| The chemical composition of meteoric precipitation is influenced by its source,complex atmospheric chemical process and cloud formation path.The samples of different types of rainfall in in summer of Nanchang were collected at high frequency in this study from July to September 2018.the characteristics of water-soluble ions and inorganic nitrogen isotope composition in different types of rainfall were systematically analyzed,of typhoon rainfall（MARIA and MANGKHUT）,local rainfall（shower and thundershower）and frontal rain.The sources of water-soluble ions and inorganic nitrogen isotopes in different types of rainfall were investigated by using enrichment factors,backward trajectory analysis,nitrogen isotope technique and stable isotope mixing model（SIAR）based on R language.This study shows that:（1）The total water-soluble ion concentration in Nanchang（324.6±168.1μeq/L）,The average concentration of water-soluble ions from different rainfall types was local rainfall（417.5μeq/L）>frontal rain（223.2μeq/L）>MARIA（145.5μeq/L）>MANGKHUT（47.7μeq/L）.（2）The backward track analysis of different types of rainfall air mass shows that the trace lines of local rainfall are shorter and distributed in Jiangxi province.The rainfall air mass of typhoon rainfall（MARIA and MANGKHUT）is transmitted from the sea to the land,and the frontal rain is affected by the transmission of cold air mass in the north.（3）The analysis results of water-soluble ions characteristics in different types of rainfall in Nanchang showed that some Cl-,Na+,Mg2+in typhoon（MARIA and MANGKHUT）and frontal rain were contributed by Marine sources,the others Cl-was mainly from anthropogenic sources,and the others Mg2+was mainly from soil.In local rainfall,Cl-and Mg2+are basically from anthropogenic sources,and Mg2+from soil sources.In all types of rainfall,SO42-,NH4+NO3-are mainly from anthropogenic sources,while Ca2+and K+are mainly from soil sources.（4）The average concentration of NO3-in different types of rainfall was local rainfall（68.5±18.8μeq/L）>frontal rain（44.2±29.9μeq/L）>MARIA（10.0±5.3μeq/L）>MANGKHUT（2.6±1.9μeq/L）;The averageδ15N-NO3-values in different types of rainfall was MANGKHUT（2.3±1.8‰）>local rainfall（-2.4±1.3‰）>MARIA（-2.5±1.0‰）>frontal rain（-3.0±2.4‰）;But the averageδ18O-NO3-value in different types of rainfall,frontal rain（+69.7±2.4‰）>local rainfall（+65.1±5.6‰）>MARIA（+58.2±4.0‰）>MANGKHUT（+57.9±4.7‰）.（5）The δ18O-NO3-value frontal rain>local rainfall>MARIA and MANGKHUT in different types of rainfall,This is consistent with the latitude distribution of different rainfall moisture transmission paths,which come from high latitudes,δ18O-NO3-value is more positive.In all types of rainfall,NO3-mainly comes from automobile exhaust,and biomass combustion is the potential contribution source.In local rainfall NO3-also comes from nitrogen fixation by lightning,and NO3-in typhoon MANGKHUT is significantly affected by coal-fired power plants.（6）The concentration of NH4+in typhoon rainfall（MARIA and MANGKHUT）was（45.6±15.2μeq/L和4.6±0.0μeq/L）,significantly lower than that in local rainfall and frontal rain（116.6±40.0μeq/L和69.2±39.2μeq/L）,but the value ofδ15N-NH4+in typhoon rainfall（MARIA and MANGKHUT）was-4.7±1.8‰and-4.9±1.3‰,significantly higher than that in local rainfall and frontal rain（-7.5±3.0‰and-8.9±4.8‰）.（7）The contributions of automobile exhaust,coal combustion,human and animal excretion and fertilizer volatilization from four sources of NH4+in typhoon rainfall（MARIA and MANGKHUT）are close to 25%.Contributions of various sources of NH4+in local rainfall and frontal rain were 35.0%and 30.7%of automobile exhaust,24.8%and 23.4%of fertilizer volatilization,21.5%and 24.2%of coal combustion,and 18.7%and 21.6%of human and animal excrement. |
