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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L17816, doi:10.1029/2006GL026884, 2006
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Does atmospheric processing of saturated hydrocarbon surfaces by
NO3 lead to volatilization?
D. A. Knopf,1 J. Mak,1 S. Gross,1 and A. K. Bertram1
Received 11 May 2006; revised 12 July 2006; accepted 31 July 2006; published 14 September 2006.
[ 1 ] The heterogeneous oxidation of a saturated
hydrocarbon monolayer by NO3 was studied. A flow tube
reactor coupled to chemical ionization mass spectrometry
was used to determine the reactive uptake coefficient of
NO 3 on these surfaces, and X-ray photoelectron
spectroscopy (XPS) was used to investigate surface
oxidation and to determine if exposure to NO3 leads to
volatilization of the organic substrate. The uptake
coefficient of NO3 by an alkane monolayer is about (8.8 ±
2.5) 10 4, which may lead to competitive oxidation
compared with OH, due to the higher atmospheric
abundance of NO3 under certain conditions. The XPS
results are consistent with the formation of 1) C-O groups,
2) ketones or aldehydes, and 3) carboxylic groups. The XPS
results also suggest that NO3 does not rapidly volatilize the
organic surface: even under extremely polluted conditions,
maximum 10% of the organic layer is volatilized.
Citation: Knopf, D. A., J. Mak, S. Gross, and A. K. Bertram
(2006), Does atmospheric processing of saturated hydrocarbon
surfaces by NO3 lead to volatilization?, Geophys. Res. Lett., 33,
L17816, doi:10.1029/2006GL026884.
1. Introduction
[2] Field measurements have shown that organic material
is abundant in the atmosphere, comprising 10 –70% of the
total fine particulate mass. This organic material can be in
the form of pure organic particles, or alternatively the
organic material can be mixed with inorganic material. In
the latter case the organic material can form organic coatings on the surface of aqueous particles [Gill et al., 1983;
Ellison et al., 1999], or organic coatings adsorbed on the
surface of solid particles, such as mineral dust [Usher et al.,
2003]. While in the atmosphere, these organic particles and
organic surfaces can be modified by reactions with atmospheric oxidants such as O3, NO3, and OH [Ellison et al.,
1999; Rudich, 2003]. These heterogeneous reactions are
expected to change the hygroscopicity and toxicity of these
organic particles and organic surfaces. Due to the potential
atmospheric importance of these heterogeneous reactions,
they need to be understood and quantified.
[3] Over the past few years the heterogeneous oxidation
of unsaturated aliphatic particles and substrates have been
the focus of many studies [see, e.g., de Gouw and Lovejoy,
1998; Moise and Rudich, 2000; Wadia et al., 2000; Thomas
et al., 2001; Smith et al., 2002; Eliason et al., 2003;
Thornberry and Abbatt, 2004; Hung et al., 2005; Knopf et
1
Chemistry Department, University of British Columbia, Vancouver,
British Columbia, Canada.
Copyright 2006 by the American Geophysical Union.
0094-8276/06/2006GL026884$05.00
al., 2005; Docherty and Ziemann, 2006]. In contrast, there
have been considerably fewer studies on the heterogeneous
oxidation of saturated aliphatic particles and substrates by
atmospheric oxidants [Bertram et al., 2001; Moise and
Rudich, 2001; Eliason et al., 2004; Molina et al., 2004],
although a large fraction of condensed-phase organic material in the atmosphere consists of these organic species. In
the following we investigate the heterogeneous reactions
between NO3 radicals and a self-assembled organic monolayer of octadecanethiol (C18H38S) on gold. Octadecanethiol on gold is a methyl-terminated, C-18 alkane
monolayer. Here we use this self-assembled organic monolayer (SAM) as a proxy for organics adsorbed on solid
substrates such as mineral dust particles or urban surfaces in
the atmosphere [Diamond et al., 2000; Usher et al., 2003].
The SAM surface may also serve as a proxy for solid
organic particles in the atmosphere and a rough model for
some types of organic coatings on aqueous particles in the
atmosphere. Studies with these surfaces also enabled us to
probe the reactive processes that are confined to the gassurface interface, and separate surface and bulk processes
[Rudich, 2003].
