北京雾霾天气下气溶胶中水溶性无机盐粒径分布

Mass size distributions of the water-soluble inorganic ions in the haze-fog weather of Beijing

为了解北京雾霾天气下气溶胶中水溶性无机盐粒径分布特征,利用Andersen 8级采样器采集2010-10-07—10较严重雾霾天气时的大气气溶胶样品。用离子色谱(IC)对样品中的水溶性无机盐进行分析。结果表明,雾霾天气下,PM2.1和PM9中总水溶性无机盐的质量浓度分别为130.1μg/m3和252.2μg/m3,水溶性无机盐污染严重。SO24-、NO3-、NH4+、Ca2+是PM2.1和PM9中最主要的水溶性无机盐。SO24-、Cl-、K+主要呈现双模态分布,即在粗细粒子中均有分布;NO3-和NH4+主要呈细模态分布;Ca2+、Na+、Mg2+除在10-09呈现双模态分布外,主要呈粗粒子模态分布。气溶胶中的离子主要以NH4NO3、Ca-SO4和CaCO3的形式结合。

The paper intends to present our research report on the mass size distributions of the water-soluble inorganic ions in the haze-fog weather in Beijing in accordance with our statistical results from October 7 to 10,2010.In order to study the size distribution of water-soluble inorganic ions in HF,we have collected the particle samples by using an Andersen cascade impactor.We have also analyzed the concentrations of water-soluble inorganic ions via IC.The results of our analysis reveal that the average concentrations of the total water-soluble inorganic ions in PM2.1and PM9 are 130.1 μg/m3 and 252.2 μg/m3,which suggests the serious pollution brought about by the water-soluble inorganic ions in the HF.The secondary inorganic components（SO2-4,NO-3 and NH＋4） and Ca2＋ are the dominant contributors of water-soluble inorganic ions,accounting for 86.5% and 79.4% of the total water-soluble inorganic ions in PM2.1 and PM9,respectively.The secondary inorganic components mainly originate from the anthropogenic sources from the transformation of the precursors of SO2,NOx,NH3.Ca2＋ is mainly from the re-suspended road dust,sand-soil dust,and the construction dust.The serious air pollution in HF episodes proves to be correlated with the emission of the pollutants from the anthropogenic sources and the meteorological conditions.For example,SO2-4,Cl-and K＋ indicate a bimodal distribution,which exist both in the fine and coarse particles,with NO-3 and NH＋4 being the dominant in the fine mode.As for the existence of Ca2＋,Na＋ and Mg2＋,it can be thought that they are mainly the results of the accumulation of the coarse fraction,though they were just a bimodal distribution in Oct.9.Statistically speaking,the average equivalent ratio of ∑[cations]/∑[anions] in HF episodes turned to be 3.5,suggesting that the fine particles belong to alkaline.However,Ca2＋ is likely to be the most abundant cations in HF,which is likely the factor leading to the alkalinity of aerosol in these days.The high ratio of ∑[cations]/∑[anions] in HF is most likely due to the unmeasured carbonate.The water-soluble inorganic ions were mainly combined as NH4NO3,CaSO4 and CaCO3 in HF.