Strontium isotopes as tracers for quantifying mixing of groundwater in the alluvial plain of a coastal watershed, south-eastern Tanzania

Bakari, S. S.; Aagaard, P.; Vogt, R. D.; Ruden, F.; Johansen, I.; Vuai, S. A.

dc.creator	Bakari, S. S.
dc.creator	Aagaard, P.
dc.creator	Vogt, R. D.
dc.creator	Ruden, F.
dc.creator	Johansen, I.
dc.creator	Vuai, S. A.
dc.date	2020-03-23T08:49:39Z
dc.date	2020-03-23T08:49:39Z
dc.date	2013
dc.date.accessioned	2022-10-20T13:09:15Z
dc.date.available	2022-10-20T13:09:15Z
dc.identifier	Bakari, S. S., Aagaard, P., Vogt, R. D., Ruden, F., Johansen, I., & Vuai, S. A. (2013). Strontium isotopes as tracers for quantifying mixing of groundwater in the alluvial plain of a coastal watershed, south-eastern Tanzania. Journal of Geochemical Exploration, 130, 1-14.
dc.identifier	https://doi.org/10.1016/j.gexplo.2013.02.008
dc.identifier	http://hdl.handle.net/20.500.12661/2288
dc.identifier.uri	http://hdl.handle.net/20.500.12661/2288
dc.description	Abstract. Also available at: https://doi.org/10.1016/j.gexplo.2013.02.008
dc.description	Surface water and groundwater chemistry of the coastal aquifer systems in south-eastern Tanzania have been studied with a focus on isotopes and major ions, in order to assess the controlling hydrological and geochemical processes. 87Sr/86Sr isotope ratios have provided information about the hydrology that could not have been obtained by studying the physical and chemical characteristics of water quality alone. The data reveal a rather complex mixing pattern of various water source end-members that are subject to different hydro-geochemical processes, such as evaporation, weathering and other water–rock interactions, and seawater intrusion, which control the water quality. Data on 87Sr/86Sr ratio distribution and strontium (Sr2 +) concentration delineate three types of groundwater in the coastal aquifer system: (1) water recharged by fresh precipitation/stream water infiltration and influenced by soil processes like weathering and evaporation, (2) groundwater subjected to rock–water interactions with different bedrock types, and (3) groundwater that is brackish due to seawater intrusion. Most of the groundwater data can be modeled as strontium-poor recharge water of meteoric origin. These waters are influenced to varying degrees by soil–water interactions in the surficial aquifer material. Elevated NO3− concentrations in a few shallow aquifer samples imply sewage infiltration from domestic wastewater. Data on the 87Sr/86Sr ratios did not appear to be affected by this anthropogenic influence. High Sr ratios (> 0.711899) in the samples suspected of being contaminated by sewage as well as a couple of other shallow groundwater samples is likely to have been caused by weathering of surficial aquifer material. A lack of variation in Sr2 + content between the river water and groundwater samples reflects an efficient mixing of water during well discharge. The data also clearly demonstrate the influence of aerosol sources in rain water on the strontium isotope signatures. The results illustrate the strength of combining isotopic measurements with more conventional water chemistry data in order to obtain a better understanding of groundwater flow systems and the geochemical processes governing their chemistry.
dc.language	en
dc.publisher	Elsevier
dc.subject	Strontium isotopes
dc.subject	Stable isotopes
dc.subject	Groundwater
dc.subject	Costal aquifer
dc.subject	Geochemical processes
dc.subject	Surface water
dc.subject	Groundwater chemistry
dc.subject	Tanzania
dc.subject	Water quality
dc.subject	Hydro-geochemical process
dc.subject	Water infiltration
dc.title	Strontium isotopes as tracers for quantifying mixing of groundwater in the alluvial plain of a coastal watershed, south-eastern Tanzania
dc.type	Article