| Organic acids are important water-soluble organic compounds in atmospheric aerosols with important impacts on the environment and human health.In order to better understand the characteristics and sources of water-soluble low-molecular-weight organic acids in PM2.5in atmospheric aerosols in Nanchang City,we conducted a one-year study in Nanchang City,Jiangxi Province（January 1,2019-December 31,2019）,the main anions and cations and water-soluble low-molecular-weight organic acids in the samples were measured,and the results were analyzed and discussed,and the following results were obtained:（1）Water-soluble inorganic ions(including Cl-,SO42-,NO3-,K+,Na+,Ca2+,Mg2+,NH4+etc.)and water-soluble low-molecular-weight organic acids（including formic acid,acetic acid,oxalic acid,etc.）were detected in Nanchang area.succinic acid,glutaric acid and methanesulfonic acid),among the water-soluble inorganic ions,NO3-,SO42-and NH4+have the highest concentrations,with an average concentration of 4.92±2.61μg/m3 and 6.02±2.52μg/m3,respectively and 3.67±1.80μg/m3;the most important water-soluble organic acids were formic acid,acetic acid and oxalic acid,whose annual average concentrations were0.33±0.28μg/m3,0.28±0.16μg/m3 and 0.81±0.47μg/m3,respectively.They all showed seasonal changes in autumn and winter than in spring and summer,which were consistent with the changes in PM2.5 concentrations.There is a good correlation between water-soluble inorganic ions and water-soluble low-molecular-weight organic acids,which may have the same source.（2）In this study,the ratio of formic acid to acetic acid（F/A）,the correlation analysis between low-molecular-weight organic acids and inorganic ions and gaseous pollutants,the air mass backward trajectory model（HYSPLIT）analysis,etc.were used to determine the year of 2019.The source of water-soluble low-molecular-weight organic acids in PM2.5 in Nanchang City,the results show that water-soluble low-molecular-weight organic acids come from the combined contribution of primary emission and secondary transformation.（3）The contribution of water-soluble low-molecular-weight organic acids（formic acid,acetic acid,and oxalic acid）to PM2.5 free acidity in Nanchang is about 0.1%,and the contribution of inorganic acids to acidity exceeds 95%.And And the free acidity of PM2.5 has obvious temporality,,and the specific performance is autumn（1.44±1.57）>winter（0.97±1.13）>spring（0.80±0.94）>summer（0.37±0.29）.The change trend is related to organic acids.the same concentration.（4）The concentration of gaseous pollutants and meteorological conditions in Nanchang City showed a consistent temporal trend with the concentration of water-soluble low-molecular-weight organic acids in PM2.5.And there is a good positive correlation between them,these results indicate that they may have the same source,or the emission of gaseous pollution has a certain effect on the formation of water-soluble low molecules.Meteorological conditions also had an important influence on the concentration of water-soluble organic acids in PM2.5.The main water-soluble organic acids in Nanchang showed a certain negative correlation with meteorological conditions.It shows that the higher the temperature,the faster the wind speed,or the greater the precipitation,the generation of water-soluble organic acids may be reduced. |
