Research On The Air Quality Status Of 14 Cities In Jiangsu And Shanghai And The Characteristics Of VOCs In Suqian City

While the economic development and urbanization process of the Jiangsu and Shanghai areas are developing rapidly,the problem of air pollution has become more significant.Based on the data of 6 pollutant concentrations from 99 monitoring sites in 14 cities in Jiangsu and Shanghai from 2015 to 2020,this paper studies the time distribution characteristics and urban distribution characteristics of air quality in 14 cities in Jiangsu and Shanghai,and compares the environmental air quality and pollutant concentration levels.The change characteristics of different time scales,focusing on the analysis of the daily change characteristics,correlation and influence factors of PM_2.5 and O₃.Through continuous sampling at multiple points,the pollution characteristics of VOCs in summer in Suqian and their contribution to O₃ and SOA were analyzed,and the source of VOCs was analyzed in conjunction with the PMF receptor model.The main conclusions of this paper are:(1)From 2015 to 2020,the air quality in the 14cities of Jiangsu and Shanghai will generally improve,but there are differences between cities.Among them,the increase in Suqian is the most momentous,and the decrease in Wuxi is the most significant.AQI and 6 pollutants show a decreasing trend year by year.From the average seasonal change,PM_2.5,PM₁₀,SO₂,NO₂ and CO are high in winter and low in summer,and O₃ is high in summer and low in winter.From the perspective of monthly average changes,the monthly average concentration changes of PM_2.5,CO,PM₁₀,SO₂,and NO₂ showed a"U"-shaped curve distribution,and the monthly average concentration of O₃showed a bimodal curve distribution.In most cities,PM₁₀ and PM_2.5 reached the lowest and highest values in August and January,respectively;while O₃ was highest in June and July,and lowest in January and December.(2)The air quality difference between 14 cities in Suzhou and Shanghai is mainly related to PM_2.5,PM₁₀,and O₃.In terms of spatial distribution,AQI,PM₁₀,and PM_2.5 show a trend of increasing gradually from southeast to northwest.Xuzhou,Suqian,and Huai'an are high value areas,while Shanghai,Suzhou,and Nantong are low-value areas.The latitudinal distribution of NO₂ is roughly expressed as southern cities>northern cities,with Changzhou,Shanghai,Suzhou,and Nanjing being high value centers.High-value centers of O₃ are located in the central cities of Yangzhou.Taizhou and Yancheng,and the low-value centers are located in the northern cities of Lianyungang and Xuzhou.The CO concentration is approximately in the east<west,and Nanjing,Xuzhou,and Suqian are high-value areas.(3)The average daily concentration of PM_2.5 in the cities of Jiangsu and Shanghai showed a bimodal pattern.Peak concentration of PM_2.5 appears around 08:00.The bottom value appears around 16:00-17:00,and the second peak appears at22:00-24:00.The diurnal variation trend of O₃ presents an obvious unimodal pattern,reaching a peak at 13:00-15:00.Cities in Jiangsu and Shanghai showed significant O₃ pollution characteristics and PM_2.5 pollution characteristics in summer and winter,respectively.Elevated concentrations of PM_2.5 will inhibit ozone pollution.When the ozone concentration is higher than 100?g/m³,P-O is positively correlated,and this trend becomes more significant as the O₃ concentration increases.From the perspective of seasonal distribution,P-O is negatively correlated in winter.There is a good correlation in summer.In terms of correlation with meteorological elements,temperature is negatively correlated with PM_2.5,and positively correlated with O₃.A relative humidity level of 70%-80%is conducive to the accumulation of PM_2.5 and O₃.It is beneficial to the accumulation of pollutants under small wind conditions,and promotes the diffusion and dilution of pollutants under high wind conditions.(4)depending on the analysis of VOCs in Suqian City,alkanes(55.8%)and aromatic hydrocarbons(19.4%)are the main VOCs in Suqian City.The variation characteristics of the four VOCs components(alkanes,alkenes,acetylene and aromatics)are relatively consistent.C2?C5 alkanes,acetylene,ethylene,toluene,m/p-xylene are the principal VOCs pollutants in Suqian.The contribution ratios of the four types of VOCs in Suqian to O₃ are:aromatic hydrocarbons(38.3%?50.3%)>olefins(31.3%?36.7%)>alkanes(16.5%?23.5%)>acetylene(1.3%?1.9%).Aromatichydrocarbonsare the principal contributors of SOA.The highest sources of VOCs in Suqian include:motor vehicle exhaust,natural sources,paint use,solvent volatilization,factory emissions,oil and gas volatilization,combustion sources,and petrochemical sources.