Permeable reactive barriers (PRB) are a valuable weapon in the armoury of methods able to remediate contaminated ground. Developed first in temperate areas, reactive barriers are increasingly being installed in areas of freezing ground in both northern and southern hemispheres (Poland et al. 2001; Snape et al. 2001a, 2002). These environments create special challenges for the installation and operation of any remediation technology, and PRB are no exception. Particular challenges include ice formation in the barrier media, leading to temporary or permanent changes in barrier hydraulics, inefficient or ineffective reaction kinetics and exchange capacities at low temperatures, slow rates of biodegradation, and quarantine constraints on the choice of microbial agents able to be used in the degradation of organic contaminants. Despite these constraints, PRB offer particular advantages to the remediation of areas of freezing ground. Although expensive and requiring a good deal of site characterisation prior to installation, PRB are inexpensive to operate, and properly designed they can work for decades with only routine monitoring. As PRB work passively using the hydraulic gradient of the aquifer, they have low energy requirements. Barriers can be customised to suit the particular characteristics of the site, in terms of topography and the type of treatment required. These advantages are particularly important, given that many contaminated sites in areas of freezing ground are visited infrequently or seasonally.

The use of PRB is in its infancy, with few barriers having been installed earlier than 1994. Because of this youth, PRB require a greater monitoring effort to prove their success than other remediation methods. However, it is likely that, given the ongoing exploration and use of areas of freezing ground, more barriers will be installed in both hemispheres over the next decade. Whereas at present few barriers deal with petroleum hydrocarbons, it is also likely that dealing with this type of contaminant will increase in the future as hydrocarbon pollution in the Arctic increases

Damian B. Gore

Department of Environment and Geography, Macquarie University, NSW 2109, Australia e-mail: [email protected]

R. Margesin (ed.) Permafrost Soils, Soil Biology 16,

DOI: 10.1007/978-3-540-69371-0, © Springer-Verlag Berlin Heidelberg 2009

(Poland et al. 2003). In Antarctica, the Protocol on Environmental Protection to the Antarctic Treaty stipulates that contaminated sites must be remediated unless doing so would result in a greater adverse environmental impact than leaving the sites untouched (Snape et al. 2001b). This favours the passive technology of permeable reactive barriers rather than more invasive remediation operations.

This chapter overviews the design of PRB, discusses the various types of reactive media used to treat a wide range of contaminants, and details the special considerations that should be given when installing, operating and decommissioning such barriers in areas of permafrost soils.

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