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current vacancies


The Chair's research programme in Watershed Biogeochemistry was designed in response to anticipated increases in sulphur (S) and nitrogen (N) emissions from Ontario Power Generation Inc. In 1996, fossil power accounted for just 13% of OPG's total power production capacity, but increased to 27% by 1999. Fuelling and technology measures were employed by OPG to keep emission rates below the emissions cap set by regulation, but deposition of strong acid anions (sulphate and nitrate) was expected almost certainly to rise in response to increased emissions. As well, emissions and possibly deposition of trace metals such as mercury (Hg) and copper (Cu) were anticipated to increase. In addition to changing acid deposition rates, there is strong evidence that climate patterns in many parts of the world including Ontario are being altered very substantially as a result of global increases in greenhouse gas concentrations, and that changes in stratospheric ozone are influencing the level of ultraviolet radiation that is reaching the earth's surface. Moreover, other stressors are affecting our environment on a large spatial scale. It is also evident that these stresses do not act independently, but interact in ways that accelerate ecosystem degradation.

In Canada, nearly 45% of the land area is considered sensitive to acid deposition, and lakes and watersheds located on the Canadian Shield are considered the most vulnerable, due to the low buffering capacity of the typically shallow soils that overlay Shield bedrock. A large portion of eastern Canada, including much of Ontario and Quebec as well as the Atlantic Provinces is underlain by granitic bedrock of the Canadian Shield, and this area also receives the highest levels of acid deposition in the country.

The Watershed Biogeochemistry research programme focuses on lakes and their catchments located in the Muskoka-Haliburton region of south-central Ontario, an area which receives currently approximately 50 meq/m2 of SO4 and 55 meq/m2 N (as NO3-, NH4+) annually, and is almost entirely underlain by acid-sensitive soils. A number of catchments in this region have been studied since the early 1980s, and have shown negative chemical and biological effects of acidification.

In response to past reductions in industrial emissions, however, about 40% of the lakes studied in this region have recently shown signs of recovery (as indicated by decreasing sulphate concentration), while the remaining 60% have shown no positive response to changes in deposition. It is apparent that the response of lakes and their catchments to changes in acid deposition is variable, and is likely modified by within-catchment processes.

Projects conducted as part of the research programme are intended to improve our understanding of the way in which biogeochemical processes in lakes' watersheds control their rate of degradation when the deposition of strong acids increases and their rate of recovery when acid deposition rates decline. Furthermore, because it is now apparent that environmental perturbations such as acid deposition do not act in isolation, but are often augmented or offset by other factors, the interaction between changes in climate and acid deposition will be a major focus of the research. The research programme considers the effects of specific climate perturbations such as summer droughts on the chemical and biological response of aquatic ecosystems, and attempts to differentiate between those effects mediated by changes in acid deposition and those brought about by a varying climate.

four projects were initiated to address these research objectives:

I. Evaluation of existing environmental data in Ontario related to surface and groundwater chemistry, to assess the likelihood that expected changes in acid deposition will result in measurable changes in water quality. The analysis will include chemical and paleolimnological data, and will look at the effects of both changing acid deposition rates and climate. More details...

II. Measurement of the chemical and biological response of aquatic ecosystems to changes in OPG's sulphur emissions including: (a) measurement and modeling of the chemical response of a representative set of lakes and their terrestrial catchments (b) assessment of biological effects using simple indicators, and (c) evaluation of the changes in mercury deposition related to fossil fuel use. More details...

III. Evaluation of the interrelationships between climate change, the sulphur cycle in lakes and watersheds, and changes in emission and deposition of acid precursors, with specific reference to El Niņo episodes. More details...

IV. Investigation of the role of dissolved organic carbon (DOC) in integrating the effects of multiple stressors including acid deposition, changing climate and others. More details...

since the establishment of the chair, the programme has grown to include additional research projects in the Muskoka-Haliburton region, and in other areas of eastern Canada. follow the links to see more information about the projects.