夏季南海气溶胶微量元素浓度、溶解度及干沉降通量

搭载国家自然科学基金委南海东北部共享航次（NORC2017-05）,于2017年6月9日-8月11日在南海东北部采集气溶胶样品,使用淋溶装置得到气溶胶中微量元素（Al、Fe、Ti、Cr、V、Ba、Mn、Co、Ni、Pb、Cu、Zn）的溶解态浓度和溶解动力学曲线,混酸消解后用高分辨率电感耦合等离子体质谱测得其总浓度,并计算溶解度和干沉降通量.结果表明,夏季南海北部气溶胶中微量元素溶解态浓度、总浓度和干沉降通量均小于大多数陆架边缘海.微量元素溶解度相对较大,原因主要是气溶胶颗粒经过长距离输运后粒径较小,且经历的大气酸过程和云过程对元素溶解度影响显著.气溶胶中微量元素在Milli-Q水中25 min左右达到溶解平衡,后续以pH=2的HCl淋溶.酸淋溶过程中大部分微量金属的溶解度略有增加,约占水溶出量的30%~50%,而Pb在酸溶液中显著溶出,酸溶出量可达水溶出量的140%,表现出潜在的环境效应.夏季大气气溶胶输送的Fe占南海东北部混合层溶解态Fe的0.13%~6.00%,对浮游植物初级生产具有一定的支持功能.

Trace element concentrations, solubilities and dry deposition fluxes in aerosol samples collected in the South China Sea in summer

From June 9 to August 11 2017, aerosol samples were collected during the shared voyage carried out in the northeast South China Sea (SCS, NORC2017-05) which was supported by the National Natural Science Foundation of China. Dissolvable concentration and kinetic dissolution concentration of trace elements (TEs) in the aerosol samples, including Al, Fe, Ti, Cr, V, Ba, Mn, Co, Ni, Pb, Cu and Zn, are analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after leaching experiments using different leaching solvents. Total concentrations of TEs in the aerosol samples are analyzed by ICP-MS after mixed acid digestion. Solubilities and dry deposition fluxes of TEs are calculated based on dissolvable and total concentrations. The dissolvable concentrations, total concentrations and dry deposition fluxes of TEs in the aerosol samples of the northeast SCS in summer are lower than those in other marginal seas. However, the solubility of TEs in the northeast SCS is relatively higher, mainly due to the small particle size of aerosol particles after long-distance transportation, and the atmospheric acid and cloud processes that they undergo have a significant effect on the solubility. The kinetic dissolution of TEs in the aerosol samples reached equilibrium in Milli-Q water for about 25 minutes, followed by leaching with pH=2 HCl solution. The solubility of most TEs in acid leaching increased slightly, accounting for about 30%~50% of water dissolution. However, Pb showed significant dissolution in the acid solution, up to 140% of water dissolution, indicating potential environmental effects. We estimate the contribution of dissolvable Fe from atmospheric depositions to the surface mixed layer of northeast SCS, which accounts for nearly 0.13%~6.00% of the stock dissolved Fe and has potential influence on the primary productivity in the northeast SCS in summer.