呼包鄂地区沙尘期间大气污染特征研究

Characteristics of Dust Pollution Days in Hohhot-Baotou-Ordos Region,China

为研究沙尘天气下典型大气污染特征,选择呼和浩特市、包头市、鄂尔多斯市(简称“呼包鄂地区”)为研究对象,分析了呼包鄂地区2016年春季3月1日-5月31日的PM10与PM2.5数据,利用CMB(化学质量平衡)受体模型、后向轨迹模型研究了呼包鄂地区污染源的特征,通过富集因子法评估了人类活动对沙尘天气的影响,最终通过特征比值法对沙尘天气与非沙尘天气进行了区分.结果表明:①沙尘天气与非沙尘天气时,呼包鄂地区PM10、PM2.5中主要化学组分均为Si、Ca、Al、Fe、OC、SO4^2-与NO^3-.沙尘天气时,ρ(PM10)与ρ(PM2.5)的差值大于非沙尘天气,较高的ρ(Al)、ρ(Si)、ρ(Ca)说明呼包鄂地区受到较大的沙尘天气影响.②CMB受体模型源解析结果表明,沙尘天气时扬尘源对PM10与PM2.5的贡献率分别为59.3%、48.7%,说明PM 10和PM2.5的主要污染源均为扬尘源.后向轨迹模式模拟表明,呼包鄂地区的沙尘主要来自其西北部地区.③元素Na、K、Mg的EF(富集因子)在PM10与PM2.5中均大于1.0,Si、Cu的EF在PM2.5中均大于1.0,但在PM10中小于或等于1.0;依据EF表征级别,自然因素对PM2.5和PM 10的影响程度均较大,并且PM2.5受人类活动影响的程度大于PM10.通过特征比值发现,ρ(Si)/ρ(Al)大于1.7且ρ(Si)/ρ(Fe)大于2.2可作为呼包鄂地区典型沙尘天气的界定.研究显示,呼包鄂地区春季受到较大程度的沙尘影响,这些沙尘主要来自其西北部地区,通过特征比值法可以对呼包鄂地区沙尘天气进行界定.

In order to understand the characteristics of dust pollution,PM10 and PM2.5 samples were collected in Hohhot-Baotou-Ordos Region from March 1 st to May 31 st,2016,and chemical species were analyzed,including organic carbon,elemental carbon,inorganic ions and elements.The chemical mass balance receptor model(CMB)and backward trajectory model were used to infer and quantify the source impacts.The enrichment factor was used to evaluate the effect of human activities on PM during the dust pollution days,and the characteristic ratios were determined to identify the dust pollution days.The results showed that the main chemical components in PM10 and PM2.5 in Hohhot-Baotou-Ordos Region were Si,Ca,Al,Fe,OC,SO4^2-,NO^3-.The difference betweenρ(PM10)andρ(PM2.5)during the dust pollution days was greater than that in non-dust pollution days.The highρ(Al),ρ(Si),ρ(Ca)during the dust pollution days indicated that PM was greatly affected by the dust.Source apportionment results showed that the dust was the largest contributor to PM 10(59.3%)and PM 2.5(48.7%)during the dust pollution days.The backward trajectory model results showed that the dust in Hohhot-Baotou-Ordos Regions mainly came from the northwest.The enrichment factors of elements Na,K and Mg were all greater than 1.0 in PM10 and PM2.5,and Si and Cu were greater than 1.0 in PM2.5,but less than or equal to 1.0 in PM10.It indicated that natural factors had significant influence on both PM2.5 and PM10,while human activities showed larger influence on PM2.5 than PM 10.ρ(Si)/ρ(Al)was greater than 1.7 andρ(Si)/ρ(Fe)was greater than 2.2 during the dust pollution days,which could be an indicator to identify the dust pollution day in Hohhot-Baotou-Ordos Region.The results showed that the Hohhot-Baotou-Ordos Region is mainly affected by the dust in spring,which mainly came from the northwest of Hohhot-Baotou-Ordos Region,and the characteristic ratios can be used to define the dust pollution days.