[A-CG41] 海洋表層－大気間の生物地球化学

[ACG41-P01] 複素散乱振幅センサーを用いた海水粒子の粒径別濃度と粒子種の分析

*吉田 淳¹、當房 豊¹、足立 光司²、茂木 信宏³、川合 義美⁴、笹岡 晃征⁴、小池 真⁵ (1.国立極地研究所、2.気象研究所、3.東京都立大学、4.海洋研究開発機構、5.東京大学)

キーワード：海水粒子、海洋エアロゾル、生物地球化学循環

Oceanic suspended particulate matter (SPM) plays important roles in the coupling of climate and biogeochemical cycles via ocean-atmosphere interactions. However, methods for quantifying the properties of SPM in seawater have not yet been well established. Here we present the application of the recently developed complex amplitude sensor (CAS) for analyzing the complex forward-scattering amplitude of individual SPM (0.2–5.0 µm in diameter) obtained at depths of 0–100 m during a research cruise in the northwest Pacific. The measured distribution of the complex amplitude indicated that the CAS-derived SPM data can be roughly classified into five major types. The comparison with the complex amplitude data on reference samples combined with scanning electron microscopy suggests that these types would be mainly attributed to diatom fragments, carbonaceous materials (likely, organic matter), mineral dusts, iron oxides, or black carbon. The depth profiles reveal that higher concentrations of SPM, presumably dominated by diatom fragments and carbonaceous materials with peak diameters of 0.7–1.0 µm, were typically observed along with the layers of elevated chlorophyll a concentrations and turbidity values. Based on this case study, we discuss potentials and challenges of the CAS instrument in measuring the size-resolved concentrations and compositions of SPM in seawater.