Heavy metal contamination of Yellow River alluvial sediments, northwest China

This study concerns the distribution and potential sources of elevated heavy metal concentrations (Cr, Ni, Pb, Zn) in alluvial sediments of the Yellow River close to an industrial area in northwest China. Sediment samples were collected from 25 locations and analyzed for common ions (Na+, K+, Ca2+, Mg2+, Cl-, SO4 (2-), HCO3 (-)), total salts, and heavy metals (Cr, Ni, Pb, Zn). Concentrations of Cr, Ni, Pb, and Zn were found to exceed background values observed at up-gradient sites and in surrounding non-industrialized areas. The surficial sediments can be classified as slightly polluted and seem to present a low, albeit significant potential ecological risk in the center of the study area where elevated Cr, Ni, Pb, and Zn appear to be associated with the presence of several industrial plants and a wastewater drainage ditch. Correlation and multivariate analyses confirm that the heavy metal pollution is anthropogenic in origin. Urgent action is required at both administrative and technical levels to avoid further degradation of the sediments by industrial waste. Necessary measures include the establishment of soil, sediment and water monitoring programs, a strengthening of compliance standards and greater enforcement of regulations.