Spatial and environmental characteristics of colloidal trace Cu in the surface water of the Yellow River Estuary, China.

Dynamic variations in chemical composition and size distribution of dissolved copper (Cu) along the river-sea interface in the Yellow River Estuary (China) were investigated. On average, ~64% and ~8% of bulk dissolved Cu (<0.45 µm) were partitioned in the <1 kDa fraction and 1-100 kDa, respectively. The other 28% were in the 100 kDa-0.45 µm colloids, which indicates that this fraction may dominate the overall morphology of colloidal Cu. The <3 kDa Cu fraction was susceptible to environmental parameters and the >3 kDa fraction was related to the behavior of dissolved organic carbon. 1-100 kDa Cu migrated more violently than >100 kDa Cu and tended to be a stable polymer, with stability increasing towards the sea. The source of <1 kDa Cu was complex and may be supplemented by the decomposition of small molecular colloids and the addition of the sediments or particles ligands.