Alkyl Nitrate, Hydroxyalkyl Nitrate, and Hydroxycarbonyl Formation from the NOx−Air Photooxidations of C5−C8 n-Alkanes

Arey, Janet; Aschmann, Sara M.; Kwok, and Eric S. C.; Atkinson, Roger

doi:10.1021/jp003292z

Cited by 231 publications

(396 citation statements)

References 30 publications

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“…A source sample collected downwind of a working oil well with an oil storage tank showed elevated levels of CH 4 and C 2 -C 7 alkanes ( Table 2). The composition of hydrocarbons in this sample was similar to the composition of ''associated gas'' (i.e., found in conjunction with crude oil) (10,11). ''Nonassociated gas'' typically contains a higher percentage of methane and lower percentages of heavier alkanes (10).…”

Section: Discussionsupporting

confidence: 63%

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Katzenstein

Doezema

Simpson

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

132

137

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Light alkane hydrocarbons are present in major quantities in the near-surface atmosphere of Texas, Oklahoma, and Kansas during both autumn and spring seasons. In spring 2002, maximum mixing ratios of ethane [34 parts per 10 9 by volume (ppbv)], propane (20 ppbv), and n-butane (13 ppbv) were observed in north-central Texas. The elevated alkane mixing ratios are attributed to emissions from the oil and natural gas industry. Measured alkyl nitrate mixing ratios were comparable to urban smog values, indicating active photochemistry in the presence of nitrogen oxides, and therefore with abundant formation of tropospheric ozone. We estimate that 4 -6 teragrams of methane are released annually within the region and represents a significant fraction of the estimated total U.S. emissions. This result suggests that total U.S. natural gas emissions may have been underestimated. Annual ethane emissions from the study region are estimated to be 0.3-0.5 teragrams.W e have performed two regional studies in different seasons of hydrocarbon and halocarbon mixing ratios in surfacelevel air sampled within the southwestern United States. Elevated atmospheric mixing ratios of C 1 -C 4 alkanes and C 2 -C 4 alkyl nitrates (RONO 2 ) were measured over much of the region during both studies. The alkyl nitrate enhancements show that significant photochemistry analogous to urban smog formation is occurring within the source region. The release of hydrocarbons into the atmosphere contributes to photochemical ozone (O 3 ) production, with related adverse health effects, reduction in plant growth, and climate change (1-3). The production, storage, and transport of oil and natural gas are a major global source of hydrocarbons into the atmosphere (4), and the southwestern states have some of the largest oil and natural gas reserves in the United States. Although the U.S. natural gas industry has been estimated to account for Ϸ20% of the total U.S. anthropogenic methane (CH 4 ) emissions (5), the global budgets of light (C 2 -C 4 ) alkanes, including their emissions from the oil and natural gas industry, are more poorly assessed.The C 2 -C 4 alkanes have globally averaged lifetimes ranging from Ϸ2 months for ethane to several days for the butanes (6). Because of their short lifetimes, the atmospheric concentrations of light alkanes are variable and depend on the number and strength of nearby emission sources. By contrast, CH 4 is by far the most abundant hydrocarbon in the atmosphere, in part because of its 8-year atmospheric lifetime (7), which allows it to be widely distributed throughout both the northern and southern hemispheres. The greater reactivity of C 2 -C 4 alkanes relative to CH 4 ensures that a much larger fraction of the former will react in the area where the emissions occur, making the combined C 2 -C 4 alkane contributions more important for local and regional O 3 formation than the influence of the incremental local increases in CH 4 .In the troposphere, photochemical O 3 production begins with the attack of parent hydrocarbon...

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Section: Discussionsupporting

confidence: 63%

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Katzenstein

Doezema

Simpson

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

132

137

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“…The plateau value of 0.202 for OH addition-normalized yields of β-HN formed from 2-methyl-1-alkene reactions is higher than the value of 0.162 measured for reactions of linear 1-alkenes, but lower than the value of ≈0.3 expected for secondary alkyl nitrates formed from reactions of n alkanes (11,16). The lower yields of β-HN are due to weakening of the O-O bond in the β-hydroxyperoxy radical-NO complex, RO-O-NO, by hydrogen bonding between hydroxy and peroxy groups (9).…”

Section: Resultsmentioning

confidence: 56%

Yields ofβ-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates formed from OH radical-initiated reactions of 2-methyl-1-alkenes

Matsunaga

Ziemann

2009

Proc. Natl. Acad. Sci. U.S.A.

