Colloidal Pumping:  Evidence for the Coagulation Process Using Natural Colloids Tagged with 203Hg

• Published in: Environmental science & technology 1996-10, Vol.30 (11), p.3335-3340
• Main Authors: Stordal, Mary C, Santschi, Peter H, Gill, Gary A
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical phenomena; Case studies; Chemical reactions; Environmental monitoring; Exact sciences and technology; Mercury; Natural water pollution; Pollution; Rivers; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es9601806

Colloids isolated from waters of the Trinity River (Texas) were tagged with high specific activity mercury (203Hg) and re-equilibrated with ultrafiltered water and particles. The transfer of radioisotopic Hg from the colloidal pool to the particulate pool was monitored over a 5-day period. The experiment was repeated with a range of particle concentrations from 10 to 82 mg/L and at salinities of 13.6 and 24.5. Partitioning of 203Hg to particles and colloids during the radiotracer experiments was comparable or slightly higher than that observed for stable Hg in Galveston Bay. In all cases, 203Hg was transferred from the colloidal pool (1 kDa−0.4 μm), consisting mostly of macromolecular organic matter, to the particulate pool (>0.4 μm), indicating that colloids serve as an intermediary in the transfer and removal of Hg and perhaps other trace metals in natural systems. The rate of transfer was determined by applying an ir reversible kinetic model to the data. The transfer ap peared to occur by two processes, a fast (