Contamination and Potential Ecology Risk of Heavy Metals in the Sediment of the Cau river, Vietnam

Five sediment cores collected at the Cau river section flowing through Thai Nguyen were analyzed to evaluate the vertical profile, enrichments, and contamination of six heavy metals including Cu, Pb, Zn, Cr, As, and Cd. The impacts of investigated metals on ecology were estimated by the toxic unit and the potential ecological risk index. The obtained mean heavy metal concentration in the five sediment cores for investigated metals was: Cd (0.56 - 1.74 mg kg−1) < As (10.2 - 32.3 mg kg−1) < Cr (12.1 - 36.2 mg kg−1) < Cu (16.0 - 51.2 mg kg−1) < Pb (24.5 - 85.5 mg kg−1) < Zn (48.2 - 151 mg kg−1). The spatial distribution and vertical patterns of heavy metal concentration in the sediment cores differed substantially among the investigated sites. Among the six investigated heavy metals, Cr was of natural origin while the remaining 5 metals (Cu, Pb, Zn, As, Cd) came primarily from human activities. Based on the classification using EF, Igeo, and PLI, sediment at S3, where there was a concentration of discharge from main activities of the area, was strongly contaminated with heavy metals. The other sites (S1, S2, S4, and S5) were in the condition slightly contaminated with heavy metals. As and Cd were mostly associated to the overall pollution load index of heavy metals in the sediment of the Cau river. The highest STU and considerable risk from heavy metals were observed at S3. Sediment at S1, S2, S4, and S5 posed a moderate ecological risk.