Organic Acid Study Of Precipitation In Chengdu Longquanyi District

The organic acids in precipitation are mainly the organic acids that can dissolve in water.They consist of formic acid,acetic acid,oxalic acid,etc.The study on organic acids in the precipitation can show their influence on precipitation acidity;meanwhile,it can show the source of organic acids in a certain extent,such as vegetation emission and human activity.Most of the previous studies focus on the inorganic acids in the acid rain,while fewer of them focus on the organic acids.The previous studies only focus on the analysis of confrontation variation within different seasons.With the increase of car,photochemical smog and industrial waste gas,there is an increasing tendency of the organic acids in precipitation formed by photochemical oxidation,it is necessary to make an analysis of the formation and source of organic acids in the precipitation.Inorganic and organic anions in each precipitation are measured to get the chemical composition of wet deposition with ion chromatograph and cations with atomic absorption spectroscopy.The correlation analysis and principal component analysis were adopted to analyze the samples in order to explore the origin and formation of organic acids,In order to provide a basis for future research and management of organic acids in precipitation.The research conclusions are as follows:(1)Among all the organic acid in the samples,acetic acid content is supreme;formic acid takes second place;oxalic acid content is the lowest.The total concentration of organic anion is 3.2056mg/L which accounts for 18% of the total anion.The datum show that inorganic acid is an important constituent of the rainfall within Longquanyi district,and organic acid is nonnegligible.(2)The relation analysis shows that formic acid and acetic acid have a better relation,and the tight relation shows that formic acid and acetic acid have a similar emission density and emission source.The positive ions have a lower relation with organic acid in the rainfall,which shows that the source of organic acid has an indistinctive relation with positive ions.(3)The main source of organic acid is anthropogenic emission.(4)The contractive analysis of concentration between samples of initial rain and the entire rain shows that acetic acid and oxalic acid mainly come from washout under the cloud,while formic acid comes from washout under the cloud and other sources,for example,photochemical oxidation.