Biofilm growth widely occurs at the sediment-water interface, which may affect the mass exchange and exhibit biogeochemical impacts. Here, the release of Cu was studied using sediment spiked with CuCl<sub>2</sub> in designed T-cell microcosms. The sediment was exposed to the sampled lake water from Tsinghua University with additional nutrients to ensure high activities of microorganisms. A peristaltic pump was used to adjust the flow velocity and refresh the experimental water. The experiments were conducted around 25 °C under both natural lighting and shading treatment, to mimic the cases with and without biofilm growth (including two T-cells under natural lighting, two T-cells with shading treatment, and one T-cell under natural lighting but without Cu spiking as a blank). The whole experiment lasted two months, during which the overlying water was sampled periodically to measure the release characteristics of Cu from the spiked sediment, and the DGT and microelectrode were also used to estimate the changes of Cu concentration and O<sub>2</sub> profile in the sediment, respectively. Surface sediment was also sampled every week to quantify the biomass evolution, and then the effects of biofilm growth on Cu release were statistically analyzed. Results show that the biomass increased with the cultivation periods under natural lighting, which affected the Cu release as compared with the case of shading treatment (i.e., without biofilm growth). Moreover, the CapSim 4.0 model developed by Reible Research Group was applied to model the Cu release by setting a biofilm layer (probably as a potential natural capping layer) above the contaminated sediment. Different cases with a wide range of biofilm properties were considered, and their effects on Cu release were numerically predicted. It is shown that the simulation with consideration of biofilm effects can better predict the release characteristics, which may further provide references for the protection of aqueous ecosystem.

Effects of biofilm growth on the release of Cu from contaminated sediment

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