Research Brief 90Superfund Basic Research ProgramThe Impact of Chlorine on Hexavalent Chromium EmissionsRelease Date: 06/05/2002 Superfund sites seldom contain a single toxic chemical, but instead are often contaminated with complex mixtures of organic and inorganic compounds. The interactions and ultimate toxicity of these mixtures are often unknown and their presence complicates efforts to assess the risks of exposure at Superfund sites and to identify the best remediation strategy. In addition to identifying the most efficient overall clean-up strategy, site managers must ensure that remediation of one contaminant does not result in the transformation of another contaminant into a physical and chemical form that is difficult to control or inherently more toxic. Thermal remediation is an effective remediation technology to clean soils contaminated with volatile organic compounds such as TCE, PCBs and PAHs. Dr. Ian Kennedy at the University of California, Davis is leading a team of researchers in studies to determine the risk to human populations as a result of the release of chlorinated by-products such as heavy metals or dioxins during thermal remediation at Superfund sites. Specifically, they are investigating the impact of the presence of chlorine on the chemical and physical state of chromium (Cr) emissions. Chromium has been detected at over 300 Superfund sites as the result of discharges from chrome plating, leather tanning, and textile operations and airborne emissions of metal-bearing solids chemical manufacturing facilities, the iron and steel industries, and combustion of natural gas, oil, and coal. The toxicity of chromium depends strongly on several factors:
Dr. Kennedy conducted tests using a laminar (non-turbulent) flame to evaluate the impact of chlorine on the formation of Cr(VI) and the partitioning between solid and vapor phases. The researchers measured total Cr added to the test system and collected emissions from the flame using filters to collect particulate matter and solvents to collect vapor phase species. They measured Cr(VI) emissions using a spectrophotometric method and total Cr on the filter via X-ray fluorescence. The results of the study showed:
Dr. Kennedy believes that the formation of an oxychloride (CrO2Cl2) in the cooler post-combustion gases contributes strongly to the increase in Cr(VI) emissions. If true, modification of mixing rates of combustion products with surrounding air could serve as a control strategy. This research represents a significant contribution to our efforts to address important technical issues that limit the implementation of thermal technologies in Superfund site remediation. For More Information Contact: Ian M. KennedyDepartment of Mechanical & Aeronautical Engineering 2094 Bainer Hall Davis, CA 95616 Tel: 530-752-2796 Email: To learn more about this research, please refer to the following sources:
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