Institute of Low Temperature Science, Hokkaido University, Sapporo, 060-0819, Japan.
Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan.
Sci Rep. 2018 Oct 5;8(1):14861. doi: 10.1038/s41598-018-32864-7.
It is critical to understand how variations in chemical composition in surface seawater (SSW) affect the chemistry of marine atmospheric aerosols. We investigated the sea-to-air transfer of dissolved organic carbon (DOC) via cruise measurements of both ambient aerosols and SSW in the Oyashio and its coastal regions, the western subarctic Pacific during early spring. Sea spray aerosols (SSAs) were selected based on the stable carbon isotope ratio of water-soluble organic carbon (WSOC) (δC) and concentrations of glucose as a molecular tracer in marine aerosols together with local surface wind speed data. For both SSA and SSW samples, excitation-emission matrices were obtained to examine the transfer of fluorescent organic material. We found that the ratios of fluorescence intensity of humic-like and protein-like substances in the submicrometer SSAs were significantly larger than those in the bulk SSW (~63%). This ratio was also larger for the supermicrometer SSAs than for the SSW. The results suggest significant decomposition of protein-like DOC on a timescale of <12-24 h and/or preferential production of humic-like substances in the atmospheric aerosols regardless of the particle size. This study provides unique insights into the complex transfer of DOC from the ocean surface to the atmosphere.
了解表层海水中化学成分的变化如何影响海洋大气气溶胶的化学性质至关重要。我们通过在早春期间对西北太平洋鄂霍次克海及其沿海地区的大气气溶胶和表层海水进行的实地测量，研究了通过海气传输溶解有机碳（DOC）的情况。根据水溶性有机碳（WSOC）（δC）的稳定碳同位素比值和葡萄糖作为海洋气溶胶中分子示踪剂的浓度，以及当地表面风速数据，选择了海水飞沫气溶胶（SSA）。对于 SSA 和 SSW 样品，我们获得了激发-发射矩阵，以检查荧光有机物质的转移。我们发现，亚微米级 SSAs 中类腐殖质和类蛋白物质的荧光强度比值明显大于 SSW（约 63%）。对于超微米级 SSAs，这一比值也大于 SSW。结果表明，在<12-24 h 的时间尺度上，类蛋白 DOC 发生了显著分解，或者在大气气溶胶中优先产生了类腐殖质物质，而与颗粒大小无关。本研究为从海洋表面向大气中传输 DOC 的复杂过程提供了独特的见解。
