Pollution Characteristics Of Atmospheric Carbonyls In Coking Plant And Its Surrounding In Summer

Aldehyde and ketone compounds are important components of oxygen-containing volatile organic compounds（OVOCs）in the atmosphere,are important precursors of ozone（O₃）generation,and play an important role in tropospheric atmospheric photochemical reactions.Due to the key roles of aldehydes and ketones in atmospheric oxidative capacity and O₃ formation,the aldehydes and ketones cannot be ignored when establishing a scientific O₃pollution control strategy.In this paper,four sites affected by coking are selected and monitored,including two coking plant surrounding sites（Linfen Municipal Party Committee,and the primary school in Guxian County,Linfen City）and two coking plant sites（Zhengtai Coking Plant and Lida Coking Plant）.According to the obtained data of aldehydes and ketones and air quality conventional pollutants,the pollution variation characteristics of aldehydes and ketones in the area affected by coking were studied.The reactivity of aldehydes and ketones at each sampling point,and the effects of aldehydes and ketones from different sources on ozone generation,and finally the health risk assessment of formaldehyde and acetaldehyde at each sampling point was carried out.This study showed that during the observation period,nine aldehyde-ketone compounds,including formaldehyde,acetaldehyde,acetone,propionaldehyde,butyraldehyde,crotonaldehyde,MACR,valeraldehyde,and hexanal,were detected at the three sites in Guxian.Acetaldehyde,acetone,propionaldehyde,butyraldehyde,crotonaldehyde,MACR,valeraldehyde,m-methylbenzaldehyde and 2,5-dimethylbenzaldehyde,a total of 10aldehyde-ketone compounds were detected at Linfen Municipal Party Committee site.Formaldehyde,acetone and acetaldehyde were all the most abundant aldehyde-ketone species at the four observation sites,accounting for more than 80%.The acetaldehyde concentration in the two coking plant sites were much higher than the coking plant surrounding sites.Acetone was the most mixed species among the three sites due to its lower photochemical reactivity.Compared with the primary school,both the two coking plants had a smaller divergence coefficient indicating that the pollution sources of the primary and the coking plant were different.The diurnal variation of aldehydes and ketones in the ambient air of the two coking plants were much higher during the daytime than at night,indicating the effect of photochemical secondary generation on the concentration of aldehydes and ketones in the coking plants.Among the ambient aldehydes and ketones around the coking plant,the daily changes of formaldehyde were much higher during the daytime than at night,while the changes of acetaldehyde and acetone were smaller.The C1/C2 ratio of the coking plant is the lowest,which is greatly affected by anthropogenic sources.According to the multiple linear regression analysis,it is concluded that the primary source（48%）is the main source of formaldehyde in primary schools,the acetaldehyde is mainly affected by the primary source（41.8%）and the background source（45.2%）,and the acetone is mainly affected by the background source（44.3%）.This is mainly due to the large amount of pollutants emitted by the coking plant near the primary school and the special terrain.The formaldehyde of the municipal party committee is affected by the primary source（36.6%）and the secondary source（35.8%）,which is mainly related to the complex pollution sources around the municipal party committee and the emission of a large amount of aldehyde and ketone precursors.Primary school and municipal committees have obtained four sources of secondary generation,dust and vehicle exhaust emissions,industrial emissions and other sources through PMF source analysis.The primary school accounted for42.76%,28.81%,24.51%and 3.92%,respectively;while the municipal party committee accounted for 47.49%,22.57%,27.6%and 2.33%respectively.According to the cluster analysis results of the 24-h backward trajectory of the air mass during the observation period of the primary school and the municipal party committee,it shows that the trajectory air mass from the south of Linfen City has a greater impact on the concentration of aldehydes and ketones.In addition,this paper finds for the first time that the vertical transport of clean air masses containing high concentrations of O₃ and NO₃·at 900 meters high can lead to an increase in the secondary generation of formaldehyde at night.During the observation period,the municipal party committee was severely affected by photochemistry,followed by the primary school and Zhengtai Coking Plant,and finally Lida Coking Plant.Formaldehyde,acetaldehyde and MACR were the most photochemically reactive species in the area affected by coking.The average MIR values of atmospheric aldehydes and ketones at the three stations in Guxian were comparable to those of valeraldehyde(5.08g·g^-1),while the average MIR values of atmospheric aldehydes and ketones of the Municipal Party Committee were similar to those of butyraldehyde(5.97g·g^-1)is equivalent,which further indicates that the photochemical reactivity of the municipal party committee is stronger.The analysis of the effect of aldehydes and ketones on O₃ generation in different emission sources shows that photochemical secondary generated aldehydes and ketones contribute the most to O₃,followed by motor vehicle emissions.In addition,the impact of industrial emissions on O₃ cannot be ignored.Through the health risk assessment of formaldehyde and acetaldehyde in the areas affected by coking,it is understood that in the atmosphere of the areas affected by coking,formaldehyde has a great impact on human health,and acetaldehyde also has a certain carcinogenic risk to the local residents.In order to ensure the healthy life of the local residents,it is recommended to strictly control the surrounding motor vehicle exhaust,solvent volatilization and industrial emissions and other pollution sources;on the other hand,local residents should try to avoid exposure to high concentrations of formaldehyde and acetaldehyde（10:00-16:00）.