Abstract
The effect of the solid/solution ratio on the extraction of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) by 0.1 M hydrochloric (HCl) and 0.1 M nitric (HNO3) acids from agricultural soils and river-sediments in Hanoi, Vietnam was studied. For the agricultural soils, the solid/solution ratios of 1/5 and 1/25 and kind of acid had no significant effect on the concentration of extractable heavy metals. By contrast, a marked solid/solution ratio effect on the concentration of heavy metals extracted by the two acids was observed for river sediments. A substantial increase in the concentration was obtained by decreasing the solid/solution ratio from 1/5 to 1/25, and the concentration of heavy metals extracted with the 1/25 ratio had a significant and positive correlation with the total concentration for all six heavy metals. The concentration of extractable heavy metals in the sediments collected from the sites near location of factories was high, indicating that the sediments could be toxic not only quantitatively, but also qualitatively, especially true for Cd in which the concentration extracted with the solid/solution ratio of 1/25 was over 70% of the total concentration.