The correlation between chemical composition and arsenic contamination in groundwater of the Northwest Hanoi

Abstract

The chemical composition of groundwater samples in 50 tubewells in the northwest Hanoi was determined in this study. The analysis result showed that groundwater in this area is contaminated by a number of trace elements such as arsenic (As), iron, manganise, and ammonium. Arsenic concentrations in tubewells were relatively different, ranging from under 5 to 334 µg/l; over 40% of the samples had higher As concentration than the Vietnam Standard for arsenic in groundwater (50 µg/l). Iron concentrations were high with 50% samples exceeding the standard concentration in groundwater (5 mg/l). The contamination of ammonia in groundwater was dominant here, 90% of the studied wells with higher contents of ammonia than the standard (0.1 mg/l). The distribution of arsenic seems to be closely related to the alteration of the redox conditions in the aquifers. High arsenic concentrations were found in groundwater areas with high iron and ammonia concentrations and also high composition of absorption competition as phosphate.