Publications by authors named "Eliot A Atekwana"

We investigated the spatial and temporal variations of the stable isotope composition of hydrogen (δD) and oxygen (δO) and the total dissolved ions (TDI) concentrations in the Okavango River in the middle Kalahari Desert. We aimed to elucidate the role of evaporation in controlling river solute enrichment from samples collected at a one- to two-month frequency from nine stations along a ∼460 km river transect for one year. We found that the δD and δO composition and the TDI concentrations increased downriver.

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We investigated hourly time-series of total dissolved solids (TDS) in the Okavango River at the inlet and outlet of the Okavango Delta (Delta) in semi-arid Botswana. We estimated the solute flux into and out of the Delta. Our objectives were to (1) document the temporal variations of solutes (represented by TDS) in the Okavango River and determine the processes that control the variations in solute concentrations and (2) quantify the solute load into and out of the Delta.

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The concentrations of nitrate (NO), major ions, and dissolved inorganic carbon (DIC) and the stable carbon isotopes of DIC (δC) in shallow groundwater below a 45 × 60 m residential property was investigated over a period of 38 months. Our aim was to identify the processes which control the spatial and temporal distribution of NO in the shallow groundwater and assess water-rock interactions linked to denitrification. Groundwater sampled quarterly from eight locations showed an average NO concentration of 36.

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Surface waters are a major pathway of carbon cycling between the atmosphere and the earth's surface. Yet studies describing water column processes that affect carbon cycling do not consider the effects of dilution by precipitation. In this study, we conducted a laboratory experiment in which we prepared undiluted (100%) and snowmelt diluted 25, 50, and 75% by volume of samples of NaHCO solution and lake and river water and then exposed them to the laboratory atmosphere for up to 1000 h.

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We investigated the spatial variations in the concentrations of dissolved inorganic carbon (DIC), the stable carbon isotopic composition (δ(13)C) of DIC and the δ(13)C of carbonate precipitated from neutral mine drainage interacting with the atmospheric CO2(g). We assessed the chemical, DIC and δ(13)CDIC evolution of the mine drainage and the δ(13)C evolution of carbonate precipitates for a distance of 562 m from the end of an 8 km tunnel that drains a mine. Our results show that as the mine drainage interacts with atmospheric CO2(g) the outgassing of CO2 due to the high initial partial pressure of CO2 (pCO2) causes the DIC to evolve under kinetic conditions followed by equilibration and then under equilibrium conditions.

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The interdependence between geoelectrical signatures at underground petroleum plumes and the structures of subsurface microbial communities was investigated. For sediments contaminated with light non-aqueous-phase liquids, anomalous high conductivity values have been observed. Vertical changes in the geoelectrical properties of the sediments were concomitant with significant changes in the microbial community structures as determined by the construction and evaluation of 16S rRNA gene libraries.

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Geochemical and stable carbon isotope data from closely spaced vertical intervals in a hydrocarbon-impacted aquifer were used to assess the relationship between biodegradation, mineral weathering, and enhanced bulk conductivity zones. The results show that depth zones of enhanced bulk conductivity in the contaminated aquifer had higher total dissolved solids (TDS) compared to background groundwater. The higher TDS in contaminated groundwater were due to elevated ion concentrations from enhanced mineral weathering.

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