The concentrations of heavy metals in soil and rice plants around the landfill area in Dong Thang commune, Co Do District, Can Tho City, Viet Nam needed to be assessed for environmental pollution. Soil samples were collected from four sites (three sites S1, S2, S3 near and one site S4 far away from the landfill area) at soil depths of 0 to 25 and 25 to 50 cm. The rice and soil samples were simultaneously collected at the same locations for analysis of heavy metals. The heavy metals Mn, Zn, Cu, Cr, Ni, Pb and Cd were analyzed using atomic absorption spectroscopy. Six heavy metals including Mn, Zn, Cu, Cr, Ni, and Pb were detected and ranged from 12.3 to 291.0 mg/L for the top soil and 11.2 to 370.0 mg/L for 25 to 50 cm soil layer. However, concentrations of Ni, Cu, and Pb in soil tended to decrease while Mn, Zn and Cr tended to increase with an increase of soil depth near the landfill. A similar tendency of heavy metal concentration with depth was found at S4 except for Cu. The decreasing order of the selected heavy metals concentrations in the two soil layers at near the landfill was Mn>Zn>Ni>Cr>Cu>Pb and these concentrations of heavy metals were within the limits of QCVN 03-MT: 2015/BTNMT and Canadian Council of Ministers of the Environment (CCME, 2007). The result of the bioaccumulation factor (BAF) in rice plants showed that the selected heavy metals were accumulated more in the root rather than the stem-leaf and grain. Mn was accumulated dominantly in both root and stemleaf, while Zn, Cu, and Pb only accumulated in the root. Thus, result of this study suggests that is essential to collect and treat the heavy metals in the leachate properly to minimize the distribution of heavy metals to the paddy soil environment.
Bioremediation of cadmium-contaminated paddy soil using an autotrophic and heterotrophic mixture