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Scott Fendorf Stanford University

Processes Responsible for Arsenic in Groundwater of South/Southeast Asia. Scott Fendorf Stanford University. CONTRIBUTORS Ben Kocar Matt Polizzotto Yoko Masue Samantha Ying Kate Tufano Jason Stuckey. COLLABORATORS Mickey Sampson, RDI RDI staff

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Scott Fendorf Stanford University

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  1. Processes Responsible for Arsenic in Groundwater of South/Southeast Asia Scott Fendorf Stanford University

  2. CONTRIBUTORS • Ben Kocar • Matt Polizzotto • Yoko Masue • Samantha Ying • Kate Tufano • Jason Stuckey • COLLABORATORS • Mickey Sampson, RDI • RDI staff • Chad Saltikov, UC Santa Cruz • Charlie Harvey, MIT • Uli Mayer, Univ. British Columbia Mekong River, Cambodia

  3. 1.2 Billion People Lack Access to ‘Safe’ Drinking Water

  4. Water Quality in South/South East Asia >700 Million People without Safe Water

  5. A Problem of Water Quality, Not Quantity

  6. Pathogen Laden Water

  7. Natural Filtration Himalaya Pathogens Filter Clay Aquifer extraction

  8. The Great Hope

  9. Surface Water Use Arsenicosis Groundwater Use Groundwater Irrigation Bangladesh Water Use 1970 1980 1960

  10. The Largest Mass Poisoning in History: Arsenic in Groundwater

  11. Region of Impact

  12. Major River Systems of Asia being Impacted

  13. Impacted Population Red River Delta: 17 million Ganges Delta: 125-143 million Irrawaddy and Salween River Delta: 10-15 million Mekong River Delta: 20-30 million

  14. Conditions in Bangladesh Exposure (> 10 ppb) 60,000,000 people (46%) Arsenicosis 2,000,000 people (1.8%) >200,000 people ( 0.2%) Skin Cancer Internal Cancers 3,000-7,000 people/y *Based on epidemiological reports from 2003

  15. Major Questions • What is the source of arsenic? • Why is it in the groundwater? • Are the levels changing? • What are mitigation options?

  16. Where did the arsenic come from? Mekong River, Cambodia

  17. Fe(OH)3 + H2AsO4-  HxAsO4 Fe(OH)3 (s) Weathering and Transport Arsenic Bearing Sulfide Minerals Arsenic Bearing Iron Oxides (rust) Oxidation of arsenic-bearing sulfide minerals FeAsS + 3.5O2 + 4H2O  Fe(OH)3 + SO42- + H2AsO4- + 3H+

  18. Origin of the Poison (arsenic) FeAsS+ 3.5O2 + 4H2O  Fe(OH)3+ SO42- +H2AsO4-+ 3H+ Fe(OH)3+H2AsO4-HxAsO4nFe(OH)3 (s)

  19. As-solids Floodplain Arsenic Source

  20. Why Is Arsenic in the Groundwater? Hydrologic Constraints Biogeochemical Mechanisms How are Arsenic Concentrations Changing?

  21. Clay Wetlands Mekong River Aquifer Examining Arsenic in the Mekong Delta

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