[4] Two types of experiments were carried out: in the first
set of experiments, we used a flow tube reactor coupled to
chemical ionization mass spectrometry (CIMS) [Knopf et
al., 2005] to determine the reactive uptake coefficient () of
NO3 on the saturated hydrocarbon surfaces (the reactive
uptake coefficient is defined as the fraction of collisions
with the surface that result in a reaction). In the second set
of experiments X-ray photoelectron spectroscopy (XPS)
was used to investigate surface oxidation and to determine
if exposure to NO3 (in the presence of O2) leads to
volatilization of the organic substrate. The last set of experiments was motivated by a recent study by Molina et al.
[2004]. Using atmospherically relevant exposures of OH,
these authors showed that OH-initiated oxidation of alkane
self-assembled monolayers (in the presence of O2, NOx, and
H2O) leads to rapid volatilization of the organic substrate.
Moise and Rudich also studied heterogeneous reactions on
self-assembled alkane monolayers and observed partial loss
of the organic surface after exposure to Cl and Br radicals in
the presence of O2 [Moise and Rudich, 2001]. In the gas
phase, the mechanisms of the reactions between NO3, OH,
Cl, and Br radicals with alkanes are similar (all involve
alkyl, alkoxy, and alkylperoxy radicals). However, the NO3 +
alkane reaction in the gas phase is slower compared to
gas-phase reactions between OH + alkanes and Cl +
alkanes. If the NO3 + alkane reaction rate on and in
the organic monolayer is significantly enhanced compared
to equivalent reactions in the gas phase, it seems reasonable to speculate that NO3 will lead to volatilization of
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Table 1. Reactive Uptake Coefficients, , of Different Atmospheric Radicals by Organic Surfacesa
Oxidant
NO3
Cl
Br
OH
Surface
ODT (C18H38S)
liquid n-hexadecane
frozen n-hexadecane
OTS (C18H37Cl3Si)
OTS (C18H37Cl3Si)
OTS (C18H37Cl3Si)
OTS (C18H37Cl3Si)
Atmospheric Concentration
(8.8 ± 2.5)
(2.6 ± 0.8)
(3.8 ± 1.0)
>0.1e
(3.0 ± 1.0)
>0.2f
g
0.29 +0.71
0.15
10
10
10
4b
10
2e
c
50 ppt
50 pptc
50 pptc
4 10 4 pptc
0.04 ppte
0.04 pptc
0.04 pptc
3d
4d
[radical]/molecule cm
3
6
1.1 10
3.25 106
4.75 105
1.0 103
3.0 104
2.0 105
2.9 105
a
In addition, the product of and the atmospheric radical concentration ([radical]) is given to assess the importance of the radicals to atmospheric
oxidation. (The table has been adapted from Moise and Rudich [2001].)
b
This work.
c
Finlayson-Pitts and Pitts [2000].
d
Moise et al. [2002].
e
Moise and Rudich [2001].
f
Molina et al. [2004].
g
Bertram et al. [2001].
alkane monolayers using atmospherically relevant exposures, if OH and Cl lead to volatilization.
2. Experimental
[5] A description of the preparation methods of ODT on
gold is given by Ishida et al. [1997]. All chemicals were
purchased from Aldrich. N2O5 was generated by reacting
NO2 with an excess amount of O3 in a flow system as
described previously in the literature [Schott and Davidson,
1958].
[6] Measurements of the reactive uptake coefficient were
carried out with a cylindrical flow reactor coupled to a
chemical ionization mass spectrometer [Knopf et al., 2005].
SAMs were prepared on a gold tube with an inside diameter
of about 20 mm, and this tube was located in the flow tube
reactor. NO3 radicals were produced by passing N2O5
through a Teflon coated glass oven held at 423 K. At the
exit of the flow cell, N2O5 and NO3 were detected using
chemical ionization with either I or SF6 as the reagent ion.
The NO3 concentrations used in the uptake experiments
(as well as NO3 concentrations used in the measurements of
the extent of surface oxidation and volatilization) ranged
from 2 1011 to 4 1011 molecule cm 3, which is higher
than typical atmospheric concentrations. Due to experimental
constraints it was not possible to use lower NO3 concentrations in our experiments. Further work is needed to verify
that the reactive uptake coefficient and reaction products do
not change at lower NO3 concentrations.
[7] For the measurements of the extent of surface oxidation and volatilization using XPS, SAMs were prepared on
gold coated silicone (100) wafers as mentioned above.
