英语翻译Text:Type and Sources of Air PollutantsWhat Is Air Pollu

英语翻译
Text:Type and Sources of Air Pollutants
What Is Air Pollution?Air pollution is normally defined an air that contains one or more chemicals in high enough concentrations to harm humans,other animals,vegentation or materials.There are two major types of air pollutants.A primary air pollutant is a chemical added directely to the air that occurs in a harmful concentration.It can be a natural air component,such as carbon dioxide,that rises above its normal concentration,or something not usually found in the air,such as a lead compound emitted by cars burning leaded gasoline.A secondary air pollutant is a harmful chemical formed in the atmosphere through a chemical reaction among air components.Serios air pollution usually results over a city or other area that is emitting high levels of pollutants during a period of air stagnation.The geographic location of some heavily populated cities,such as Los Angelles and Mexico City,makes them particularly susceptible to frequent air stagnation and pollution buildup.
We must be careful about depending solely on concentration values in determinimg the severity air pollutants.By themselves,measured concentrations tell us nothing about the danger caused by pollutants,because threshold levels,synergy,and biological magnification are also determining factors.In addition,we run into the issue of conflicting views of what constitutes harm.
Major air pollutants following are the 11 major types of air pollutants;
1.Carbon oxides:carbon monoxide (CO),carbon dioxide (CO2).
2.Sulfur oxides:sulfur dioxide (SO2),sulfur trioxide (SO3).
3.Nitrogen oxides:nitrous oxide (N2O),nitric oxide (NO),nitrogen dioxide (NO2).
4.Hydrocarbons ( organic compounds containing carbon and hydrogen):methane(CH4),butane (C4H10),Benzene (C6H6).
5.Photochemical oxidants:ozone (O3),PAN (a group of peroxyacylnitrates),and various aldehydes.
6.Particulates (solid particles or liquid droplets suspended in air):smoke,dust,soot,asbestos,metallic particles (such as lead,beryllium cadmium),oil,salt spray,sulfate salts.
7.Other inorganic compounds; asbestos,hydrogen fluoride (HF),hydrogen sulfide (H2S),ammonia (NH3),sulfur acid (H2SO4),nitric acid (HNO3).
8.Other organic ( carbon-containing) compounds:pesticides ,herbicides,various alcohols,acids,and other chemicals.
9.Radioactive substances:tritium,radon,emissions form fossil fuel and nuclear poeer plants.
10.Heat.
11.Noise.
The following table summarizes the major sources of these pollutants.