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

Highlights: • Colloidal Cu heterogeneity in size and variation was studied in the YRE. • LMW-Cu migrated more violently than HMW-Cu and stabilized with increasing salinity. • • Strong ligand, mixing process and desorption co-regulated colloidal Cu of the YRE. 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 (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.