A model for the concentration of lead and polychlorinated biphenyls in lake sediment

The physicochemical basis of the total particle flux model, which describes the anthropogenic concentration of a chemical in lake sediment using the anthropogenic flux from the atmosphere, total particle flux in the lake, hydraulic loading (q) and distribution coefficient of the chemical (Kd), was investigated. It was found that the influence of q and Kd can be neglected if Kd is greater than a critical value of 400–600 m3 kgDS−1 and a simplified model with a total particle flux of 0.163 ± 0.0240 kgDS m−2 year−1 was derived for lakes in sub-regions of the UK and Ireland. The total particle flux value was shown to be realistic, as it converts to an average sediment yield of 13 tonnes km−2 year−1, a value similar to direct estimates for the region of 10–30 and a value of 13 for similar sized catchments. As the field Kd value for Pb and PCBs in lakes and rivers is greater than the critical value, the simplified model is a physicochemical description of the anthropogenic concentration of these chemicals in lake sediment at the regional and global scales. However, the field Kd for Zn, Cu, Cd, Hg, Ni, PAHs, OCs, chlorobenzenes and chlorophenols is less than the critical value and so the simplified model does not apply to these contaminants.