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personal watercraft

(Encyclopedia)personal watercraft (PWC), a lightweight vessel usually less than 16 ft (5 m) long that uses an inboard water jet pump, powered by an internal-combustion engine, as its primary source of propulsion. T...

hygiene

(Encyclopedia)hygiene, science of preserving and promoting the health of both the individual and the community. It has many aspects: personal hygiene (proper living habits, cleanliness of body and clothing, healthf...

acid rain

(Encyclopedia)acid rain or acid deposition, form of precipitation (rain, snow, sleet, or hail) containing high levels of sulfuric or nitric acids (pH below 5.5–5.6). Produced when sulfur dioxide and various nitro...

United Nations Conference on Environment and Development

(Encyclopedia)United Nations Conference on Environment and Development (UNCED) or Earth Summit, an 11-day meeting held in June, 1992, in Rio de Janeiro, Brazil, to discuss the global conflict between economic devel...

smog

(Encyclopedia)smog smŏg [key] [smoke+fog], dense, visible air pollution. Smog is commonly of two types. The gray smog of older industrial cities like London and New York derives from the massive combustion of coal...

liquefied petroleum gas

(Encyclopedia)liquefied petroleum gas or LPG, mixture of gases, chiefly propane and butane, produced commercially from petroleum and stored under pressure to keep it in a liquid state. The boiling point of liquefie...

biosphere

(Encyclopedia)biosphere, irregularly shaped envelope of the earth's air, water, and land encompassing the heights and depths at which living things exist. The biosphere is a closed and self-regulating system (see e...

lignite

(Encyclopedia)lignite lĭgˈnīt [key] or brown coal, carbonaceous fuel intermediate between coal and peat, brown or yellowish in color and woody in texture. It contains more moisture than coal and tends to dry and...

atmosphere

(Encyclopedia)CE5 Atmosphere atmosphere [Gr.,=sphere of air], the mixture of gases surrounding a celestial body with sufficient gravity to maintain it. Although some details about the atmospheres of other plane...

Norilsk

(Encyclopedia)Norilsk nərēlskˈ [key], city (1989 pop. 175,000), Krasnoyarsk Territory, N Siberian Russia. The northernmost major city of Russia and the world's second largest city (after Murmansk) above the Arct...