Examining the use of the partition coefficient in quantifying sorption of heavy metals in permo-triassic sandstone aquifers

Batty, Timothy Alexander (2016). Examining the use of the partition coefficient in quantifying sorption of heavy metals in permo-triassic sandstone aquifers. University of Birmingham. Ph.D.

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Abstract

Hydrogeologists using the partition coefficient, or K\(_d\) approach, to quantify attachment (sorption and / or ion exchange) of heavy metal(s) in aquifers have expressed reservations about its oversimplification of the geochemistry involved, potentially undermining predictions of contaminant fate and therefore jeopardising effective remediation efforts. The aims of this project were to determine the validity of the K\(_d\) approach for the Permo-Triassic sandstone – a common aquifer type worldwide – and to propose a better way of quantifying attachment for metal ions.

After characterising a sample of Permo-Triassic sandstone by way of a suite of batch experiments, the geochemical code PHREEQC was used to interpret the results using simulations incorporating both surface complexation theory and ion exchange. These demonstrated, by approximately matching attachment isotherm plots of Zn, that the model was a robust representation of the sandstone. This model was then adapted to simulate transport of Zn through a representative aquifer in a range of conditions to determine the potential importance of sorption in metal transport. The results confirmed the variability in the system with regard to pH influences, the fluctuating dominance of ion exchange and sorption, the presence of competing ions, and the resultant outcomes for Zn transport. It is expected that these results are similar for metals with chemistry similar to that of Zn.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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