Distributions of transition elements in the surface sediments of the Yellow Sea

We report the distributions of transition elements in the surface sediments of the Yellow Sea including the coastal areas of both Korea and China. The maximum concentrations of LOI (loss on ignition), Al, and transition elements (Ti, V, Cr, Fe, Co, Ni, Zn and Cu), except Mn, are found in the central Yellow Sea where clay minerals predominate. A good positive correlation between silt plus clay contents and most of the transition elements (Ti, V, Cr, Fe, Co, Ni, Zn, and Cu, r=0.72–0.91) suggests that the distribution patterns of these elements are strongly controlled by quartz dilution. The distribution pattern of Mn is opposite to the other transition elements, displaying the maximum concentrations in the shallower regions where coarse sediments predominate. Higher Mn enrichment factors (max. EF: 3.0) and higher Mn/Fe ratios in the coastal sandy regions (relative to those in the other study areas and in suspended matter of the source rivers) suggest the presence of authigenic Mn by forming an oxidizing condition due to higher porosity but lower organic contents. In contrast, relatively lower Mn/Al ratios and lower enrichment factors (mean EF: 0.7) are observed in the central Yellow Sea where maximum organic contents are present. This suggests that the dissolutions of Mn oxides take place in the central Yellow Sea sediments by oxygen reduction during decomposition of organic matters.