Study On Pollution Characteristics,influencing Factors And Sources Of Secondary Inorganic Components In PM₁₀ In Jinhua City

Sulfate(SO₄^2-)and nitrate（NO₃^-）are the most important components of the secondary inorganic components in atmospheric particulates.A clear understanding of their pollution characteristics,influencing factors,formation and evolution and their sources in the process of air pollution will be useful for in-depth understanding of the formation and dissipation of air pollution.In this study,samples of PM₁₀were collected in Jinhua City with a time resolution of every two hours during the sampling period from December 2019 to January 2020（winter）and June 2020 to August 2020（summer）.And measured the concentration of SO₄^2-and NO₃^-in the sample.The effects of meteorological conditions（solar illumination conditions,environmental relative humidity,environmental temperature）and four gaseous pollutants（SO₂,NO₂,O₃,CO）on the secondary inorganic components in atmospheric particulate matter were analyzed from the seasonal and diurnal variation characteristics.And through the method of multiple linear regression,the key factors for the formation of secondary inorganic components are found.and further through the backward trajectory method and the weighted concentration analysis model（CWT）,the sources of the secondary inorganic component carrier PM₁₀and gaseous precursors（SO₂,NO₂）were analyzed.The main conclusions of the research are as follows:（1）The temperature,humidity,PM₁₀,gaseous pollutants（SO₂,NO₂,O₃,CO）and NO₃^-in Jinhua City all have obvious seasonal variation characteristics,while the seasonal variation of SO₄^2-is not obvious.Temperature and O₃are higher in summer than in winter,relative humidity,PM₁₀,SO₂,NO₂,CO,and NO₃^-concentration are higher in winter than in summer,and SO₄^2-concentration is similar in summer and winter.（2）The conditions of high humidity and low temperature in winter are conducive to the conversion of SO₂to SO₄^2-,and the liquid phase reaction is the main way for the formation of SO₄^2-.The gas phase reaction in summer is the main way for the formation of SO₄^2-,and the increase in temperature is beneficial to the conversion of SO₂to SO₄^2-.However,whether in winter or summer,,atmospheric illumination has little effect on the conversion of SO₂to SO₄^2-,and solar radiation can only be observed in summer to have a certain promotion effect on SOR,indicating that atmospheric photochemical process is not the main source of atmospheric SO₄^2-in the study area.（3）Whether in winter or summer,low humidity is conducive to the conversion of NO₂to NO₃^-,indicating that the gas phase reaction is the main way of conversion to NO₃^-in the study area.Sunlight has a significant effect on NOR.No matter in winter or summer,the NOR value during the day is greater than the NOR value at night under the same conditions.This shows that sunlight promotes the formation of NO₃^-,and atmospheric photochemical processes are the main source of atmospheric NO₃^-.（4）Whether in winter or summer,the correlation between atmospheric O₃concentration and NOR is much higher than that between atmospheric O₃concentration and SOR in the same period,indicating that atmospheric O₃promotes the generation of NO₃^-more than that of O₃promotes the generation of SO₄^2-.Whether in winter or summer,the effect of CO on SOR is much greater than that on NOR.The presence of CO in the atmosphere can weaken the conversion efficiency of SO₂to SO₄^2-,but has limited effect on the conversion of NO₂to NO₃^-.（5）The analysis of SO₄^2-,NO₃^-in the secondary inorganic components in summer and winter,the multiple linear regression equation of different meteorological conditions and gaseous pollutants shows that the concentration of SO₂and relative humidity have the main effect on the concentration of SO₄^2-in winter.The influence factors on SO₄^2-concentration in summer were not significant.NO₂concentration,O₃concentration,temperature,relative humidity and solar altitude are the main factors affecting NO₃^-concentration in winter.CO concentration,O₃concentration,temperature,relative humidity and solar altitude are the main factors that affect the concentration of NO₃^-in summer.