Bioturbation-driven transport of hydrophobic organic contaminants from bed sediment

Compared to molecular diffusion the bioturbation-driven soluble fraction transport for hydrophobic organic chemicals (HOCs) from bed sediment is rapid, and it increases with increasing partitioning on the particle phase. This behavior is supported by three sets of data: one is PCB from the Hudson River, NY, and the other two sets are PAHs and chlorinated benzenes in laboratory microcosms. The proposed mechanisms for this behavior are: (1) biotubation of particle-bound HOCs from depth through the upper decimeter of the bed to the interface, (2) rapid chemical desorption at the sediment-water interface followed by (3) transport through the benthic boundary layer to the water column. Based on this mechanism, a simple transport equation is developed, then used to correlate the data and extract intrinsic transport coefficients. These in-bed particle biodiffusivities and benthic boundary layer coefficients are comparable to other reported measurements.