Chemical mass balance model

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. 

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,... 

FIGURE 16.30 Relative source contributions to VOC from a chemical mass balance model and from an emissions inventory (adapted from Harley et al., 1992). Note that this does not include all sources of VOC in this area. 

McLaren, R., A. W. Gertler, D. N. Wittorff, W. Belzer, T. Dann, and D. L. Singleton, Real-World Measurements of Exhaust and Evaporative Emissions in the Cassiar Tunnel Predicted by Chemical Mass Balance Modeling, Environ. Sci. Technol., 30, 3001-3009 (1996b). 

Figure 27.4 A simple chemical mass balance model.

Figure 27.5 Information provided by a chemical mass balance model. The annual mass budget of benzo[a]pyrene in Massachusetts Bay is shown.

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). 

Chemical mass balance models can actually only provide information on the relative amounts of different reservoirs, not on their spatial distribution. A mantle structure in which blobs of relict primitive mantle are maintained throughout a variously depleted and enriched lower mantle may be possible (e.g., Becker et al. (1999) Figure 9(c)), or true primitive mantle... 

Several attempts have been made to model these processes. Taylor and Fox (1996) studied the Waimakariri River in New Zealand. They modeled equilibrium of DIC with atmospheric CO2 using a chemical mass-balance model that accounts for the kinetics of CO2 equilibration between the aqueous and gas phase. Their results show that the measured 5 C values of the river water cannot be explained solely by equilibrium with atmospheric CO2, and that an addition of biogenic CO2 is necessary to account for the measurements. While their model represents a step forward in kinetic considerations of atmospheric CO2 exchange in river systems, their model does not account for DIC uptake by phytoplankton via photosynthesis, which would cause biological recycling and increases in 6 C of the residual riverine DIC pool. 

Watson et al. [83] recently undertook a review of the application of chemical mass balance modelling as a source apportionment technique for VOCs. The model assumes that the concentration of a chemical pollutant in a given sampling site is the summation of the contributions of all of the sources of the pollutants at the site. Thus, the concentration of the pollutant at the site can be predicted using the following equation [84] ... 

Won D, Shaw CY, Biesenthal TA, Lusztyk E, Magee RJ (2002) Applications of chemical mass balance modeling to indoor VOCs. Proceedings of the 9th international conference on indoor air quality and climate. Monterey, CA, USA, p 268... 

Crust-mantle chemical mass-balance models offer important constraints on compositional variations in the mantle, but their constraints on the size of the various reservoirs involved depend critically on uncertainties in the estimates of the bulk composition of the continental crust, the degree of depletion of the complementary depleted mantle, and the existence of enriched reservoirs in Earth s interior, for example, possibly significant volumes of subducted oceanic crust. This last item was left out of the mass-balance models that suggested that the upper and lower mantle are chemically distinct. Chapter 2.03 makes it clear that much of the chemical and isotopic heterogeneity observed in oceanic volcanic rocks reflects various mixtures of depleted mantle with different types of recycled subducted crust. With this realization, and excepting the noble gas evidence for undegassed mantle, some of the characteristics of what was once labeled... 

Input Data for Chemical Mass Balance Modelling... 

Non-methane volatile organie eompounds (NMVOC) were measured at various sites representing different areas and different emission sources in the city of Wuppertal, Germany. The measurements covered volatile hydrocarbons in the range of C2-C10 and oxygenated hydrocarbons such as alcohols, ketones and esters. Samples were collected using Carbotrap and Carbosieve Sill solid adsorption tubes and analysed off-line by thermal desorption and GC-FID analysis. Measurement results were used to create the input data for the source apportionment analysis with the Chemical Mass Balance Modelling technique. Emission profiles for traffic and solvent use were calculated. 

To perform the source apportionment the Chemical Mass Balance model applies the emission profiles from traffic and solvent use to the NMVOCs concentrations measmed at the different receptors point in Wuppertal. Measurements were performed down-wind from the city centre, in areas close to the factories and workshop producing or using solvents, in dense traffic areas and in residential areas. The characteristics of the receptor points are presented in Table 2. 

Niedojadlo, A., K.H. Becker, R. Kurtenbach, P. Wiesen New measurements of NMVOC concentrations in the city air of Wuppertal Source apportionment by Chemical Mass Balance Modelling, Atmos. Environ. manuscript in preparation (2005). 

Javitz HS, Watson JG and Robinson N (1988) Performance of the chemical mass balance model with simulated local scale aerosols. Atmos Environ 22 2309-2322. 

Shi G-L, Li X, Feng Y-C, Wang Y-Q, Wu J-H, Li L, Zhu T (2009) Combined source apportionment, using positive matrix fachnization-chemical mass balance and principal component analysis/multiple linear regression-chemical mass balance models. Atmos Environ... 

So far, considerable information of the gaseous exhaust pipe emission factors and some of particulate matter is available from the 1990s. More recent studies reported emission factors for PM mass, organic carbon (OC), elemental carbon (EC) and some metals, which improved present knowledge about composition and size distribution of particulate motor vehicle emissions, and more important which allowed the creation of emission profiles—a prerequisite for source apportionment studies with statistic methods such as chemical mass balance models. However, since fuel composition, engines and vehicle technologies evolve (Kleeman et al. 2000) data on the combined mass emission rate and chemical composition of primary particle emissions from motor vehicles need to be updated periodically. 

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