Journal of Geochemical Exploration
Journal of Geochemical Exploration
5 years ago

Understanding the hydrogeochemical evolution of groundwater in Precambrian basement aquifers: A case study of Bugesera region in Burundi

This study investigates hydrogeochemical processes controlling groundwater evolution in a Precambrian basement aquifer situated in northeastern Burundi, in Bugesera region. The hydrogeochemistry has been evaluated based on the analytical results of 143 water samples comprising 66 samples from shallow wells, 61 samples from springs, and 16 samples from the shallow lakes. While the stability diagrams, the evolutionary sequence of groundwater inferred from the Piper diagram and bivariate plots highlight the weathering of aluminosilicates as the primary process controlling groundwater chemistry in this aquifer, the increasing trend of chloride levels between the highlands (recharge area) and the depression of Bugesera (discharge area) and the random distribution of high nitrate content even in water samples from springs suggest that additional processes such as evaporative concentration and anthropogenic pollution play a secondary role in the hydrogeochemical evolution of groundwater. The spatial distribution of different hydrogeochemical parameters shows a general increasing trend from the highlands where water samples, mainly from springs, show low mineralisation (TDS=26–152mg/l) and low pH (field pH=4.6–6.6), towards the depression of Bugesera where higher values of mineralisation (TDS=44–3229mg/l) and pH (field pH=5.6–7.7) are observed. The overriding control of aluminosilicates weathering on the hydrogeochemical evolution of groundwater in Bugesera region is clearly demonstrated by the predominance of NaHCO3 and CaHCO3 water types and the cross-plots which show an increasing trend of alkaline and alkaline earth cations (Na+ +K+ +Ca2+ +Mg2+) released from the weathering of aluminosilicates along the flow line. Moreover, the poor correlation between the concentrations of SiO2 and Na+, Ca2+, Mg2+, K+, HCO3 – and TDS reflects the incongruent character of the weathering of aluminosilicates which causes part of the silica released from the weathering of silicates to be taken up into the neoformation of clay minerals. The anthropogenic pollution is reflected by the occurrence of NaNO3, CaNO3, KNO3 and NaSO4 types even in spring water.

Publisher URL: www.sciencedirect.com/science

DOI: S0375674218300013

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.