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Issue 6, 2014
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Geochemical evolution of groundwater salinity at basin scale: a case study from Datong basin, northern China

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Abstract

A hydrogeochemical investigation using integrated methods of stable isotopes (18O, 2H), 87Sr/86Sr ratios, Cl/Br ratios, chloride-mass balance, mass balance and hydrogeochemical modeling was conducted to interpret the geochemical evolution of groundwater salinity in Datong basin, northern China. The δ2H, δ18O ratios in precipitation exhibited a local meteoric water line of δ2H = 6.4 δ18O −5 (R2 = 0.94), while those in groundwater suggested their meteoric origin in a historically colder climatic regime with a speculated recharge rate of less than 20.5 mm overall per year, in addition to recharge from a component of deep residual ancient lake water enriched with Br. According to the Sr isotope binary mixing model, the mixing of recharges from the Shentou karst springs (24%), the western margins (11%) and the eastern margins (65%) accounts for the groundwater from the deep aquifers of the down-gradient parts in the central basin is a possible mixing mechanism. In Datong, hydrolysis of silicate minerals is the most important hydrogeochemical process responsible for groundwater chemistry, in addition to dissolution of carbonate and evaporites. In the recharge areas, silicate chemical weathering is typically at the bisiallitization stage, while that in the central basin is mostly at the monosiallitization stage with limited evidence of being in equilibrium with gibbsite. Na exchange with bound Ca, Mg prevails at basin scale, and intensifies with groundwater salinity, while Ca, Mg exchange with bound Na locally occurs in the east pluvial and alluvial plains. Although groundwater salinity increases with the progress of water-rock/sediment interactions along the flow path, as a result of carbonate solubility control and continuous evapotranspiration, Na–HCO3 and Na–Cl–SO4 types of water are usually characterized respectively in the deep and the shallow aquifers of an inland basin with a silicate terrain in an arid climatic regime.

Graphical abstract: Geochemical evolution of groundwater salinity at basin scale: a case study from Datong basin, northern China

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Publication details

The article was received on 07 Jan 2014, accepted on 19 Feb 2014 and first published on 19 Feb 2014


Article type: Paper
DOI: 10.1039/C4EM00019F
Citation: Environ. Sci.: Processes Impacts, 2014,16, 1469-1479
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    Geochemical evolution of groundwater salinity at basin scale: a case study from Datong basin, northern China

    Y. Wu and Y. Wang, Environ. Sci.: Processes Impacts, 2014, 16, 1469
    DOI: 10.1039/C4EM00019F

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