Abstract
Starting from measured river concentrations, emission factors of 158 organic compounds out of 199 analyzed belonging to different groups of priority and emerging contaminants [pesticides (25), pharmaceuticals and hormones (81), perfluoroalkyl substances (PFASs) (18), industrial compounds (12), drugs of abuse (8) and personal care products (14)] have been estimated by inverse modeling. The Llobregat river was taken as case study representative of Mediterranean rivers. Industrial compounds and pharmaceuticals are the dominant groups (range of 104mg·1000inhab−1·d−1). Personal care products, pesticides, PFASs and illegal drugs showed a load approximately one order of magnitude smaller. Considered on a single compound basis industrial compounds still dominate (range of ca. 103mg·1000inhab−1·d−1) over other classes. Generally, the results are within the range when compared to previously published estimations for other river basins. River attenuation expressed as the percentage fraction of microcontaminants eliminated was quantified. On average they were around 60–70% of the amount discharged for all classes, except for PFASs, that are poorly eliminated (ca. 20% on average). Uncertainties associated with the calculated emissions have been estimated by Monte-Carlo methods (15,000 runs) and typically show coefficients of variation of ca. 120%. Sensitivities associated with the various variables involved in the calculations (river discharge, river length, concentration, elimination constant, hydraulic travel time and river velocity) have been assessed as well. For the intervals chosen for the different variables, all show sensitivities exceeding unity (1.14 to 3.43), tending to amplify the variation of the emission. River velocity and basin length showed the highest sensitivity value. Even considering the limitations of the approach used, inverse modeling can provide a useful tool for management purposes facilitating the quantification of release rates of chemicals into the aquatic environment.
Highlights
Developed societies are characterized by a growing use of chemicals in their urban, industry and agriculture activities (Muir and Howard, 2006; Arnot et al, 2006)
The present study aims at estimating the emission of ca. 160 priority and emerging contaminants belonging to different families in a Mediterranean basin (Llobregat river basin, Sabater et al, 2012) by inverse modeling using the minimal amount of information
The average emission factors expressed in mg·1000 inhab−1·d−1 for the organic contaminants studied showed substantial variability as expressed by the standard deviation of the distribution obtained after the Monte-Carlo analysis (Table 1)
Summary
Developed societies are characterized by a growing use of chemicals in their urban, industry and agriculture activities (Muir and Howard, 2006; Arnot et al, 2006). Among the hundreds of thousands of different commercially available chemicals, the so called ‘emerging contaminants’ are of special concern These are defined as chemicals, whose environmental relevance has been only recently highlighted due to either new scientific findings or because their environmental occurrence has been evidenced owing to the progress achieved by analytical techniques (Barceló and Petrovic, 2007). Pharmaceuticals and personal care products, endocrine disrupting chemicals (ECD), pesticides, illicit drugs, perfluoroalkyl substances (PFASs) and other industrial compounds are just some relevant examples. All these families are characterized by their widespread introduction into the environment, the lack of knowledge as regards their middle or long-term effects in the human health and the ecosystems, as well as the fact that they are generally only poorly covered by existing regulations (Schwarzenbach et al, 2006). Knowledge about their environmental occurrence, fate and inputs discharged are of great relevance
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