Extractability of heavy metals in sediments and farmland soil in the To Lich and Kim Nguu River system

The purpose of the present study was to evaluate the availability and mobility of heavy metals in sediments and farmland soils in the To Lich and Kim Nguu River system through the amount of heavy metals extracted with acids and its percentage to total metal concentration. Twelve sediment samples were collected from the To-Lich, Kim-Nguu River and 19 soil samples were colleted at two different locations in agricultural field and pappy field along the river. The results showed that the highest amount of heavy metals extracted from the sediment samples with 0.5 M HC1 and 0.1 M HNO ₃ was in the order of Zn > Cr > Cu > Pb > Ni > Cd and Cr > Zn > Ni > Cu > Pb > Cd, respectively. The average percentage of the amount of extractable metals to the total metal concentration for the agricultural soil was the highest for Ni (70%), followed by Cr (65%), Cd (50%), Zn (20%), Pb (10%) and Cu (7%), suggesting that Ni is more labile and available to plants than other elements. The average percentage for the paddy soil was the highest for Cr (75%), followed by Ni (50%), Cd (40%), Zn (30%), Pb (20%) and Cu (15%), suggesting the highest availability of Cr to plants. In general, the amount of the extracted heavy metals was similar between the agricultural and paddy soil. The amount of heavy metals extracted with 0.5 M HC1 was greater than that extracted with 0.1 M HNO ₃ for all metals except Cr.