Temporal And Spatial Variations Of Atmospheric Pollutants And Its Influencing Factors In Chongqing Urban Areas

The increasingly serious urban atmospheric pollution has brought serious harm to the ecological environment and human health.The Chongqing urban areas is a typical mountain city,and because of its special mountainous terrain and meteorological conditions and other factors,the atmospheric pollutants spread slowly.Using the atmospheric pollutants concentration data of 17 atmospheric environmental quality monitoring stations in the main urban area of Chongqing from 2015 to 2016 and the meteorological data of the sampling points of Huxi Town,and then using the methods of wavelet transform,spatial interpolation and trajectory clustering,through time and spatial scale,analysis the temporal and spatial variation characteristics and influencing factors of atmospheric pollutants in Chongqing urban areas.The results are as follows:1 In addition to O₃,the main trends of atmospheric pollutants in Chongqing city were mostly U-shaped.Monthly trends of atmospheric particulate matter concentration is "Single peak valley",high concentrations of January and February mainly,March and August in low concentration.The change trend of NO₂,SO₂ and CO concentration is relatively flat,and the concentration of high and low value is similar to that of the particles.The concentration of O₃ is generally bimodal.The seasonal variation characteristics,except O₃,the concentration of pollutants in the air were high in winter and low in summer.The concentration of particulate matter is winter > spring >autumn > summer,NO₂,SO₂,CO concentration in winter,autumn > spring > summer,O₃ is just the opposite.The concentration of particulate matter in the order of winter,spring,autumn and summer;NO₂,SO₂,CO concentration in the order of winter,autumn,spring and summer;O₃ is just the opposite.According to the results of wavelet analysis,there are five scales of PM_2.5 and PM₁₀ between 2015 and 2016,and the first main period is about 183 d.NO₂,SO₂,CO and O₃ have three or more periodic changes,the first main cycle were 183 d,182d,181 d and 161 d.2 The Concentration spatial distributions of PM_2.5,PM₁₀ and NO₂ are generally low in the south and high in north,and the high value area is mainly concentrated in the middle and west of the city.The low value area is mainly in the northwest ofJinyun Mountain and the northern suburb of the city.The spatial distribution of SO₂ is gradually decreasing from south to north,and the high value area in the south is mainly in the southwest of Banan District.Concentration of CO was broken like a massive distribution,the concentration of low-value areas appear mostly in mountain terrain.Concentration spatial distribution of O₃ is just the opposite of NO₂,it ’ s high in northwest,low in the Midwest.The concentration spatial distribution of PM_2.5 in the season is mainly characterized by high concentration in the central urban area,low concentration in the northwest and urban suburbs,and difference of concentration is mainly characterized by high in winter and low in summer.Concentration spatial distribution of O₃ is just the opposite of PM_2.5.3 Population density and housing construction area were positively correlated with PM_2.5,PM₁₀ and NO₂,and negatively correlated with O₃,SO₂ and CO,while negatively correlated with traffic mileage,but the correlation was not significant.From the whole year,the atmospheric temperature,humidity,total radiation,precipitation and wind speed are negatively correlated with PM_2.5,PM₁₀,NO₂,SO₂,and CO,and the atmospheric pressure and wind direction are positively correlated with its.The concentration of O₃ is just the opposite of above pollutants.In the daily precipitation less than 5mm,the scavenging activity is smaller;More than 5mm,the scavenging activity increases with the precipitation increase.The average clearance rate of summer precipitation intensity is negative from O₃ to NO₂,PM_2.5,SO₂,PM₁₀.The average removal rate of airborne pollutants is negative for 5 hours or less.The average clearance rates of PM₁₀,NO₂ and SO₂ were the highest at 10¹0h,10¹5h and 15²0h precipitation.The average removal rate of summer precipitation was in the order of SO₂>PM₁₀>NO₂>PM_2.5>O₃.The cumulative precipitation size is negatively correlated with the concentration of particulate matter.4 From the results of trajectory clustering analysis,the concentration of pollutants in winter is mainly affected by short-distance airflow from Tibet and Sichuan areas,while the effect of long-distance airflow is relatively small.During the three heavy pollution processes,the atmospheric pollution is mainly affected by the southwest air mass,the northwest and the southeast air mass,which is shorter and moving slower than that of the near ground.