Tempo-Spacial Characteristics Of Air Quality In Wuhan And The Influence Of Meteorological Parameters

The rapid development of population and economy has led to a sharp increase in energy consumption,which has stretched the capacity of limited environmental capacity to accommodate atmospheric pollutants.As a result,environmental pollution problems occurs more and more frequently.With the arising of the public awareness of environmental protection,air pollution has drawn great attention from our government and the general public..Based on data sets of the concentrations of six criteria air pollutants(PM₁₀,PM_2.5,SO₂,NO₂,CO,O₃)and related meteorological parameters from 2005-2017,multivariate statistical methods such as factor analysis and cluster analysis were employed to analyze the spatial and temporal distribution of pollutants in Wuhan.In addition,correlations among various pollutants and meteorological variables were explored.Main results are as follows:1.During 2005-2017,annual mean concentrations of SO₂,PM₁₀,PM_2.5,and O₃fluctuated slightly,showing a weak decline trend.As for NO₂,large inter-annual variation was observed.On the other hand,the average annual concentration of CO during these years were relatively stable.The average annual concentrations of SO₂met the Class II standard of national ambient air quality standard.However,PM_2.5 and NO₂ levels exceeded the Class II standard..With the exception of 2012,the average annual concentrations of PM₁₀ were all higher than the limit value set in the national air quality standard.2.Distinctive seasonal and monthly variation patterns were observed.The concentrations of SO₂,NO₂,PM₁₀,PM_2.5 and CO were high in winter and low in summer,while the concentration of O3 showed an opposite seasonal trend.The concentrations of SO₂,NO₂,PM₁₀,PM_2.5 and CO were significantly higher in December,January and February than those in other months,with the highest in January.For O₃,the peak value occurred in June and the lowest in December.3.Different pollutants showed different diurnal variation patterns.NO₂ and CO concentration peaked at 3:00-4:00 and lowest value occurred at 15:00 and 17:00.The lowest or second lowest level for SO₂ was observed at 3:00,then increased gradually to reach the early peak at 9:00-10:00.PM10 and PM_2.5 had a trough at 17:00-18:00,while the peak was not prominent.Diurnal curve of O₃ exhibited a trough and a peak at 8:00-9:00 and18:00-19:00,respectively,which was in contrary with NO₂ curve.4.Concentrations of PM₁₀,NO₂ and CO in urban area were higher than those in the suburban area.On the other hand,elevated levels for O₃ and SO₂ were found at the suburban area.Especially,high concentrations for O₃ and SO₂ were noticed in the northern part and southern part,respectively.The spatial distribution of pollutants showed that the air quality of Qingshan District,which is highly developed in industry,is relatively poor.Furthermore,both factor analysis and clustering analysis showed that 21 monitoring sites could be classified as relatively clean areas,areas mainly affected by O₃ and NO₂,and those with serious pollution.5.The correlation among various pollutants and meteorological parameters in different seasons is different.For example,O₃ was significantly positively correlated with temperature in spring,summer and autumn,but not the case in winter.Different pollutants exhibited different relationship with meteorological variables in the same season.For example,in summer,SO₂,PM₁₀ and O₃ were significantly negatively correlated with relative humidity,while CO was positively correlated with relative humidity.There was a significant positive correlation between SO₂,NO₂,PM₁₀,O₃,CO and PM_2.5.It should be mentioned that when the rainfall and wind speed are within a certain range,they can more effectively promote the removal and dilution of pollutants.6.Analysis of a typical heavy pollution episode showed that the formation of secondary fine particles was the main pollutants.Vehicular emission and the incomplete combustion of fuel contributed to the formation of this heavy pollution episode.Variation trend of PM_2.5 concentration and meteorological parameters showed that low temperature,high pressure and high wind speed would lead to the accumulation of pollutants.Furthermore,factor analysis and clustering analysis in 21monitoring sites during the heavy pollution event revealed that the classification of monitoring sites was also different due to the difference in the number of main components extracted under different types of weather condition and the meaning of each principal component.Nevertheless,pollutant concentrations at each monitoring site are all affected by geographical location,local pollution source intensity and meteorological variables.