Source apportionment

Unhke ambient VOCs, which originate predominantly from vehicular and industrial emissions, indoor VOCs have numerous and diverse origins. Therefore, source apportionment is an important factor in source control and the prime driving force for many lAQ studies. It can be accomplished by many methods, including the following. 

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Receptor models are powerful tools for source apportionment of particulates because a vast amount of particulate species characterization data have been collected at many sampling sites worldwide, and because many aerosol species are primary pollutants. Most of the information available is for elemental concentrations, eg, lead, nickel, and alurninum, although more recent measurements have provided data on concentrations of ionic species and carbonaceous compounds. At a sampling (or receptor) site, the aerosol mass concentration of each species i is... 

EEA- European Environmental Agency (2005) Source apportionment of nitrogen and phosphorus inputs into the aquatic environment. Environmental Assessment report No 7. Available at http //www.eea.europa.eu/publications/eea report 2005 7 (June 2009)... 

W. Van Borm, Source Apportionment of Atmospheric Particles by Electron Probe X-ray Microanalysis and Receptor Models. Doctoral Thesis, University of Antwerp, 1989. 

Jinhui L, Huabo D, Pixing S (2011) Heavy metal contamination of surface soil in electronic waste dismantling area site investigation and source-apportionment analysis. Waste Manag... 

Relationship Between Personal, Outdoor and Indoor Air Concentrations (RIOPA) The overall goal of the national multicenter (Elizabeth, NJ, Houston, TX, and Los Angeles County, CA) RIOPA study is to establish a scientific foundation for effective, timely, public health intervention strategies. Outdoor, indoor, and personal exposures of adults and children to PM are measured and evaluated by mass, elemental, chemical, and source apportionment analyses in the other research programs. Non-smoking asthmatic and non-asthmatic adults and their children are included. Monitoring occurs... 

Gatz, D.F., "Source Apportionment of Rain Water Impurities In Central Illinois," presented at 76th A.P.C.A. Meeting,... 

KittoM. 1993. Trace-element patterns in fuel oils and gasolines for use in source apportionment. Air Waste 43(10) 1381-1388. 

Koutrakis P, Briggs S, Leaderer B. 1992. Source apportionment of indoor aerosols in Suffolk and onondaga counties new york. Environ Sci Technol 26(3) 521-527. 

Schauer JJ, Rogge WF, Hildemann LM, Mazurek MA, Cass GR, Simoneit BRT, Source apportionment for airborne particulate matter using organic compounds as tfxcets, Atmos Environ 30 3837—3855, 1996. 

Schauer JJ, Gass GR, Source apportionment of wintertime gas-phase air pollutants using organic compounds as tracers. Environ Sci Technol 32 1821—1832, 2000. 

Johnson DL, Davis BL, Dzubay TG, et al. 1984. Chemical and physical analyses of Houston aerosol for interlaboratory comparison of source apportionment procedures. Atmos Environ 18 1539-1553. 

Review of the Chemical Receptor Model of Aerosol Source Apportionment... 

There are two general types of aerosol source apportionment methods dispersion models and receptor models. Receptor models are divided into microscopic methods and chemical methods. Chemical mass balance, principal component factor analysis, target transformation factor analysis, etc. are all based on the same mathematical model and simply represent different approaches to solution of the fundamental receptor model equation. All require conservation of mass, as well as source composition information for qualitative analysis and a mass balance for a quantitative analysis. Each interpretive approach to the receptor model yields unique information useful in establishing the credibility of a study s final results. Source apportionment sutdies using the receptor model should include interpretation of the chemical data set by both multivariate methods. 

Although source oriented dispersion models are invaluable predictive tools, their ability to quantify the Impact of a source is limited. Receptor oriented methods of source apportionment, however, have evolved in recent years to the point where they now clearly form a new discipline of air pollution science. ( 1, ) This new discipline is distinctly different from dispersion modeling and has demonstrated that it can quantitatively apportion source contributions to particle levels. Receptor models are not pre-... 

Each source apportionment tool (Figure 2) has Its unique strengths and limitations, and each can provide valuable Insight Into sources contributing to air particulate levels. The most cost effective tool or set of tools, however, will depend on the nature of the airshed, potential sources and the accuracy and precision of source apportionment required. 

The Information provided by these models Is circumstantial In nature and the results from a single Interpretive approach at this stage of model evolution may be Insufficient to develop the level of confidence required to support strong action or clear decisions. The objective of source apportionment studies must be to build a strong enough bridge of circumstantial Information (Figure 3) to quantitatively relate a source to an Impact. Thus, the entire Information base must support and be Internally consistent with a study s conclusions to provide decision makers with confidence that their actions will result In Improved air quality. 

Figure 1. Schematic comparison of source apportionment methods...

Figure 3. Circumstantial source apportionment information. Contribution based on establishing other circumstances that afford reasonable inference of the source...

Urban aerosols are complex mixtures of chemicals contributed by many different sources. One objective of an aerosol source apportionment study is to separate or resolve the contribution of specific sources or source types from the collection of all possible sources, and quantify their contributions. 

The filter material of choice is a thin teflon membrane since it minimizes artifact formation and maximizes analytical sensitivity by X-ray fluorescence analysis. Although X-ray fluorescence (XRF) may not be the only analytical technique used, it is generally accepted as being the most cost effective analysis for source apportionment. ( 2) Its background and therefore, analytical sensitivity, is dependent on the filters surface density. The analytical sensitivity of XRF for aerosols deposited on a stretched teflon membrane with a density of about 0.3 to 0.4 mg/cm, for example, is about three times greater than an aerosol deposited on a cellulose based filter with a surface density of about 4 mg/cm. This difference can be translated into either more information for the same analytical costs or the same information for a lower analysis cost. 

The interpretation stage consists of applying one or all of the chemical receptor model approaches to interpreting the chemical data generated. The objective of a source apportionment study is the support of effective control action. The level of confidence required to initiate this action may be established with a single receptor model interpretive approach or it may require information from additional interpretive approaches, wind sector analysis, (, ... 

The first step of any source apportionment study should therefore include a thorough review of potential sources, their chemistry and time dependence, if the highest level of confidence is to be established in the final results. 

A source apportionment study using the receptor model should include interpretation of the chemical data set by both multivariate and chemical mass balance methods The most critical steps in a receptor model study are the initial review of potential source characteristics and the development of an appropriate study plan. 

The major limitation of microscopic receptor models is that the analytical method, the classification of particles possessing a defined set of properties, has not been separated from the source apportionment of those particles. Equation 2 has never been used in this application. The source identification takes place by recognition of the particle bv the microscopist and thus is difficult to standardize. 

Cooper, J.A. and Watson, J.G. (1980). "Receptor Oriented Methods of Air Particulate Source Apportionment," Journal of the Air Pollution Control Association, 30, 1115. 

Without the benefit of the data base improvement programs, 27 million dollars in Industrial controls would likely have been the key element in a new control strategy yet would have only provided one-third of the reduction required to meet standards. Instead, a more effective mix of point and area source controls will likely be adopted and, at considerably less cost to (and with considerably more effectiveness for) the community. Once the capability is developed, CMB estimates of source Impacts can be used to track the progress of the strategy on a source-class basis using actual air samples, (in addition to emission estimates) to measure the effectiveness of the controls. Oregon s Source Apportionment Program and the Future... 

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