Environmental Earth System Science (EESS) Ph.D. Thesis/ Oral Defense for Laura E. Erban
Title: GROUNDWATER EXPLOITATION AND ARSENIC OCCURRENCE IN THE MEKONG DELTA AQUIFER SYSTEM- by Laura E. Erban
Department: Environmental Earth System Science (EESS)
Advisor: Steve Gorelick
This talk comprises the public portion of the PhD dissertation defense from approximately 2pm- 3pm
(Light refreshments will be served at 1:30PM)
Abtract: The Mekong Delta is home to over 20 million people living in Cambodia and Vietnam, many of whom rely on groundwater contaminated with arsenic. Groundwater arsenic occurs naturally here, as in many other river basins across South and Southeast Asia, but the extent and spread of contamination is also mediated by human activities. This dissertation is concerned with the consequences of intensive groundwater exploitation for the distribution of naturally-occurring arsenic in the Vietnamese portion of the Mekong Delta. The work uses spatially-exhaustive measurements of arsenic in wells throughout the multi-aquifer system combined with ancillary 3D physico-chemical observations from ground and satellite-based data collection campaigns and numerical modeling. Synthesis of these methods reveals that deep wells in heavily-pumped regions of the Delta are widely contaminated. Here, I propose that this deep contamination results from a previously unrecognized mechanism: solute release from compacting clays that are effectively squeezed during the exploitation of adjacent aquifers. Along with presenting the support for this new mechanism, I analyze large-scale trends and controls on arsenic and recent land subsidence rates throughout the Vietnamese portion of the Delta. Results serve to explain the current, baseline status of arsenic occurrence and probe the potential for remote detection of human-induced contamination events. Recommendations are given for future research aimed at informing responsible water resources management in arsenic-prone systems.