Emission area-specific

This method for obtaining components for receptor models has several advantages relative to other methods. First, the component will be determined at the receptor sites, after any condensation, coagulation or fallout during transit has occurred. Second, It may include fugitive emissions from the source as well as ducted emissions. Third, the measurements are made at the same time and with the same device as the ambient sampling. Fourth, the measurements are made on emissions from specific sources In the local area, not just on the same class of source somewhere else. Fifth, the measurements do not require cooperation of the source operators or Intrusion upon their property. 

Air measurement in a chamber or cell initially produces the concentration C(t) at the time t of the measurement. To enable better comparability of the measured data the specific emission rate (SER) independent of air exchange and loading is to be preferred. The SER describes the product-specific emission behavior, for example, as area-specific emission rate (SERA) with the unit pg/(rn h) or as unit-based specific emission rate (SERu) with the unit gg/(unit h). 

Table 10.7 Area specific emission rates of VOCs.

The term area specific emission rate is used in parallel with the term emission factor. ... 

Table 15.2 Area specific (SERa) and unit specific (SER ) emission rates for different household and consumer products. See original references for analytical details.

Tichenor and Mason (1988) have shown that m-dichlorobenzene and p-dichloroberizene are common ingredients of moth crystals. Thus, area specific emission rates up to 1.4 x 107pg/(m2h) of these compounds were measured by Sparks et al. (1990). Similarly, Sheldon et al. (1988a, 1988b) and Wallace et al. 

Cation Site Distribution, Thin-film EDS analysis can also be used to quantitatively determine the site occupancy of atoms in a known crystal structure. Atom Location by Channeling Enhanced Microanalysis (ALCHEMI) is a technique which utilises electronchanneling enhanced X-ray emission for specific atoms in a crystal when appropriately oriented relative to the incident beam [43]. The method involves no adjustable parameters, can be used on relatively small areas of sample and provides fractional occupancies of atom positions [44] Unlike X-ray diffraction which has had limited success with adjacent elements in the periodic table [e.g. 45], ALCHEMI can provide site occupancies for adjacent elements and is relatively insensitive to sample thickness or the precise electron beam orientation [44] ... 

In addition to the formation of new secondary nanoparticles, there are also primary emissions of nanoparticles to the atmosphere, most importantly from high temperature combustion. While there are no published emissions inventories specifically for nanoparticles, Cass et al. (2000) estimate that approximately 85% of the mass of primary ultrafine particles (Dp <100 nm) in the Los Angeles area is emitted from combustion sources. On-road vehicles are estimated to account for approximately 40% of ultrafine particle mass. Similar results are reported for the United Kingdom, with a somewhat greater contribution (60% of total) from vehicles (Harrison et al. 2000). Observations in... 

Another approach that is commonly used to evaluate the emission rates of VOCs in indoor microenvironments is to estimate an area-specific emission rate (SER). This approach assumes that VOCs are homogeneously mixed in the environment and that SER can be calculated with the following equation [10] ... 

SERj area specific emission rate in micrograms per square metre per hour. SERp length specific emission rate in micrograms per metre per hour. 

Specific emission rate Product specific rate describing the mass of a volatile organic compound emitted from a product per unit time at a given time from the start of the test. The area-specific emission rate, SERg, is used in the standard. Several other specific emission rates can be defined according to different requirements, for example, length-specific emission rate, SERi, volume-specific emission rate, SER, and unit-specific emission rate, SER,. The term area-specific emission rate is sometimes used in parallel with the term emission factor. 

The SER describes the product-specific emission behavior for selected chemical compounds (VOCx) or the sum of the emissions (TVOC), e.g. as an area-specific emission rate (SER ) measured in pg/(m h), or as a piece-related unit-specific emission rate (SERjj) measured in pg/(unit h). 

Gunnarsen L. (1997) The influence of area-specific ventilation rate on the emissions from construction products. Indoor Air, 7, 116-120. 

The FLEC is mainly used for the determination of area-specific emission rate, (SER ) at constant temperature, relative humidity and air exchange rate. 

A procedure for the determination of area-specific emission rates (SER ) from sources on site in buildings has also been developed (Nordtest, 1998). During such measurements the air supply may consist of pure synthetic air from, e.g., a mobile gas bottle. 

In another case study, Zellweger et al., (1997e) studied the emission of hexanal fi om linoleum in an office. SER measured with the FLEC (both on-site and in-lab) correlated well with the area-specific emission rates (SER ) calculated on ventilation rate and room air concentrations. The FLEC measurements also revealed that low-volatility compounds such as glycol ethers from the room air had absorbed on the linoleum, although the linoleum initially did not emit any glycols. Relatively often, low-volatility VOCs are subject to sink effects. 

Table 3.3-3. Area-specific emission rates for different types of furniture coating. The substrates are given in parentheses.

X 10 pg/(m h)) when spread on surfaces. Knoppel and Schauenburg (1987, 1989) have identified 84 VOCs in ten different waxes and detergents. Area-specific emission rates ranged from 1.2 x 10 pg/(m h) to 2.6 x 10 pg/(m h). Colombo et al. (1990) have determined unit-specific emission rates of 2.7 x 10" pg/hand 1.9 x 10 pg/h for furniture spray polish and floor wax paste, respectively. Sparks et al. (1990) have published an emission rate of 1.4 x 10 pg/(m h) for a wood floor wax. 

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