Das Projekt "Arsenic contamination of Ogosta river: Linking biogeochemical processes in floodplain soils with river system dynamics" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Biogeochemie und Schadstoffdynamik durchgeführt. The sustainable management of land, which has been heavily contaminated by industrial or mining activities, poses an important challenge to many industrialized countries, including Bulgaria. This project focuses on arsenic (As) contamination in NW Bulgaria, where the floodplains of the Ogosta river received large amounts of As-rich mining wastes near Chiprovtsi between 1964 and 1979. The goals of the project are (i) to investigate the magnitude and spatial distribution of As contamination in floodplain soils and sediments in relation to river system dynamics, (ii) to improve the process-oriented understanding of As release from soils to river and groundwater by microbial and physico-chemical processes during periods of low and high flow, and (iii) to explore advanced approaches for integrating process-oriented, molecular scale knowledge and river-system scale information to better understand As speciation, As fluxes, and impacts on water quality at the river-system scale. The project is expected to yield novel process-oriented knowledge on the dynamics of As in highly contaminated river floodplains. New ways of integrating molecular-scale and river-system scale information will be explored, which can then also be applied to other river systems in Bulgaria. The project will provide the scientific basis for river management and potential remediation strategies for Ogosta river. Ultimately, it will help protect the local population from adverse health effects arising from the legacy pollution with As and other heavy metals by former mining.