Modelling localized sources of sediment in mountain catchments for provenance studies

A hydrology–sediment modelling framework based on the model Topkapi-ETH combined with basin geomorphic mapping is used to investigate the role of localized sediment sources in a mountain river basin (Kleine Emme, Switzerland). The periodic sediment mobilization from incised areas and landslides by hillslope runoff and river discharge is simulated in addition to overland flow erosion to quantify their contributions to suspended sediment fluxes. The framework simulates the suspended sediment load provenance at the outlet and its temporal dynamics, by routing fine sediment along topographically driven pathways from the distinct sediment sources to the outlet. We show that accounting for localized sediment sources substantially improves the modelling of observed sediment concentrations and loads at the outlet compared to overland flow erosion alone. We demonstrate that the modelled river basin can shift between channel-process and hillslope-process dominant behaviour depending on the model parameter describing gully competence on landslide surfaces. The simulations in which channel processes dominate were found to be more consistent with observations, and with two independent validations in the Kleine Emme, by topographic analysis of surface roughness and by sediment tracing with ¹⁰ Be concentrations. This research shows that spatially explicit modelling can be used to infer the dominant sediment production process in a river basin, to inform and optimize sediment sampling strategies for denudation rate estimates, and in general to support sediment provenance studies. © 2020 John Wiley & Sons, Ltd.     

Zielvorgaben für Pflanzenschutzmittelwirkstoffe und andere Schadstoffe in Oberflächengewässern

Quality Targets for Pesticides and Other Pollutants in Surface Waters Surface waters are not only adversely affected by industrial and municipal wastewaters but also by diffuse sources. For the control of the ecological water quality, so‐called quality targets are set. The quality targets are threshold concentrations for hazardous substances related to the protected goods like water ecosystems, drinking water supply, sediments, or fishing. In this paper, quality targets for the protection of aquatic life in surface waters were derived on the basis of a concept developed by the International Commission for the Protection of the Rhine (Internationale Kommission zum Schutze des Rheins – IKSR). The quality targets for the selected hazardous substances, which mainly belong to the chemical class of pesticides, were calculated using ecotoxicological results for species of bacteria, algae, fish, and small crustaceans, as the four trophic standards of the water ecosystem. In cooperation with the Federal Environmental Agency (Umweltbundesamt – UBA) the effect data were taken from ecotoxicological data bases. According to the concept of the IKSR, the lowest test result for the most sensitive species was multiplied by an assessment factor. This proceeding concerns the difficulty in describing the complex interactions in water ecosystems with toxicity data of single laboratory experiments for a few organisms. For seven pesticides quality targets below 0.1 μg/L were proposed. These results show that the ecotoxicologically based quality targets might be even lower than the limit values for pesticides in drinking water of 0.1 μg/L. But for most of the substances the determined values are significantly higher. The great concentration range of quality targets demonstrates distinctly that one standard concentration for all pesticides could not be given with regard to the different effects on aquatic organisms.     

On the formation of diaplectic glass: Shock and thermal experiments with plagioclase of different chemical compositions

This contribution addresses the role of chemical composition, pressure, temperature, and time during the shock transformation of plagioclase into diaplectic glass—i.e., maskelynite. Plagioclase of An_50‐57 and An₉₄ was recovered as almost fully isotropic maskelynite from room temperature shock experiments at 28 and 24 GPa. The refractive index (RI) decreased to values of a quenched mineral glass for An_50‐57 plagioclase shocked to 45 GPa and shows a maximum in An₉₄ plagioclase shocked to 41.5 GPa. The An₉₄ plagioclase experiments can serve as shock thermobarometer for lunar highland rocks and howardite, eucrite, and diogenite meteorites. Shock experiments at 28, 32, 36, and 45 GPa and initial temperatures of 77 and 293 K on plagioclase (An_50‐57) produced materials with identical optical and Raman spectroscopic properties. In the low temperature (<540 K) region, the formation of maskelynite is entirely controlled by shock pressure. The RI of maskelynite decreased in heating experiments of 5 min at temperatures of >770 K, thus, providing a conservative upper limit for the postshock temperature history of the rock. Although shock recovery experiments and static pressure experiments differ by nine orders of magnitude in typical time scale (microseconds versus hours), the amorphization of plagioclase occurs at similar pressure and temperature conditions with both methods. The experimental shock calibration of plagioclase can, together with other minerals, be used as shock thermobarometer for naturally shocked rocks.     

Towards a ‘new form of governance’ in science-policy relations in the European Maritime Policy

This article seeks to identify the key principles that should guide the definition of the mandate and institutional structure for acquiring scientific advice in support of the European Maritime Policy. The EU has stated that, as concerns the Maritime Policy, the relations between science and policy ought to reflect a ‘new form of governance’. Far from being an easy task, however, the EU has observed that there are problems of credibility and legitimacy in the relations between science and society (including policymakers), which first need to be overcome. Against this background, the article draws on some of the newest conceptual and empirical research on science-policy relations, which has sought to analyse and ultimately provide frameworks for overcoming such challenges. On this basis, the article investigates the principles that need to be applied to constitute a ‘new form of governance’ as a means of paving the way toward a more credible and legitimate use of scientific data, information and knowledge within policymaking and implementation processes.