一次沙尘事件对沿海及海洋大气气溶胶中金属粒径分布的影响

Impact of a Dust Event on the Size Distribution of Metal Elements in Atmospheric Aerosols at a Coastal Region and over the Ocean

于2016年3～4月在青岛、东海及西北太平洋连续采集了气溶胶分级样品,测定了样品中Al、Na、Fe、Mg、K、Cu、Pb、Cd等金属元素的浓度,分析了沙尘事件下气溶胶中金属元素的粒径分布特征,并初步讨论了气溶胶中金属来源及影响因素.结果表明,受此次沙尘事件影响青岛近岸样品中Al、Fe、K、Na、Cu、Pb的浓度增加了85%～1 400%,而金属Cd浓度降低8%;海洋样品中Al、Fe、K、Cu、Pb、Cd浓度增加了163%～4 580%,而Na浓度降低62%.沙尘对气溶胶中金属元素的粒径分布影响显著,青岛近岸和海洋气溶胶中K由双模态分布变为粗模态分布; Pb、Cd由细模态分布变为双模态分布;Cu仍呈双模态分布,但粗颗粒上的占比增加; Al、Fe、Mg、Na则保持粗模态分布.沙尘事件对近岸与海洋样品的影响不同,青岛近岸沙尘气溶胶中Al、Fe、Mg、Na、K的峰值粒径位于2. 1～3. 3μm,而海洋样品的峰值向粗粒径移动至3. 3～4. 7μm;沙尘影响下近岸气溶胶中Al、Fe、Mg、Na、K、Pb、Cd在粗颗粒上的占比下降了1%～35%,而东海样品中这些金属的粗粒子占比上升了4%～33%,可能与吸湿增长以及沙尘的传输路径和高度有关.

Size-segregated aerosol samples were collected in the Qingdao coastal region and over the East Sea and the Pacific Northwest from March to April in 2016, and the concentration of metal elements (Al, Na, Fe, Mg, K, Cu, Pb, and Cd) were analyzed. The characteristics and the variation in the size distribution of the metal elements in the samples during dusty weather were discussed, as well as the sources and factors that influence the metals. The results indicated that the concentration of Al, Fe, K, Na, Cu, and Pb in the aerosols in the Qingdao coastal samples increased significantly by 85%-1400%, while the concentration of Cd decreased by 8%;the concentrations of Al, Fe, K, Cu, Pb, and Cd in the samples over the ocean increased by 163%-4580%, while the concentration of Na decreased by 62% during dusty weather. In addition, the size distribution of K changed from a double-peak to a coarse peak mode;that of Pb and Cd changed from a fine peak mode to a double-peak distribution. Cu still presented a double-peak distribution in which the proportion of coarse particles increased;Al, Fe, Mg, and Na showed little variation in their size distribution with a single peak in coarse mode. The dust event had different effects on the size distributions of the metal elements in the coastal and marine aerosol samples. The size distribution of the metal elements (Al, Fe, Mg, Na, and K) in the aerosols collected at the Qingdao coastal site had one peak of 2.1-3.3 μm during dusty weather;the peak moved to 3.3-4.7 μm for marine samples. In addition, the proportion of Al, Fe, Mg, Na, K, Pb, and Cd in the coarse mode decreased by 1%-35% for dust aerosol samples collected in Qingdao coastal region, whereas the proportion of these metals in coarse mode increased by 4%-33% for samples collected over the East Sea. This difference may be related to the hygroscopic growth, transport path, and height of the dust.