Author: Geological and Mineral Survey of Vietnam, Northern Hydrogeological Engineering Geological Division
Groundwater pollution, specially arsenic pollution, is very harmful to health . In Vietnam a recent study by UNICEF and some other organizations in the Hanoi area and part of the Red River Delta Plain showed signs of arsenic pollution. UNICEF has planned two phases to investigate this issue starting with this survey. UNICEF has collaborated with the Northern Hydrogeological Engineering Geological Division belonging to the Geological and Mineral Survey of Vietnam to investigate, survey, sample and analysis the parameters in groundwater and waste water: pH, temperature, electric conductivity, dissolved oxygen, Eh, alkalinity, ammonia, arsenic, manganese, iron in 500 points in Hanoi area.
Purpose / Objective
Identify the magnitude of arsenic contamination in Holocene and Pleistoncene aquifers in and around Hanoi.
498 ground water samples were collected from tube wells of the 2 main water aquifers: Holocene upper aquifer (Qh) and Pleistocene lower aquifer (QP). They were tested using an Atomic Absorption Spectrometer.
Key Findings and Conclusions
About 73.3% of samples met the requirement of having an arsenic content lower than 0.05 mg/l. Mostly, the inner city districts and the southern part of Hanoi suburbs show a higher percentage of arsenic content in the ground water. The distribution of the pollution areas coincides with the distribution area of high pollution of ammonia. Comparing these findings with a previous study in this area, we conclude there is a sign of arsenic contamination in the southern part of Hanoi.
The content of manganese and iron in both aquifers is higher than standard limitation. The pollution scale is 81.5% and 70.8% respectively for the upper aquifer, and 87.6% and 82.9% for the lower aquifer. The high pollution area is in the centre and the strip along the Red River and Duong River.
Reasons are still not yet defined, but possible sources are man-made waste, groundwater exploitation, and the naturally high content of heavy minerals in the soil
More study is needed to define the magnitude of arsenic prevalence in ground water. A future study is proposed that looks at the status of groundwater exploitation; quantity of wells, pumping rate, aquifer, and schedule of exploitation. An investigation into the degree of groundwater pollution by heavy metals in general, and arsenic in particular, in the environmental pollution in the whole Bacbo Plain is recommended.
Continue warning the government of the possible arsenic risk; set up a combined work group to develop an action plan for the future including studying treatment technology and creating groundwater flow models and ground water transport models.
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Water and Environmental Sanitation