These surfaces were exposed in the flow tube reactor to
NO3 exposures ranging from 0 to 0.093 atm sec/1000 in the
presence of O2 (concentrations of approximately 1016
molecule cm 3). XPS measurements were performed using
an achromatic Al K X-ray source at a photon energy of
1486.6 eV and using an electron take-off angle of 90°.
3. Results and Discussion
3.1. Measurements of the Reactive Uptake Coefficient
[8] The reactive uptake coefficient was derived from the
first order loss rate of NO3, which was corrected for
concentration gradients that form close to the flow-tube
wall because of uptake by the organic surface [Knopf et al.,
2005]. The gas-phase diffusion constant of NO3 in He was
taken as 345 cm2 s 1 [Rudich et al., 1996]. Based on our
measurements, the reactive uptake coefficient of NO3 by a
fresh ODT surface is (8.8 ± 2.5) 10 4. The experimental
conditions were chosen in a way that at most 25% of the
methyl groups of the monolayer were oxidized during the
uptake measurements. The uptake of NO3 by Teflon is
about one order of magnitude slower than the uptake by
ODT.
[9] Table 1 represents a summary of our reactive uptake
measurements as well as previous measurements employing
various alkane substrates and atmospherically relevant radicals. The uptake of NO3 by the ODT monolayer is slightly
faster than the uptake by the frozen organic liquid. This
small difference could be due to a difference in surface
concentration of reactive sites or may be due to a temperature dependence of . Table 1 also shows that the reactivity
of Cl, Br, and OH radicals with octadecyltrichlorosilane,
another type of C-18 alkane monolayer, is significantly
higher compared to the reactivity of NO3 with ODT.
[10] In Table 1, we have included atmospheric concentrations of the various radical species. These values will
vary with location and environmental conditions and hence
should be considered as approximate numbers. In addition
we have included in Table 1 [radical], where [radical] is
the approximate atmospheric concentration in units of
molecule cm 3. [radical] is a more relevant parameter
for assessing the importance of the various radicals to
atmospheric oxidation, compared with just , since the
number of radicals lost to an organic surface will be
proportional to [radical]. The [radical] values for
NO3 are similar to OH, which suggests that heterogeneous
oxidation by NO3 could potentially compete with OH under
certain atmospheric conditions. Moise and Rudich [2001]
previously reached this conclusion based on their measurements with liquid and frozen organic surfaces.
3.2. Studies of Surface Oxidation and Volatilization
[11] Figure 1 shows the C(1s) region of the XPS spectra
obtained for different NO3 exposures. The increasing shoulder at higher binding energies within the C(1s) region with
increasing NO3 exposure indicates the oxidation of the
organic surface. For the unexposed sample only one peak
at 285 eV was observed. This peak is due to methyl or
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[13] To determine the fraction of the carbon oxidized as a
function of time, we calculated the atomic ratio of the
oxidized carbon (Cox) to Ctotal, both determined from the
fits shown in Figure 1a. These ratios are plotted in Figure 2b.
Figure 2b suggests that approximately 17% of the alkyl
chain is oxidized for NO3 exposures of 0.0302 atm sec/
1000. It should be noted that exposure of the organic layer
solely to O2 concentrations of about 1016 molecule cm 3
did not lead to oxidation of the monolayer.
[14] From the XPS data, we also calculated the atomic
ratio of total oxygen (O) to Ctotal as a function of NO3
exposure, determined from the integrated O(1s) and C(1s)
intensities and the respective atomic sensitivity factors. The
results of these calculations are plotted in Figure 2c and
suggest that the atomic O/Ctotal ratio is approximately 0.2
after an exposure of 0.0302 atm sec/1000. Both Figures 2b
and 2c show that NO3 leads to oxidation of the organic
surface using atmospherically relevant exposures.
Figure 1. (a) XPS spectra of the C(1s) region for an ODT
monolayer exposed to NO3 concentrations of 0 – 0.093 atm
sec/1000. Also included are the Gaussian-Lorentzian peaks
from the fitting procedure. The spectra are shifted vertically
for better visibility. (b) An enlarged view of the best fit of
the C(1s) region for an ODT monolayer exposed to NO3
concentrations of 0.093 atm sec/1000.
