Chemical mass balance method

Toriyama S, Shimada H, Arakawa H, et al. 1991. An estimate of source contrihution of atmospheric aerosols in Toyama Prefecture by chemical mass balance method. Nippon Kagaku Kaishi N5 454-464. 

This approach has clearly allowed the resolution of the sources with results that appear to be very competitive to the chemical mass balance method. However, it was not necessary to make initial assumptions regarding the number of particle sources or their elemental composition. Additional studies need to be made to test the accuracy and precision with which such resolutions can be made. 

The chemical mass balance method starts with a single column vector from the ambient data matrix, C]. This vector represents the chemical concentrations for the kth filter, which is combined with the best available estimates of the source compositions from the fractional composition matrix, Fij> to form a series of linear equations in which the Mj are the only unknowns. This set of equations is then solved by the least squares method to obtain the best fit of the ambient chemical data on a single filter. 

A substantial amount of confusion (9,10.13,14) has recently developed as to an approach s dependence on conservation of mass. As Cooper and Watson ( ) have noted, the F j factors refer to the source chemistry as it arrives at the receptor. It is assumed with the conservation of mass that the Fj j as might be measured at a receptor, is the same as have been measured at the source. As noted above, this may not be valid depending on the source and the method used for source sampling. The chemical mass balance method incorporates the F j directly in its calculations and as a result is often perceived as having a greater dependence on this assumption than methods such as factor analysis which do not use Fy values in their calculations. Factor analysis methods, however, identify abstract factors, which explain variability. It is impossible to attribute a common... 

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. 

Core, J.E. Hanrahan, P.L. Cooper, J.A. "Air Particulate Control Strategy Development A New Approach Using Chemical Mass Balance Methods." This symposium. 

The source contributions of aerosol formed from gaseous emissions, such as sulfate, nitrate and certain organic species, cannot be quantified by chemical mass balance methods, Watson (9>) proposes a unique source type which will put an upper limit on the contributions of secondary aerosol sources, but it cannot attribute those contributions to specific emitters. 

Next, the applications have to be validated and placed into standardized forms. Validation should consist of two steps. First, simulated data sets of aerosol properties should be generated from pre-selected source contributions as did Watson in his simulation studies of the chemical mass balance method. These data should be perturbed with the types of uncertainties expected under field conditions. The types of sources and their contributions predicted by the receptor model application should be compared with the known source model values and the extent of perturbation tolerable should be assessed. 

A New Approach Using Chemical Mass Balance Methods... 

Sources of Portland s total suspended particulate mass (Figure 1) were successfully identified by Chemical Mass Balance methods ( ). The key results of the study were as follows ... 

Application of Chemical Mass Balance Methods to the Identification of Major Aerosol Sources in the Medford Airshed", Interim Report to the State of Oregon Department of Environmental Quality, November 1979. 

Cooper, J. A. and J. G. Watson. Portland Aerosol Characterization Study (PACS). Application of Chemical Mass Balance Methods to the Identification of Major Aerosol Sources in the Portland Airshod. Final report Summary. Prepared for the Portland Air Quality Maintenance Area Advisory Committee and the Oregon Department of Environmental Quality. April 23, 1979. 

There are a number of different types of source apportionment models, including the chemical mass balance method, factor analysis, multiple linear regression analysis, and Lagrangian modeling. The chemical... 

A more powerful and flexible method, and one that is widely used in watershed weathering studies, relates changes in the chemistry of input-output waters to reactions between the waters and solid phases in the system. This approach, termed chemical mass balance (method (iii)), is considered the best way of making quantitative estimates of rates of elemental transfers in the Earth s surface environment (Clayton, 1979). In method (iii), the hydrochemical method developed by Garrels and Mackenzie (1967), mineralogy and composition of the primary and secondary phases must be well characterized. The composition and volume of the initial water and the final water must be... 

Core, J. E., Hanrahan, P. L., and Cooper, J, A. (1981 Air Pollution Control Strategy Development A New Approach Using Chemical Mass Balance Methods in Atmospheric Aerosol Source/Air Quality Relations, in Macias, E. S and Hopke, D. (Eds.). Symposiim Series No. 167, American Chemical Society, Wa.s iington. D.C., p. 107. 

Receptor Modeling Source Apportionment 380 Basic Concepts 380 Chemical Mass Balance Method 381 Portland Aerosol Characterization Study 382 Relating the CMB to Aerosol Dynamics 385... 

Core JE, Hanrahan PL and Cooper JA (1981) Air particulate control strategy development - a new approach using chemical mass balance methods. In Macias ES and Hopke PK, eds. Atmospheric Aerosols Source/Air Quality Relationships. ACS Symposium Series 167. Washington, DC. 

If the source fingerprints, for each of n sources are known and the number of sources is less than or equal to the number of measured species (n < m), an estimate for the solution to the system of equations (3) can be obtained. If m > n, then the set of equations is overdetermined, and least-squares or linear programming techniques are used to solve for L. This is the basis of the chemical mass balance (CMB) method (20,21). If each source emits a particular species unique to it, then a very simple tracer technique can be used (5). Examples of commonly used tracers are lead and bromine from mobile sources, nickel from fuel oil, and sodium from sea salt. The condition that each source have a unique tracer species is not often met in practice. 

