Variation Characteristics Of PM₁₀ And Reactive Gases And Its Influencing Factors At Lin'an Regional Background Station In Yangtze River Delta Region

Concentration variations of PM₁₀ and reactive gases in the Yangtze River Delta Region were analyzed and its influencing factors were investigate,using data of PM₁₀ mass concentration?2010 – 2015?,reactive gases?2006-2008 and 2013-2015?and main meteorological factors at the regional representative Lin'an Regional Atmosphere Background Station.The results show that:?1?PM₁₀ mass concentration met the Grade 2 Standard specified in the Ambient Air Quality Standards?GB3096-2012?for 96.17% of the time during 2010 – 2015.Diurnal PM₁₀ mass concentration peaked at 9:00 and 20:00,hit the low at 6:00 and 13:00,and was higher on weekend than on weekdays,aka the “weekend effect”.Monthly variation showed the lowest PM₁₀ mass concentration in July in summer and the highest in January,which negatively correlated with visibility.Annual average of PM₁₀ mass concentration at Lin'an decreased from 79?g/m³ to 56?g/m³ from 2010 to 2015,which is a moderate concentration level in China.?2?During 2006-2008 and 2013-2015,reactive gases concentration met the high compliance rate,and SO₂ decreased significantly.Diurnal concentration in NO_X and CO peaked at 8:00 or 9:00 and 19:00,and NO_X,SO₂ and CO hit the low at 14:00,while O₃ was the same variation as the solar radiation."Weekend effect" was obviously,and the result showed that 5.21% change in CO and 10.38% change in SO₂,which is the most significant.Annual average of NO_X had no change obvious,while SO₂ fell 86.0%,CO fell 15% and O₃ rose 12%.?3?PM₁₀ mass concentration correlated well with relative humidity,daily precipitation and local air pressure,which reached the correlation coefficient of-0.367,-0.254 and 0.249.Stronger wind also has greater impact on PM₁₀ mass concentration,because the maximum wind speed correlation coefficient was-0.119 while the 10 minutes wind speed was-0.087.Air pressure and relative humidity correlated well with reactive gas concentration?correlation = 0.379,0.394,0.174,-0.261 and correlation =-0.380,-0.374,-0.205,0.253?,and the reactive gases are all interconnected each other well.?4?Back-trajectories and cluster analysis reveal that prevailing air masses were from the northwest and the north in spring,autumn,and winter?the probability of occurrence was 36.5%,43.7% and 35.3%?,and from the sea and the coastal areas in the east in summer?with a probability of 34.7%?.Throughout the years,the dominant air masses were from the north?47.5% in 2010,55.8% in 2011,53.6% in 2012,51.1% in 2013 and 42.6% in 2015?,followed by southerly and east marine air masses.It is concluded that the majority air mass at Lin'an arrived from Anhui?39.0%?,northern Zhejiang,eastern ocean?30.1%?,and southern Guangdong,Fujian,western Zhejiang?22.0%?,and long-distance rapid transport from northern region?8.8%?.?5?Potential source contribution function?PSCF?and concentration-weighted trajectory?CWT?results suggest that PM₁₀ and reactive gases pollution mainly originated from the areas around the Yangtze River Delta region,including Shanghai,Anhui,Jiangsu and Zhejiang Provinces.