Effects of aging on the digestive solubilization of Cu from sediments

Solubilization of particulate Cu by different solutions, mimicking digestive fluids of deposit-feeders, was quantified in stable isotope 65Cu-spiked sediments (with 3 days-2 months Cu-sediment contact time or aging). Copper solubilization generally decreased with prolonged aging. However, such decrease became less evident after 1 month and equilibrium of Cu in sediments could be reached after 2 months. Aging effects on Cu solubilization can be explained by the changes in Cu geochemical fractionation with aging: Cu generally transferred from more mobile phases (carbonate and Fe–Mn associated) to more refractory phases (organic associated and residual phase). Besides Cu geochemical fractionation, digestive fluid composition and different Cu solubilization pathways involved, as well as sedimentary organic content, could all affect the digestive solubilization of Cu and its change with aging. Our results emphasize the necessity of considering Cu aging in laboratory sediment toxicity experiments, and in risk assessment of Cu contaminated sediments.

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► Cu digestive solubilization decreases with Cu-sediment contact time.
► Cu may reach equilibrium in sediments after 2 months of aging.
► Cu redistribution to organic associated phase may explain Cu aging effects.
► Digestive fluid composition affects Cu digestive solubilization and aging effects.
► Cu stable isotope offers many advantages in Cu aging studies.