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Proactive disclosure Print version   | |  Environmental geochemistry and geochemical hazards
Compiled by R.D. Knight and R.A. Klassen, contributions by: Boyle, D.R., Carson, J.M., Charbonneau, B.W., Day, S.J.A., Friske, P.W.B., Garrett, R.G., Hall, G.E.M., Henderson, P., Hetu, R.J, Kettles I.M, Klassen, R.A., McCurdy, M.W., McMartin, I., Plouffe, A., Rasmussen, P.E., Shilts. W.W., and Thorleifson, L.H.
Environmental geochemistry studies the chemical elements comprising the bedrock and soils of the earth's surface. It is concerned both with their abundance and distribution, the diverse natural processes -physical, chemical, and biological, that affect their chemical form and mobility, and their origin - either natural or human-related. It is a research field based on the scientific disciplines of geology, chemistry, and biology, and is critical for effective management of our natural resources and health protection. The application and value of geological research to environmental geochemistry is illustrated by nine different studies located in diverse geological terrains of Canada. The focus is on thematic aspects that relate to hazards, and emphasis is placed on a small group of elements that can represent a health risk, either at high or low concentrations. They include: i) non-metals, fluorine and arsenic, ii) metals, cadmium, lead, mercury, and zinc, and iii) radioactive elements, uranium, thorium, and radon. A wide range of health problems can result from either ingestion or exposure to them. Some, like cadmium and arsenic, are known to be harmful to living organisms even in trace amounts (measured in parts per million or even parts per billion) depending on their chemical form. Although the natural environment is complex and varied, a geological framework provides a sound basis for environmental planning and risk assessment. In Canada, our soils are the result of a recent (< 80, 000 years) geological past dominated by glaciation. The geochemical variation that is a distinctive characteristic of our Canadian geological landscape reflects the great diversity of bedrock types and their erosion and transport by the ice sheets. Since glaciation, natural weathering, soil-forming, and biological processes have all combined to change the chemical forms and residence sites of elements; those forms readily taken in by plants and animals are 'bioavailable', and those that are not are 'nonbioavailable'. The release of elements into groundwater further contributes to their movement through the environment. Depending both on their form and concentration, the different bioavailable elements can be either helpful as nutrients, or harmful. Although the uptake of elements in a plant or animal is controlled by many things, including water, temperature, light, mineral host, and life form, geology is a paramount control on background variations in the geochemical landscape.
The Geological Survey of Canada (GSC) contributes to environmental geochemistry by defining the geological and geochemical framework of Canada's surficial landscape. The framework is represented by the results of both regional geochemical and geophysical surveys, and by detailed process studies associated with surficial mapping, mineral exploration , and metals in the environment programs. Through its surveys, the range and concentration of many elements have been mapped across large parts of Canada. Although the elements can be derived from pollutants, including solid and liquid wastes and airborne emissions, the geochemical landscape is largely the product of bedrock geology and glaciation.
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