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Issue 1, 2012
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Linking groundwaters of high CO2 to aluminium levels in rivers: the case for the upper Severn in mid-Wales

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Abstract

Al is a critical ecotoxicant in surface waters impacted by acidic deposition. Apart from the most acidic surface waters, Al concentrations are often considered to be controlled by Al(OH)3 or aluminosilicate (clay) solubility for modelling studies. For many UK rivers there is no clear evidence for such solubility controls even though there is the potential under moderately acidic/alkaline conditions. Here, Al solubility in ground and river water is compared for acid sensitive catchments in mid-Wales. The results reveal that there may be a solubility control within the groundwater but a more complex state of affairs within the river. The groundwater is of high CO2 content and once in the river it degasses to raise pH. However, there is limited change in Al concentration and hence the solubility relationship is lost. The results flag the potential importance of groundwater solubility controls for Al and the potential for the groundwater zone to act as an Al filter. For positive alkalinity groundwaters, the high CO2 levels depress the pH to near the value for minimum Al solubility. However, there is no simple groundwater end-member. Examining Al solubility controls solely within the rivers provides cryptic and misleading clues to the hydrogeological controls for Al within catchments. Assessing the within-catchment processes requires direct measurement with full consideration of both inorganic and organic attenuation.

Graphical abstract: Linking groundwaters of high CO2 to aluminium levels in rivers: the case for the upper Severn in mid-Wales

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Publication details

The article was received on 13 Jul 2011, accepted on 22 Sep 2011 and first published on 19 Oct 2011


Article type: Paper
DOI: 10.1039/C1EM10562K
Citation: J. Environ. Monit., 2012,14, 34-40
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    Linking groundwaters of high CO2 to aluminium levels in rivers: the case for the upper Severn in mid-Wales

    C. Neal, P. Rowland and M. Neal, J. Environ. Monit., 2012, 14, 34
    DOI: 10.1039/C1EM10562K

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