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Stability of Inorganic Selenium and Chromium Species for Environmental Analysis
Oral Presentation
Prepared by R. Wolf, J. Morrison
U. S. Geological Survey, Denver Federal Center, MS 964D, Denver , CO, 80225, United States
Contact Information: rwolf@usgs.gov; 303-236-2470
ABSTRACT
There is increasing interest in the determination of the species or chemical form of potentially toxic elements such as selenium and chromium. In arid landscapes, selenium and other naturally-occurring trace elements released during weathering can become concentrated in soluble salt phases that form in soils resulting in increased amounts of selenium in watersheds and, in some cases, exceeding state and federal water quality limits. The potential toxicity of the selenium to aquatic organisms can vary dramatically with the oxidation state of the selenium. One of the challenges of performing speciation analyses on field samples is maintaining the element in the chemical form found at sample collection through sample transport and storage until analysis, especially in the presence of other constituents that can cause redox reactions (e.g. iron or organic matter). A long-term stability test was performed on water samples collected and refrigerated without any sample preservation. Samples were spiked with known amounts selenium (IV) and selenium (VI) and then analyzed at two time points to test for interconversion of species. The results of this study will be presented and discussed.
Hexavalent chromium, Cr(VI), in drinking water has been the topic of much concern. However, there are limited data available on the stability of Cr(VI) in sample and standard solutions or in the human body as water containing hexavalent chromium is ingested. The U. S. Geological Survey (USGS) has developed in vitro methods to assess bioaccessibility of metals from geochemical and environmental samples using simulated biofluids to approximate the conditions in the human lungs, stomach, and intestine. The results of stability studies performed on Cr(VI) as a function of pH in simulated lung, gastric, and intestinal fluids at various concentrations of Cr(VI) and the possible use of ascorbic acid as a Cr(VI) reducing agent will be presented and discussed.
Oral Presentation
Prepared by R. Wolf, J. Morrison
U. S. Geological Survey, Denver Federal Center, MS 964D, Denver , CO, 80225, United States
Contact Information: rwolf@usgs.gov; 303-236-2470
ABSTRACT
There is increasing interest in the determination of the species or chemical form of potentially toxic elements such as selenium and chromium. In arid landscapes, selenium and other naturally-occurring trace elements released during weathering can become concentrated in soluble salt phases that form in soils resulting in increased amounts of selenium in watersheds and, in some cases, exceeding state and federal water quality limits. The potential toxicity of the selenium to aquatic organisms can vary dramatically with the oxidation state of the selenium. One of the challenges of performing speciation analyses on field samples is maintaining the element in the chemical form found at sample collection through sample transport and storage until analysis, especially in the presence of other constituents that can cause redox reactions (e.g. iron or organic matter). A long-term stability test was performed on water samples collected and refrigerated without any sample preservation. Samples were spiked with known amounts selenium (IV) and selenium (VI) and then analyzed at two time points to test for interconversion of species. The results of this study will be presented and discussed.
Hexavalent chromium, Cr(VI), in drinking water has been the topic of much concern. However, there are limited data available on the stability of Cr(VI) in sample and standard solutions or in the human body as water containing hexavalent chromium is ingested. The U. S. Geological Survey (USGS) has developed in vitro methods to assess bioaccessibility of metals from geochemical and environmental samples using simulated biofluids to approximate the conditions in the human lungs, stomach, and intestine. The results of stability studies performed on Cr(VI) as a function of pH in simulated lung, gastric, and intestinal fluids at various concentrations of Cr(VI) and the possible use of ascorbic acid as a Cr(VI) reducing agent will be presented and discussed.