海洋透光层代表性铁氧化物半导体矿物——针铁矿和纤铁矿光还原特性及其环境效应

Photoreduction Characteristics and Environmental Effects of Representative Iron Oxide Semiconducting Minerals-goethite and Lepidocrocite in the Marine Euphotic Zone

海洋透光层中广泛分布铁氧化物半导体矿物;铁对大多数有机生命体都是必不可少的。本文以透光层中的代表性铁氧化物半导体矿物——针铁矿和纤铁矿为例,对比分析了针铁矿和纤铁矿的半导体特性及光还原特性,结果发现在海洋透光层偏碱性环境中针铁矿和纤铁矿可发生光还原溶出Fe^(2+)。对合成针铁矿和纤铁矿进行了系统的矿物学表征、光电化学测试,结果显示纤铁矿光电响应活性强于针铁矿,其平均光电流密度约为针铁矿的20倍。在模拟海水中进行针铁矿和纤铁矿的光还原实验,结果显示反应12天,针铁矿和纤铁矿光照组溶出Fe^(2+)的溶度比无光组分别高约1640%和328.33%,光激发纤铁矿Fe^(2+)最大溶出量比针铁矿高约33.62%,表明纤铁矿光催化活性较针铁矿更强。这种光诱导铁氧化物半导体矿物溶出Fe^(2+)可能进一步影响透光层本源微生物群落结构并参与关键地球化学元素循环过程。

Semiconducting iron minerals are widespread in the marine euphotic zone. Iron is essential for most living organisms. In this paper, goethite and lepidocrocite, two representative semiconducting iron minerals in the euphotic zone, were taken to comparatively analyze their semiconducting properties and photoreduction characteristics, and to study if Fe^(2+)could be dissolved from photoreduction of goethite and lepidocrocite in a relatively alkaline environment in the marine euphotic zone. The synthesized goethite and lepidocrocite were systematically characterized by mineralogical analyses and electrochemical measurements. The results indicated that the average photocurrent density of lepidocrocite was about 20 times of that of goethite, which means that the photoelectric response activity of lepidocrocite was much more intensive than that of goethite. The photoreduction experiments of goethite and lepidocrocite were conducted in the simulated seawater. The results demonstrated that after 12 days, contents of the dissolved Fe^(2+)of the simulated seawater by the goethite and lepidocrocite photoreduction with light are about 1640% and 328.33% higher than those by the goethite and lepidocrocite photoreduction without light, respectively. Notably, the maximum amount of dissolved Fe^(2+)from lepidocrocite by its photoreduction was about 33.62% higher than that of dissolved Fe^(2+)from goethite, indicating that the photocatalytic property of lepidocrocite was more active than that of goethite. The dissolved Fe^(2+)from semiconducting iron minerals by their photoreduction may further affect the native microbial community structure and participant in the key geochemical element cycle in the marine euphotic zone.