methylene functional groups. After exposure to NO3, the
main peak at about 285 eV remains, but a shoulder was
observed at higher energies due to the oxidation of the
alkane monolayer. We fit the total C(1s) region with four
overlapping Gaussian-Lorentzian peaks. In Figure 1b an
enlarged view of the C(1s) region obtained with a NO3
exposure of 0.093 atm sec/1000 is shown as well as the
Gaussian-Lorentzian fits to the data. Note that using four
peaks gave superior fitting results compared to using three
peaks. The chemical shifts discussed here were obtained
from the fitting procedure of all XPS spectra and are given
as average values with standard deviations. The chemical
shift of about 1.5 ± 0.5 eV is consistent with the formation
of C-O or C-O-O functional groups on the surface [Briggs
and Seah, 1990]. The chemical shift at about 3.1 ± 0.6 is
consistent with ketones or aldehydes, and the shift at
approximately 4.7 ± 0.5 eV is consistent with carboxylic
groups [Briggs and Seah, 1990].
[12] To assess the amount of volatilization of the organic
surface, we have plotted in Figure 2a the atomic ratio of the
total carbon (Ctotal) to the total gold (Au) derived from the
integrated C(1s) and Au(4f) intensities and the necessary
atomic sensitivity factors. The error bars (which represent
±1) were derived from 4 independent exposure experiments of ODT using equal NO3 concentrations. The vertical
line in Figure 2 indicates an exposure of 0.0302 atm sec/
1000, which is equivalent to exposing the surface to an NO3
concentration of 50 ppt NO3 (24 hour average) for one
week. A linear fit to the data shown in Figure 2a gives a
maximum carbon loss of about 7.5% (within 95% of
confidence) for NO3 exposures of 0.0302 atm sec/1000.
Based on this, we suggest that NO3 does not lead to rapid
volatilization of organic monolayers under atmospheric
conditions.
Figure 2. A summary of the XPS results. (a) The atomic
ratio of the total carbon, Ctotal, to total gold, Au. The solid
line is a linear fit to the data, and the dotted lines correspond
to the 95% confidence limit. (b) The atomic ratio of
oxidized carbon, Cox, to Ctotal determined by fitting the
C(1s) spectrum with Gaussian-Lorentzian peaks (see text
for further details). (c) The atomic ratio of total oxygen, O,
to Ctotal as a function of NO3 exposure. The dashed line
indicates atmospheric NO3 concentrations of 50 ppt (24 hour
average) persisting for one week.
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KNOPF ET AL.: PROCESSING OF ORGANIC SURFACES BY NO3
Figure 3. Proposed oxidation mechanism of alkane
surfaces by NO3 in presence of NO2 and O2 and based on
gas-phase chemistry.
[15] In addition to monitoring the C(1s) and O(1s)
signals, we also monitored the N(1s) signal; however, the
XPS measurements only show a small increase in the N(1s)
signal. About 1% of the total surface elemental composition
has been assigned as nitrogen based on the N(1s) signal at
NO3 exposures higher than 0.032 atm sec/1000. The binding energy of the N(1s) signal could be attributed to a nitrate
group. We have also monitored the S(2p) signal from the
monolayer. At exposures less than 0.03 atm sec/1000, the
sulfur is not oxidized. At long exposures of approximately
0.08 atm sec/1000, the sulfur is oxidized to sulfonate due to
reactions with NO3. This, however, can account for only a
small amount of the O(1s) signal in the XPS spectrum.
3.3. Oxidation Mechanism
[16] Shown in Figure 3 is the proposed mechanism for
oxidation of an alkane monolayer by NO3 radicals based on
gas-phase chemistry. We assume that the same reactions can
occur on the SAM as in the gas-phase, although the relative
importance of the pathways can be significantly different on
and in the organic monolayer compared to the gas-phase.
We use the XPS data to speculate on the importance of the
different reaction pathways for the saturated hydrocarbon
surfaces.
[17] The initial reaction step in the oxidation process is
the abstraction of a hydrogen atom from a methyl or
methylene group of the alkyl chain to form HNO3 and an
alkyl radical. Our experiments were not optimized to
measure HNO3, and as a result we were not able to
determine if this product remained on the surface or
evaporated during NO3 exposures. The XPS measurements
indicated that only 1% of the total surface elemental
composition after exposure to NO3 was due to nitrogen.
However, the HNO3 could have evaporated during the XPS
measurements. The second reaction step is the transformation of an alkyl radical into a peroxy radical in the presence
of O2 [Atkinson, 1997]. In the presence of NO2, peroxynitrates may form (which may subsequently thermally decompose) [Atkinson, 1997]. The peroxy radical can also
react with NO3 to form an alkoxy radical, NO2, and O2.
