Electrokinetic migration of nitrate through heterogeneous granular porous media

Gill, Richard T., Thornton, Steven F., Harbottle, Michael J. ORCID: https://orcid.org/0000-0002-6443-5340 and Smith, Jonathan W.N. 2015. Electrokinetic migration of nitrate through heterogeneous granular porous media. Ground Water Monitoring and Remediation 35 (3) , pp. 46-56. 10.1111/gwmr.12107

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Abstract

This study investigates and quantifies the influence of physical heterogeneity in granular porous media, represented by materials with different hydraulic conductivity, on the migration of nitrate, used as an amendment to enhance bioremediation, under an electric field. Laboratory experiments were conducted in a bench-scale test cell under a low applied direct current using glass bead and clay mixes and synthetic groundwater to represent ideal conditions. The experiments included bromide tracer tests in homogeneous settings to deduce controls on electrokinetic transport of inorganic solutes in the different materials, and comparison of nitrate migration under homogeneous and heterogeneous scenarios. The results indicate that physical heterogeneity of subsurface materials, represented by a contrast between a higher-hydraulic conductivity and lower-hydraulic conductivity material normal to the direction of the applied electric field exerts the following controls on nitrate migration: (1) a spatial change in nitrate migration rate due to changes in effective ionic mobility and subsequent accumulation of nitrate at the interface between these materials; and (2) a spatial change in the voltage gradient distribution across the hydraulic conductivity contrast, due to the inverse relationship with effective ionic mobility. These factors will contribute to higher mass transport of nitrate through low hydraulic conductivity zones in heterogeneous porous media, relative to homogeneous host materials. Overall electrokinetic migration of amendments such as nitrate can be increased in heterogeneous granular porous media to enhance the in situ bioremediation of organic contaminants present in low hydraulic conductivity zones.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TD Environmental technology. Sanitary engineering
Additional Information:	This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Publisher:	Wiley
ISSN:	1069-3629
Funders:	EPSRC, Shell Global Solutions (UK) Ltd
Date of First Compliant Deposit:	30 March 2016
Date of Acceptance:	9 February 2015
Last Modified:	11 May 2023 22:42
URI:	https://orca.cardiff.ac.uk/id/eprint/72374

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