| Carbonyls are a kind of important oxygen-containing volatile organic compounds（OVOCs）in the ambient air.They are not only important precursors of photochemical smog formation,but also important components of photochemical smog.At the same time,they have adverse effects on the ecological environment and human health.At present,carbonyls have become a research hotspot in the field of atmospheric environmental science.In this study,field observations of carbonyls were carried out simultaneously in 8 cities of Chengdu Plain Urban Agglomeration from August 4 to 18,2019.The pollution characteristics,atmospheric photochemical reaction activity,formation mechanism and sources of carbonyls were comparatively studied by using a variety of data analysis methods,and the human health risks of toxic and harmful carbonyls were assessed.The results showed that there was a regional ozone pollution episode in Chengdu Plain Urban Agglomeration during the observation period,and the total concentration of carbonyls in most sites was higher in pollution days than that in clean days.The spatial distribution of carbonyls was similar to that of ozone;The diurnal variation of carbonyls in most sites was consistent with that of ozone,which was higher in the daytime and lower in the nighttime.The average concentration of carbonyls in Chengdu Plain Urban Agglomeration was 17.90 ppbv,among which formaldehyde（36.4%—64.3%）,acetone（12.4%—28.1%）and acetaldehyde（8.2%—47.3%）were the most abundant species.Formaldehyde and acetaldehyde were the species with the highest atmospheric photochemical reaction activity at each site in the Chengdu Plain urban agglomeration.The OH radical consumption rate of most carbonyls species was higher in pollution days than in clean days;The average maximum incremental reactivity of carbonyls was similar to that of benzenes(3.04 g·g-1)on both pollution and clean days,indicating that carbonyls in Chengdu Plain Urban Agglomeration had strong atmospheric photochemical reactivity.The PMF source apportionment results of carbonyls at the regional level of Chengdu Plain Urban Agglomeration identified four sources:anthropogenic primary emission,plant primary emission and background,secondary and other sources.The contributions of secondary formation for formaldehyde,acetaldehyde and acetone were41%,42%and 44%,respectively;The results of multiple linear regression analysis showed that the secondary formation of formaldehyde,acetaldehyde and acetone accounted for 20%—50%,17%—54%and 22%—55%,respectively.Based on the OBM model,the photochemical oxidation of alkenes and isoprene was found to be the main pathway for the secondary formation of formaldehyde;The secondary formation of acetaldehyde and acetone is controlled by alkenes and alkanes,respectively.The pollution of carbonyls is affected by the transportation along Mianyang—Deyang—Chengdu line in Sichuan Province.Formaldehyde and acetaldehyde in the ambient air around each site of Chengdu Plain urban agglomeration have carcinogenic health risks to the exposed population,while formaldehyde in the ambient air around most sites has non-carcinogenic health risks to the exposed population.The carcinogenic health risk value and non-carcinogenic risk quotient value of formaldehyde and acetaldehyde in the ambient air around most sites were higher in pollution days than in clean days.In conclusion,great importance should be attached to the emission control of local carbonyls and their key precursors in Chengdu Plain Urban Agglomeration,and build an efficient joint prevention and control mechanism with the surrounding areas.So as to effectively reduce the contribution of higher on the polluted day to ozone pollution and protect the health of the population. |
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