This paper identifies and discusses terminology used in discussion of disturbance, damage, and rehabilitation in frozen soils and related ecosystems, and provides a vocabulary that may help scientists from different disciplines to identify management objectives and reach common purposes.

The Protocol on Environmental Protection to the Antarctic Treaty requires that past and present work sites be cleaned up unless removal would result in greater adverse environmental impact than leaving the contaminant in its existing location. In the early 1990s Australia began the documentation of contaminated sites associated with its research stations, which resulted in an extensive record of contamination at abandoned stations and waste-disposal sites. Currently the technical capability to remediate these sites does not exist because of environmental challenges that are unique to the cold regions. Investigations indicate that clean-up operations in the past have proceeded without adequate precautions and without effective monitoring. To address these problems, three research priorities have been identified to assist meeting international and national obligations to clean up these sites. They are: understanding contaminant mobilisation processes; development of ecological risk assessment for use in monitoring and setting priorities; and development of clean-up and remediation procedures. This study provides sufficient information to guide the completion of a clean-up at Casey Station and to indicate how other similar sites should be managed. The next stage is to develop the theory into an operational plan to include detailed protocols for clean-up, monitoring, site remediation, and management of the waste stream from site to final repository. To achieve this, the Australian Antarctic Division has established a contaminated sites taskforce to facilitate the transition from research and development of techniques to implementation of suitable clean-up options.

Buried pits (sumps), used for the disposal of drilling muds in the Mackenzie Delta area of Arctic Canada, provide an opportunity for assessing the effectiveness of ice-bonded permafrost sediments as a containment for industrial wastes. Potassium chloride (KCI) added to drilling muds as a freezing-point depressant provides a suitable tracer, because it is easily identified and natural concentrations in sediment pore water are typically low (less than 0.02 g l−1; potassium). Muds with KCI concentrations of up to 10% by weight (100 g l−1) have been used. In the vicinity of sumps, potassium is found at elevated concentrations of up to several g l−1 in the seasonal thaw layer (active layer) at distances well beyond what would be expected from diffusive transport alone. Within the level alluvial silts of the modern Mackenzie Delta, KCI has moved up to 50 m laterally from sump edges. On surrounding tundra uplands, KCI has migrated several hundred metres downslope within the active layer.

Although ice-rich permafrost sediments appear to form an effective barrier against downward movement of solutes, thawing ice lenses and veins within the active layer greatly increase the lateral hydraulic conductivity in this zone during the thaw season. Compared with unfrozen silty sediments, the large pores left by thawed ice fabric in the same sediment after a freeze–thaw cycle have been shown to increase the hydraulic conductivity up to four orders of magnitude. This phenomenon is probably common in thawing, ice-rich sediments and presumably favours accelerated downhill movement of solutes. On level ground, it is anticipated that KCI movement is promoted by fluid densities approaching that of sea water. Laboratory experiments with thawed sand and both unfrozen and thawing Mackenzie Delta silt confirm the existence of density-driven solute movement and the importance of thawing ice fabric in promoting solute movement. The thawed ice fabric of active-layer sediments and the presence of a frost table promote lateral movement of fluids when a density or elevation gradient is present. These tendencies widen the area potentially affected by contaminant migration from abandoned waste sites and they may also promote the movement of contaminants that escape from future containments.

The physical behaviour of oil interacting with soils subjected to seasonal frost or permafrost was investigated. An experimental programme was carried out to investigate the transportation and spreading of oil on a frozen surface, and transportation and accumulation of oil into freezing or frozen soils. The results show that spreading of oil at the surface at air temperatures below freezing depends on oil composition, soil temperature, and the type of mineral surface. It was observed that an ice surface has the least spreading and the greatest wetting angle of the surfaces studied. The oil penetration into frozen soils depends on soil and oil composition and temperature conditions. It was observed, as expected, that oil accumulation in frozen soils decreases with increasing ice content in the pores. However, penetration of oil components is observed even in completely ice-saturated soils. Freezing of oil-saturated soils causes a redistribution of the oil components. In sandy soils, the oil concentrates in a thawed zone in front of the freezing front; in clay soils, the oil can accumulate in the frozen zone under certain temperature conditions. A summary of the influence of various factors affecting oil behaviour in frozen and freezing soils is presented based on the experimental data and published data from other authors.

