Heavy Metal Concentration in Sediments of the Nhue River and its Water-Irrigated Farmland Soil in the Suburbs of Hanoi, Vietnam

The heavy metal pollution of sediment in the Nhue River, which receives wastewater from the To Lich and Kim Nguu River system, was investigated together with the effects of use of this water for irrigation of the surrounding farmland. Eighty soil samples and 40 sediment samples were collected from six locations in the Nhue River and two locations in the To Lich River for chemical and physical analyses. The results showed that the sediments in the Nhue River are heavily polluted by metals (71-420 mg/kg for Cu, 77-433 mg/kg for Pb, 150-350 mg/kg for Zn, 0.7-8.7 mg/kg for Cd, 80-583 mg/kg for Cr, and 32-70 mg/kg for Ni). There were positive correlations between heavy metal concentration and both clay and organic matter contents in the sediment samples. The concentrations of all metals in soil samples were much higher than the background levels in the farmland, Cd, Cu, and Pb, exceeding Vietnamese standards for agricultural grounds.