大洋溶解铁的物质来源及其同位素示踪

铁（Fe）作为海洋初级生产所必需的微量和限制性营养元素影响着海洋生物群落结构、生态功能以及碳循环，理解溶解Fe的物质来源及其对气候变化的响应具有重要的科学意义。早期研究多强调风尘输入是维持大洋Fe循环的主要机制。近年来，随着海水Fe分析数据的积累,尤其是痕量元素及其同位素海洋生物地球化学循环研究计划（GEOTRACES）的开展，陆架沉积物和热液活动所释放Fe的贡献开始越来越受到重视。尽管如此，不同物源对开阔大洋溶解Fe的影响依然存在相当的不确定性。以海水溶解Fe的化学组分为出发点，强调有机配体对大洋Fe循环的决定性作用，综述了不同来源Fe的通量估计和第四纪大洋Fe来源的研究争议。铁同位素为理解大洋Fe的物源演变提供了新的工具。讨论了不同物源的Fe同位素特征，并提出结合沉积物的活动性Fe同位素和组分研究可能为理解过去陆架-热液活动-风尘输出与输运Fe的机制提供全新视角。

The sources of dissolved iron in the global ocean and isotopic tracing

Iron is an essential trace element to oceanic primary productivity, which may influence the structure of marine biological community, ecological function, and carbon cycle. It is therefore of great importance to understand the sources and supply of dissolved Fe to the ocean and its responses to the global climate change. Early studies often emphasize dust input as the mechanism to maintain oceanic Fe cycling. In recent years, with the increase in Fe data, especially along with the launch of GEOTRACES program, the important role of dissolved Fe released from continental shelf sediments and hydrothermal activities has been highlighted. Nevertheless, there still remain considerable uncertainties regarding the contribution of Fe to the open ocean from different sources. Our review begun with characterizing the chemical speciation of dissolved Fe, especially of organic ligand in oceanic Fe cycling, and then presented flux estimation of different Fe sources as well as the debates regarding the oceanic Fe fertilization during the time of Quaternary. Iron isotopes provide a new tool for studying the evolution of Fe sources. We have discussed the Fe isotope signatures of different sources, and proposed that the combination of isotopes and speciation analysis of sedimentary reactive Fe might provide a new perspective in understanding the mechanism of Fe export and transport from continental shelf, hydrothermal activity, and dust in the past.