|关键词: 稳定同位素 环境效应 降水 胶莱平原
|Stable isotopic characteristics of hydrogen and oxygen in precipitation in Jiaolai Plain
WANG Ying, CUI Buli, LI Dongsheng, WANG Yaxuan
School of Resources and Environmental Engineering, Ludong University, Yantai 264025, China
|Background, aim, and scope Precipitation is a critical component of the water-cycle processes, and the main source of terrestrial water resources. A prerequisite for using isotopic techniques to study the regional water cycle is to examine the stable isotopic composition of its precipitation. The findings are of great significance for in-depth understanding of the water-cycle processes. The main purpose of this study is to explore the temporal and spatial changes of precipitation isotopes in the study area and determine the environmental impact of these precipitation isotopes. Materials and methods In this study, each event of precipitation was sampled and used to investigate the characteristics of stable isotopes (δ2H and δ18O, respectively) in precipitation on the Jiaolai Plain and its surrounding areas. The water vapor sources of precipitation over the plain were revealed through a comparative analysis of seasonal variations in precipitation isotopes among the stations located along different vapor transport paths. Results The results showed that the local meteoric water line (LMWL) was δ2H=6.38 δ18O+0.72, with a gradient less than 8. The temperature effect of the δ18O of precipitation was significant (P<0.001). The amount effect of the δ18O of precipitation was significant (P<0.05). Discussion The precipitation process was affected by non-equilibrium evaporation occurred when the drops fell below the cloud base. The relationship between the δ18O of the precipitation and the altitude on the Jiaolai Plain showed that the δ18O of the precipitation had an inverse relationship with altitude during the sapling period, meaning that it gradually depleted with altitude, although it was not significant. The δ18O of precipitation in Jiaolai Plain and other stations (Baotou, Shijiazhuang, Tokyo and Nanjing) were higher than Urumqi and Qiqihar, and their d-excess values were greater than 10, indicating that during the control period of the Westerlies (from October to May), the main water vapor source of plain precipitation was local evaporation, and the influence of polar water vapor was small. At the same time, during the period controlled by the East Asian Monsoon (from June to September), the d-excess value of the plain was similar to that of Tokyo and Qiqihar. Therefore, the precipitation in these three places has similar water vapor sources, that is, the water vapor evaporated from the adjacent Pacific Ocean. The water vapor source of the precipitation was controlled predominantly by the East Asian Monsoon from June to September, with the main source being evaporation from the adjacent Pacific Ocean. The plain was controlled by Westerlies from October through May, with the predominant vapor source being local evaporation. Water vapor from the polar region had minimal impact. Conclusions Significant temperature and amount effects existed in theδ18O of precipitation, although the altitude effect was not significant. The main water vapor source of the precipitation was evaporated from the adjacent Pacific Ocean from June to September, while the predominant vapor source was local evaporation from October through May, and water vapor from the polar region had minimal impact. Recommendations and perspectives Several studies showed that the precipitation isotopes were significantly depleted when affected by the typhoon weather system. So it is necessary to further study the stable isotope characteristics of hydrogen and oxygen of precipitation during typhoon. These findings can serve as the basis for studying surface water—groundwater—seawater transformations, and the water-cycle in the Jiaolai Plain.
|Key words: stable isotopes environmental effects precipitation Jiaolai Plain