The State of Canada's Environment — 1996

Glossary of Selected Terms - T

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Sources for definitions

tailings: Material rejected from a mill after most of the recoverable valuable minerals have been extracted (Whiteway 1990). Tailings are generally finely ground rock particles that are transported as a water slurry to a storage area, known as a tailings pond, at the mine site. Usually the tailings composition is similar to the parent ore body and may therefore contain metals, sulphides, salts, or radioactive materials.

tcdd: See dioxins and furans.

temperate forest: One of the three main forest types in the world, composed mainly of deciduous trees (Natural Resources Canada 1994). The other two types are the northern (boreal), largely evergreen forest and the tropical evergreen forest.

tertiary wastewater treatment: Removal of nitrates, phosphates, organochlorine compounds, salts, acids, metals, and toxic organic compounds after secondary wastewater treatment (Wells and Rolston 1991). See also primary wastewater treatment.

threatened: In this report, this term refers to an official designation assigned by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The term describes any indigenous species, subspecies, or geographically separate population that is likely to become endangered in Canada if the factors affecting its vulnerability are not reversed. See also endangered, extinct, extirpated, and vulnerable.

timber licence: A licence to cut and remove timber from Crown lands (adapted from Natural Resources Canada 1994).

time series: A sequence of data derived from consecutive observations taken in the same manner and at equal time intervals (Environment Canada 1995).

total ozone: The ozone present in a column of Earth's atmosphere. Total ozone includes both ground-level ozone and stratospheric ozone.

toxaphene: C₆H₁₀Cl₈; toxic organochlorine compound used as an insecticide (Lapedes 1978).

toxic: Pertains to any substance if it is entering or may enter the environment in a quantity or concentration or under conditions having or that may have an immediate or long-term effect on the environment (including living organisms within it) or constituting or that may constitute a danger to human life or health (adapted from Government of Canada 1988).

toxicity: The inherent potential or capacity of a material to cause adverse effects in a living organism (Wells and Rolston 1991).

traditional ecological knowledge (tek): The knowledge base acquired by indigenous and local peoples over many hundreds of years through direct contact with the environment. This knowledge includes an intimate and detailed knowledge of plants, animals, and natural phenomena, the development and use of appropriate technologies for hunting, fishing, trapping, agriculture, and forestry, and a holistic knowledge or "world view" that parallels the scientific discipline of ecology (Centre for Traditional Knowledge, personal communication). See also Indigenous ecological and environmental knowledge.

tree canopy: See canopy (tree).

tree farm licence: A specific tenure arrangement found only in British Columbia that grants exclusive timber harvesting rights and management responsibilities within the area licensed (Natural Resources Canada 1994).

tree-length harvesting: A method of harvesting that includes felling a tree, cutting off its top, and delimbing it before transporting the tree to a mill (Natural Resources Canada 1994).

trend: A persistent tendency in the slope of a time series (Environment Canada 1995).

trophic: Relating to processes of energy and nutrient transfer from one or more organisms to others in an ecosystem (Wells and Rolston 1991). See also eutrophic, trophic level, and trophic status.

trophic level: Functional classification of organisms in a community according to feeding relationships; the first trophic level includes green plants, the second level includes herbivores, and so on (Upper Great Lakes Connecting Channels Study, Management Committee 1988). See also eutrophic, trophic, and trophic status.

trophic status: A measure of the biological productivity in a body of water. Aquatic ecosystems are characterized as oligotrophic (low productivity), mesotrophic (medium productivity), or eutrophic (high productivity) (Environment Canada et al. 1988). See also trophic and trophic level.

troposphere: Lowest layer of the atmosphere, extending from ground level to about 11 km above the Earth (Greater Vancouver Regional District 1994). Contains about 95% of the Earth's air and ends at the tropopause, the point at which atmospheric temperature starts to increase instead of decrease as one moves farther from the Earth (modified from Arms 1990).

tropospheric ozone: See ground-level ozone.

tss (total suspended solids): The total amount of fibres or particles found in effluent (Forestry Canada 1993).

turbid: Refers to water that is cloudy or murky as a result of suspended sediment. Water may become turbid as a result of soil erosion, from injections of effluents containing particulate matter, or through the churning up of bottom sediments (e.g., via boat traffic in a body of water or by dredging activities).

turbidity: The state of being turbid.