The atmospheric oxidation of dimethyl sulfide (DMS)
represents a major natural source of atmospheric sulfate aerosols. However,
there remain large uncertainties in our understanding of the underlying
chemistry that governs the product distribution and sulfate yield from DMS
oxidation. Here, chamber experiments were conducted to simulate gas-phase
OH-initiated oxidation of DMS under a range of reaction conditions. Most
importantly, the bimolecular lifetime (τbi) of the peroxy radical
CH3SCH2OO was varied over several orders of magnitude, enabling
the examination of the role of peroxy radical isomerization reactions on
product formation. An array of analytical instruments was used to measure
nearly all sulfur-containing species in the reaction mixture, and results
were compared with a near-explicit chemical mechanism. When relative
humidity was low, “sulfur closure” was achieved under both high-NO (τbi<0.1 s) and low-NO (τbi>10 s)
conditions, though product distributions were substantially different in the
two cases. Under high-NO conditions, approximately half the product sulfur
was in the particle phase, as methane sulfonic acid (MSA) and sulfate, with
most of the remainder as SO2 (which in the atmosphere would eventually
oxidize to sulfate or be lost to deposition). Under low-NO conditions,
hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), formed from
CH3SCH2OO isomerization, dominates the sulfur budget over the
course of the experiment, suppressing or delaying the formation of SO2
and particulate matter. The isomerization rate constant of
CH3SCH2OO at 295 K is found to be 0.13±0.03 s-1, in
broad agreement with other recent laboratory measurements. The rate
constants for the OH oxidation of key first-generation oxidation products
(HPMTF and methyl thioformate, MTF) were also determined (kOH+HPMTF=2.1×10-11 cm3 molec.-1 s-1, kOH+MTF=1.35×10-11 cm3 molec.-1 s-1). Product measurements
agree reasonably well with mechanistic predictions in terms of total sulfur
distribution and concentrations of most individual species, though the
mechanism overpredicts sulfate and underpredicts MSA under high-NO
conditions. Lastly, results from high-relative-humidity conditions suggest efficient
heterogenous loss of at least some gas-phase products.
Introduction
Dimethyl sulfide (DMS), emitted by marine phytoplankton, is an important
natural source of sulfur to the atmosphere (Kloster et al., 2006; Lana et al.,
2011). The atmospheric oxidation of DMS represents a dominant source of
non-sea-salt sulfate aerosols and as such can play an important role in
global aerosol climate effects (Charlson et al., 1987; Rap
et al., 2013). The chemistry by which DMS oxidizes to form sulfate is highly
complex: the mechanism includes multiple branch points and intermediate
species, and many reaction rates and product yields are uncertain and/or
highly dependent on reaction conditions (Barnes et al., 2006; Hoffmann et al.,
2016). As a result, many large-scale models adopt a highly simplified DMS
chemistry with fixed SO2 yields, usually without inclusion of other
intermediates (Chin
et al., 1996; Huijnen et al., 2010; Kloster et al., 2006; Lamarque et al.,
2012). Such a simplified approach may lead to errors in predicted aerosol
radiative effects, in the past, present, and future atmospheres (Fung et al., 2022).
The major daytime sink of DMS is its reaction with OH radicals. The detailed
DMS + OH reaction scheme is shown in Fig. 1. A key branch point in DMS + OH is the methylthiomethylperoxy radical (CH3SCH2OO) formed
from H-atom abstraction followed by O2 addition. The subsequent
chemistry of this radical plays a determining role in the overall product
distribution and thus likely influences the amount of sulfate aerosols that
is ultimately formed. As with all large RO2 species,
CH3SCH2OO radicals may undergo bimolecular reactions (with NO and
HO2) or unimolecular reaction via a recently identified (Berndt
et al., 2019; Veres et al., 2020; Wu et al., 2015; Ye et al., 2021; Jernigan
et al., 2022a) isomerization channel:
R1CH3SCH2OO+NO→CH3SCH2O+NO2R2CH3SCH2OO+HO2→CH3SCH2OOH+O2R3CH3SCH2OO→CH2SCH2OOH.
The CH3SCH2O radical formed from the NO pathway (Reaction R1) forms
SO2, sulfate, and methane sulfonic acid (MSA) (Barnes et al., 2006).
