Assessing nitrate pollution in the Kinshasa groundwater system using a hybrid approach
(2016)
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- Abstract
- This thesis studies the groundwater pollution by nitrate in the region of Kinshasa (DR Congo) using an integrated methodological approach combining physicochemical, isotopic and modeling analyses. The first main objective is to assess the groundwater quality and to identify the sources of nitrate. The groundwater is poorly mineralized and nitrate is one of the major ions contributing to the mineralization processes. The combined use of hydrochemical properties and multiple isotope tracers allows identifying and separating the sources of nitrate and elucidating complex mixing processes. The Bayesian mixing model of nitrogen and oxygen isotopes in nitrate provides general ordering of proportional source contributions. Two multivariate statistical approaches allow linking the measured groundwater nitrate to different land use attributes and demonstrate the overwhelming impact of poorly planned urbanization on groundwater nitrate contamination. The second main objective is to assess the regional groundwater contamination by mapping the groundwater body vulnerability and the nitrate concentrations which are measured on sparsely distributed sampling stations. The parametric vulnerability model is first modified and calibrated to predict the intrinsic vulnerability and the groundwater pollution risk to nitrate. A Bayesian data fusion approach is subsequently implemented to map the nitrate concentrations in areas located far away from monitoring stations. This approach reduces considerably uncertainty in regionally predicted concentration. Finally, a tracing experiment allows estimating vertical travel times through the vadose zone. The implemented hybrid approach is translated in state-of-the-art groundwater quality risk maps which are pivotal for designing future protection and management programs of the Kinshasa groundwater system.
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Citations
Mfumu Kihumba, A. (2016). Assessing nitrate pollution in the Kinshasa groundwater system using a hybrid approach. https://hdl.handle.net/2078.5/58762