Talk, SETAC Europe, Nantes: 2016-05-22 - 2016-05-26
Abstract:
Persistence is an undesirable property of chemicals that is difficult to measure in the real environment. Junge relationships describe the correlation between the relative standard deviation of concentrations of chemicals and their residence times. Once calibrated for a set of compounds and/or locations they can potentially be used to estimate the persistence of pollutants. The parameter b in the Junge equation is a measure of the strength of the relationship between variability in concentrations and residence time. [1] [2] In this study we explored Junge relationships relating the background concentrations of chemical pollutants to their degradation half-lives in the Danube River. The concentrations of four hypothetical chemicals with biodegradation half-lives of 7, 15, 30 and 90 days were obtained using the STREAM-EU model [3] assuming emissions from urban waste-water as proportional to population. Junge relationships were calculated to derive (1) “Temporal” relationships from variability during the year at each of the stations, and (2) “Spatial” relationships from variability between the stations on each day of the year. Subsequently, a Junge relationship was calculated from the data of the Joint Danube Survey (JSD) sampling campaign [4] for caffeine and six pharmaceuticals: benzafibrate, carbamazepine, diclofenac, gemfibrozil, ibuprofen and sulfamethoxazole. Half-lives of the compounds were gathered from literature. We found Junge relationships in the Danube in both modelled and measured concentrations. Results from STREAM-EU show clear Junge relationships for the 4 theoretical chemicals in the Danube. The parameter b ranges between 0.1 and 0.8 for the temporal analysis and from 0.1 to 0.4 for the spatial analysis. The higher b values in the temporal analysis are found in the locations downstream (i.e. Romania), were population and emissions are relatively low. For the spatial analysis, the higher values of b are found in the months of October and November. The analysis of pharmaceuticals and caffeine data obtained from the JSD, also shows a Junge relationship with b of 0.25. Modelling results suggest that Junge relationships are more likely to be found during October or November and downstream in the Danube, but this has not been confirmed yet with monitoring data. Measurements within the optimal spatial and temporal conditions defined by the modeling analysis could potentially be used to estimate the persistence of other chemical pollutants.