Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Biogeochemical transformations of arsenic in circumneutral freshwater sediments

Biogeochemical transformations of arsenic in circumneutral freshwater sediments Arsenic is a wide-spread contaminant of soils and sediments, andmany watersheds worldwide regularly experience severe arsenic loading. While the toxicityof arsenic to plants and animals is well recognized, the geochemical and biological transformationsthat alter its bioavailability in the environment are multifaceted and remain poorly understood.This communication provides a brief overview of our current understanding of the biogeochemistryof arsenic in circumneutral freshwater sediments, placing special emphasis on microbialtransformations. Arsenic can reside in a number of oxidation states and complex ions. The commoninorganic aqueous species at circumneutral pH are the negatively charged arsenates(H2AsVO4 - and HasVO4 2-) and zero-charged arsenite(H3AsIIIO3 0). Arsenic undergoes diagenesis in response to both physicaland biogeochemical processes. It accumulates in oxic sediments by adsorption on and/orco-precipitation with hydrous iron and manganese oxides. Burial of such sediments in anoxic/suboxicenvironments favors their reduction, releasing Fe(II), Mn(II) and associatedadsorbed/coprecipitated As. Upward advection can translocate these cations and As into theoverlying oxic zone where they may reprecipitate. Alternatively, As may be repartitioned tothe sulfidic phase, forming precipitates such as arsenopyrite and orpiment. Soluble and adsorbedAs species undergo biotic transformations. As(V) can serve as the terminal electronacceptor in the biological oxidation of organic matter, and the limited number of microbes capableof this transformations are diverse in their phylogeny and physiology. Fe(III)-respiring bacteriacan mobilize both As(V) and As(III) bound to ferric oxides by the reductive dissolution ofiron-arsenate minerals. SO4 2--reducing bacteria canpromote deposition of As(III) as sulfide minerals via their production of sulfide. A limited number of As(III)-oxidizing bacteriahave been identified, some of which couple this reaction to growth. Lastly, prokaryotic andeukaryotic microbes can alter arsenic toxicity either by coupling cellular export to its reductionor by converting inorganic As to organo-arsenical compounds. The degree to which each ofthese metabolic transformations influences As mobilization or sequestration in differentsedimentary matrices remains to be established. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biodegradation Springer Journals

Biogeochemical transformations of arsenic in circumneutral freshwater sediments

Loading next page...
 
/lp/springer-journals/biogeochemical-transformations-of-arsenic-in-circumneutral-freshwater-Ntkn4z2qYJ

References (98)

Publisher
Springer Journals
Copyright
Copyright © 2003 by Kluwer Academic Publishers
Subject
Environment; Geochemistry; Soil Science & Conservation; Terrestrial Pollution; Waste Management/Waste Technology; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution
ISSN
0923-9820
eISSN
1572-9729
DOI
10.1023/A:1024031700533
Publisher site
See Article on Publisher Site

Abstract

Arsenic is a wide-spread contaminant of soils and sediments, andmany watersheds worldwide regularly experience severe arsenic loading. While the toxicityof arsenic to plants and animals is well recognized, the geochemical and biological transformationsthat alter its bioavailability in the environment are multifaceted and remain poorly understood.This communication provides a brief overview of our current understanding of the biogeochemistryof arsenic in circumneutral freshwater sediments, placing special emphasis on microbialtransformations. Arsenic can reside in a number of oxidation states and complex ions. The commoninorganic aqueous species at circumneutral pH are the negatively charged arsenates(H2AsVO4 - and HasVO4 2-) and zero-charged arsenite(H3AsIIIO3 0). Arsenic undergoes diagenesis in response to both physicaland biogeochemical processes. It accumulates in oxic sediments by adsorption on and/orco-precipitation with hydrous iron and manganese oxides. Burial of such sediments in anoxic/suboxicenvironments favors their reduction, releasing Fe(II), Mn(II) and associatedadsorbed/coprecipitated As. Upward advection can translocate these cations and As into theoverlying oxic zone where they may reprecipitate. Alternatively, As may be repartitioned tothe sulfidic phase, forming precipitates such as arsenopyrite and orpiment. Soluble and adsorbedAs species undergo biotic transformations. As(V) can serve as the terminal electronacceptor in the biological oxidation of organic matter, and the limited number of microbes capableof this transformations are diverse in their phylogeny and physiology. Fe(III)-respiring bacteriacan mobilize both As(V) and As(III) bound to ferric oxides by the reductive dissolution ofiron-arsenate minerals. SO4 2--reducing bacteria canpromote deposition of As(III) as sulfide minerals via their production of sulfide. A limited number of As(III)-oxidizing bacteriahave been identified, some of which couple this reaction to growth. Lastly, prokaryotic andeukaryotic microbes can alter arsenic toxicity either by coupling cellular export to its reductionor by converting inorganic As to organo-arsenical compounds. The degree to which each ofthese metabolic transformations influences As mobilization or sequestration in differentsedimentary matrices remains to be established.

Journal

BiodegradationSpringer Journals

Published: Oct 5, 2004

There are no references for this article.