Introduction

Organic material in the atmosphere may exist in either the gas phase or in particles. For the purposes of this chapter, atmospheric organic material will be divided into three classes, defined by the phase distribution of the organic material in the atmosphere. Gas phase compounds will include those organic compounds which are present only in the gas phase. This will include essentially all non-aromatic organic material with fewer than about 12-14 carbon atoms. Nonvolatile organic material will include those compounds which are present in particles and whose concentrations in the gas phase are negligible compared to the particulate material. Semi-volatile organic material includes those compounds which are present in equilibrium between the gas and parti-culate phases in the atmosphere and for whom the concentrations in both phases are signiRcant. The collection of gas phase and nonvolatile organic material is relatively straightforward. However, the

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accurate determination of the phase distribution of semi-volatile organic material requires the use of diffusion denuder technology.

Correct assessment of the contribution of Rne particulate carbonaceous material to various atmospheric processes is dependent on the accurate determination and characterization of fine particulate organic material as a function of particle size. Several studies have shown that about one-third of the mass of fine particulate matter (dia. <2.5 |im) collected on filters in remote desert regions of the Southwest U.S. is organic compounds and elemental carbon. Similar fractions of carbonaceous material are found in particles collected on Rlters in western urban areas. In the eastern United States sulfate is the major component of Rlter collected airborne Rne particles. However, organic material comprises one-fourth or more of the Rne particulate mass. In the Northwest, organic material has been found to be the dominant Rne partic-ulate component. However, unless proper sampling procedures are used to collect particulate material, the composition of organic material in Rne particles will be signiRcantly underestimated due to losses from the semi-volatile particulate organic fraction during sample collection, i.e. a 'negative' sampling artifact.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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