Project

Groundwater; Arsenic; Geogenic contamination; Mineralogy; Geochemistry; Hydrochemistry; Environmental physics; Reactive transport modelling; Risk identification; Health prevention; Water management

Lead
Weltweit beziehen mehr als 150 Millionen Menschen ihr Trinkwasser aus Arsen-kontaminiertem Grundwasser. Das Halbmetall ist natürlicherweise in Sedimenten enthalten und wird unter stark anoxischen Bedingungen im Grundwasser freigesetzt. Arsens ist geruchs- und geschmacklos, aber für den Menschen sehr giftig. Über längere Zeit eingenommen können selbst bei tiefen Konzentrationen schwerwiegende Gesundheitsschäden auftreten, wie Hyperpigmentierung, Leber- und Nierenschäden, Herz-Kreislauf-Erkrankungen und Krebs.Grundwässer mit hohem respektive tiefem Arsengehalt sind durch unterschiedliche Redox-Bedingungen gekennzeichnet und oft nur durch schmale Übergangszonen voneinander getrennt. Bisher ist unklar in welchem Ausmass solche Redox-Gradienten die Mobilisierung, den Transport aber auch die Rückhaltung von Arsen bestimmen. Daher soll nun das komplexe Zusammenspiel von mineralogischen, mikrobiologischen, hydrologischen und geochemischen Prozessen untersucht werden.
Lay summary
Inhalt und Ziel des Forschungsprojekts Übergeordnetes Ziel ist die Wissenslücken hinsichtlich der Arsenmobilität in anoxischen Grundwasserleitern durch einen bewusst integrativen und interdisziplinären Ansatz zu schliessen. In diesem Deutsch-Schweizerischen Projekt arbeiten  Forscher aus verschiedenen Disziplinen sehr eng zusammen (1-Mineralogie & Geochemie, Karlsruhe Institut für Technologie; 2-Mikrobiologie, Uni Tübingen; 3-Hydrochemie & Umweltphysik, Eawag Dübendorf; 4-Reaktive Transportmodellierung, Uni Tübingen) und Feldforschung mit der Uni Hanoi in Vietnam. Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts Aufgrund der weltweit boomenden Grundwassernutzung steigt das Risiko dass qualitativ einwandfreie Grundwasserleiter langfristig kontaminiert werden. Die erworbenen Kenntnisse sollen Grundlagen bilden um Risikogebiete auszuscheiden und einer schleichenden Arsengefährdung entgegenzuwirken. Dies ist von direktem Nutzen für Bevölkerung, Behörden sowie Medizin und Naturwissenschaften.

Direct link to Lay Summary

Last update: 25.04.2017

Active participation

Communication	Title	Media	Place	Year

Title	Year

Elevated levels of arsenic (As) in groundwater are a health problem affecting over 100 million people worldwide, particularly in the densely populated river deltas of South and Southeast Asia. Aquifers containing low and high As levels are characterized by highly contrasting redox conditions that are often separated by Fe-dominated transition zones. Such redox fronts play a crucial role with regard to As advection and retention, consequently preventing safe aquifers from contamination with As. However, because of the constantly growing water demand and increasing groundwater abstraction, aquifers being currently not affected by As are at risk of becoming As-polluted in the future.Despite more than a decade of research, it remains largely unknown to which extent sorption of As at Fe-dominated redox fronts delays the contamination of low-As aquifers under enhanced advective flow conditions. Without addressing this key issue in a comprehensive, multidisciplinary manner, it is not possible to make reliable and robust predictions about the time scale over which low-As aquifers are likely to become contaminated by incursion of water from adjacent As-bearing aquifers.We hypothesize that the stability and persistence of the redox transition zones in space and time are largely controlled by the mutual interaction of (a) transport processes, (b) microbial activity and (c) the stability of As host mineral phases (mainly Fe-bearing). We postulate that the abundance and type of Fe phases as well as of As species vary across the transition zones as a result of the availability of electron donors and acceptors, the activity of specific microbial communities, and the overall water exchange and solute transport. Furthermore, we expect that external sources of dissolved organic carbon, e.g. by vertical aquifer-aquitard exchange, foster As mobilization and enrichment in groundwater.The overarching goal of this proposed multidisciplinary research project is to assess potential future As contamination of currently 'safe' groundwaters by understanding and predicting the long-term mobility of As under enhanced hydraulic forcing across Fe-dominated redox transition zones in aquifer systems.The simultaneous characterization of these key processes on As-dynamics and their interactions will be carried out in a test field in Vietnam, which has previously been characterized by our research consortium and is particularly suitable to reach our research goals. Data obtained will be integrated in an advanced reactive transport model that couples physical transport and exchange with the key bio-geochemical reactions. This integrated model will allow to analyze the future evolution of the relevant redox fronts in time and space and the fate of As. To our knowledge, such a comprehensive approach involving all key disciplines has not been carried out to date and will, thus, significantly enhance our understanding and our ability to predict As mobility in groundwaters.