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This paper presents the determination of horizontal and vertical hydraulic conductivity in large-particle-sized tyre-derived aggregate (TDA) – that is, TDA with particle sizes over 50 mm – as a sub...

The storage and transportation of pore gasses in overburden and reclamation soil covers were evaluated using statistical analyses and finite difference numerical modelling to guide mine operators regarding practical issues surrounding the construction of overburden landforms, design of soil cover systems and management of reclamation sites. Factors that were found to impact gas transfer were soil moisture, soil temperature, differential pressures and dry bulk density of the overburden landform. Furthermore, the construction of the overburden landform appears to be more impactful to pore-gas dynamics than the design of the soil covers. Practicable recommendations can therefore be inferred to facilitate simultaneously methane oxidation in the uppermost horizon of the overburden while maintaining sufficient pore-gas oxygen in the plant-rooting zone of the soil covers to facilitate growth and survivability of reclamation vegetation. It is recommended that overburden be placed to approximately 1·6 Mg/m3. Mine operators should also recognise and manage extreme moisture conditions in the soil covers and uppermost overburden to mitigate restrictions in gas exchange and methane oxidation.

Pore-gas dynamics in single-layered and multi-layered soil covers were characterised in a mine cover testing programme for the reclamation of lean oil sand overburden. Pore-gas concentrations of oxygen and carbon dioxide in the upper 1·5 m of soil covers and overburden did not reach the threshold that poses a risk for plant growth. Below 1·5 m in the overburden, however, oxygen dropped to 0% and carbon dioxide rose to >16%. While methane concentrations were typically 35%. Novel subsurface flux chambers were designed and fabricated to measure directly oxygen ingress through soil covers and carbon dioxide efflux from overburden into soil covers. Oxygen fluxes peaked at 18·0 kg/(m2 a) and carbon dioxide fluxes peaked at 2·3 kg/(m2 a). Soil cover material and placement thickness affected gas flux rates. Diffusive fluxes were calculated from soil gas profiles by estimating diffusion coefficients from position-dependent soil moisture and temperature. Advective fluxes were calculated from pressure gradients and in situ air conductivity. Advection dominated over diffusion in soil covers except for one location that was either a localised zone of microbial activity (hydrocarbon degradation or methane oxidation) or the overburden was coarser textured and responded quickly to barometric pressure fluctuations.

In Northern Alberta, Canada, large volumes of low-grade ‘lean’ oil sand (LOS) overburden are translocated during the surface mining of oil sands and remain in future reclaimed landscapes. The objectives addressed in this paper are to (a) characterise the on-site petroleum hydrocarbon (PHC) content of LOS; (b) evaluate the effect of LOS temperature on rates of carbon dioxide (CO2) flux and PHC biodegradation and (c) evaluate the potential for PHC to leach from LOS into groundwater. The results show that LOS is predominantly composed of heavier F3 and F4 PHC fractions, the temperature appears to affect carbon dioxide fluxes and PHC degradation rates and it is unlikely that the presence of LOS in reclamation soils will release significant quantities of PHC into groundwater.

Climate change, fishing, and aquaculture have affected and will continue to influence Canadian marine biodiversity, albeit at different spatial scales. The Arctic is notably affected by reduced quality and quantity of sea ice caused by global warming, and by concomitant and forecasted changes in ocean productivity, species ecology, and human activity. The Atlantic has been especially impacted by severe overfishing and human-induced alterations to food webs. Climate change, fishing, and aquaculture have all affected, to varying degrees, biodiversity on Canada’s Pacific coast. Past and projected trends in key biodiversity stressors reveal marked change. Oceanographic trends include increasing surface water temperatures, reduced salinity, increased acidity, and, in some areas, reduced oxygen. Reductions in Canada’s fishery catches (those in 2009 were half those of the late 1980s), followed by reductions in fishing pressure, are associated with dramatic changes in the species composition of commercial catches in the Atlantic (formerly groundfish, now predominantly invertebrates and pelagic fish) and the Pacific (formerly salmon, now predominantly groundfish). Aquaculture, dominated by the farming of Atlantic salmon, grew rapidly from the early 1980s until 2002 and has since stabilized. Climate change is forecast to affect marine biodiversity by shifting species distributions, changing species community composition, decoupling the timing of species’ resource requirements and resource availability, and reducing habitat quality. Harvest-related reductions in fish abundance, many by 80% or more, coupled with fishing-induced changes to food webs, are impairing the capacity of species to recover or even persist. Open-sea aquaculture net pens affect biodiversity by (i) habitat alteration resulting from organic wastes, chemical inputs, and use of nonnative species; (ii) exchange of pathogens between farmed and wild species; and (iii) interbreeding between wild fish and farmed escapees. Physical and biological changes in the oceans, along with direct anthropogenic impacts, are modifying Canadian marine biodiversity with implications for food security and the social and economic well-being of coastal communities. To assess the consequences of changes in biodiversity for Canada’s oceans and society, it is necessary to understand the current state of marine biodiversity and how it might be affected by projected changes in climate and human uses.