an example study area. A total of 1747 precipitation samples were collected from 25 sampling points from May 2013 to July 2014. The results showed that the elevation effects of delta O-18 and delta H-2 of precipitation in the Pan-Hexi region were - 0.07 parts per thousand/100 m and - 0.17 parts per thousand/100 m, respectively. However, the elevation effects of delta O-18 and delta H-2 were lower in the oasis area than the mountainous section of the study area. The temperature effect was significant in the oasis area when the temperature was < 10 degrees C and > 15 degrees C, but it was only significant in the mountain area when the temperature was < 0 degrees C. The evaporation rate of falling raindrops (f) and the enrichment rate (E) were significantly higher in the oasis area (E: 34.87%; f: 20%) than in the mountain area (E: 20.56%; f: 11.71%), and the E and f values showed a significant decreasing trend from oasis area to mountain area. Sub-cloud evaporation had a significant effect on the stable isotopes in precipitation. It was found that if f increases by 1%, E increases by 0.58% in the oasis area and by 0.86% in the mountain area. The precipitation amount effect mainly occurs during summer (June to August) in the Pan-Hexi region, especially in the oasis area. This effect was caused mainly by sub-cloud evaporation rather than by monsoon circulation. Further analysis demonstrated that when precipitation is higher, sub-cloud evaporation of falling raindrops is lower and enrichment of delta O-18 is weaker. Therefore, rainfall events with higher precipitation amounts had more depleted delta O-18 and vice versa. Thus, it can be concluded that precipitation amount effect in the study area is dominated by sub-cloud evaporation, which provides new information pertaining to the isotopic evolution of precipitation in arid regions.