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溶解有机质与铁氧化物相互作用过程对重金属再迁移的影响

张磊1,2,宋柳霆1,2**,郑晓笛1,2,滕彦国1,2,王金生1,2   

  1. (1北京师范大学水科学研究院, 北京 100875; 2地下水污染控制与修复教育部工程研究中心, 北京 100875)
  • 出版日期:2014-08-10 发布日期:2014-08-10

The remobilization of heavy metals influenced by interaction of DOM and iron oxides.

ZHANG Lei1,2, SONG Liu-ting1,2**, ZHENG Xiao-di1,2, TENG Yan-guo1,2, WANG Jin-sheng1,2   

  1. (1 College of Water Sciences, Beijing Normal University, Beijing 100875, China; 2 Engineering Research Center of Groundwater Pollution Control and Remediation, Ministry of Education, Beijing 100875, China)
  • Online:2014-08-10 Published:2014-08-10

摘要:

水体中的溶解有机质(DOM)可与铁氧化物发生广泛的相互作用,进而对重金属再迁移产生重要影响,因而开展DOM与铁氧化物相互作用过程及其对重金属再迁移影响的实验研究,将有助于深化认识有毒重金属的迁移转化规律及其二次污染风险。本文对还原条件下不同浓度的DOM与铁氧化物的相互作用过程及其对重金属(Pb和As)再迁移的影响进行了研究。Pb、As浓度变化和铁氧化物絮体IR光谱分析结果表明:(1)DOM与铁氧化物的相互作用能明显增强还原环境下铁氧化物中Pb的再释放,并对As的再迁移产生一定的影响;(2)铁氧化物絮体主要通过Fe(III)与DOM中的羟基和羧基形成配位键而发生相互作用,Fe(III)易形成粒径更小的无定形铁氧化物,有利于铁氧化物的还原溶解,进而增强铁氧化物絮体中Pb、As的再释放;DOM使还原溶解后的Fe(II)难以形成二次沉淀矿物,不仅减弱了Pb、As再次进入固相的机会,而且溶解态Fe(II)浓度的增高能够进一步催化γFeOOH到α-FeOOH的相转化过程,进而促进铁氧化物絮体中Pb、As元素的再释放;此外,DOM还可以通过竞争吸附作用过程减弱铁氧化物对Pb、As的吸附,这可能也是溶液中Pb、As浓度增高的原因。本研究为进一步深化认识还原环境下重金属的二次污染风险,进而制定科学合理的水环境管理和保护措施提供了科学依据。
 

关键词: 冠层反射率, 敏感性分析, 亚热带森林, PROSPECT5模型, 4SAIL模型

Abstract: The interactions between dissolved organic matter (DOM) and Fe oxdies are common in surface and subsurface water environments. The study of these interaction processes will help better understand the remobilization of toxic heavy metals and the risk of their secondary pollution. In this study, an experiment was carried out with different DOM concentrations on the remobilization of heavy metals influenced by the interaction of DOM and iron oxides. The Pb and As concentrations and the infrared spectra of iron oxides flocs showed that the interactions of iron oxides and flocs promoted a significant increase of remobilization of Pb, and a slight increase of As as well. Iron oxides interact with dissolved organic matter via complexation to hydroxyl and carboxyl groups. With the presence of DOM, iron oxides precipitated as flocs with smaller particle sizes and lower structural order, which made the formed iron oxides easy to be reductively dissolved to promote the remobilization of Pb and As as well. Furthermore, the iron secondary mineral precipitation was delayed by DOM, which would prevent the sequestration of Pb and As. Besides, the increase of Fe(II) concentration catalyzed the transformation of iron oxides from γ-FeOOH to α-FeOOH, further promoting the release of Pb and As into solutions. The competitive adsorption of NOM precluded the adsorption of Pb and As onto the iron oxides, which may also cause the increase of Pb and As concentrations in solutions. This study provides useful information for a better understanding of the secondary pollution risks of heavy metals, and provides further scientific evidence for the management and protection of water environments in a rational way.

Key words: subtropical forest, canopy reflectance, 4SAIL model, sensitivity analysis, PROSPECT5 model