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Air Quality Part 2

Tham khảo tài liệu 'air quality part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 18 Air Quality 6. Non Methane Volatile Organic Compounds The anthropogenic fraction of atmospheric VOCs is related to the unprecedented usage of fossil fuels for transport the production of consumer goods and various industrial processes in the past centuries. The distinction between biogenic and anthropogenic VOCs in the atmosphere is far from straightforward because many VOC species are produced by both sources. Emissions of alkanes and alkenes for example are dominated by anthropogenic sources but are also produced by soils wetlands and oceans. Koppmann 2007 The larges sources of NMVOC emissions are use of fossil fuel in transportation and chemistry industry. Mobile sources can be divided into emissions from the exhaust and fugitive emissions by evaporation. Stationary emissions from the use of fossil fuel are due to industrial applications e.g. refineries and chemical sector . Emissions related to production storage and delivery of fossil fuels predominately occur in those regions where extensive fossil fuel drilling activities exist. However fugitive emissions can also occur from the transport and distribution of the fuel such as ships road tankers and fuel stations. After their release into the atmosphere VOCs are oxygenated by photochemical processes which finally lead to their removal from the atmosphere. For most VOCs the process is initiated by atmospheric radicals like OH O3 NO3 and Cl with the OH radical being by far the most important reactant. The atmospheric lifetime of an individual VOC species is dependent on its chemical structure the radical concentration and the intensity of solar radiation. When VOCs are degraded in polluted air masses NO is oxygenated to NO2 which then gets photolysed and contributes to the formation of tropospheric ozone a key issue in air pollution control. In the EU-27 NMVOC emissions declined by just under 45 between 1990 and 2006. Twenty-three countries reported reductions Belgium Germany Luxembourg the Netherlands and .