广西环境空气中醛酮类化合物污染特征研究

Study on Pollution Characteristics of Aldehydes and Ketones in Guangxi

为探究广西醛酮类化合物的污染状况,选择2022年9—10月和2023年5—6月臭氧质量浓度较高时段,分别对广西臭氧质量浓度较高的典型城市如南宁、桂林、北海、贵港、百色、贺州和来宾等城市的环境空气中醛酮类化合物进行监测,分析不同城市醛酮类化合物的季节特征、浓度水平、组分特征以及臭氧生成潜势(OFP),并利用比值法对醛酮类化合物的来源进行初判。研究结果表明,南宁、桂林和来宾等典型城市醛酮类化合物质量浓度季节特征与臭氧一致,均表现为秋季(2022年9—10月)高于春夏季(2023年5—6月);监测期间,广西醛酮类物质平均质量浓度为23.64μg/m~3,其中贺州最高,为31.30μg/m~3,北海最低,为13.58μg/m~3,与其他城市相比,广西各市醛酮类化合物质量浓度处于中等偏下水平;各城市的醛酮类化合物化学组分中甲醛占比最高,占比为43.8%(贺州)~58.2%(贵港);各城市OFP值为77.32μg/m~3(北海)~159.35μg/m~3(贵港),其中甲醛对OFP贡献最大,贡献占比为52.1%(北海)~70.1%(贵港)。各城市甲醛和乙醛的质量浓度比值(C1/C2)为2.55~3.22,醛酮类化合物主要以机动车尾气排放以及人为源碳氢化合物氧化为主,其中北海和百色的C1/C2均在2.6左右,受机动车尾气等人为源影响更明显,在臭氧污染期间须加强机动车尾气等人为源管控。

In order to investigate the pollution of aldehydes and ketones in Guangxi,the aldehydes and ketones in ambient air in typical cities,including Nanning,Guilin,Beihai,Guigang,Baise,Hezhou and Laibin,were monitored from September to October 2022 and from May to June 2023.The concentration level,component characteristics and the ozone formation potential(OFP)of the main aldehydes and ketones in different cities were analyzed,and the source of aldehydes and ketones were analyzed by the ratio method.The study showed that the typical cities in Guangxi,such as Nanning,Guilin and Laibin,exhibited a similar seasonal pattern of aldehydes and ketones mass concentrations to ozone with higher concentrations in autumn(September-October 2022)compared to spring and summer(May—June 2023).During the monitoring period,the average concentration of aldehydes and ketones in Guangxi was 23.64μg/m 3,with the highest concentration in Hezhou(31.30μg/m 3)and the lowest concentration in Beihai(13.58μg/m 3).Compared with other cities,the concentration level of aldehydes and ketones in ambient air in cities of Guangxi was below average.Formaldehyde accounted for the highest proportion,ranged from 43.8%to 58.2%.The OFP in each city ranged from 77.32μg/m 3(Beihai)to 159.35μg/m 3(Guigang),among them,formaldehyde contributed the most to OFP,accounting for 52.1%~70.1%.The ratio of formaldehyde to acetaldehyde(C1/C2)in seven cities ranged from 2.55 to 3.22,indicating aldehydes and ketones originate from vehicle exhaust emissions and anthropogenic sources of hydrocarbon oxidation.Notably,Beihai and Baise had C1/C2 ratio around 2.6,indicating a more significant impact from vehicle exhaust and other anthropogenic source,it is necessary to strengthen the control of relevant emission source during ozone pollution.