Arsenate uptake, sequestration and reduction by a freshwater cyanobacterium : a potenial biologic control of arsenic in South Texas /
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| Format: | Thesis eBook |
| Language: | English |
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[College Station, Tex.] :
[Texas A&M University],
[2005]
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| Online Access: | Link to OAK Trust copy |
| Abstract: | The toxicity and adverse health effects of arsenic are widely known. It is generally accepted that sorption/desorption reactions with oxy-hydroxide minerals (iron, manganese) control the fate and transport of inorganic arsenic in surface waters through adsorption and precipitation-dissolution processes. In terrestrial environments with limited reactive iron, recent data suggest organoarsenicals are potentially important components of the biogeochemical cycling of arsenic in near-surface environments. Elevated arsenic levels are common in South Texas from geogenic processes (weathering of As-containing rock units) and anthropogenic sources (a byproduct from decades of uranium mining). Sediments collected from South Texas show low reactive iron concentrations, undetectable in many areas, making oxy-hydroxide controls on arsenic unlikely. Studies have shown that eukaryotic algae isolated from arsenic-contaminated waters have increased tolerance to arsenate toxicity and the ability to uptake and biotransform arsenate. In this experiment, net uptake of arsenic over time by a freshwater cyanobacterium never previously exposed to arsenate was quantified as a function of increasing As concentrations and increasing N:P ratios. Toxic effects were not evident when comparing cyanobacterial growth, though extractions indicate accumulation of intracellular arsenic by the cyanobacterium. Increasing N:P ratios has minimal effect on net arsenate uptake over an 18 day period. However, cyanobacteria were shown to reduce arsenate at rates faster than the system can re-oxidize the arsenic suggesting gross arsenate uptake may be much higher. Widespread arsenate reduction by cyanobacterial blooms would increase arsenic mobility and potential toxicity and may be useful as a biomarker of arsenic exposure in oxic surface water environments. |
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| Item Description: | "Major Subject: Geology" Title from author supplied metadata (automated record created on Sep. 21, 2005.) Vita. Abstract. Electronic resource. |
| Format: | Mode of access: World Wide Web. System requirements: World Wide Web access and Adobe Acrobat Reader. |
| Bibliography: | Includes bibliographical references. |