| Yunnan-Guizhou Plateau(YGP)is located in the southwest China as a remote region with the clean atmospheric environment compared with eastern and central China.However,with the accelerating development,urban environment has become increasingly prominent in recent 4 years.Therefore,variations of urban air quality in YGP need to be further studied urgently for protecting the ecological environment.Guiyang,as the provincial capital,situated in the eastern YGP,with a typical urban area of low-latitude in plateau.The atmospheric environment background over the YGP and variations of urban air quality in Guiyang with atmospheric compound pollution and meteorological effects were analyzed based on environmental monitoring,meteorological observation soundings,AOD from MODIS remote sensing,measurement of solar radiation,urban resident populations and total energy consumption data from 2013 to 2016 for comprehensive understanding urban atmospheric environment changes and meteorological drives in YGP.The main conclusions are as follows:1)There is clean air environment in YGP,with the regional annual averages of AOD below 0.2.The seasonal variations are denoted as spring>winter>autumn>summer.The spatial distribution concentrations of SO2、NO2、CO、O3、PM10 and PM2.5,affected by the regional transport of air pollutants from the Sichuan Basin,South Asia and the northwest Peral River Delta,presented lower in western YGP and higher in eastern YGP with the siginificant impact of topography on AOD.2)Expect for SO2,other air pollutant concentrations in Guiyang were lower than in Nanjing of the Yangtze River Delta during the same period.In 2013-2016,the concentrations of SO2、NO2、CO、PM10 and PM2.5 have decreased gradually as O3 has been significantly increased.The pollution frequency of O3,PM10 and PM2.5 was 0.5%,4.9%and 10.3%respectively.Industry still plays a leading role in urban air quality.Except for the concentration of O3 presenting suburbs>industrial area>residential area,other pollutants reveal industrial area>suburbs>residential area.3)Seasonal variations of ratio PM2.5/PM10 were ranged with winter(0.65-0.82)>autumn(0.57-0.70)>spring(0.53-0.68)>summer(0.42-0.58).O3 dominated atmospheric oxidation OX,contributing about 63%.Though urban atmospheric oxidation is at low level,a high conversion rate of secondary particles could reach 54.16%.Guiyang has experirenced urban compound pollution obviously with the reversed relations between O3 and PM2.5 in winter and summer.Strong atmospheric oxidation in summer promoted higher concentrations of secondary PM2.5 increasing significantly.Then PM2.5 weakens solar radiation to inhibit photochemical actions in winter.4)It is similar to a stable atmospheric condition with calm wind speed varying between 0.5-1.8m/s.Precipitation is abundant in summer,but deficient in winter.Thus accumulation of precipitation are 416.65 and 67.22 mm respectively.The BLH at 8 a.m was annually averged 1234.7 m,with summertime 1489.2 m,and wintertime 819.2 m as well as decreased to 866,995.4 and 666.3 m at 20 p.m respectively in the annual,summertime and wintertime averages.Air pollution processes were typically controlled by four patterns of ground weather situations.Temperature,air pressure,solar radiation and BLH are the key factors affecting urban air quality.The complex terrain over YGP could weaken the ability of wind for air pollutant transport.The East Asian monsoon climate with seasonal changes of precipitation in YGP excerted the scavenging effect on PM2.5 in summer and the hygroscopicity of PM2.5 in winter in Guiyang. |