The alkyl radical derived from Reaction (R3) will react with O2 to form
OOCH2SCH2OOH, which will undergo a second isomerization reaction
at a rate substantially faster than that of Reaction (R3) (Wu et al., 2015;
Crounse et al., 2013), forming hydroperoxymethyl thioformate (HPMTF,
HOOCH2SCHO), as shown in Fig. 1. In addition to Reactions (R1–R3),
CH3SCH2OO may also react with other RO2 radicals (Barnes et al., 2006), though this process is likely to be minor
under atmospheric conditions.
Gas-phase DMS + OH oxidation mechanism. Measured
closed-shell products are shown in bold. Reactions in black are taken from
MCM (Master Chemical Mechanism); reactions in red, related to hydroperoxymethyl thioformate (HPMTF,
HOOCH2SCHO) chemistry, are taken from Wu et al. (2015). Products that do not contain
sulfur are not shown. The
CH3SO2 radical (marked in
blue) represents a link between addition and abstraction pathway products.
Note that several products are shown multiple times.
The branching fraction of the CH3SCH2OO radical depends on the
concentrations of NO and HO2 and the rate constants of Reactions (R1–R3).
The rate constant for the isomerization reaction, kisom, is
particularly uncertain, as values determined in previous studies span a very
wide range, from ∼0.04 to ∼2 s-1
near room temperature (Berndt
et al., 2019; Veres et al., 2020; Wu et al., 2015; Ye et al., 2021; Jernigan
et al., 2022a). This highlights a major challenge in predicting
CH3SCH2OO branching and the subsequent aerosol formation, both in
the pristine atmosphere and in environments affected by anthropogenic
emissions.
Most previous experimental studies investigating DMS oxidation have examined
individual products and reaction steps in isolation (Barnes
et al., 2006; Berndt et al., 2019; Jernigan et al., 2022a; Mihalopoulos et
al., 1992; Patroescu et al., 1996); very few studies of the entire
multiphase and multistep reaction system have been conducted, especially
under conditions in which the recently discovered isomerization pathway
(Reaction R3) may compete. Therefore, there have been relatively few
experimental tests of our overall understanding of the reaction system, by
comparison against predictions by state-of-the-art reaction mechanisms.
Recently, we conducted laboratory measurements of a broad suite of organic
sulfur products and sulfate aerosols from DMS + OH and estimated
kisom to be 0.09 s-1 (0.03–0.3 s-1, 1σg) (Ye et al., 2021); however this was for a
single reaction condition only (<5 % relative humidity, ∼1 ppb NO), and SO2 (a major inorganic sulfur-containing product) was not measured.
Here we extend our previous work by conducting a series of chamber
experiments of DMS + OH under a wide range of values of the
CH3SCH2OO bimolecular lifetime (τbi) and
comprehensively characterizing sulfur-containing products (organic and
inorganic, gas-phase and particulate), with the aim of accounting for all
(or nearly all) reacted sulfur. Such “sulfur closure” measurements enable
direct comparisons with predictions from a mechanistic model, in order to
assess our current mechanistic understanding and identify possible gaps in
this understanding. These measurements also enable the determination of key
kinetic parameters in the reaction systems. In one experiment, we vary
τbi over a wide range to estimate the kisom of the
CH3SCH2OO radical, obtaining a kisom with a much smaller
uncertainty range than in our previous study. The rate constants for the OH
oxidation of key first-generation oxidation products (HPMTF and methyl
thioformate, MTF) are also determined. Lastly, we investigate the effect of
relative humidity (RH) on the DMS + OH product distributions.
Method and materials
Experiments were conducted in a 7.5 m3 temperature-controlled
environmental chamber, held at 295 K (Hunter et al., 2014).
The chamber is surrounded by 48 ultraviolet lights (Q-Lab) with a peak
irradiance at 340 nm. Before each experiment, the chamber was flushed by
zero air (AADCO, 737 series) for at least 12 h to ensure a clean gas and
particle background. Throughout the course of each experiment, a constant
flow of zero air was introduced into the chamber to replenish the flow drawn
by the instruments. For high-RH experiments, the replenishment flow was
first sent through a bubbler filled with Milli-Q water before entering the
chamber. The rate of chamber dilution was derived by measuring the decay of
acetonitrile, injected at low concentrations (5 ppb) in the beginning of
each experiment. The overall dilution lifetime was approximately 10 h.
