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Monitored Natural Attenuation of Inorganics

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Monitored Natural Attenuation of Inorganics

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    1. Monitored Natural Attenuation of Inorganics USEPA Scientist - to - Scientist Meeting Las Vegas, Nevada June 14 - 15, 2000 Robert W. Puls, Ph.D. National Risk Management Research Laboratory

    2. OSWER Directive on MNA Recognizes monitored natural attenuation of inorganics in ground water and soils Requires knowledge of specific mechanisms Most applicable when contaminant is irreversibly immobilized

    3. Presentation Topics Monitored Natural Attenuation of Metals Processes controlling MNA Site Characterization Issues Research Questions Factors Affecting MNA of Metals NRMRL/SPRD Research

    5. Site Characterization - Inorganics Monitored Natural Attenuation

    6. Research Questions for MNA of Inorganics What are the important processes to measure for natural attenuation for metal contaminants? How do you make these measurements? How do you integrate these data to understand the behavior of the system?

    7. Factors Affecting MNA of Inorganics Speciation (e.g. Cr(III), Cr(VI), As(III), As(V) Geochemical factors pH Eh DO Water chemistry Microbial activity Sorbents Mineralogy

    9. NRMRL Research on MNA of Inorganics Laboratory studies of the role of mineralogy for MNA Arsenic and Iron (Hydr)oxides (6400) Solid phase speciation/extractions (4279) Arsenic and Iron sulfides (7060) Field studies of the natural attenuation of arsenic in an urban watershed (6401)

    10. MNA of As in an Urban Watershed Aberjona watershed in Woburn, MA (industriplex site); pesticide manufacturer and tannery Cooperative effort between ORD/NRMRL and region 1 Involves ground water, surface water, soils and sediments Provide part of the science needed to develop guidance on MNA for metals

    11. Industriplex Site, Woburn, MA

    12. Holding Area Halls Brook

    13. Plume Discharge into HBHA

    15. Project Goal

    21. Natural Attenuation of Metals During Sulfide Formation Task 7060 (Richard Wilkin)

    22. Objectives (Task 7060) Laboratory studies to identify mechanisms of metal uptake and evaluate rates Focus on As, Ni, Zn, Mn Identify controls on attenuation capacity => reactive Fe, sulfate, organic C Identify controls on formation of pure Me-sulfide vs. co-precipitation with Fe Develop practices for field monitoring

    23. Monitoring Oxidation-Reduction Processes in Ground waters, Sediments, and Soils Task 6403 (Richard Wilkin) Objectives DO methods comparison Winkler titrations, colorimetric, electrodes Eh interpretation: H2S/S° equilibrium Develop methods to partition S in the solid phase AVS, CRS, S°, S-organic, S-sulfate

    24. EPA Workshop on Monitoring Oxidation-Reduction Processes for Ground Water Restoration

    25. Task 4279 - Natural Attenuation of Inorganic Contaminants (Lab-based) Reliable/acceptable extractions to assess speciation on the solid phase? Reliable/acceptable methods to assess oxidation capacities for soils/seds? Reliable/acceptable methods to assess reduction capacities for soils/seds? Cheap, fast, reliable analytical methods for solid phase speciation assessments?

    26. Summary NRMRL/SPRD MNA Research Mineralogy role in MNA (arsenic) Fe and S cycling Solid phase analyses, site assessment extraction methods Sample collection, preservation methods arsenic speciation solids analyses Development of MNA protocols for field application

    27. NRMRL/SPRD MNA Research & Mining Arsenic a common contaminant of mine wastes Fe and S cycling important processes for mine waste site assessment and treatment Solid phase analyses and extraction methods important for mine waste assessments MNA may be an important part of any mine waste remedial measure

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