Receptor mass balance

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. 

The two most widespread statistical receptor models in the literature are regression model of chemical mass balance (CMB) and target transformation factor analysis (TTFA) (. ) The questions to be answered by the receptor models are ... 

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. 

It needs to be emphasized at this point that a model is a mathematical representation of the real world. If two models have the same mathematical representation of the real world, they are, in fact, the same model. Chemical mass balance, principal component factor analysis, target transformation factor analysis, etc. have, for all practical purposes. Identical mathematical representations (Equation 1) of the real world and start with the same input data matrices (Figure 4). The principal difference in these "different receptor models is their approach to the solution of either Equation (1) or Equation (2). 

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. 

Three generic types of receptor model have been identified, chemical mass balance, multivariate, and microscopical identification. Each one has certain requirements for input data to provide a specified output. An approach which combines receptor and source models, source/ receptor model hybridization, has also been proposed, but it needs further study. 

Receptor models presently in use can be classified into one of four categories chemical mass balance, multivariate, microscopic, and source/receptor hybrids. Each classification will be treated individually, though it will become apparent that they are closely related. 

The Chemical Mass Balance Receptor Model. Equation 1 which... 

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. 

While the chemical mass balance receptor model is easily derivable from the source model and the elements of its solution system are fairly easy to present, this is not the case for multivariate receptor models. Watson (9) has carried through the calculations of the source-receptor model relationship for the correlation and principal components models in forty-three equation-laden pages. 

Microscopic Identification Models. Many different optical and chemical properties of single aerosol particles can be measured by microscopic identification and classification in order to distinguish particles originating in one source type from those originating in another. The microscopic analysis receptor model takes the form of the chemical mass balance equations presented in Equation 1. 

The microscopic receptor model can include many more aerosol properties than have been used in the chemical mass balance and multivariate models. The data inputs required for this model are the ambient properties measurements and the source properties measurements. To estimate the confidence Interval of the calculated source contributions the uncertainties of the source and receptor measurements are also required. Microscopists generally agree that a list of likely source contributors, their location with respect to the receptor, and windflow during sampling are helpful in confirming their source assignments. 

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 to identifying contributing sources was badly needed if a new round of emission control regulations were to be successful. Following technical review of the alternatives, a comprehensive plan Incorporating a Chemical Mass Balance(3,4) receptor model was adopted. This... 

Vega, E., I. Garcia, D. Apam, M. E. Ruiz, and M. Barbiaux, Application of a Chemical Mass Balance Receptor Model to Respirable Particulate Matter in Mexico City, J. Air Waste Manage. Assoc., 47, 524-529 (1997). 

Masclet and co-workers (1986) have also developed a relative PAH decay index. They used it, for example, to identify various major sources of urban pollution and developed a model for PAH concentrations at receptor sites. An interesting and relevant area that is beyond the scope of this chapter is the use of PAHs as organic tracers and incorporating their relative decay rates (reactivities) into such receptor-source, chemical mass balance models. Use of relative rates can significantly improve such model performances (e.g., see Daisey et al., 1986 Masclet et al., 1986 Pistikopoulos et al., 1990a, 1990b Lee et al., 1993 Li and Kamens,... 

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). 

Accurate knowledge of compositions of particles released by pollution sources is required by receptor modelers, e.g., for Chemical Mass Balances (CMBs). To improve model calculations, we have developed a source-composition library of data from journals, reports, and unpublished work. The library makes the data readily available and also helps to identify what new data are most needed. The library includes data for 21 studies of coal-fired plants. These data were used to investigate effects of coal type, pollution control device, and particle size on plant emissions. 

CYP3A4 metabolizes 1 to four metabolites, whose activities at V]a and V2 receptors are 3-50% and 50-100% that of 1, respectively.28 However, the combined exposure to these metabolites after i.v. administration of 1 is only 7% that of parent, so their contribution to the clinical effect is minimal. A mass-balance study with radiolabeled 1 revealed that 83% of the dose to be eliminated in the feces, with the remainder being eliminated in the urine.28... 

