地学前缘 ›› 2020, Vol. 27 ›› Issue (5): 218-226.DOI: 10.13745/j.esf.sf.2020.5.49

• 表生成因矿物学:地表环境及其修复 • 上一篇    下一篇

磷灰石对湖泊沉积物中水铁矿稳定性的制约

骆少勇,周跃飞,刘星   

  1. 1. 昆明理工大学 国土资源工程学院, 云南 昆明 650093
    2. 合肥工业大学 资源与环境工程学院, 安徽 合肥 230009
  • 收稿日期:2020-04-20 修回日期:2020-06-28 出版日期:2020-09-25 发布日期:2020-09-25
  • 通讯作者: 刘星(1956—),男,博士,教授,主要从事成因矿物学与找矿矿物学研究。
  • 作者简介:骆少勇(1976—),男,硕士,讲师,主要从事找矿矿物学与环境矿物学研究。E-mail:luoshaoyong@kust.edu.cn
  • 基金资助:

    国家自然科学基金项目(41462003,41872043)

Effect of apatite on the stability of ferrihydrite in lacustrine sediments

LUO Shaoyong, ZHOU Yuefei, LIU Xing   

  1. 1. Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China
    2. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
  • Received:2020-04-20 Revised:2020-06-28 Online:2020-09-25 Published:2020-09-25

摘要:

通过在滇池开展原位实验,研究探讨了湖泊沉积物中磷灰石制约水铁矿分解和转化的机制,以及二者共存时的环境效应。结果表明:将水铁矿放置到沉积物中1个月,矿物保持稳定;放置时间达到3个月时,添加磷灰石实验中水铁矿发生了显著物相转变。冬天(12—2月)实验中,转化产物随深度的变化趋势为针铁矿+磁(赤)铁矿→针铁矿+纤铁矿→针铁矿;夏天(6—9月)实验中,转化产物随深度的变化趋势为针铁矿+纤铁矿+磁(赤)铁矿→针铁矿+纤铁矿→未转化。透射电镜分析结果显示冬天实验中生成的磁性铁氧化物为纳米磁铁矿和磁赤铁矿,夏天实验中产生的则主要为纳米磁铁矿。X射线光电子能谱分析结果显示冬天表层实验样品具有较高P含量。分析表明的湖泊沉积物中磷灰石促进水铁矿转化的过程为:(1)微生物促进磷灰石溶解;(2)磷灰石溶解释放的P促进铁还原菌生长;(3)铁还原菌促进水铁矿还原;(4)水铁矿还原产生的溶解态Fe2+催化水铁矿向针铁矿、纤铁矿和磁铁矿转化。冬天及沉积氧化还原界面最适宜磷灰石分解菌和铁还原菌生长,水铁矿的转化和P释放能力也更强,相应地内源磷释放的风险也更大。

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关键词: 水铁矿, 磷灰石, 湖泊沉积物, 氧化还原界面, 稳定性, 转化

Abstract:

In this study, we set out to investigate the mechanism of apatite-mediated dissolution and transformation of ferrihydrite in lacustrine sediments, and the synergic environmental effect of both minerals. We carried out in-situ ferrihydrite transformation experiments in the Dianchi Lake, Yunnan Province, China. The results show that ferrihydrite remained stable in 1-month cultured samples, whereas in apatite-added samples we observed obvious mineral phase transformation after 3-month culturing. The change of newly formed iron mineral assemblage composition with depth in the top 50 cm sedimentary layer were goethite+magnetite/maghemite → goethite+lepidocrocite → goethiten in the winter experiments, or goethite+lepidocrocite+magnetite/maghemite → goethite+lepidocrocite → no new mineral in the summer experiments. Transmission electron microscopy observations show that magnetic minerals formed in winter are nanosized magnetite and maghemite, while in summer they are mainly magnetite. X-ray photoelectron spectroscopy analysis only found P in 3-month cultured samples in winter at a sedimentary depth of no more than 20 cm. The experimental results suggest that the progressive steps in the apatite-mediated ferrihydrite transformation process in lacustrine sediments are as follows: (1) apatite is dissolved by microorganisms and P is released during dissolution; (2) dissolved P promotes iron-reducing bacterial growth; (3) iron-reducing bacteria promote ferrihydrite reduction and release of dissolved Fe2+; and (4) dissolved Fe2+ catalyzes the transformation of ferrihydrite to goethite, lepidocrocite, and magnetite. In winter at the sedimentary redox boundary, the functional microorganisms responsible for apatite dissolution and ferrihydrite reduction can grow better, thus the risk of endogenous phosphorus release is much greater.

Key words: ferrihydrite, apatite, lacustrine sediment, redox boundary, stability, transformation

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