Vietnam, located in Southeast Asia, is an agricultural country with a
population of 88 million. The residents are concentrated mainly in the
Red River Delta in the North and in the Mekong River Delta in the
South. For example, 18 million inhabitants presently live in the Red
River Delta, with a density of about 1200 inhabitants/km2, making this
one of the most populous areas of the world. In the Red River Delta,
groundwater pumped from the Holocene aquifer by household tube
wells is commonly used as drinking water and for bathing and washing.
Arsenic is released from Holocene sediments in the delta to groundwater
due to reductive dissolution fromiron(hydr)oxides triggered by sedimentary
organic matter . Recent
study revealed that Pleistocene aquifer, which has low concentration of
arsenic, is contaminated by arsenic through variations in groundwater
flow conditions and redox state of sediments induced by pumping of groundwater. Arsenic contamination
of groundwater in Vietnam was first discovered in the
Hanoi region in 1998, with at an average concentration of 159 μg/L
. This is fifteen times higher than the drinking water
standard for arsenic in Vietnam (10 μg/L) and the WHO guideline for arsenic in drinking water
(10 μg/L) . The magnitude of groundwater arsenic contamination
is therefore comparable to the situation in Bangladesh and
West Bengal, India .