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来源：学生作业帮助网 编辑：六六作业网 时间：2024/11/17 05:41:43
求这篇作文
求这篇作文
求这篇作文
Many people take smog as fog,which is wrong.Smog is a type of air pollution; the word "smog" was made in the early 20th century as a portmanteau of the words smoke and fog to refer to smoky fog.The word was then intended to refer to what was sometimes known as pea soup fog,a familiar and serious problem in London from the 19th century to the mid 20th century.This kind of smog is caused by the burning of large amounts of coal within a city; this smog contains soot particulates from smoke,sulfur dioxide and other components.Modern smog,as found for example in Los Angeles,is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.The atmospheric pollution levels of Beijing,Shanghai and other cities are very high,which is why among the top ten most polluted cities there are eight Chinese cities.