Distribution characteristics, source identification and risk assessment of heavy metals in surface sediments of the Yellow River, China

Heavy metals in river sediments pose major threats to aquatic ecological environments and public health. This study investigated the characteristics, sources, and risks of heavy metals in surface sediments from the mainstream of the Yellow River. The grain size, loss on ignition (LOI), and content of Mn, Zn, V, Ni, Pb, and Cr in 61 samples were measured. The contamination level was evaluated using six indices, namely sediment quality guidelines (SQGs), contamination factor (C-f), geo-accumulation index (I-geo), modified degree of contamination (mC(d)), potential ecological risk index (RI), and pollution load index (PLI), and their spatial distribution was determined through Kriging interpolation. The sources of heavy metals were defined using multivariate statistical analyses, namely Pearson's correlation analysis (P'CA), principal component analysis (PCA), and cluster analysis (CA). The results show that Pb has the highest ecological risk, followed by Cr, Ni, and V, whereas Mn and Zn pose no risk. Mn and Zn mainly originate from natural processes, while Cr from anthropogenic process. V, Pb, and Ni are most likely from mixed sources. The ecological risk of heavy metals increases significantly when the Yellow River passes through the Loess Plateau. Furthermore, compared with SQGs and C-f, the assessments of heavy metal contamination by I-geo, RI, mC(d) and PLI are more objective and accurate. This study provides a powerful reference for contamination control and ecological security in the Yellow River Basin.