关键词: 安庆地区, 大气降水, 氢氧稳定同位素, 过量氘, 相对湿度, 气团轨迹, 水汽来源

Abstract: [Objective] It is critical to examine the characteristics of hydrogen (δD) and oxygen (δ¹⁸O) stable isotopes in the precipitation as well as the source and migration process of regional atmospheric precipitation in Anqing that help reveal the mechanism of the hydrological cycle in the forest ecosystem of Anhui Province along the Yangtze River in response to climate change.[Method]Using a stable isotope technique, we analyzed the compositions of δD and δ¹⁸O in 155 precipitation samples between June 2015 and June 2017 in Anqing, and examined the local meteoric water line. To analyze whether and how the climatic factor affects the compositions of δD and δ¹⁸O in the precipitation, we established the relationships of δD (δ¹⁸O) to the precipitation and temperature. We traced the sources of atmospheric water in Anqing by calculating the D-excess (d) in the precipitation, and verified the results of the sources through HYSPLIT model.[Result]The relationship between δD and δ¹⁸O in the precipitation in Anqing was δD=(8.08 ±0.06)δ¹⁸O+(10.84±0.48) (R²=0.99, n=155). The stable isotopes δD and δ¹⁸O were significantly negatively associated with temperature (P<0.01), while no significant correlation was found between the stable isotopes and the precipitation (P>0.05). The D-excess(d) was close to the global average (10‰), suggesting that the precipitation in the area was mainly affected by the ocean monsoon. The results of air mass back trajectories of the precipitation were calculated by the HYSPLIT model and showed that there were different sources of atmospheric vapor in Anqing. In spring, the atmospheric vapor was affected by the local evaporation and continental air mass from north and south China, and was likely influenced by the Pacific southeast monsoon when rainfall was heavy. In other seasons, atmospheric vapor sources were mainly impacted by the South China Sea air mass, Pacific southeast monsoon, and southwest monsoon of India Ocean.[Conclusion]In this study, the precipitation in Anqing was primarily influenced by atmospheric vapor from the ocean. Differing from the traditional stable isotopes theory of temperature effect, a opposite temperature effect was found in the precipitation in Anqing, this is probably attributable to the latitudes of Anqing, suggesting that different geographical locations probably influenced the composition of δD and δ¹⁸O in the precipitation. Therefore, further studies understand the influences are needed.

Key words: Anqing, meteoric water, hydrogen and oxygen stable isotopes, D-excess, relative humidity, water vapor trajectory, water resource