城市环境过程

地理科学学院基地班 郭梦婕 10111710317 Air Pollution Mengjie Guo Abstract This paper systematically analyzed the problems of air pollution, the variety of pollutants and their harms to mankind and environment, and we described the technical and non-technical countermeasures of preventing air pollution in city.

Keywords Source;Pollutant;Distribution;Dynamics;Effects;Methods:Remediation. Air pollution.

1 Introduction With the rapid development of the economy, urbanization and transportation, almost all types of air pollution problems, which were experienced for nearly a century in developed countries, exploded in China within last two decades. Complex air pollution, characterized by regional photochemical smog and haze exhibited an increasing trend in recent years in rapidly developing regions such as the North China Plain, the Yangtze River Delta and the Pearl River Delta. Air pollution is normally defined as air that contains one or more chemicals in high enough concentrations to harm humans, other animals, vegetation or materials.

2 Pollutant Types There are two major types of air pollutants. A primary air pollutant is a chemical added directly to the air that occurs in a harm 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. Serious air pollution usually results over a city or other area that is emitting high levels of pollutants during a period of air stagnation. Major air pollution following are the 11 major types of air pollution. a) Carbon oxides: carbon monoxide, carbon dioxide. b) Sulfur oxides: sulfur dioxide, sulfur trioxide. c) Nitrogen oxides: nitrous oxide, nitric oxide, nitrogen dioxide. d) Hydrocarbons(Organic compounds containing carbon and hydrogen): methane, butane, benzene e) Particulates(solid particles or liquid droplets suspended in the air): smoke, dust, soot, asbestos, metallic particles(such as lead, beryllium, cadmium), oil, salt spray, sulfate salts. f) Other inorganic compounds: asbestos, hydrogen fluoride(HF), hydrogen sulfide, ammonia, sulfur acid, nitric acid. g) Other organic (carbon-containing) compounds: pesticides, herbicides, various alcohols, acids and other chemicals. h) Radioactive substances: tritium,radon, emissions from fossil fuel and nuclear power plants. i) Photochemical oxidants:ozone, PAN(a group of peroxyacyl nitrates), and various aldehydes. l) Heat. k) Noise.

3 Source There are various locations, activities or factors which are responsible for releasing pollutants into the atmosphere. These sources can be classified into two major categories: anthropogenic sources and natural sources.

3.1 Anthropogenic Sources a) Industrial pollution source: It includes exhausting gas emitted by producing process and fuel burning, such as smoke stacks of power plants, manufacturing facilities and waste incinerators, as well as furnaces and other types of fuel-burning heating devices. In developing and poor countries, traditional biomass burning is the major source of air pollutants, traditional biomass includes wood, crop waste and dung. b) Agricultural pollution source: Using pesticides and fertilizers in a wrong way,it can release harmful volatile matter go into the air. c) Domestic pollution sources: Burning the garbage will release the toxics up into the air, and heating system and oven can also emit toxic gas. Waste deposition in landfills, which generate methane. Methane is highly flammable and may form explosive mixtures with air. Methane is also an asphyxiant and may displace oxygen in an enclosed space. d) Traffic pollution sources: Mobile sources include motor vehicles, marine vessels, and aircraft, is the main source of air pollution.

3.2 Natural Source a) Methane, emitted by the digestion of food by animals, for example cattle. b) Smoke and carbon monoxide from wildfires. c) Volcanic activity, which produces sulfur, chlorine, and ash particulates. d) Vegetation, in some regions, emits environmentally significant amounts of VOCs on warmer days. These VOCs react with primary anthropogenic pollutants—