Concentrations of all species reported below have been corrected for
dilution.
The evolving chemical composition of the reaction mixture was monitored by a
suite of real-time instruments located outside the chamber. The
Supplement provides instrument details, as well as the sulfur
species detected by each instrument (Table S2). Briefly, DMS and lightly
oxygenated gaseous species were measured by a Vocus proton-transfer-reaction
time-of-flight mass spectrometer (Vocus PTR-MS, Aerodyne Research Inc.) (Krechmer et al., 2018). More oxygenated gaseous species were
measured by an iodide time-of-flight chemical ionization mass spectrometer
(I- CIMS, Aerodyne Research Inc.) (Lee
et al., 2014) and an ammonium time-of-flight chemical ionization mass
spectrometer (NH4+ CIMS, Ionicon Analytik) (Zaytsev et al., 2019). SO2 was
detected by a compact tunable infrared laser direct absorption spectrometer
(TILDAS, Aerodyne Research Inc.) (McManus et al., 2011, 1995). Particle-phase products, namely sulfate and MSA, were measured by an
aerosol mass spectrometer (AMS, Aerodyne Research Inc.) (DeCarlo et al., 2006). The
quantification of MSA was determined from the AMS tracer ion
CH3SO2+ (see the Supplement); this ion is believed
to be unique to MSA (or methyl sulfonate), with negligible contributions from
other sulfur-containing species (Hodshire et
al., 2019; Huang et al., 2015). Our multi-instrument approach enables the
measurement of essentially all closed-shelled sulfur products known in the
DMS oxidation mechanism, except for carbonyl sulfide (OCS), which accounts for a very small
(less than a couple percent) sulfur yield from DMS oxidation (Barnes et al., 1994; Jernigan et al., 2022a).
Complementary instruments include an ozone monitor (2B Technologies), a
NO–NO2–NOx analyzer (Thermo Scientific), a scanning mobility
particle sizer (TSI), and a temperature and RH sensor (TE Connectivity).
More details of the instruments, including their calibrations and
measurement uncertainties, are provided in the Supplement.
a To better separate HPMTF from N2O5, DMS-13C2 was
used in low-NO experiments.
b Bimolecular lifetime of the CH3SCH2OO radical, calculated
as τbi=(kRO2+HO2[HO2]+kRO2+NO[NO])-1.
c Experiments 2a and b were carried out as part of a single oxidation
experiment; initially (Exp. 2a) OH was generated from H2O2
photolysis (low-NO conditions), and then (Exp. 2b) 70 ppb of NO was injected into the
chamber.
d13C data in Experiment 3 were used to calculate
kisom; HONO was added multiple times in the experiment.
e The vaporizer in the AMS was operated at 800 ∘C. AMS
calibration was done separately for 800 ∘C.
The experiments carried out in this study are listed in Table 1. At the
beginning of each experiment, DMS, the acetonitrile dilution tracer, seed
particles, and the OH precursor were added to the chamber and allowed to
become well mixed. Total concentrations of DMS introduced to the chamber
were similar among all experiments. In dry experiments, seed particles
(ammonium nitrate) were added into the chamber via first atomization
followed by drying, providing surface area for condensing vapors. In high-RH
experiments, seed particles (sodium chloride and sodium nitrate) were
introduced without drying, remaining as liquid particles under the chamber
RH. Particle condensation timescales (seconds to tens of seconds) were much
shorter than the condensation timescale of low-volatility species onto the
chamber wall (∼2000 s, as determined previously for this
chamber, Zaytsev et al., 2019). In these experiments, non-sulfate seeds were
used to avoid interferences when quantifying secondary sulfate in the
aerosols. For low-RH experiments (Exp. 1–3), ammonium nitrate seed particles
were used, since dry ammonium nitrate particles are expected to be
chemically inert. For the high-RH high-NO experiment (Exp. 4), NaCl
particles were used. As discussed below, major products are similar to those
in the high-NO dry experiment, suggesting that the NaCl seed particles in
Exp. 4 have little to no effect on the product distribution in these
experiments. More studies are needed to constrain the effects of different
seed particles on the reactive uptake of DMS oxidation products (Jernigan et
al., 2022b).
