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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

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