Controlling factors and distribution of geochemical characteristics of the surface sediments in the Yellow River Delta

The distribution characteristics of 16 elements in the surface sediments from 180 sites in the Yellow River Delta were analyzed. The effects of sediment grain size, hydrodynamic environment, and material sources on geochemical characteristics of the surface sediments were analyzed using multivariate statistical analysis, numerical modelling, and element ratio; and the main controlling factors of geochemical characteristics of surface sediments in the study area were discussed. Based on the distribution of geochemical elements, the study area was divided into six geochemical regions by cluster analysis. Most of the elements (TFe₂O₃, Al₂O₃, MgO, MnO, K₂O, Cr, Ni, Cu) in Regions I-2, I-3, II-2, and the eastern part of II-1 are characterzied by elevated concentrations, and the sediment grain size in these areas is fine. The contents of SiO₂ are higher in Regions I-1 and II-3, and the sediment grain size is coarser. Results show that tidal current controled the initiation and transport of sediment in the study area, and tidal residual currents affected the enrichment of fine-grained sediment and most elements. Local hydrodynamic environment controlled the spatial pattern of grain size in surface sediments. Obvious regional differences in material input from the Yellow River and human activities were revealed. The modern Yellow River estuary was strongly controlled by material input from the Yellow River. Human activities had a stronger impact on Chengbei Old Yellow River estuary, especially Cd, Zn, Pb and P₂O₅. Natural factors were the main factors on the geochemical distribution of surface sediments, while human activities further alytered the spatial distribution of some elements.