沙尘天气对兰州市大气污染物置换和叠加作用

摘要

本文分析了2014～2015年兰州市春季沙尘天气期间颗粒污染物PM10、PM25及气态污染物SO2、NO2、CO和O3质量浓度的演变规律.结果表明,沙尘天气造成PM10和PM2.5浓度上升,而SO2、NO2和CO浓度表现为降低(置换型)或升高(叠加型),O3浓度受沙尘天气影响不明显.置换型的PM10和PM2.5平均质量浓度分别为1086.9和286μg/m3,SO2、NO2和CO平均质量浓度分别为16.7、41.0和1.02x103μg/m3.叠加型的PM10和PM2.5平均质量浓度分别为383.2和116.2μg/m3,SO2、NO2和CO平均质量浓度分别为24.5、49.1和1.19×103μg/m3.置换型的PM10和PM2.5平均质量浓度分别为叠加型的2.8和2.4倍,叠加型的SO2、NO2和CO平均质量浓度分别为置换型的1.47、1.2和1.17倍.置换型对应的气象条件为近地面东北方向大风、显著降温和高压,即强冷空气活动时,PM10和PM2.5浓度上升,而SO2、NO2和CO浓度显著减小,沙尘源地主要为塔克拉玛干沙漠和青藏高原北部地区,影响气流多为1500～6000m高空西北气流.叠加型则为近地面东北风向弱风,气温和气压无明显波动,即弱冷空气活动时,初期PM10和PM2.5浓度上升,同时SO2、NO2和CO浓度略下降,而后PM10和PM2.5维持高值时SO2、NO2和CO浓度亦上升,沙尘源地主要为巴丹吉林沙漠,影响气流多为1500m以下低空西北气流.%Characteristics of the concentrations of particulate pollutants PM10,PM2.5 and gaseous pollutants SO2,NO2,CO and O3 during spring dust storms in 2014 and 2015 were analyzed.The result showed that dust storms could cause the increasement of PM10 and PM2.5 for both the replacement type and the addition type,while the decreasement of SO2、NO2 and CO for the replacement type,while the increasement for the addition type.However,the concentration of O3 almost kept stable during spring dust storms.For the replacement type,the average concentrations of PM10 and PM2.5 were 1086.9 and 286μg/m3 respectively,and those of SO2,NO2 and CO were 6.7,41.0 and 1.02× 103μg/m3 respectively.For the addition type,the average concentrations of PM10 and PM2.5 were 383.2 and 116.2μg/m3 respectively,and those of SO2,NO2 and CO were 24.5,49.1 and 1.19× 103μg/m3respectively.In short,the average concentrations of PM10 and PM2.5 of the replacement type were 2.8 and 2.4 times more than those of the addition type,and the average concentrations of SO2,NO2 and CO of the replacement type were 1.47,1.2 and 1.17times more than those of the addition type.The meteorological conditions of the replacement type were strong northeast wind near surface,significant temperature decreasement and high pressure.In other words,strong cold air activity resulted in increase of PM10 and PM2.5 and decrease of SO2,NO2 and CO.The dust sources of this type were in Taklimakan Desert and the northern part of Qinghai Tibet Plateau,and the influence flow were high-altitude northwest wind at the height of 1500 to 6000 meters.However,the meteorological conditions of the addition type were weak northeast wind near surface,no significant change of temperature and pressure.In other words,weak cold air activity resulted in increacement of PM10 and PM2.5 and decreacement of SO2,NO2 and CO at the early stage.And then,the concentrations of PM10 and PM2.5 kept at high levels,and the concentrations of SO2,NO2 and CO start to rise.The dust source of this type were mainly in Badan Jilin desert,and the influence flow was low-altitude northwest wind below 1500meters.