Precipitation chemistry in the Source Region of the Yangtze River

A study of ions sources and water vapor sources was carried out from April 1, 2016 to October 31, 2018, at Zhimenda(ZMD), Qumalai(QML) and Tuotuohe(TTH) in the source region of the Yangtze River to obtain preliminary quantitative results for the contributions of the ion and water vapor sources. In the study, 489 precipitation samples analyzed for pH, EC, and ionic concentrations were evaluated by using neutralization factor analysis, factor analysis, and trajectory analysis. The results revealed that Na+ was derived mainly from crustal sources. However, K+, Mg2+, and Ca2+ were only mainly controlled by crustal sources, with contribution rates of 93.60%, 58.88%, and 98.10%, respectively. Marine sources made the greatest contribution to Cl− (99.03%). The most important contributor of NO3− (99.52%) and SO42− (83.23%) was anthropogenic sources. F− was mainly controlled by crustal sources and anthropogenic sources. Although there were different water vapor paths in different seasons at different sample sites, water vapor in the study area was mainly controlled by westerly circulation and monsoon circulation. The largest contributions of westerly circulation were for Cl− and K+, whereas monsoon circulation mainly contributed the ionic concentration of NH4+. However, the largest number of ions was contributed by a westerly circulation–monsoon circulation pattern. These ions were F−, NO2−, SO42−, Li+, Na+, Mg2+, and Ca2+, with contributions of 51.20%, 41.60%, 42.30%, 53.68%, 40.36%, 40.22%, and 34.20% of the total, respectively. NO3− was mainly contributed by westerly circulation–regional circulation. •Different season will have different water vapor path in different sample sites.•Water vapor mainly controlled by westerly and monsoon circulation in the study area.•The contribution of ion sources to major ions in precipitation was quantified.•The contribution of water vapor sources to precipitation was quantified.