PLS (partial least squares) multiple regression technique is used to estimate contributions of various polluting sources in ambient aerosol composition. The characteristics and performance of the PLS method are compared to those of chemical mass balance regression model (CMB) and target transformation factor analysis model (TTFA). Results on the Quail Roost Data, a synthetic data set generated as a basis to compare various receptor models, is reported. PLS proves to be especially useful when the elemental compositions of both the polluting sources and the aerosol samples are measured with noise and there is a high correlation in both blocks. 

In this paper the PLS method was introduced as a new tool in calculating statistical receptor models. It was compared with the two most popular methods currently applied to aerosol data Chemical Mass Balance Model and Target Transformation Factor Analysis. The characteristics of the PLS solution were discussed and its advantages over the other methods were pointed out. PLS is especially useful, when both the predictor and response variables are measured with noise and there is high correlation in both blocks. It has been proved in several other chemical applications, that its performance is equal to or better than multiple, stepwise, principal component and ridge regression. Our goal was to create a basis for its environmental chemical application. 

Organic compounds, natural, fossil or anthropogenic, can be used to provide a chemical mass balance for atmospheric particles and a receptor model was developed that relates source contributions to mass concentrations in airborne fine particles. The approach uses organic compound distributions in both source and ambient samples to determine source contributions to the airborne particulate matter. This method was validated for southern California and is being applied in numerous other airsheds. ... 

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. 

Multivariate methods, on the other hand, resolve the major sources by analyzing the entire ambient data matrix. Factor analysis, for example, examines elemental and sample correlations in the ambient data matrix. This analysis yields the minimum number of factors required to reproduce the ambient data matrix, their relative chemical composition and their contribution to the mass variability. A major limitation in common and principal component factor analysis is the abstract nature of the factors and the difficulty these methods have in relating these factors to real world sources. Hopke, et al. (13.14) have improved the methods ability to associate these abstract factors with controllable sources by combining source data from the F matrix, with Malinowski s target transformation factor analysis program. (15) Hopke, et al. (13,14) as well as Klelnman, et al. (10) have used the results of factor analysis along with multiple regression to quantify the source contributions. Their approach is similar to the chemical mass balance approach except they use a least squares fit of the total mass on different filters Instead of a least squares fit of the chemicals on an individual filter. 

The future development of the chemical mass balance receptor model should include 1) more chemical components measured in different size ranges at both source and receptor 2) study of other mathematical methods of solving the chemical mass balance equations 3) validated and documented computer routines for calculations and error estimates and 4) extension of the chemical mass balance to an "aerosol properties balance" to apportion other aerosol indices such as light extinction. 

The development of new source apportionment methods have, for the first time, led to the development of regional particulate control strategies. Source impacts assigned using a chemical mass balance (CMB) model have been used in association with airshed dispersion models to identify emission inventory deficiencies and Improve modeling assumptions. 

Receptor models are widely used tools for apportioning concentrations of pollutants to different sources. They can be factor analytical methods (PMF, PCA, UNMIX, etc.) or chemical mass balance (CMB). On the one hand, these methods revealed to be very valuable to identify the main sources/categories of PM pollution (road traffic, secondary particles, fuel oil combustion, sea salt, etc.) but on the other hand they experienced difficulties in separating the contributions of collinear sources such as mineral dust (natural resuspension) and road dust (anthropogenic) or co-variant sources such as vehicle exhaust and road dust [34, 44, 45, 49, 55, 58, 110-113]). Significant improvements were made with the use of combination of models or constrained models such as the Multilinear Engine (ME-2). 

The mixture of PAHs present in a particular sample in many cases mirrors the sources that produce them. Several methods can be used to qualitatively identify the probable sources of PAHs. Commonly used methods include the abundance ratios of individual compounds, the fossil fuel pollution index (FFPI), and diagnostic ratios indicative of sources (petrogenic vs. pyrogenic). Quantitative apportionment of sources needs sophisticated statistical approaches such as the chemical mass balance models (Li et al., 2003). 

In this study we have employed the simultaneous collection of atmospheric particles and gases followed by multielement analysis as an approach for the determination of source-receptor relationships. A number of particulate tracer elements have previously been linked to sources (e.g., V to identify oil-fired power plant emissions, Na for marine aerosols, and Pb for motor vehicle contribution). Receptor methods commonly used to assess the interregional impact of such emissions include chemical mass balances (CMBs) and factor analysis (FA), the latter often including wind trajectories. With CMBs, source-strengths are determined (1) from the relative concentrations of marker elements measured at emission sources. When enough sample analyses are available, correlation calculations from FA and knowledge of source-emission compositions may identify groups of species from a common source type and identify potential marker elements. The source composition patterns are not necessary as the elemental concentrations in each sample are normalized to the mean value of the element. Recently a hybrid receptor model was proposed by Lewis and Stevens (2) in which the dispersion, deposition, and conversion characteristics of sulfur species in power-plant emissions... 

Chemical oceanographers have developed a host of mass balance methods for determining the importance of hydrothermal solutions to the marine mass balance of dissolved elements in the ocean. The idea is that if one knows the flow of water through hydrothermal areas and the change in concentration of the element in question... 

The chemical mass balance (CMB) method depends on the inversion of (13.11) or (13.12) to obtain the source contributions mj or Anij. Values of pi are measured at a given sampling site. The matrix Cij should also correspond to the point of measurement. Usually, however, it is assumed that the value of c,-/ is equal to (he value at the source, and fractionation by exchange with (he gas phase or by sedimentation is neglected. Hence in carrying out the chemical element balance, it is necessary to choose elements for which fractionation is not tmportanl. 

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