Spatial distribution, compositional pattern, and source apportionment of colloidal trace metals in the coastal water of Shandong Peninsula, northeastern China

The Shandong Peninsula (SP) is the largest peninsula in China hosting rich economic and agricultural activities. In this study, we investigated the behavior of dissolved Mn, Fe, Cu, Zn, Cd, and Pb and their colloidal phases in the coastal and estuarine areas of SP. Pb and Zn had the highest contamination factors of 0.22–10.15 and 0.90–4.41, respectively. The <1 kDa accounted for 23–57 % of the total dissolved phase. Mn, Fe, Cu, Zn, Cd, and Pb were more likely to bind to 100 kDa–0.45 μm colloids (21–57 %). For colloidal Fe and Cu, the adsorption-release behavior had more significant effects on their dynamics. In contrast, the changes in colloidal Mn, Cd, and Pb were mainly controlled by the combined influence of temperature, dissolved oxygen, and microbial activity. However, the 1–3 kDa Zn exhibited a greater pH-dependent dispersion and was significantly positively correlated with it.