Stable isotopic characteristics of precipitation related to the environmental controlling factors in Ningbo, East China

摘要

Hydrogen and oxygen stable isotopes (delta H-2 and delta O-18) in precipitation were analysed from June 2018 to May 2020 in Ningbo and were influenced by the subtropical monsoon climate in East China. The delta H-2 and delta O-18 values of precipitation in Ningbo varied from -90.0 to 6.0 parts per thousand and from -13.5 to -1.6 parts per thousand, respectively. The local meteoric water line (LMWL) in Ningbo was obtained as delta H-2 = 9.27 delta O-18 + 35.95 and had a larger slope and intercept compared to the global meteoric water line (GMWL) because its water vapour sources were oceans. The more negative delta O-18 values and lower deuterium excess (D-excess) of precipitation in summer were due to water vapour sources from the East China Sea, the South Sea and the Western Pacific, which are controlled by the southeasterly monsoon. In contrast, the less negative delta O-18 and higher D-excess of precipitation in winter were influenced by water vapour sources from the North Asian continent and North China transported by the northwesterly monsoon. The precipitation amount effect was significant in Ningbo, especially in summer. The inverse temperature effect was appeared in Ningbo, except winter. These two effects may be caused mainly by the monsoon climate rather than by the secondary evaporation effect.