青岛大气气溶胶中微量元素溶解度及影响因素

Solubility of trace elements in atmospheric aerosols and determination factors in Qingdao,China

利用2012年12月在青岛采集的31个总悬浮颗粒物(TSP)样品,分析其中11种微量元素的总浓度和溶解态浓度,讨论了沙尘负载、气溶胶来源、酸过程及天气条件对微量元素溶解度的影响.结果表明,Fe和Al的溶解度<5%,Pb、Ba、Bi的为10%左右,Cu、V、Cd、Mn的为20%~30%,Zn和As的约为40%.随着沙尘负载量的增加,气溶胶中微量元素溶解度呈规律性递减.气团后向轨迹聚类分析和正矩阵因子分析(PMF)结果显示,受人为源影响的气溶胶中微量元素溶解度明显高于受沙尘源影响的,受二次生成源和海洋源影响的的气溶胶中微量元素溶解度明显高于受土壤源影响的.大气酸过程是造成这些差异的主要原因.相关性分析表明,SO_4^(2-)、NO_3^-和有机酸等酸组分均对微量元素溶解度有一定影响.霾天时气溶胶中微量元素溶解度明显低于雾天的,其原因为酸组分在较高的相对湿度下更能促进微量元素溶解度的提高.

Thirty-one 24-h total suspended particulate (TSP) samples were collected at an urban site in Qingdao inDecember 2012. The total concentrations of eleven trace elements in the samples were determined as well as theirwater-extracted concentrations. The solubility was <5% (on average, the same definition is applicable for latter) for Fe andAl, ~10% for Pb, Ba and Bi, 20%~30% for Cu, V, Cd and Mn; and ~40% for Zn and As. The determination factors of thesolubility were further studied, in terms of dust loading, the origins of aerosol, acid processing and weather conditions. Ingeneral, the obtained solubility was increased with decreasing dust loadings. Combining the results from the backwardtrajectory clustering analysis and the positive matrix factorization (PMF), the solubility of trace elements in TSP mainlyoriginated from anthropogenic sources was found to be larger than the value in TSP originated from Asian dust. The samewas true when secondary and marine aerosols were compared against soil-derived aerosols. Atmospheric acidificationprocesses can increase the solubility, depending on aging extents. SO42- and NO3- as well as the organic acids played a rolein acidification processes. In addition, fog events apparently favored a higher solubility when comparing to haze eventsbecause of higher relative humidity therein.