Understanding Uranium and Arsenic sources and mobility in deep groundwater flow systems from the Altiplano MexicanoCopyright: Cauich
Understanding Uranium and Arsenic sources and mobility in deep groundwater flow systems from the Altiplano Mexicano
Project term: 2017 to 2020
Project members: Dario Cauich, Thomas R. Rüde
On the Mexican Altiplano with its semi-arid to arid climate and due to its geological condition with igneous rocks and related sediments, which have elevated concentrations of uranium and arsenic, these two trace elements show a relationship, despite their generally different redox properties and transport behavior. Therefore, these elements can be mobilized into groundwater, which is the main source for water supply of the population in these areas. There is a need to understand the processes of geogenic enrichment of uranium and arsenic in the sediments and their release to the groundwater. Therefore, the objective of the study is to understand processes controlling uranium and arsenic mobility in groundwater based on geochemical, hydrogeochemical and mineralogical characterization. Also to quantitatively support, the conceptual model of the transport of uranium and arsenic in the Calera and Villa de Reyes basins.
For that reason, this proposal will investigate in laboratorial studies the principle processes of enrichment and release with respect to rocks and sediments and the climate conditions of the Mexican Altiplano. Data from the laboratory will be used to verify hydrochemical modeling of the processes to give deeper understanding of the natural behavior of these two toxic metals. This research is different to the overwhelming majority of uranium related publications dealing with high concentration environments of uranium deposits or nuclear waste repository, as it deals with uranium as a heavy metal toxic to the kidneys and the low, but still toxicologically critical concentrations of the geogenic background.
The research questions will be:
- What is the fate of U and As released from volcanic glasses in the soils, is there a sink?
- Is the sink stable and which mechanisms can release U and As?
- What is the influence of high evaporation on groundwater chemistry and does that influence U and As mobility?
- What is the species of mobilized U?
The activities are structured into work packages
- WP 1: Intense literature survey.
- WP 2: preparation of field survey (sampling protocol).
- WP 3: sampling of groundwater.
- WP 4: sampling of rocks and soils.
- WP 5: sample preparation and analysis.
- WP 6: column tests with specific soils.
- WP 7: sampling and analyzing selected soil profiles.
- WP 8: multivariate statistical evaluation of data.
- WP 9: hydrochemical modeling.
- WP 10: attendance to conferences.
- WP 11: manuscripts to scientific journals.