Search results for "Aquifer"

Targeted delivery of hydrogen for the bioremediation of aquifers contaminated by dissolved chlorinated compounds.

2019

Dihydrogen (H2) gas injection is a promising option to enhance the reductive biodehalogenation of contaminants in groundwater. However, it is challenging to ensure its targeted delivery at the right places in plumes, and for the long times required for bioremediation. In this paper, the ability of surfactant foam to retain H2 in the saturated zone and to enhance its release in the dissolved form was compared to traditional biosparging. H2 gas was injected, either alone, or as foam, in a 2D saturated cell packed with glass beads. This cell was continuously flushed with deoxygenated water to mimic aquifer circulation, and H2 was studied both in terms of gas distribution in the cell and dissol…

Controlled treatment of a high velocity anisotropic aquifer model contaminated by hexachlorocyclohexanes

2020

International audience; Xanthan gels were assessed to control the reductive dechlorination of hexachlorocyclohexanes (HCHs) and trichlorobenzenes (TCBs) in a strong permeability contrast and high velocity sedimentary aquifer. An alkaline degradation was selected because of the low cost of NaOH and Ca(OH)2. The rheology of alkaline xanthan gels and their ability to deliver alkalinity homogeneously, while maintaining the latter, were studied. Whereas the xanthan gels behaved like non-Newtonian shear-thinning fluids, alkalinity and Ca(OH)2 microparticles had detrimental effects, yet, the latter decreased with the shear-rate. Breakthrough curves for the NaOH and Ca(OH)2 in xanthan solutions, ca…

Coarsely crystalline cryogenic cave carbonate – a new archive to estimate the Last Glacial minimum permafrost depth in Central Europe

2012

Abstract. Cryogenic cave carbonate (CCC) represents a specific type of speleothem whose precipitation is triggered by freezing of mineralized karst water. Coarsely crystalline CCC, which formed during slow freezing of water in cave pools, has been reported from 20 Central European caves located in Germany, the Czech Republic, Slovakia and Poland. All these caves are situated in an area which was glacier-free during the Weichselian. Whereas the formation of usual types of speleothems in caves of this region usually ceased during the glacials, coarsely crystalline CCC precipitation was restricted to glacial periods. Since this carbonate type represents a novel, useful paleoclimate proxy, data…

Nitrogen Loss from Pristine Carbonate-Rock Aquifers of the Hainich Critical Zone Exploratory (Germany) Is Primarily Driven by Chemolithoautotrophic A…

2017

Despite the high relevance of anaerobic ammonium oxidation (anammox) for nitrogen loss from marine systems, its relative importance compared to denitrification has less been studied in freshwater ecosystems, and our knowledge is especially scarce for groundwater. Surprisingly, phospholipid fatty acids (PLFA)-based studies identified zones with potentially active anammox bacteria within two superimposed pristine limestone aquifer assemblages of the Hainich Critical Zone Exploratory (CZE; Germany). We found anammox to contribute an estimated 83% to total nitrogen loss in suboxic groundwaters of these aquifer assemblages at rates of 3.5-4.7 nmol L -1 d -1, presumably favored over denitrificati…

The impact of urban development on aquifers in large coastal cities of West Africa: Present status and future challenges

2018

Abstract This paper investigates the coastal cities of Abidjan, Cotonou, Lagos and Douala in West Africa. Published data on these areas were aggregated in order to compare the urban development of some African huge cities and assess their impacts on groundwater. Those urban centers have experienced an exponential demographic expansion since the 1950s, with increased population densities and a geographical coverage expansion as well. The Continental Terminal aquifer, major groundwater resource taped in this region by the national water companies and local populations, shows a continuous downward trend in piezometric levels. Concerning water quality, the evolution up to the current state (sal…

Thermomineral waters of Greece: geochemical characterization

2020

Medio físico y características constructivas de galerías drenantes de aguas subálveas en ambientes semiáridos del sudeste español y Túnez

2021

Draining galleries are water collection systems that occurs frequently in various geomorphic contexts of semi-arid environments. In this article, we study those that take advantage of subalveal waters by means of different construction techniques, mainly 'cimbras' and 'cimbra-zanjas'. A comparison has been made between the Tunisian galleries and those of the Spanish SE that have these two characteristics: the exploitation of subsubalveal waters and surface detritic aquifers, and rainfall characteristics of semi-arid climates, specifically annual total rainfall between 300 and 400 mm. The work analyzes the environmental contexts of the selected galleries, especially geology, geomorphology, r…

The hydrothermal system of the Domuyo volcanic complex (Argentina): A conceptual model based on new geochemical and isotopic evidences

2016

The Domuyo volcanic complex (Neuquén Province, Argentina) hosts one of the most promising geothermal systems of Patagonia, giving rise to thermal manifestations discharging hot and Cl−-rich fluids. This study reports a complete geochemical dataset of gas and water samples collected in three years (2013, 2014 and 2015) from the main fluid discharges of this area. The chemical and isotopic composition (δD-H2O and δ18O-H2O) of waters indicates that rainwater and snow melting are the primary recharge of a hydrothermal reservoir located at relative shallow depth (400–600 m) possibly connected to a second deeper (2–3 km) reservoir. Reactive magmatic gases are completely scrubbed by the hydrotherm…

Geological, hydrogeological and geochemical characterization of aquifers in coastal areas (Ragusa-Donnalucata Area, Sicily, Italy)

2005

Carbonate groundwater systems hosted in coastal areas are of particular concern, for multi-fold reasons. First, in Sicily - as in many other islands – coastal areas are the most densely populated: this increase of anthropogenic pressure considerably raises the potential risks of groundwater contamination. This is even more dangerous considering the fact that groundwater is often the main source of potable water for coastal communities, especially since rivers and ponds near the shore are brackish. Secondly, coastal areas are the sites of potential interactions between the groundwater systems and seawater, the morphology and the location of this interface being a complex function, of groundw…

Ten years surface-atmosphere water budget from the ISAC micrometeorological base in Salento peninsula and comments on the aquifer balance

2016

Data from a ten years (2003-2013) period of activity of the ISAC-Lecce micrometeorological station have been discussed focusing on the atmosphere-surface exchange. Some suitable indices have been calculated such as the precipitation intensity, the aridity index and the ground water infiltration fraction (ratio of the difference between precipitation and real evapotranspiration and the precipitation). Possible trends of annual averages in the decadal period are considered, trying to take also into account the statistical uncertainty associated to measurement errors and missing data. The results indicate a significant increasing in the precipitation intensity together with an experimental evi…