Source emissions inventories

Because of the uncertainties In the use of source-emissions Inventories to estimate contributions from various sources to ambient levels of suspended particles, many workers have been developing and testing aerosol receptor models (1 ). The basic Idea of receptor models Is that chemical compositions of particles from various types of sources are sufficiently different that one can determine contributions from the sources by making detailed measurements of the compositions of ambient aerosols and of particles from the sources. Several computational methods have been used... 

In this paper, we have focussed on the weaknesses of our present knowledge about the compositions of particles from sources that are needed as Input for receptor models. However, despite these weaknesses, we feel that the receptor model is probably already capable of more accurate determinations of TSP contributions from various types of sources than the classical methods of source emissions inventories coupled with dispersion models. If the measurements suggested are made, then the receptor models should provide very accurate estimates of those contributions. 

California Air Resources Board (CARB), Methodology for Estimating Emissions from On-Road Motor Vehicles, Vol. I Introduction and Overview, L. Hrynchuk and B. Effa, Planning and Technical Support Division Mobile Source Emission Inventory Branch, 1996. (For information about documents or MVEI7G Model, contact Public Information Office or Transportation Activity Section, California Air Resources Board. We thank Mr. E. E. Yotter and Dr. John Holmes, Chief, Research Division, for providing this information (1999).)... 

Because of large variations in emissions from car to car and from one set of driving habits to another, it has been suggested that a mobile source emissions inventory based on total fuel consumption rather than on predetermined test cycles may be more appropriate in... 

An emission inventory is a list of the amount of pollutants from all sources entering the air in a given time period. The boundaries of the area are fixed (8). 

The method used to develop the emission inventory does have some elements of error, but the other two alternatives are expensive and subject to their own errors. The first alternative would be to monitor continually every major source in the area. The second method would be to monitor continually the pollutants in the ambient air at many points and apply appropriate diffusion equations to calculate the emissions. In practice, the most informative system would be a combination of all three, knowledgeably applied. 

To develop an emission inventory for an area, one must (1) list the types of sources for the area, such as cupolas, automobiles, and home fireplaces (2) determine the type of air pollutant emission from each of the listed sources, such as particulates and SO2 (3) examine the literature (9) to find valid emission factors for each of the pollutants of concern (e.g., "particulate emissions for open burning of tree limbs and brush are 10 kg per ton of residue consumed") (4) through an actual count, or by means of some estimating technique, determine the number and size of specific sources in the area (the number of steelmaking furnaces can be counted, but the number of home fireplaces will probably have to be estimated) and (5) multiply the appropriate numbers from (3) and (4) to obtain the total emissions and then sum the similar emissions to obtain the total for the area. 

Valid emission factors for each source of pollution are the key to the emission inventory. It is not uncommon to find emission factors differing by 50%, depending on the researcher, variables at the time of emission measurement, etc. Since it is possible to reduce the estimating errors in the... 

To implement the research provisions, the EPA plans to conduct research in emissions inventories, atmospheric modeling, source/ambient monitoring, control technologies, health, and ecological monitoring. Both ecological... 

The reasons for performing a source test differ. The test might be necessary for one or more of the following reasons (1) To obtain data concerning the emissions for an emission inventory or to identify a predominant source in the area. An example of this would be determination of the hydrocarbon release from a new type of organic solvent used in a degreasing tank. 

Using the Gaussian plume model and the other relations presented, it is possible to compute ground level concentrations C, at any receptor point (Xq, in the region resulting from each of the isolated sources in the emission inventory. Since Equation (2) is linear for zero or linear decay terms, superposition of solutions applies. The concentration distribution is available by computing the values of C, at various receptors and summing over all sources. 

The first task in selecting an abatement method is the preparation of an emission inventory. The inventory is the basis of planning and the selection of options. By the preparation of an inventory, all emission sources requiring treatment can be determined and recorded. The emission inventory... 

Estimates of urban NOx emissions and trends are generally limited to those provided by the developed countries which have the detailed emission Inventories. As In the case of other pollutants, the USA contributes the most on a per-country basis to the global NOx emissions per year. Because of the Inaccuracy of the data base used. It Is difficult to discern trends In these emissions. However, with new control technologies being Implemented for both stationary and mobile sources, downward trends In the developed countries may be more prevalent In the future years. Unfortunately, the opposite trend Is likely to occur In the developing countries. 

Previous production of pentachlorophenol, as well as the bleaching process in pulp and paper mills, has been shown to be a major source. Changes in industrial processes have resulted in a reduction of PCDD/PCDFs concentration in products. Whereas in the past the chemical industry and, to a lesser extent, the pulp and paper industry were considered to be the main sources of PCDD/PCDFs (and also the cause of many of today s contaminated sites in several industrialized countries), today s dioxin input is mainly due to thermal processes. There is still a considerable focus on waste incineration but, owing to requirements for dioxin reduction in stack gases set by several national authorities, the importance of this category has declined during the last years. Examples can be seen especially in the European emission inventories... 

Olivier JGJ, Bouwman AF, Van der Hoek KW, Berdowski JJM. 1998. Global air emission inventories for anthropogenic sources of NOx,NH3 and N2O in 1990. Environmental Pollution 102 135-148. 

There is a need today to quantify the effects of aerosol sources on ambient particulate matter loadings. Identifying the major sources of ambient particulate matter loadings was a fairly simple process when values exceeded 500 /ig/m and stack emissions were plainly visible. Control of these emitters was forthcoming and effective. At levels of 150 to 200 fxg/w , the use of annual emission inventories focused further regulatory efforts on major sources which have resulted in more successful reductions. Presently, at levels around 75-100 /ig/m, the uncertainties involved in these assessments of source contributions are greater than the contributions themselves. 

A source model incorporates measured or estimated values for an emission rate factor and the dispersion factor. Whenever either of these enter the receptor model as observables, we call it a hybrid model. The three applications considered here are emission inventory scaling, micro-inventories, and dispersion modeling of specific sources within a source type. 

Emission Inventory scaling, proposed by (24), uses the relative emission rates of two source types subject to approximately the same dispersion factor (e.g., residential heating by woodstoves and natural gas) to approximate the source contribution from the source type not included in the chemical mass balance (e.g., natural gas combustion). The ratio of the emission rates is multiplied by the contribution of the source type which was included in the balance. 

Dispersion model source impact estimates, following comparison to the CMB results, were significantly improved after emission inventory deficiencies were corrected. Pinal modeling results then provided realistic source impact estimates which could be confidently used for strategy development. 

In 1970, new efforts were underway to solve Portland s suspended particulate problem. Early efforts relied on available emission factors and industrial source testing, as a basis for the emission Inventory. The inventory was then used, with a proportional rollback model, as a basis for the new strategy. New industrial controls were Installed which resulted in a 60,000 tons per year region-wide reduction in industrial emissions. Although progress toward cleaner air was made, air quality standard violations caused by then unknown sources continued and modeling efforts failed to account for over one-half of the particulate mass. 

Completion of emission inventory and modeling assumption improvements to match dispersion model source impacts to CMB results and... 

Soil and road dust was found to be the largest single source, accounting for 55% of the particulate. Although several minor sources of rural dust were included in the area s inventory, the study identified a 19,400 ton per year deficiency in the paved road dust emission inventory. 

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