A Water Crisis for a Billion People: Pathogen and Poison Infected Waters of Asia
Conservatively, there are more than 1.2 billion people who lack access to safe drinking water, and more than 700 million of them live in South and Southeast Asia. The problem is not a lack of water but a lack of safe water-it's the water quality, not quantity in this region of the world.
On a global level, the prime culprit for degraded water quality is use of pathogen infested surface water. In South and Southeast Asia, the problem of compromised drinking water is exacerbated by groundwater being contaminated with arsenic. At present, more than 140 million people are being poisoned by drinking arsenic-laced groundwater, and the problem is growing. Arsenic is naturally derived from eroded Himalayan sediments which are transported down the major river systems and deposited in the low-lying regions (i.e., sedimentary basins) of Bangladesh, West Bengal India, Myanmar, Cambodia, Laos and Vietnam. During erosion and transport, arsenic sulfide minerals, which are the Himalayan source, are oxidatively weathered to arsenic bearing iron oxides (rust, effectively). Once deposited in the sedimentary basins or river deltas, arsenic is released to pore-water within the soils/sediments.
Using hydrologic and (bio)geochemical measurements within the minimally-disturbed Mekong Delta of Cambodia, we have revealed that arsenic is released from near-surface, river-derived sediments and transported, on a centurial time scale, through the underlying aquifer and then back to the river. Owing to similarities in geologic deposition, aquifer source rock, and regional hydrological gradients, our results represent a model for understanding pre-disturbance conditions for the major deltas of Asia and offer the ability to predict aquifer responses to currently changing land uses.
Professor Scott Fendorf leads the soil and biogeochemistry group within the School of Earth Sciences at Stanford University. He is interested in the chemical and biological processes that control the fate and movement of elements, ranging from carbon to arsenic to uranium, within soils, sediments, and surface waters.