Continental scale inverse modeling of common organic water contaminants in European rivers

The paper presents a comprehensive analysis of a pan-European data set of measured river water concentrations of 16 common polar organic chemicals. We use observed concentrations to perform a back analysis of emissions and chemical half lives through a simple two-parameter inverse model. The analysis does not allow identifying a single combination of half life and emission factor for a given chemical, but only a set of combinations which are Pareto-optimal or non-dominated. In general, the approach provides a rational basis for the screening of chemicals in rivers. With reference to the 16 chemicals considered here, estimated emission factors and half lives are reasonably consistent with the ones reported in other studies. For more precise estimates, prior knowledge about either emission factors or half lives is necessary. On the basis of the proposed approach it is possible to map continuous distributions in space of river concentrations and loads, therefore generalizing the results of a sampling campaign from discrete points, and enabling to compute the total chemical loads to European seas, by considering the range of variability of emission factors and half lives. For the considered chemicals, the sea loads range from less than 0.5 tonne/year for the less abundant or less persistent chemicals, to more than 40 tonnes/year for the most widespread and persistent ones, with an uncertainty within a factor of 2. On the basis of the results, the approach can be proposed to support decisions for the identification and management of catchment-specific chemical pollutants for the implementation of the European Water Framework Directive.

JRC.H.5 - Rural, water and ecosystem resources