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Yields of β-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from OH radical-initiated reactions of C 9 -C 15 2-methyl-1-alkenes in the presence of NO x were measured by using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph with a UVvisible (UV-vis) detector. Yields of β-hydroxynitrates and dihydroxynitrates increased with carbon number primarily due to enhanced gas-to-particle partitioning before reaching plateaus at ≈C 14 -C 15 , where the compounds were essentially entirely in the particle phase. Plateau yields of β-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates were 0.183 AE 0.005, 0.045 AE 0.005, and 0.034AE 0.005, and, after normalization for OH radical addition to the C ¼ C double bond, were 0.225 AE 0.007, 0.055 AE 0.006, and 0.042 AE 0.006. The fractions of 1-hydroxy and 2-hydroxy β-hydroxynitrate isomers were 0.90∕0.10. Yields measured here and in our previous study of reactions of linear internal alkenes and linear 1-alkenes indicate that, for these alkene classes, the relative branching ratios for forming tertiary, secondary, and primary β-hydroxyalkyl radicals by OH radical addition to the C ¼ C double bond are 4.3∕1.9∕1.0, and the branching ratios for forming β-hydroxynitrates from reactions of tertiary, secondary, and primary β-hydroxyperoxy radicals with NO are 0.25, 0.15, and 0.12. The effects of H 2 O vapor and NH 3 on yields were also explored.aerosol | atmospheric chemistry | organice nitrate | particles H ydrocarbons are emitted to the atmosphere from anthropogenic and biogenic sources. Globally, more than half are biogenic alkenes including isoprene (C 5 ), monoterpenes (C 10 ), and sesquiterpenes (C 15 ) (1). These compounds have a variety of linear, branched, and cyclic structures containing one or more C ¼ C double bonds and in the atmosphere react with OH radicals, O 3 , and NO 3 radicals to form oxidized products (2, 3). In urban and polluted rural areas where peroxy radical intermediates react primarily with NO (4), one important class of products is organic nitrates (2, 3). For example, hydroxynitrates formed from OH radical-initiated reactions of isoprene have been identified in urban air (5) and impact O 3 formation and NO x removal (6) as well as secondary organic aerosol (SOA) formation (7). It has been estimated that, globally, about two-thirds of hydroxyperoxy radicals formed from isoprene oxidation react with NO (8), a value that probably applies to other terpenes.In spite of their atmospheric importance, little is known about the chemistry of hydroxynitrates. This is primarily because of a lack of analytical methods and reference compounds (5, 9). In a recent study, Paulot et al. (10) employed chemical ionization mass spectrometry to monitor hydroxynitrates formed during isoprene photooxidation, and then used this information to help constrain a detailed chemical mechanism. Even here, however, significant uncertainties exist because many hydroxynitrate isomers could not be disti...

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“…AN, 1,4HN, and 1,4HC have been measured in the gas-phase for reactions of C 7 -C 10 alkanes, with yields of approximately 0.2, 0.05, and 0.5 (Reisen et al 2005) and with no other observed products. AN and 1,4HN yields are probably closer to ∼0.3 (Arey et al 2001) and ∼0.15 (Lim and Ziemann 2005) for reactions of larger alkanes. 1,4HC partition to particles and chamber walls where they isomerize to cyclic hemiacetals (CHA) [7] (note that the structure of the cyclic hemiacetal is that of an alkyl substituted 2-hydroxytetrahydrofuran).…”

Section: Reaction Mechanismmentioning

confidence: 69%

“…Reaction with O 2 forms a carbonyl [2] and decomposition creates two carbonyl [3, 4] plus alkyl radical pairs, with the alkyl radicals then reacting as described above. For linear alkanes with C n > 6, reactions with O 2 and decomposition are too slow to compete with isomerization (Arey et al 2001;Atkinson 2007), so carbonyl formation is negligible. Isomerization through a six-membered ring followed by reaction with O 2 forms 1,4-hydroxyperoxy radicals that react with NO similarly to alkylperoxy radicals.…”

