GRE写作Issue部分精品素材分享之污染物

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全球化对环境影响的争议

Global change has become a popular word in scientific debates on long-range structural change in the earth‟s ecology. Globalization has in the past played a major role in the controversial environmental debates. Many problems resulted in this area of discussion, in regard to the intricate linkages between globalization, government, trade and transport, and environmental decay. The current debate on the environmental effects of globalization is particularly concerned with the question whether a worldwide liberalization of trade may provoke environmental collapse. Three major environmental concerns related to trade are the domestic environmental effects caused by the use of imported products, the foreign environmental effects caused by the production of exported goods, and the environmental effects caused by transport movements needed for international trade.

危害健康的颗粒污染物

Particulate matter (soot, ash, and other solids), usually consist of unburned hydrocarbons, carbon monoxide, sulfur dioxide, various nitrogen oxides, ozone, and lead. These compounds undergo a series of chemical reactions in the presence of sunlight: the result is smog (a term used to describe a noxious mixture of fog and smoke).

The process by which these pollutants harm our bodies begins by simply taking a breath. Particulates are present everywhere, in some areas they are as dense as 100,000 per milliliter of air. The damage begins when the particulates are inhaled into the small air sacs of our lungs called alveoli. With densities such as 100,000 per milliliter a single alveolus may receive 1,500 particulates per day. These particulates cause the inflammation of the alveoli. The inflammation causes the body to produce agents in the blood that increase clotting ability, which leads to the decreased functionality of the cardiovascular system, resulting in diseases and increased mortality.

基因污染

Purebred naturally evolved region specific wild species can be threatened with extinction in a big way through the process of Genetic Pollution, i.e. uncontrolled hybridization, introgression and Genetic swamping which leads to homogenization or replacement of local genotypes as a result of either a numerical and/or fitness advantage of introduced plant or animal. Nonnative species can bring about a form of extinction of native plants and animals by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially detrimental for rare species coming into contact with more abundant ones where the abundant ones can interbreed with them swamping the entire rarer gene pool creating hybrids thus driving the entire original purebred native stock to complete extinction. Attention has to be focused on the extent of this underappreciated problem that is not always apparent from morphological (outward appearance) observations alone. Some degree of gene flow may be a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved however. Hybridization with or without introgression may, nevertheless, threaten a rare species‟ existence.

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