SUMMARY

Arsenic contamination of groundwater in West Hà Nội:  Current status and cause

Đặng Mai, Nguyễn Thùy Dương, Phạm Tiến Đức, Tống Thị Thu Hà,
Văn Thùy Linh, Nguyễn Văn Niệm, Trần Đăng Quy

Concentrations of arsenic, total iron, ammonium, bicarbonate, dissolved organic carbon, sulfate, calcium, magnesium were determined for 50 water samples collected in water wells in West Hà Nội. Samples of drill core in Quốc Oai District were also collected to determine As potential in Quaternary sediments.

Groundwater in the study area is characterized by Ca-HCO₃ or Mg-HCO₃ chemical types. Total As concentration in the analyzed wells vary between 0,015 and 182 µg/l with the average value of 29 µg/l, among that 37,3% of wells have As concentration exceeding the maximum permissible limit of WHO (10 µg/l), and 20,3% exceeding the Vietnamese National Technical Regulations on ground water quality (50 µg/l).

As shown by analyses of drill core the content of As in the majority of Quaternary sediments samples almost exceeds 10 mg/kg, some of them reach 41 mg/kg and have close correlation with iron content. This indicates high potential of arsenic in Quaternary sediments and that the adsorption in iron hydroxide is the main form of existence of As. In groundwater the content of As has positive correlation with Fe, NH₄ ⁺, DOC (dissolved organic carbon) and negative correlation with SO₄^2-, suggesting that the reduction by organic matter in sediments is the main mechanism to release As into water.

Người biên tập: GS.TSKH. Đặng Trung Thuận