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[Display omitted] • · The spatial characteristics of grain size and elemental composition in surface sediment of the Yellow River are investigated. • · The weathering nature, recycling characteristics and rock compositions are identified. • · The influence of climate condition and tectonic setting on erosion, weathering, and sedimentary recycling is elucidated. • · The provenance of surface sediment of the Yellow River is disclosed. Geochemical investigations of fluvial sediment help understand the provenance of sediment and surface processes taking place on the Earth at the watershed scale. This study is aimed at identifying the weathering and sedimentary recycling of the surface sediment of the Yellow River using the Chemical Index of Alteration (CIA), Weathering Index of Parker (WIP), Index of Compositional Variability (ICV), Mafic-Felsic-Weathering (MFW) ternary diagram, and Al-Ti-Zr ternary diagram. Source rocks compositions were clarified using Al 2 O 3 -CaO⁎+Na 2 O-K 2 O (A-CN-K), MFW, discriminant function, and Cr/V vs Y/Ni diagrams. The results demonstrated that the surface sediment of the Yellow River has experienced an overall low intensity of weathering and recycling. However, significant differences were observed in the characteristics of weathering and recycling among the upper, middle, and lower reaches, which is in turn associated with the differences in climatic conditions and tectonic settings. Source rocks manifested a typically mixed type composition, including felsic igneous rocks, intermediate igneous rocks, quartzose sedimentary rocks, and mafic components. Moreover, the sediment in the source area of the Yellow River may have originated from the clastics produced by the abrading of mountain glaciers. Sediment in the area in which the Yellow River flows through the Chinese Loess Plateau primarily originates from loess in the desert in Northwestern China. Sediment in the lower reaches does not only include the sorted sediment flowing down from the upper and middle reaches, but also that imported from regional rivers. This study can furnish a sound scientific basis for the reconstruction of the paleoclimatic and paleoenvironmental changes that affected large watersheds in arid and semi-arid areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • The spatial distribution of heavy metals in surface sediments of the Yellow River mainstream are investigated. • The contamination degree, ecological risk, and source of heavy metals are explored. • The applicability of risk assessment indices of heavy metals in sediments is elucidated. • The reliability of multivariate statistical analyses for source identification of heavy metals is confirmed. 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. [ABSTRACT FROM AUTHOR]