| Carbonyl compounds?including aldehydes and ketones?are important components of volatile organic compounds?VOCs?,and the photo-dissociation of carbonyls is an important source of atmospheric free radicals,meanwhile,carbonyl compounds play an important role in the process of ozone formation.In order to investigate the pollution characteristics,sources and reactivity of carbonyl compounds in the Beijing-Tianjin-Hebei air pollution transmission channel area,this study selected a typical rural site?Wangdu?,a typical urban site affected by industrial area?Jinan?and a typical city site?Binzhou?to carry out the field observation experiment where the carbonyl compounds samples were collected,and then analyzed by using high performance liquid chromatography?HPLC?,at the same time,the conventional atmospheric pollutants were measured by on-line monitoring instruments.The results showed that the concentration and reactivity of atmospheric carbonyls in the Beijing-Tianjin-Hebei air pollution transmission channel were high.In Jinan,the total concentration of carbonyls was 10.5±7.13 ppbv in summer and 9.72±3.56 ppbv in autumn.The total concentration of carbonyls was 8.32±3.14 ppbv in Binzhou,while the total concentration of carbonyls was 11.49±6.23 ppbv in Wangdu.Formaldehyde,acetaldehyde and acetone are the three most abundant species in the atmospheric environment of these three sites,accounting for 70%to 80%of the total carbonyl compounds.In Jinan,their concentrations were 4.75±3.19ppbv,1.72±0.76 ppbv,2.33±1.16 ppbv in summer,respectively;and 2.65±1.67 ppbv,1.83±1.17ppbv,3.75±2.21 ppbv in autumn,respectively.The concentrations of formaldehyde,acetaldehyde and acetone in Binzhou were 4.97±2.32 ppbv,1.59±1.09 ppbv,0.83±0.77 ppbv,respectively.While the concentrations of formaldehyde,acetaldehyde and acetone in Wangdu were 3.74±2.35 ppbv,3.19±2.06 ppbv,2.46±1.3 ppbv,respectively,and the concentration of carbonyls in severe air pollution conditions was twice more than that in clean days.The concentration of formaldehyde in summer was obviously higher than that in other seasons in Jinan,and the ozone concentration exceeded the air quality standard significantly,which indicated that photochemical reaction was the main source of formaldehyde in summer.In addition,the concentrations of butyraldehyde and isovaleraldehyde exceeded 1 ppbv in autumn in Jinan,which was related to local emissions and as well as regional transport during night.In urban areas,formaldehyde,acetaldehyde and acetone daily variation trends indicated the concentration of carbonyl compounds reached peak values in the early morning and late afternoon and during the night.During the morning and evening rush hours,vehicle exhaust emissions made a great contribution to the carbonyls in urban areas,while the high concentration level of carbonyls at night was related to regional emissions and transport.The results of PSCF?potential source contribution function?analysis showed that regional transport was the main source of carbonyl compounds in urban areas,while local emissions were another important source of increased nighttime concentrations.By analyzing the correlation between formaldehyde and acetaldehyde in Jinan,it was found that the source and sink of carbonyl compounds were similar in summer,while the correlation between formaldehyde and other carbonyls in autumn was relatively poor,indicated that its source was relatively complex.The diurnal variation of carbonyls in rural area was different from that in urban areas,and the daytime peak was obvious,which was related to the secondary formation by photochemical reaction.The contribution of primary emissions to formaldehyde,acetaldehyde and acetone in Wangdu was calculated by multiple linear regression as 51.27%,57.74%and 49.53%,respectively.The reactivity of carbonyl compounds in three sites was characterized by OH radical loss rate(LOH)and ozone formation potential?OFP?.The results showed that formaldehyde,acetaldehyde and butyraldehyde were the dominant species contributing to the LOH and OFP in these three sites,and the contributions of propionaldehyde could not be ignored.The results of the carcinogenic risk assessment of formaldehyde showed that they all exceeded the threshold of 10-6 in three sites,which means there is a potential carcinogenic risk for people exposed to this level of formaldehyde over a long term and they should pay more attention.This study obtained the composition and source characteristics of carbonyl compounds in typical sites of Beijing-Tianjin-Hebei air pollution transmission channel area in China,and analyzed the composition characteristics and photochemical reactivity,and preliminarily assessed the carcinogenic risk of formaldehyde.The findings of this study can provide theoretical support for formulating the pollution control strategies for atmospheric carbonyl compounds in typical areas in China. |
PDF Full Text Request