Source receptor

Atmospheric emissions of sulphur dioxide are either measured or estimated at their source and are thus calculated on a provincial or state basis for both Canada and the United States (Figure 2). While much research and debate continues, computer-based simulation models can use this emission information to provide reasonable estimates of how sulphur dioxide and sulphate (the final oxidized form of sulphur dioxide) are transported, transformed, and deposited via atmospheric air masses to selected regions. Such "source-receptor" models are of varying complexity but all are evaluated on their ability to reproduce the measured pattern of sulphate deposition over a network of acid rain monitoring stations across United States and Canada. In a joint effort of the U.S. Environmental Protection Agency and the Canadian Atmospheric Environment Service, eleven linear-chemistry atmospheric models of sulphur deposition were evaluated using data from 1980. It was found that on an annual basis, all but three models were able to simulate the observed deposition patterns within the uncertainty limits of the observations (22). 

Legislation enacted by both Canada and the United States (see the US-Canada Air Quality Accord, 1991) will, when implemented, reduce the North American emissions of sulphur dioxide by about 50% based upon the 1980 baseline. These projected emission fields have been appplied in the atmospheric source-receptor models that were described above, to provide a projected deposition field for acidic sulphate that would be expected (14). The predicted sulphate deposition fields have then subsequently been appUed in aquatic effects models that provide estimates of regional surface water acidification distributions (50). The regional acidification profiles have then been used in a model of fish species richness (51) that results in an estimate of the expected presence of fish species as compared to that expected in an unacidified case. 

Cell Line Cell Type Source Receptor... 

European countries, source-receptor relationships were evaluated for the composite region the European Union—EU15). The contribution of external anthropogenic sources to EU amounted to 12%. 

A problem In the analysis of these data Is the potential masking of some sources of variability by other correlated variables which may be difficult to quantify. For example, the potential meteorological Influences of atmospheric dispersion and mixing, scavenging differences between warm and cold clouds, variable rates of oxidation of sulfur and nitrogen species, and the dilution effect of variable rain volume may mask source-receptor chemical relationships. A particular problem Is that meteorological data and source-receptor locations share directional dependence. 

Cohen MA, Ryan PB, Spengler JD. 1991. Source-receptor study of volatile organic compounds and particulate matter in the Kanawha Valley, WV-II. Analysis of factors Contributing to VOC and particle exposure. Atmos Environ 25B 95- 107. 

Among the multivariate statistical techniques that have been used as source-receptor models, factor analysis is the most widely employed. The basic objective of factor analysis is to allow the variation within a set of data to determine the number of independent causalities, i.e. sources of particles. It also permits the combination of the measured variables into new axes for the system that can be related to specific particle sources. The principles of factor analysis are reviewed and the principal components method is illustrated by the reanalysis of aerosol composition results from Charleston, West Virginia. An alternative approach to factor analysis. Target Transformation Factor Analysis, is introduced and its application to a subset of particle composition data from the Regional Air Pollution Study (RAPS) of St. Louis, Missouri is presented. 

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. 

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. 

Hybrid Source/Receptor Models. Until now, the receptor models have been treated as if they were completely separate entities from the source models. This need not be the case. 

Two more sets of observables are Introduced Into the hybrid models the emissions factors and the dispersion factors. It Is the difficulty of quantifying these that led to the use of a receptor model over the source model In the first place, so It would seem there Is little advantage In reintroducing them. The advantage of the hybridization Is that the number of Individual emission and dispersion factors can be considerably reduced and that the relative values rather than the absolute values are used. These relative values are more accurate In most cases. Still, the uncertainties of emission and dispersion factors need to be evaluated and Incorporated Into any source/receptor hybrid model. 

Future areas of development Include theoretical formulation of source/receptor models and validation tests with real and simulated data. 

Source Characterization. All receptor models, even the source/receptor hybrids, require input data about the particulate matter sources. The multivariate models, which can conceivably be used to better estimate source compositions, require an initial knowledge of the chemical species associations in sources. 

In its simplest form of interest for policy and regulatory purposes, linearity is often treated in terms of source-receptor relationships. That is, if the emissions of the precursor S02 are lowered by 50%, will the deposition of sulfate also decrease by 50% at all receptor sites ... 

Hales, J. M., and D. S. Renne, Source-Receptor Linearity Definitions, Measurement, and Practical Implications, Atmos. Environ., 26A, 2111-2123 (1992). 

G. M. Hidy, Atmospheric Sulfur and Nitrogen Oxides Eastern North American Source Receptor Relationships, Academic Press, Odando, Fla., 1994. 

Stohl A (1996) Trajectory statistics - a new method to establish source-receptor relationships of air pollutants and its application to the transport of particulate sulfate in Europe. Atmos Environ 30 579-587... 

Characterization of variability in deposition is important for bounding uncertainties in exposure levels. Also this aspect of deposition is crucial to describing the "predictability of source-receptor relationships (SRRs)(4). 

The reliable estimation of source impact on receptor conditions is difficult from theory because of undetermined uncertainties. Inference from comparison between emissions and measurements offers an alternative to calculations. Measurements in the East have yielded ambiguous source-receptor relationships. However, evidence suggests that recent changes in sulfate deposition in the West are linked with relatively large changes in SO emissions from non-... 

Meteorological variability needs to be considered in estimating the reliability of source-receptor calculations. 

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... 

B10. Brass, A. L., Barnard, J., Patai, B. L., Salvi, D., and Rukstalis, D. B., Androgen upregulates epidermal growth factor receptor expression and binding affinity in PC3 cell lines expressing the human androgen source receptor. Cancer Res. 55, 3197-3203 (1995). 

Fig. 7.4 (a) Average surface ozone concentration (in ppb) over 8 days at 16 00. Mexican summer time for the baseline 2010 emission scenario, (b) Source-receptor relationship for the 50 grid cells with highest N02-concentrations within the conurbation of Munich during a 4 day period... 

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