Alternatively the peroxy radical can undergo self reaction,
leading to the formation of alkoxy radicals and O2 or an
alcohol and carbonyl [Atkinson, 1997]. In the gas phase, the
branching ratio for the alcohol + carbonyl channel ranges
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from about 0.3 to 0.8 for primary and secondary radicals
[Atkinson, 1997]. In the solution phase, however, the self
reaction appears to proceed only through the alcohol +
carbonyl channel for both primary and secondary radicals
[Russell, 1957]. For tertiary radicals the alcohol + carbonyl
channel is not accessible [Russell, 1957; Atkinson, 1997]. If
the alkoxy radical forms, it can decompose by scission of a
C-C bond, or can undergo isomerization to form a hydroxyalkyl radical. Alternatively the alkoxy radical can react
with O2 or NO2 to form ketones and aldehydes or alkylnitrates [Atkinson, 1997].
[18] The XPS data suggests that the C-C scission channel
was of minor importance compared to other reaction channels. Also, the XPS data show that the surface contained
only a small amount of nitrogen after exposure. This
suggests that the formation of peroxynitrates or alkynitrates
were not important under our conditions. On the other hand,
these nitrates may have formed on the surface and subsequently thermally decomposed during the XPS measurements. In a future study IR spectroscopy will be used to
further explore the possibility that nitrates resulted from
NO3-initiated oxidation.
[19] As mentioned above the C(1s) spectrum is consistent
with the formation of 1) C-O groups, 2) ketones or aldehydes, and 3) carboxylic groups. The presence of C-O,
ketones, and aldehydes, can be explained by the RO2 self
reaction leading to an alcohol and carbonyl (see Figure 3).
As mentioned above the branching ratio for the alcohol +
carbonyl channel ranges from about 0.3 to 0.8 in the gasphase, but in the solution phase the RO2 self reaction
appears to proceed only through the alcohol + carbonyl
channel. Perhaps in our experiments, the self reaction also
proceeds mainly through the alcohol + carbonyl channel.
The presence of C-O, ketones, and aldehydes, could also be
explained by the formation of an alkoxy radical followed by
isomerization to form hydroxyalkyl radicals and reaction
with O2 to form carbonyls. In terms of isomerization,
alkoxy radicals could abstract a hydrogen from a neighboring carbon chain to form C-OH groups.
[20] The presence of a carboxylic group may be due to
the formation of an aldehyde that forms at the terminal
carbon followed by reactions with NO3, O2, and NO2 to
form a peroxyacetylnitrate (PAN) [Finlayson-Pitts and
Pitts, 2000], which then decomposes during the XPS
measurements to form carboxylic groups. Further work is
needed to explore this possibility. This may be especially
important as PAN is a toxic species.
[21] The XPS results and mechanism presented above
suggest that the reactive sites in and on the organic
monolayer will decrease with time, and hence the reactive
uptake coefficient will decrease with exposure time. Preliminary measurements in our laboratory have confirmed
this trend. In the future we will carry out detailed measurements of the uptake coefficient as a function of exposure.
[22] We observed at most limited volatilization of organic
monolayers when employing NO3, while Molina et al.
[2004] observed complete volatilization when using OH
radicals. The reason for this difference is not clear. In our
experiments, we assume that HNO3 was produced in the
initial step of the reaction. It is possible that this species
remains on the surface and somehow influences the reaction
mechanism. Another issue is possible contamination of the
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KNOPF ET AL.: PROCESSING OF ORGANIC SURFACES BY NO3
monolayer by hydrocarbons from the ambient laboratory.
For the unoxidized monolayers, the C/Au ratio is in the
range expected for C18 monolayers, and only one peak was
observed in the C (1s) region, due to methyl or methylene
groups. This suggests that contamination of the unoxidized
monolayers was minor. Also, it has previously been shown
that alkanethiol monolayers replace organic contaminates
from gold substrates [Ishida et al., 1996]. We have also
carried out measurements with a C11 alcohol terminated
monolayer, and the observed C/Au ratios and O/C ratios
agreed with theoretical predictions within experimental
uncertainty, which suggests that contamination even for a
more hydrophilic monolayer is minor. However, contamination cannot be completely ruled out. Moise and Rudich
observed partial volatilization (approximately 20%) of the
saturated hydrocarbon monolayer when using Cl and Br
radicals [Moise and Rudich, 2001]. Perhaps the presence of
HNO3 can also explain the difference between NO3, Cl, and
Br.
