An Assessment of Soil Erosion and Freshwater Suspended Solid Estimates for Continental-Scale Environmental Modelling

In modelling the environmental fate of chemicals, suspended matter in surface water may play a relevant role as it controls the partitioning of substances between dissolved and adsorbed form. This is particularly important for hydrophobic/non-polar chemicals with high octanol/water partition coefficient (Kow). For a wide class of chemicals, it is then important to evaluate suspended solids concentration in surface waters in order to model the mechanisms of their transport in the environment. Reported values of suspended particulate matter (SPM) or total suspended solids (TSS) range from less than 1 to more than 200 mg l-1, with peaks even orders of magnitude higher. A number of studies highlight that a huge variability is intrinsic for this parameter. Nevertheless, predictive models and estimation methods have been proposed that can provide information on relevant spatial patterns of SPM or TSS. The paper examines two families of models, namely models oriented to sediment concentration or flux estimates and models oriented to soil erosion estimates, which have been widely used at the European scale. Predicted sediment concentration from these models is compared with available TSS and SPM measurements. The analysis points out how soil erosion oriented models can be seen as favourable to depict the fate of pollutants removed from soil, while sediment yield oriented models better fit for pollutants directly emitted to water and then subject to sequestration by solids. Based on the results of the analyses, a blueprint for description of the sediment compartment in chemical fate and transport models is proposed.JRC.H.5-Rural, water and ecosystem resource