Study On Air Pollution Characteristics And Main Pollutants In Suzhou City

In Suzhou,the sustained and rapid development of economy has driven the progress of urbanization,the number of all kinds of enterprises is on the increase,scale has been expanded year by year,the speed of energy consumption is accelerating,and the motor vehicle inventory is rise rapidly more.In recent years,the days of atmospheric pollution are always hovered around 30%,atmospheric environment quality is not very optimistic,air pollution is not simply coal-smoke pollution,but shows the characteristics of mixed pollution.This research adopted the fuzzy comprehensive evaluation method to study atmospheric environment quality in Suzhou since 2013 to 2015,determined the membership grade of the city’s air quality and the main atmospheric pollutants;it analyzed the time variation characteristics of the main atmospheric pollutants based on the monitoring data,as well as the air quality index and the correlation of meteorological conditions;at the same time,in 2015,for example,it adopted the emission factor method to analyze the main source of atmospheric pollutants in Suzhou,and the contribution of different pollution sources.The conclusions are as follows:（1）According to exceed multiple method,the weights of different pollution factors are determined,the weights of air pollutants in Suzhou in descending order are: NO₂,PM2.5,PM10,O3,SO₂,and CO,therefore the main pollutant in Suzhou is NO₂,followed by PM2.5,then PM10,O3,SO₂,finally is CO.（2）The air quality level of Suzhou was Level Ⅲ in 2013,of which PM10 belonged to Level II,PM2.5 and NO₂ belonged to Level III,SO₂,CO and O3 were below Level I standard,belonged to Level I;air quality of Suzhou was Level II in 2014,of which PM10 belonged to Level II,PM2.5 and NO₂ belonged to Level III,SO₂,CO and O3 were lower than Level I standard,belonged to Level I;air quality of Suzhou city was Level II in 2015,of which PM10,PM2.5 and NO₂ belonged to Level II,SO₂,CO and O3 belonged to Level I.（3）The diurnal variation of AQI in Suzhou is remarkable.AQI value from 1 to 5 o’clock is gradually reduced,the air quality in this period is better;6 when AQI value reaches the first peak at 6 o’clock;air pollution is showed a trend of slow serious from 6 to 12 o’clock,and AQI value reaches the second peak at 11 o’clock;air quality improves slightly from 12 to 13 o’clock;AQI reaches the third peak of the day at 14 o’clock,15-19 AQI value is gradually increased from 15 to 19 o’clock,and AQI reaches the highest value of the day at 19 o’clock,as the air pollution in this period of time is the worst of the day;then AQI value decreases almost linearly in the following period of 20 to 24 o’clock,the pollutant concentration in the air is gradually reduced,and the air quality is gradually getting better.（4）The monthly variation of air quality in Suzhou city is obvious,shows an "U" variation trend.AQI is higher in January,exceeds Level II standard limits,air quality is Level III;AQI in February is slightly reduced than January;March to September,AQI index shows a trend of slow decline,and achieves the lowest in September,during this period,air quality is the best month of the year;September to December,AQI index shows a trend of rapid increase,and the air pollution is increasingly serious.（5）The concentration atmospheric pollutants in Suzhou present an obvious tendency of changing over season alternant.The concentration of PM2.5 is higher in spring and winter,and is relatively lower in summer and autumn;the level of PM10 is different in different seasons,pollution is most serious in winter,followed by spring,then autumn,concentration is the lowest in summer,the average concentration of the winter is reached 1.5 times of the summer;SO₂ pollution is serious both in autumn and winter,but no big changes in spring and summer;since 2013 to 2014,NO₂ pollution was concentrated in spring,autumn and winter,concentration was lower in summer,while in 2015,the NO₂ pollution was the worst in winter,concentration was slightly lower in spring and summer,concentration was the lowest in autumn;the concentration of CO was higher in autumn and winter,and lower in spring,concentration was the lowest in summer;O3 pollution was mainly in summer and spring,pollution was lighter in autumn,and the lightest in winter.（6）The monthly average AQI in Suzhou presents correlation with meteorological factors,including temperature,precipitation amount,relative humidity and wind power.AQI is highly negative correlated to the temperature,and the correlation is up to 0.88,which indicates that the impact of temperature on air quality is significant,namely,the higher of the temperature it is,the lower of AQI index it will be;the correlation of AQI to precipitation amount is-0.62,which illustrates the impact of precipitation amount on AQI is significant,season with higher precipitation amount,the air quality index is lower;the correlation coefficient of AQI and relative humidity is-0.41,which indicates the impact of the relative humidity on AQI is smaller in Suzhou;the impact of wind power on AQI is obvious,the correlation coefficient of AQI and wind power is 0.5,which illustrates that air quality index decreases with the increase of wind power.（7）Among 27 manufacturing industries,ferrous metal smelting and rolling processing industry,paper making and paper products industry,chemical raw materials and chemical products manufacturing,textile,computer communications,and other electronic equipment manufacturing industry are the main emission source,the sum of PM10 and PM2.5,SO₂,NOx,CO and VOCs emissions are accounted for 82.68%,82.36%,91.81%,87.20%,85.47% and 84.12% of the total respectively.（8）Different types of motor vehicles,the contribution rate of the exhaust emission to atmospheric pollutants is different.For PM10 and PM2.5,the heavy truck shares the highest part,followed by station wagon;emissions of SO₂ of station wagon is the largest,heavy truck took the second place,in numerous models,the emissions of NOx of station wagon accounts for the highest proportion,the emissions of heavy duty truck are lower than the station wagon,which is the second largest model contributed to the NOx emission;station wagon is a major model contributed to the VOCs and CO emissions.（9）The emissions of different sources of atmospheric pollutants are quite different.Electricity,heat power production and supply,and inorganized construction dust non-point source are the primary source of PM10;electricity,heat power production and supply industry have contributed the most to PM2.5,achieves 24.70%;the contribution of non-point source of production process to PM2.5 is slightly lower,its value is 22.35%;the SO₂ are mainly from electricity and heat power production,supply industry and industrial combustion source,both are accounted for 81.31% of the total;electricity,heat power production and supply industry are the main sources of NOx,followed by the vehicle exhaust and emission of industrial combustion source;CO is mainly from production process,followed by motor vehicle exhaust;VOCs emission sources are mainly motor vehicle exhaust and non-point source of production process,and the share rate of the rest emission sources is relatively lower.