4. Summary and Conclusions
[23] The results suggest that even under extremely polluted
conditions, i.e. NO3 concentrations of 100 ppt (24 hour
average) persisting for one week [Finlayson-Pitts and Pitts,
2000], maximum 10% of the organic monolayer is volatilized. Our results are relevant to organics adsorbed on solid
substrates such as mineral dust particles or urban surfaces in
the atmosphere. Our results may also be relevant for solid
organic particles in the atmosphere and for organic coatings
on aqueous particles. In terms of liquid organic aerosols, there
have only been a few studies that have investigated reactions
between liquid organic aerosols and films and atmospherically relevant radicals [Eliason et al., 2004; Hung et al.,
2005; Docherty and Ziemann, 2006]. The recent studies
by Hung et al. [2005] and Docherty and Ziemann [2006]
appear to suggest that decomposition and volatilization by
radical-initiated oxidation may not be important for unsaturated and saturated liquid organic particles in low
NOx environments. (See the work by Docherty and
Ziemann [2006] for a full discussion on this topic.) More
work is still needed, however, to completely understand
radical-initiated oxidation of atmospherically relevant particles and films.
[24] Acknowledgments. The authors thank J. Thornton, I. Suh,
R. Atkinson, and P. J. Ziemann for advice on preparation of N2O5 and K. C.
Wong and K. A. R. Mitchell for assistance with XPS measurements. We also
thank P. J. Ziemann for several helpful discussions on the manuscript and for
pointing out the importance of the alcohol + carbonyl pathway. This work was
funded by NSERC, CFCAS, and CFI.
References
Atkinson, R. (1997), Gas-phase tropospheric chemistry of volatile organic
compounds: 1. Alkanes and alkenes, J. Phys. Chem. Ref. Data, 26(2),
215 – 290.
Bertram, A. K., A. V. Ivanov, M. Hunter, L. T. Molina, and M. J. Molina
(2001), The reaction probability of OH on organic surfaces of tropospheric interest, J. Phys. Chem. A, 105, 9415 – 9421.
Briggs, D., and M. P. Seah (1990), Practical Surface Analysis, Salle and
Sauerländer, Chichester, U. K.
de Gouw, J. A., and E. R. Lovejoy (1998), Reactive uptake of ozone by
liquid organic compounds, Geophys. Res. Lett., 25(6), 931 – 934.
Diamond, M. L., S. E. Gingrich, K. Fertuck, B. E. McCarry, G. A. Stern,
B. Billeck, B. Grift, D. Brooker, and T. D. Yager (2000), Evidence for
L17816
organic film on an impervious urban surface: Characterization and
potential teratogenic effects, Environ. Sci. Technol., 34(14), 2900 – 2908.
Docherty, K. S., and P. J. Ziemann (2006), Reaction of oleic acid particles
with NO3 radicals: Products, mechanism, and implications for radicalinitiated organic aerosol oxidation, J. Phys. Chem. A, 110, 3567 – 3577.
Eliason, T. L., S. Aloisio, D. J. Donaldson, D. J. Cziczo, and V. Vaida
(2003), Processing of unsaturated organic acid films and aerosols by
ozone, Atmos. Environ., 37(16), 2207 – 2219.
Eliason, T. L., J. B. Gilman, and V. Vaida (2004), Oxidation of organic
films relevant to atmospheric aerosols, Atmos. Environ., 38(9), 1367 –
1378.
Ellison, G. B., A. F. Tuck, and V. Vaida (1999), Atmospheric processing of
organic aerosols, J. Geophys. Res., 104(D9), 11,633 – 11,641.
Finlayson-Pitts, B. J., and J. N. Pitts (2000), Chemistry of the Upper and
Lower Atmosphere: Theory, Experiments and Applications, 969 pp.,
Elsevier, New York.
Gill, P. S., T. E. Graedel, and C. J. Weschler (1983), Organic films on
atmospheric aerosol-particles, fog droplets, cloud droplets, raindrops,
and snowflakes, Rev. Geophys., 21(4), 903 – 920.
Hung, H. M., Y. Katrib, and S. T. Martin (2005), Products and mechanisms
of the reaction of oleic acid with ozone and nitrate radical, J. Phys. Chem.
