Secondary aerosol organic aerosols

FIGURE 3-5 Hourly variatioiis of secondary aerosol organics, nitrates, sulfates, and ammonium as percent of total aerosol. Pasadena, Califixnia, July 25, 1973. Reprinted with permis from Grosjean and Friedlandn. ... 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

The transformation of arenes in the troposphere has been discussed in detail (Arey 1998). Their destruction can be mediated by reaction with hydroxyl radicals, and from naphthalene a wide range of compounds is produced, including 1- and 2-naphthols, 2-formylcinnamaldehyde, phthalic anhydride, and with less certainty 1,4-naphthoquinone and 2,3-epoxynaphthoquinone. Both 1- and 2-nitronaphthalene were formed through the intervention of NO2 (Bunce et al. 1997). Attention has also been directed to the composition of secondary organic aerosols from the photooxidation of monocyclic aromatic hydrocarbons in the presence of NO (Eorstner et al. 1997) the main products from a range of alkylated aromatics were 2,5-furandione and the 3-methyl and 3-ethyl congeners. 

Forstner HJL, RC Flagan, JH Seinfeld (1997) Secondary organic aerosol from the photoxodation of aromatic hydrocarbons molecular composition. Environ Sci Technol 31 1345-1358. 

FIGURE 3-1 Contnd strat es for primary and secondary organic aerosols. 

FIGURE 3-16 Evolution of tiie volume distribution of secondary organic aerosol generated in smog diamber with 1-ppm cydcdieiene, 0.33-ppm NO, and 0.17-ppm NO,. Time from bottom to top 0, 203, 412, 631. 863, 1,109, 1,364, and 1,626 s. Compare with Rgures 3-22 and 3-26. Reprinted with permission from Heisler. ... 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

Secondary organic aerosols—formed by gas-phase reaction between nitrogen oxide, ozone, and hydrocarbons—constitute an important fraction of urban photochemical smog. Data obtained at high ozone concentrations (0.67 ppm) can be taken as an upper limit of the contribution of secondary organic aerosols to the organic aerosol fraction and total... 

Industrial processes primary organic aerosols from, 48 secondary organk aerosols from, 101 Infmed spectra of aerosols, 68 Inhalation. See also Respiratory tystem of ozone, 165... 

Sleiman M, Destaillats H, Smith JD, Liu C-L, Ahmed M, Wilson KR et al (2010) Secondary organic aerosol formation from ozone-initiated reactions with nicotine and second hand tobacco smoke. Atmos Environ 44 4191 198... 

Temperature-programmed thermal desorption particle beam MS of collected secondary aerosol particles shows that the major ozonization products of normal alkenes in an environmental chamber include organic hydroperoxides, peroxides, final ozonides and monocarboxylic acids. Attempts to analyze these compounds by GC result in their decomposition to simpler molecules". 

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. 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

Rosen, Hansen, Dod and Novakov found a high correlation between optical absorptivity and the particulate carbon loading in 24-h samples from several California cities ( 5). Elemental carbon, a primary pollutant which is directly related to the absorptivity, was found to be a large fraction of the carbonaceous aerosol. They were able to place a low limit on the amount of secondary organic aerosol produced in correlation with ozone. 

We have also looked for the presence of increased secondary organic aerosol by calculating the fine aerosol mass balance in both summer and winter during periods of high and low sulfate concentrations. Formation of secondary sulfate aerosol can cause elevated levels of sulfates and has been linked to periods of regional scale haziness in the eastern U.S. (17). 

Pankow, J. F An Absorption Model of the Gas/Aerosol Partitioning Involved in the Formation of Secondary Organic Aerosol, Atmos. Environ., 28, 189-193 (1994b). 

The yields of secondary organic aerosols from a series of aromatic hydrocarbon-NOx oxidations have been measured by Odum et al. (1997a, 1997b). They showed that the total secondary organic aerosol formed from a mixture of aromatic hydrocarbons can be approximated as the sum of the individual contributions. Based on their experiments, the yield of secondary organic aerosols expressed as the total organic particle mass concentrations formed, AM, (in fxg m 3), divided by the mass concentration of aromatic precursor reacted, A (aromatic), is given by... 

The yield of secondary organic aerosol depends on the organic particle mass concentration because of the gas-particle partioning of the semivolatile organic products (see later). Thus, Odum et al. (1996) showed that the yield of secondary organic aerosol, Y, is given by... 

In Eq. (LL), M is the concentration of the condensed-phase organic (in igm 3) available to absorb semivolatile organic products, ( is a constant that relates the concentration of the ith secondary organic aerosol component formed, C, to the amount of parent precursor organic reacted i.e., C, (ng m ) 1000a, A(parent organic in p,g m 3), and Kom i is the gas-particle partioning coefficient for the ith component. As discussed in more detail in Section D, Kim j is in effect an equilibrium constant between the condensed- and gas-phase concentrations. 

Thus, if a particle secondary oxidation product does not get partitioned efficiently into the condensed phase (i.e., KtmJ is small) or the available organic condensed phase for uptake of the semivolatile product is small, Eq. (LL) reduces to Y M(lE ,/fnlI1/ and the secondary organic aerosol yield is proportional to the amount of condensed phase available for uptake of the low-volatily gaseous products. On the other hand, if KomJ and M are large, Eq. (LL) becomes Y Ea, independent of the amount of condensed phase available for product uptake. 

Figure 9.53, for example, shows a plot of the yield of secondary organic aerosol from the VOC-NOx oxidation in air of some aromatic compounds as a function... 

FIGURE 9.53 Yield (Y) of secondary organic aerosol as a function of the amount of aerosol generated, AM , during the VOC-NO. oxidations in air of some aromatic hydrocarbons (adapted from Odum et al., 1997b). 

In short, the same types of aerosol organic products have been identified both in model systems and in polluted urban ambient air and can generally be rationalized based on the oxidation of known constituents of air. The measured yields of organics in the particles can depend on the amount of particle phase available for uptake of the organic if it is semivolatile and partitions between the gas and condensed phases. This partitioning, and its dependence on the amount of condensed phase available, may be at least in part responsible for discrepancies in the yields of secondary organic aerosol reported in a number of studies. 

Figure 9.63, for example, plots log K against log pL for the partitioning of a series of PAH (see Chapter 10) between the gas phase and particles of either dioctyl phthalate (DOP) or secondary organic aerosol (SOA) generated from the photooxidation of gasoline vapor (Liang et al., 1997). The slope of the plot for uptake into DOP is 1.09 and that for uptake into SOA is... 

FIGURE 9.63 Plots of om-phase-normalized gas-particle partitioning constant log Kp iun vs logarithm of the subcooled liquid vapor pressure, log pL, for a series of semivolatile PAHs partitioning on ( ) dioctyl phthalate (DOP) or (a) secondary organic aerosol (SOA) from photooxidized gasoline vapor. PAHs are as follows naphthalene, A acenaphthalene, B fluorene, C and C phenanthrene, D and D anthracene, E and E fluoranthene, F and F pyrene, G and G chrysene, H (adapted from Liang el al., 1997). 

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