The pharmacokinetic evaluation of biopharmaceuticals is generally simplified by the usual metabolism of products to small peptides and to amino acids, and thus classical biotransformation and metabolism studies are rarely necessary. Routine studies to assess mass balance are not useful. However, both single- and multiple-dose toxicokinetic data are essential in safety pharmacology asessments, and these can be complicated by two factors (1) biphasic clearance with a saturable, initial, receptor-dependent clearance phase, which may cause nonlinearity in dose-exposure relationships and doseresponses [14] and (2) antibody production against an antigenic biopharmaceutical that can alter clearance or activity in more chronic repeat-dose safety studies in the preclinical model. 

Reactive Organic Chemical Mass Balance (Friedlander). In the original formulation of the CMB receptor model (1) it was recognized that the fractional amounts of various chemical species emitted by a source are not necessarily conserved during the transport of the species to the receptor site. This could occur through both physical (differential dispersion or deposition) or chemical (removal due to atmospheric reactions) processes. This possibility was acknowledged by writing the CMB equations in the form... 

Trace element compositions of airborne particles are important for determining sources and behavior of regional aerosol, as emissions from major sources are characterized by their elemental composition patterns. We have investigated airborne trace elements in a complex regional environment through application of receptor models. A subset (200) of fine fraction samples collected by Shaw and Paur (1,2) in the Ohio River Valley (ORV) and analyzed by x-ray fluorescence (XRF) were re-analyzed by instrumental neutron activation analysis (INAA). The combined data set, XRF plus INAA, was subjected to receptor-model interpretations, including chemical mass balances (CMBs) and factor analysis (FA). Back trajectories of air masses were calculated for each sampling period and used with XRF data to select samples to be analyzed by INAA. 

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... 

Henry R. C. (1992) Dealing with near collinearity in chemical mass balance receptor models. Atmos. Environ. 26A(5), 933-938. 

In hydrogel containing fixed concentrations of immobilized ligand and receptor L,ot and respectively, the mass balance for receptor (R) sites within a finite mass of gel can be written as [67]... 

Accurately estimating the total amount of acid deposited on a receptor, such as a lake, or a forest, is problematic because acids are deposited by difficult-to-quantify dry processes as well as wet processes. The wet deposition of both sulfuric and nitric acids is believed to account for only about half of the total deposition of these acids on surface waters, soils, and vegetation. Data from whole watershed mass balance studies (e.g., Table 4-13) support the hypothesis that total deposition of sulfate considerably exceeds what is measured in the form of wet deposition alone. A significant amount of H2S04 is deposited as sulfate aerosols, such as ammonium sulfate ](NH4)2S04]. The direct absorption of S03, followed by oxidation of S03 to H2S04 at the absorbing surface, is another deposition mechanism. Dry deposition of nitric acid includes sorption of nitric acid vapor onto surfaces, as well as deposition... 

Mass balance can be calculated from the amount of drug remaining in the donor, washings, skin and cumulative amount in receptor. 

Equations (45.13) and (45.14) assume that the mAb binds stoichiometrically with the target receptor in a 1 1 ratio, and Eq. (45.14) assumes that the total number of target receptors remains constant. Since the binding to target receptors was assumed to be in equilibrium at all times, binding was also taken into account when mAb is transferred from the dose compartment to the central compartment, with the central compartment only accounting for free mAb that is in equilibrium with bound mAb. Although not immediately apparent, these model structures preserve the overall mass balance in the model. 

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... 

For the assessment of the contribution of the emission categories to the observed NMVOC concentrations the Chemical Mass Balance (CMB) modelling technique, version 8 from United States Environmental Protection Agency (Watson et al., 1998 Watson et al., 2001) was selected. The method uses source specific ratios between the emission rates of certain set of compounds and aims to recognise these fingerprints, or soiuce profiles, in the profile measured at the receptor point. As a result the CMB model delivers contributions from each source type to the total ambient NMVOC and individual hydrocarbon species at receptor points and their uncertainties. 

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