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USE OF REDOX-SENSITIVE METALS ENRICHMENT FACTORS AS INDICATORS OF LOW DESSOLVED OXYGEN
Citation:
Boothman, W S. AND S Rego. USE OF REDOX-SENSITIVE METALS ENRICHMENT FACTORS AS INDICATORS OF LOW DESSOLVED OXYGEN. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Austin, TX, November 9-13, 2003.
Description:
Low dissolved oxygen (DO) is one adverse response to excessive eutrophication in U. S. coastal waters. For dissolved oxygen criteria to be effective, it is necessary to measure DO levels and impacts over large spatial scales. However, biological responses to low DO are often dependent on the duration as well as severity of the oxygen deficiency, whereas directly measured concentrations of DO can vary significantly in both space and time, and thus large numbers of measurements may be required to adequately characterize the spatial and temporal extent of low DO conditions in a water body. One alternative to direct measurement of DO is measurement of "redox-sensitive" metals such as U, Re and Mo, which are highly enriched in reducing sediments due to very low crustal abundance, conservative behavior in oxic seawater and greatly decreased solubility in lower oxidation states. Differential patterns of enrichment may be used to discern both the spatial extent and duration of anoxic bottom water conditions. Sediment cores were collected from 4 sites in Narragansett Bay that experienced dissolved oxygen concentrations during summer/fall 2002 ranging from highly oxygenated to completely anoxic. Conditions also varied temporally, with bottom waters that were anoxic in summer becoming oxygenated in early autumn. Spatial and temporal variation of profiles of redox sensitive metals U, Re and Mo in these cores will be presented to illustrate the use of concentrations and enrichment factors of redox-sensitive metals in sediments as indicators of hypoxic, anoxic and euxinic (sulfide-containing) conditions in waters overlying the sediments. The kinetics of enrichment or remobilization of the metals will also be compared with the short term variation of oxygen concentrations.