Mineral dust is the major source of external micro-nutrients such as iron (Fe) to the open ocean. However, large uncertainties in model estimates of Fe emissions and aerosol-bearing Fe solubility (i.e., the ratio of labile Fe (L_Fe) to total Fe (T_Fe)) in the Southern Hemisphere (SH) hampered accurate estimates of atmospheric delivery of bioavailable Fe to the Southern Ocean. This study applied an inverse modeling technique to a global aerosol chemistry transport model (IMPACT) in order to optimize predictions of mineral aerosol Fe concentrations based on recent observational data over Australian coastal regions (110°E–160°E and 10°S–41°S). The optimized (a posteriori) model did not only better capture aerosol T_Fe concentrations downwind from Australian dust outbreak but also successfully reproduced enhanced Fe solubility (7.8 ± 8.4%) and resulted in much better agreement of L_Fe concentrations with the field measurements (1.4 ± 1.5 vs. 1.4 ± 2.3 ng Fe m^–3). The a posteriori model estimates suggested that bushfires contributed a large fraction of L_Fe concentrations in aerosols, although substantial contribution from missing sources (e.g., coal mining activities, volcanic eruption, and secondary formation) was still inferred. These findings may have important implications for the projection of future micro-nutrient supply to the oceans as increasing frequency and intensity of open biomass burning are projected in the SH.

中文翻译：

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基于逆模型的澳大利亚沿海地区气溶胶铁溶解度评估：丛林大火对南半球生物可利用铁浓度的影响

矿物粉尘是外部微营养素的主要来源，例如通向海洋的铁（Fe）。然而，在南半球（SH）的铁排放量和含气溶胶的铁溶解度（即不稳定的铁（L _Fe）与总铁（T _Fe）之比）的模型估计中，存在很大的不确定性，这妨碍了对大气排放的准确估计。生物可利用的铁到南大洋。为了对基于澳大利亚沿海地区（110°E–160°E和10°S–41）的最新观测数据的矿物气溶胶中铁的浓度预测进行优化，本研究将逆建模技术应用于全球气溶胶化学迁移模型（IMPACT） °S）。优化的（后验）模型不仅可以更好地捕获气溶胶T _Fe浓度从澳大利亚粉尘暴发顺风而下，但还成功地再现了增强的铁溶解度（7.8±8.4％），并导致L _Fe浓度与现场测量结果更好地吻合（1.4±1.5 vs. 1.4±2.3 ng Fe m ^–3）。后验模型估计表明，尽管仍推测缺少来源（例如，煤炭开采活动，火山喷发和次生地层）的大量贡献，但丛林大火在气溶胶中占_LFe浓度的很大一部分。这些发现可能对未来海洋微量营养素供应的预测具有重要意义，因为在上海，预计开放式生物质燃烧的频率和强度将会增加。