A, 109, 4517 – 4530.
Ishida, T., N. Nishida, S. Tsuneda, M. Hara, H. Sasabe, and W. Knoll
(1996), Alkyl chain length effect on growth kinetics of n-alkanethiol
self-assembled monolayers on gold studied by X-ray photoelectron spectroscopy, Jpn. J. Appl. Phys., Part 2, 35(12B), L1710 – L1713.
Ishida, T., S. Tsuneda, N. Nishida, M. Hara, H. Sasabe, and W. Knoll
(1997), Surface-conditioning effect of gold substrates on octadecanethiol
self-assembled monolayer growth, Langmuir, 13(17), 4638 – 4643.
Knopf, D. A., L. M. Anthony, and A. K. Bertram (2005), Reactive uptake
of O3 by multicomponent and multiphase mixtures containing oleic acid,
J. Phys. Chem. A, 109, 5579 – 5589.
Moise, T., and Y. Rudich (2000), Reactive uptake of ozone by proxies for
organic aerosols: Surface versus bulk processes, J. Geophys. Res.,
105(D11), 14,667 – 14,676.
Moise, T., and Y. Rudich (2001), Uptake of Cl and Br by organic surfaces:
A perspective on organic aerosols processing by tropospheric oxidants,
Geophys. Res. Lett., 28(21), 4083 – 4086.
Moise, T., R. K. Talukdar, G. J. Frost, R. W. Fox, and Y. Rudich (2002),
Reactive uptake of NO3 by liquid and frozen organics, J. Geophys. Res.,
107(D2), 4014, doi:10.1029/2001JD000334.
Molina, M. J., A. V. Ivanov, S. Trakhtenberg, and L. T. Molina (2004),
Atmospheric evolution of organic aerosol, Geophys. Res. Lett., 31(22),
L22104, doi:10.1029/2004GL020910.
Rudich, Y. (2003), Laboratory perspectives on the chemical transformations
of organic matter in atmospheric particles, Chem. Rev., 103(12), 5097 –
5124.
Rudich, Y., R. K. Talukdar, T. Imamura, R. W. Fox, and A. R. Ravishankara
(1996), Uptake of NO3 on KI solutions: Rate coefficient for the NO3+I
reaction and gas-phase diffusion coefficients for NO3, Chem. Phys. Lett.,
261(4 – 5), 467 – 473.
Russell, G. A. (1957), Deuterium-isotope effects in the autooxidation of
aralkyl hydrocarbons: Mechanism of the interaction of peroxy radicals,
J. Am. Chem. Soc., 79, 3871 – 3877.
Schott, G., and N. Davidson (1958), Shock waves in chemical kinetics: The
decomposition of N2O5 at high temperatures, J. Am. Chem. Soc., 80,
1841 – 1853.
Smith, G. D., E. Woods, C. L. DeForest, T. Baer, and R. E. Miller (2002),
Reactive uptake of ozone by oleic acid aerosol particles: Application
of single-particle mass spectrometry to heterogeneous reaction kinetics,
J. Phys. Chem. A, 106, 8085 – 8095.
Thomas, E. R., G. J. Frost, and Y. Rudich (2001), Reactive uptake of ozone
by proxies for organic aerosols: Surface-bound and gas-phase products,
J. Geophys. Res., 106(D3), 3045 – 3056.
Thornberry, T., and J. P. D. Abbatt (2004), Heterogeneous reaction of ozone
with liquid unsaturated fatty acids: Detailed kinetics and gas-phase product studies, Phys. Chem. Chem. Phys., 6(1), 84 – 93.
Usher, C. R., A. E. Michel, and V. H. Grassian (2003), Reactions on
mineral dust, Chem. Rev., 103(12), 4883 – 4939.
Wadia, Y., D. J. Tobias, R. Stafford, and B. J. Finlayson-Pitts (2000), Realtime monitoring of the kinetics and gas-phase products of the reaction of
ozone with an unsaturated phospholipid at the air-water interface, Langmuir, 16(24), 9321 – 9330.
A. K. Bertram, S. Gross, D. A. Knopf, and J. Mak, Department of
Chemistry, University of British Columbia, 2036 Main Mall, Vancouver,
BC, Canada V6T 1Z1. ([email protected]; [email protected];
[email protected]; [email protected])
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