Section: Reaction Mechanismmentioning

confidence: 99%

“…In the atmosphere, alkanes only react at significant rates with OH radicals, with typical atmospheric lifetimes of a day (Atkinson and Arey 2003). The products of these reactions consist of a variety of oxygenated compounds (Atkinson 1997;Arey et al 2001;Atkinson and Arey 2003;Lim and Ziemann 2005); some of these, especially those with multiple functional groups, can condense to form secondary organic aerosol (SOA) (Lim and Ziemann 2005;Kroll and Seinfeld 2008). SOA comprises a significant fraction of the mass of atmospheric fine (diameter ≤ 2.5 µm) particles (Zhang et al 2007), which have important effects on visibility, global climate, and human health (Andrea and Crutzen 1997;Seinfeld and Pandis 1998;Englert 2004).…”

Section: Introductionmentioning

confidence: 99%

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Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NO_x

Lim

Ziemann

2009

Aerosol Science and Technology

148

201

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The effects of molecular structure on the products and mechanisms of SOA formation from OH radical-initiated reactions of linear, branched, and cyclic alkanes in the presence of NO x were investigated in a series of environmental chamber experiments. SOA mass spectra were obtained in real time and off line using a thermal desorption particle beam mass spectrometer and used to identify reaction products. Real-time mass spectra were used to classify products according to their temporal behavior, and off-line temperature-programmed thermal desorption analysis of collected SOA was used to separate products by volatility prior to mass spectral analysis and to gain information on compound vapor pressures. A reaction mechanism that includes gas-and particle-phase reactions was developed that explains the formation of SOA products and is consistent with the various lines of mass spectral information. Results indicate that the SOA products formed from the reactions of linear, branched, and cyclic alkanes are similar, but differ in a few important ways. Proposed first-generation SOA products include alkyl nitrates, 1,4-hydroxynitrates, 1,4-hydroxycarbonyls, and dihydroxycarbonyls. The 1,4-hydroxycarbonyls and dihydroxycarbonyls rapidly isomerize in the particle phase to cyclic hemiacetals that then dehydrate to volatile dihydrofurans. This conversion process is catalyzed by HNO 3 formed in the chamber and is slowed by the presence of NH 3 . Volatile products can react further with OH radicals, forming multi-generation products containing various combinations of the same functional groups present in firstgeneration products. For linear and branched alkanes, the products are acyclic or monocyclic, whereas for cyclic alkanes they are acyclic, monocyclic, or bicyclic. Some of the products, especially those formed from ring-opening reactions of cyclic alkanes appear This material is based on work supported by the National Science Foundation under Grants ATM-0234586 and ATM-0650061. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation (NSF). We also thank Roger Atkinson for helpful discussions.Address correspondence to Paul J. Ziemann, Air Pollution Research Center, University of California, 900 University Ave., Riverside, CA, 92521 USA. E-mail: paul.ziemann@ucr.edu to be low volatility oligomers. The implications of the results for the formation of atmospheric SOA are discussed.

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Alkyl Nitrate, Hydroxyalkyl Nitrate, and Hydroxycarbonyl Formation from the NO_x−Air Photooxidations of C₅−C₈ n-Alkanes

Cited by 231 publications

References 30 publications

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Yields ofβ-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates formed from OH radical-initiated reactions of 2-methyl-1-alkenes

Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NO_x

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Alkyl Nitrate, Hydroxyalkyl Nitrate, and Hydroxycarbonyl Formation from the NOx−Air Photooxidations of C5−C8 n-Alkanes

Cited by 231 publications

References 30 publications

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Extensive regional atmospheric hydrocarbon pollution in the southwestern United States

Yields ofβ-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates formed from OH radical-initiated reactions of 2-methyl-1-alkenes

Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NOx

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Alkyl Nitrate, Hydroxyalkyl Nitrate, and Hydroxycarbonyl Formation from the NO_x−Air Photooxidations of C₅−C₈ n-Alkanes

Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NO_x