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

Neal, Colin; Rowland, Philip; Neal, Margaret. 2012 Linking groundwaters of high CO2 to aluminium levels in rivers: the case for the upper Severn in mid-Wales. Journal of Environmental Monitoring, 14 (1). 34-40.

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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.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
UKCEH and CEH Sections/Science Areas: Acreman
UKCEH Fellows
ISSN: 1464-0325
Additional Information. Not used in RCUK Gateway to Research.: This document is the author’s final manuscript version of the journal article following the peer review process. Some differences between this and the publisher’s version may remain. You are advised to consult the publisher’s version if you wish to cite from this article.
NORA Subject Terms: Chemistry
Date made live: 10 Jan 2012 10:47 +0 (UTC)

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