| In this study,the typical points of Jinan were selected as the Shijiancezhan,Jiangongxueyuan,Jichuangerchang,and Paomaling.Those four points were identified as urban area,petrochemical area,painting area,and southern mountainous area according to the distribution area of the points and the typical emission sources nearby for functional area identification.Through continuous field observations,the pollution characteristics of ozone（O3）and volatile organic compounds（VOCs）in the ambient air of Jinan were analyzed.The influence of VOCs on O3 production was analyzed,and the O3production mechanism and sensitive species were analyzed based on the Master Chemical Mechanism（MCM）model.and the empirical kinetic simulation method（EKMA）was used to determine the optimal reduction ratio of VOCs and NOX.The source analysis of VOCs in different regions was combined with the characteristic ratio method and PMF as follows:（1）The results of O3 pollution characteristics were found that O3 concentration levels continue to improve in 2019-2021,with urban areas（189.35μg/m3）>painting areas（188.33μg/m3）>petrochemical areas（186.88μg/m3）in 2021,with 21.64%,21.39%,and 19.18%of days exceeding the standard,respectively.These O3 concentration levels are higher than those in Beijing-Tianjin-Hebei and surrounding areas（171.00μg/m3）.O3 concentration levels in the southern mountainous areas are significantly lower than those in other regions,but O3concentrations continue to rise in 2019-2021,with O3 concentration levels of 169.05μg/m3 in2021.O3 concentrations in painting areas,petrochemical areas,and urban areas are significantly higher in May-September,and O3 diurnal hourly changes have obvious single-peak characteristics,with changes in O3 concentrations in urban areas being higher during the day and lower at night,while in mountainous areas they are slower to rise during the day and lower at night.On O3 pollution days,O3 is weakly and positively correlated with PM10,PM2.5,and SO2 in urban areas,strongly and negatively correlated with NO and NO2,and O3 is positively correlated with other pollutants in mountainous areas;on O3 non-pollution days,O3 is negatively correlated with other pollutants,with the strongest correlation with NO2（0.68—0.72）.O3 is negatively correlated with temperature,solar radiation,and wind speed were positively correlated,with the largest correlation coefficient with temperature and negative correlation with humidity.At high O3 pollution levels,correlations with meteorological factors were enhanced,and the correlation between O3 and meteorological factors was weaker in southern mountainous areas.（2）The results of VOCs pollution characteristics show that the annual average concentration of VOCs in different regions in 2021 is in the order of petrochemical area（187.09μg/m3）>urban area（113.97μg/m3）>southern mountainous area（33.87μg/m3）.Except for the southern mountainous area,VOCs concentration in other functional areas in winter significantly reduced,among which the painting area VOCs concentration decreased the most.Petrochemical area alkanes accounted for the largest proportion,the dominant species is isopentane,with summer and winter concentrations of 38.18 and 30.67μg/m3,respectively.Painting area VOCs aromatic hydrocarbons accounted for the largest proportion,the dominant species is m/p-xylene（18.90μg/m3）and methylene chloride（16.27μg/m3）.Alkanes contribute the most to urban and southern mountainous areas.The results of the spatial distribution characteristics of VOCs based on the satellite interpretation analysis of formaldehyde（HCHO）2019-2021 showed that the HCHO column concentrations were higher in June than in December in the same year due to the strong atmospheric oxidation capacity in summer and the influence of plant-derived VOCs.There was a significant increase in HCHO column concentrations in Jinan from 2020 to 2021,and the high values of their concentrations spread from central and southwestern Jinan to the northern and southeastern regions.（3）The results of the analysis of the influence of VOCs on O3 formation based on ozone formation potential show that different regions of OFP petrochemical zone>urban area>southern mountainous area,and olefins are the components contributing the most to O3formation,followed by alkanes and aromatic hydrocarbons.Both ozone summer and winter ozone formation potential painting areas have the largest contribution of aromatic hydrocarbons to ozone formation（67.00%and 37.00%）,and the dominant species is m/p-xylene;petrochemical area has the largest contribution of alkanes（40.00%）in summer,and isoprene is the dominant species.Urban area has the largest contribution of olefins,and the dominant species is 1-butene.Southern mountainous area has the dominant species isoprene.The hourly variation characteristics of VOCs in different regions are influenced by the emission sources near the points,and O3 in petrochemical,painting,and urban areas mainly originates from photochemical reactions,while O3 in southern mountainous areas mainly originates from regional transport.O3 concentrations in each region are influenced by the variation of NOX and VOCs concentrations in a certain range,and low concentrations of NOX have a promotion effect on O3 production,while higher concentrations of NOX will inhibit O3production.（4）Based on the simulation of O3 production mechanism by MCM model,the results show that the O3 production rate in summer in petrochemical area（37.34 ppb/h）>urban area（14.19ppb/h）>painting area（12.61 ppb/h）>southern mountainous area（5.88 ppb/h）,the O3production rate in winter is lower than that in summer.The main pathways of O3 production are HO2+NO and RO2+NO（CH3O2+NO and other RO2+NO）,with the highest contribution of RO2+NO pathway in the painting area in summer and the largest contribution of HO2+NO in other regions.The O3 sensitivity experimental diagnosis results show that O3 production in each region is mainly controlled by VOCs,with O3 production being the most sensitive to cis-2-butene,trans-2-butene,m/para-xylene and isoprene in urban area,petrochemical area,painting area and southern mountainous area.The results of EKMA in Jinan show that under different pollution levels of O3,good,light,and moderate pollution VOCs/NOX are 4.13:1,3.24:1,and3.19:1,respectively.Most of the dates during the simulation period are in the VOCs control area.（5）VOCs source analysis results show that urban areas are more influenced by solvent use sources（35.1%）,oil and gas volatilization sources（25.2%）,and motor vehicle emission sources（19%）.VOCs in petrochemical areas mainly originate from oil and gas volatilization from petrochemical enterprises（35.4%）and VOCs in painting areas mainly originate from solvent use sources（37.9%）.Combined with VOCs dominant species analysis in each region,the dominant VOCs species that need to be controlled in the urban area are methylene chloride,1-butene,and cis-2-butene,which mainly originate from solvent use volatilization and motor vehicle emissions.The dominant species in the petrochemical area are isopentane and anti-2-butene,which mainly originate from oil gas volatilization.The dominant species that need to be controlled in the painting area are m/p-xylene,which are the main components of organic solvents.Therefore,the key species of VOCs in different regions are influenced by the emission sources,and should be controlled according to the analysis results and key species. |
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