海南红树林泥炭沉积物中的有机质与黄铁矿赋存特征研究
首发时间:2011-01-05
摘要:海南福田滨海红树林沉积物中的有机质含量较高,TOC和TS平均值分别为7.74%和2.83%,C/N平均值为21.6,显示其有机质主要来源于红树等高等植物,并且随着深度增加有机质含量呈缓慢增加趋势。沉积物中的硫主要以铁硫化物(黄铁矿)出现,且以莓球状黄铁矿为主,平均占黄铁矿总数的90%以上,自形晶较少。莓球状黄铁矿的平均粒径为7.0μm,平均最大粒径达到31μm,反应了生物扰动下红树林沉积物中的氧化还原条件的多变性,即在表层以下的厌氧还原条件下具有微氧化的微环境特征。纵向上,60cm深度之上的样品平均粒径较小,意味着生物扰动一定程度上抑制了黄铁矿颗粒的生长,并且可能存在黄铁矿的氧化。而60cm深度以下莓状黄铁矿的平均粒径以及最大粒径明显增大粒径,说明沉积氧化还原环境的相对稳定并且有充足的物源输入,而氧化还原条件尤其是氧化剂的影响可能是莓状黄铁矿颗粒变化的主要因素。80cm深度以下样品具有明显的二次生长现象,可能是受到沉积环境的突然变化,例如海平面的变化导致FeS和氧化剂的再输入,从而影响黄铁矿生长。
关键词: 生物地球化学 莓球状黄铁矿 氧化还原状态 硫酸盐还原菌 红树林湿地
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The Characteristics of Organic Matter and Pyrite in the Sediments of Coastal Mangrove Peat in Hainan Island
Abstract:This paper studies the organic matter and pyrite of peat from Futian of Hainan Island. The results show that the contents of organic matter is high: the average TOC and TS contents are up to 7,74% and 2.83%. And the average C/N ratio is up to 21.6, which means the organic matter of the mangrove peat are mainly from the higher plants as the mangroves. And organic matter content was slowly increasing with the depth. It is noteworthy that the major composition of iron sulphide in coastal mangrove sediments is pyrite and mostly(>90%) in the form of framboidal pyrites instead of euhedral crystal. The average size of framboidal pyrites is 7.0μm, and the average maximum diameter is 31μm,which reflecting the variability of redox conditions under the bioturbation by the roots and the crabs. Above the 60cm depth the average size of framboids is smaller, which means the bioturbation may inhibit the growth of framboidal particles, and there may exist the oxidation of pyrite. And below 60cm the average and maximum size of framboids significantly increase, indicating that the redox environment of deposition is relatively stable and there are adequate source input as OM and iron ion. Below 80cm there exists significant secondary growth of pyrites, which may be subject to sudden change in depositional environment, such as changes in sea level.
Keywords: geochemistry framboidal pyrite redox sulfate-reducing bacteria mangrove peat
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海南红树林泥炭沉积物中的有机质与黄铁矿赋存特征研究
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