Heterotrophic and hydrocarbon-degrading microbial populations in soils from different depths in a permafrost soil profile at a hydrocarbon-contaminated site at Ny-Ålesund, Svalbard, were examined and compared to the populations present at a pristine site. The objective was to investigate whether the populations were enhanced after 12 years of exposure to hydrocarbons. Based on air and soil temperature data, it is concluded that the microorganisms living in these environments are cold-adapted. Proliferation of the populations by a factor of 100–1000 was measured in the layers where mineral oil was present in high concentrations. This indicates that the populations responded to the additional carbon source by degradation and growth on hydrocarbons or hydrocarbon metabolites. A high number of intrinsic heterotrophic and hydrocarbon-degrading bacteria is a prerequisite for in situ bioremediation of contaminated sites. Although the hydrocarbon-degrading activities of the populations are not known, the results show that the population sizes probably do not represent the limiting factor in a bioremedial action at this contaminated Arctic permafrost site.

A geochemical study of the Severnaya Dvina estuary was carried out during two oceanographic cruises to the White Sea. The amount and distribution of trace (Mn, Co, Cu, Ni, Pb, and Zn) and major (Al and Fe) elements in suspended particulate matter and sediments were determined. The main source of most metals studied was river discharge. A metal speciation study showed that the prevailing form is in the estuarine sediments, the minerals of which incorporated 60–99% of the total metal contents. Two zones of metal accumulation were found in sediments that were considered as local geochemical barriers within the major river–sea barrier.

Vertical freezing of clayey suspensions contaminated by heavy metals was conducted. A small unidirectional thermal gradient applied to a sample placed in a parallelopipedic cell led to the low-rate propagation of an upward freezing front. During this propagation, segregation of salts occurred and the non-solidified phase ahead of the freezing front became enriched with metallic salts. Moreover, some of the non-miscible particles in suspension were repelled by the freezing front. Therefore, the solidified phase became poorer with metallic pollutants bound to such nonmiscible particles as clayey colloids or complexes. Thus, artificial cooling was able to purify a suspension contaminated by heavy metals that exist in various chemical forms. This paper presents results for different experimental conditions and physico-chemical parameters such as the pH and the ratio between the concentrations of metallic cations and clay particles. The influence of these physico-chemical parameters on the speciations of lead and on the efficiency of this method is discussed. These freezing tests carried out on polluted soils should succeed in their remediation. This new method is called ‘cryoremediation’.

Oil exploration and production in the Arctic regions has resulted in spills of petroleum and salt water in tundra ecosystems. The transportation and use of refined petroleum in Arctic regions has also led to spills, and the cleanup and ecosystem restoration in these systems can often be complicated by the existence of ice-rich soil permafrost. Compaction, removal, or tearing of the protective vegetation and organic soil can result in thermokarsting and associated changes in plant communities, which may persist for decades. Such problems led the State of Alaska to establish recovery-based clean-up regulations for spills to tundra.

A review was conducted of published literature, government agency spill files, and industry reports concerning spills of petroleum and saline water in tundra regions. A tundra spill database was created, which allows the determination of the spill frequency of refined petroleum, crude oil, and saline water. Refined-petroleum spills are more common and smaller than crude-oil and saline-water spills. Most spills are to wet tundra during winter, and winter spills are more effectively cleaned up than those in summer. In winter, snow contains most spills, frozen soil and frozen water bodies prevent much soil penetration, plants are dormant, and operation of heavy equipment is feasible on frozen ground. The use of fire to reduce the volume of petroleum spills in winter is not recommended. Heat from burning petroleum can melt snow, thaw soil, and allow the penetration of petroleum into soil.

Effective remediation of petroleum-contaminated soils in the Arctic is becoming increasingly important as the magnitude of environmental risks becomes better defined. Unfortunately, some of the solutions implemented in southern Canada are too costly to use in the Arctic. However, effective remediation is still necessary. Consequently, traditional techniques are employed, such as excavation and landfarming, which are disruptive to the immediate soils, permafrost, and the surrounding habitat. These remedial methods, however, are becoming unacceptable to First Nations people in some Canadian Arctic communities. This paper describes preliminary results from an in-situ biodegradation study of petroleum-contaminated soils. This technique has the potential to provide an easily applied effective solution to the problem of devising a low cost and uncontroversial method of remediation. Based on bench-scale laboratory feasibility studies, it has been determined that the zone of contaminated soil at the Whitehorse Airport is suitable for in-situ bioremediation application.