Copper(I)/copper(II) reactions in an urban river

The bathocuproine spectrophotometric method for Cu(I) analysis was considerably improved by pre-concentration on C₁₈ columns and selective elution into methanol:water (90:10); a detection limit of 0.1 μg l^-1 was found. Concentrations of Cu(I) in an urban river (2.4-7.5 μg l^-1) varied with solar UV radiation, measured at 365 nm. Mechanisms of photoreduction were studied through Cu(I) scavenging experiments, while the relative importance of particles, colloids and microorganisms were investigated through dilution/filtration. Cu(I)/Cu(II) speciation in the urban river appears to be altered under daylight conditions through a photoreduction process involving Fe(II)/Fe(III), H₂O₂ and dissolved and colloidal organic compounds. Low oxygen conditions in the urban river hinder reoxidation and lead to the high Cu(I) concentrations found.