Control of Fluvial Architecture on the Spatial Distribution of Arsenic Rich Ground Water

Control of Fluvial Architecture on the Spatial Distribution of Arsenic Rich Ground Water

Schaepman, G.

Bruining, J. (mentor)
Donselaar, M.E. (mentor)
Slob, E.C. (mentor)
Bhatt, A. (mentor)

Civil Engineering and Geosciences

Geoscience & Engineering

2012-01-17

In Bihar, India, arsenic rich aquifers are used as a drinking water source by millions of people, even though the arsenic concentration in some places is so high it causes serious health issues. The arsenic concentrations in the aquifers show a large spatial variability, one that is presently unpredictable. The most important factors which play a role in arsenic distribution are the source (natural occurring minerals) and the redox conditions, which enable the arsenic to be released from the minerals. There is a relation between fluvial deposits and redox conditions. In addition, fluvial deposits are known to be heterogeneous, which has large influence on flow regimes. The objective of this study is therefore to investigate the fluvial deposits in the region, and to predict the control they have on the distribution of arsenic. To do so, the architecture of a point bar attached to a clay plug is mapped in the region of Bakhorapur, Bhojpur District, Bihar, India. This was done by interpreting Google Earth satellite images, with executing a transient electromagnetic survey and by drilling two boreholes of 50 m (including well logs); the cores were ultimately studied in detail. The three methods indicate that up to 28 m, two stacked, heterogeneous and laterally continuous 10-15 m thick point bars are present. Below these extensive conglomerate and coarse sand bodies of braided river origin are recognized. The end result is a geological model concept, in which fluvial reservoir architecture elements of importance for flow regimes are highlighted. The geological model concept suggests that both the initial place of release and the spreading of arsenic are to a large extent controlled by the 3D architecture of the fluvial deposits. The concept can be turned into a static model and used for flow calculations such that the user is able to predict arsenic spreading in the case of arsenic release from specific fluvial sediment bodies. Considering the region being full of similar point bar deposits, the concept is generally applicable throughout the region. With this, arsenic safe drinking spots can be located, helping a great number of people.

contamination
sedimentology
point bars

http://resolver.tudelft.nl/uuid:c587a99b-6ae3-4a17-b14c-357f568600c7

Student theses

master thesis

(c) 2012 Schaepman, G.