Web Release Date: June 28,
Arsenic Contamination of Groundwater and Drinking Water in Vietnam: A Human Health Threat
and
Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-8600 Dübendorf, Switzerland, and Centre of Environmental Chemistry, Hanoi University of Science, Hanoi, Vietnam
Received for review January 23, 2001
Revised manuscript received May 14, 2001
Accepted May 17, 2001
Abstract:
This is the first publication on arsenic contamination of
the Red River alluvial tract in the city of Hanoi and in the
surrounding rural districts. Due to naturally occurring
organic matter in the sediments, the groundwaters are
anoxic and rich in iron. With an average arsenic concentration
of 159 
g/L, the contamination levels varied from 1 to
3050 g/L in rural groundwater samples from private small-scale tubewells. In a highly affected rural area, the
groundwater used directly as drinking water had an average
concentration of 430 g/L. Analysis of raw groundwater
pumped from the lower aquifer for the Hanoi water supply
yielded arsenic levels of 240-320 g/L in three of eight
treatment plants and 37-82 g/L in another five plants.
Aeration and sand filtration that are applied in the treatment
plants for iron removal lowered the arsenic concentrations
to levels of 25-91 g/L, but 50% remained above the
Vietnamese Standard of 50 g/L. Extracts of sediment
samples from five bore cores showed a correlation of
arsenic and iron contents (r2 = 0.700, n = 64). The arsenic
in the sediments may be associated with iron oxyhydroxides
and released to the groundwater by reductive dissolution
of iron. Oxidation of sulfide phases could also release arsenic
to the groundwater, but sulfur concentrations in sediments
were below 1 mg/g. The high arsenic concentrations
found in the tubewells (48% above 50 g/L and 20% above
150 g/L) indicate that several million people consuming
untreated groundwater might be at a considerable risk of
chronic arsenic poisoning.
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