Assessment of Heavy Metal Pollution in the Surface Water of the Doi-Cho Dem-Ben Luc Rivers, Vietnam

Abstract

Heavy metals are a pressing concern in terms of their pollution in aquatic ecosystems because of their persistence, environmental toxicity, bioaccumulation. Aquatic environments receive heavy metals in untreated or inadequately treated wastewater from domestic, industrial, agricultural, and navigation sources. The Doi-Cho Dem-Ben Luc Rivers play the key roles of irrigation, navigation and ecological restoration. It is crucial to ascertain the pollution status, influencing factors, ecological risks, and possible sources of heavy metals in the surface water of the Doi-Cho Dem-Ben Luc Rivers. In this study, surface water from 7 sampling sites over was collected from the Doi-Cho Dem-Ben Luc Rivers, over 7 consecutive periods from April 2019 to October 2021. Each surface sample was analyzed for 9 heavy metals including Fe, Mn, Cr, Zn, Cu, Pb, Cd, Ni, As. The sampling technique and sample treatment were done based on the Standard Methods for the Examination of Water and Wastewater. The time and space variation of heavy metal concentrations were examined to test the analysis of variance (ANOVA) and correlation among all the parameters using R statistical software.
The results suggest a spatial homogeneity of heavy metals in the surface water the studied rivers. Among all nine examined heavy metals in the studied area, the concentrations of Fe (1.00 ÷ 5.06 mg/L) and Mn (0.14 ÷ 0.28 mg/L) are the highest, and the concentrations of Cr, Cd and As are the lowest that lower limit of detection. The results suggested that the mean concentrations of Fe and Mn were above the acceptable limits of the National technical regulation on surface water quality (QCVN 08-MT: 2015/BTNMT). While the concentrations of Fe, Mn, Zn, Cu, Pb, Ni do not meet the Water quality criteria for aquatic life (United State Environmental Protection Agency). Anthropogenic activities can be the main source of heavy metals in in the surface water of the Doi-Cho Dem-Ben Luc Rivers. Among the heavy metals, a significant positive correlation was observed between Fe, Mn, Zn and Ni (0.64 ÷ 0.87), whereas Cu exhibited a significant positive correlation with Ni (0.51). While Cu and Pb showed a not too strong correlation with Fe, Mn, Zn and Ni (0.25 ÷ 0.48). The distribution of heavy metals may also be influenced by properties of heavy metals and fluctuations in water flows. The results provide guidance for controlling heavry metal pollution and protectting water sources in the Doi-Cho Dem-Ben Luc Rivers.