DMS was introduced by gently heating a known volume (1–2 µL) from a
needle syringe, and the vapor was carried into the chamber by the dilution
flow. For the long τbi experiments, in which HPMTF formation was
expected (see Table 1), DMS-13C2 (99 atom % 13C, MilliporeSigma) was added as the precursor in addition to unlabeled DMS (>99 %, MilliporeSigma), in order to easily distinguish
HPMTF (C2H4SO3⚫ I-, m/z 234.893) from
N2O5 (N2O5⚫ I-, m/z 234.886) in the
I- CIMS. The use of DMS-13C2 is expected to have little
effect on the observed reaction kinetics in this study. For the high-NO
(short τbi) experiments, HONO (tens of parts per billion) was added as the OH
precursor, by passing air over a mixture of sodium nitrite and sulfuric acid
into the chamber. For low-NO (long τbi) experiments, parts per million levels of H2O2 were added as the OH precursor, by vaporizing a known
amount of 30 % H2O2 solution injected by a micro-syringe. The
H2O2 concentration was derived based on the known photon flux in
the chamber and the observed decay rate of NO. In some experiments (Exp. 2b,
3, and 5), aliquots of HONO or NO were added in the middle of the experiment
to change reaction conditions. After all reagents were well mixed
(>5 min), the UV lights were turned on to photolyze HONO and/or
H2O2, generating OH radicals and initiating the reaction. The OH
concentration was estimated from the decay of DMS (using kOH+DMS=6.97×10-12 cm3 molec.-1 s-1) (Jenkin et al., 1997;
Saunders et al., 2003) and was used to determine the equivalent atmospheric
OH exposure time, assuming [OH]atm=1.5×106 molec. cm-3.
A 0-D model (the Framework for 0-D Atmospheric Modeling, F0AM) (Wolfe et al., 2016) coupled with the Master
Chemical Mechanism (MCMv3.3.1) (Jenkin et al., 1997;
Saunders et al., 2003) was used to simulate gas-phase DMS oxidation in each
experiment. Here, the DMS scheme in the MCM was updated primarily based on
Wu et al. (2015) with the
isomerization rate constant of the CH3SCH2OO radical as 0.09 s-1, taken from our previous work (Ye
et al., 2021). The complete reaction scheme is shown in Fig. 1.
Newly added reactions with rate constants beyond the original MCM scheme are
listed in Table S1. Model inputs, including concentrations of the precursor,
oxidant, and chamber conditions including temperature, light intensity, and
dilution rate were taken directly from the measurements. The uptake or
heterogeneous reactions of water-soluble species (e.g., dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO2), methane sulfinic acid (MSIA), and HPMTF) are not considered in this modeling, though as described
below such processes may occur. In the high-NO experiments, model NO
concentrations were constrained to values measured by the
NO–NO2–NOx analyzer. In the low-NO experiment (Exp. 2a) in which
the sub-ppb-level NO concentration was near or below the detection limit
(0.4 ppb) of the NOx analyzer, the model was used to constrain
background NO concentration by matching the modeled DMS decay to the
measured decay (Ye et al., 2021). The
estimated [NO] in Exp. 2a was ∼10 ppt.
Results and discussionsComprehensive measurements of S-containing products
Figure 2a and b shows the measured product evolution from Experiments 1 and 2a
under dry conditions. A range of sulfur-containing products were measured in
both the gas and aerosol phases, shown as stacked colored traces. Changes in
concentrations are given in parts per billion of sulfur (Δ ppb S) and
are presented as a function of atmosphere-equivalent OH exposure time. Shown
in grey is the amount of DMS oxidized over the course of the experiment. By
the end of the experiment, only a fraction of the DMS had been consumed,
since OH exposures were not high enough to fully deplete the DMS. In Exp. 1
(high-NO conditions, Fig. 2a), HONO was used as the OH precursor, and the NO was kept
at ∼50 ppb by continuous addition, ensuring that the dominant
fate of the RO2 radicals was reaction with NO (τbi<0.1 s). After ∼12 h of atmosphere-equivalent OH exposure,
104 % (100 %–124 %, 1σ) of the reacted sulfur was measured
as products, indicating excellent sulfur closure. The uncertainty in sulfur
closure includes uncertainty in both gas-phase and particle-phase
measurements (see Supplement for more details). The initial dip in the first 2 h
may be due to loss of products to surfaces such as the chamber wall or
sampling lines. It is likely that there is an equilibrium between the
sampling line and the gas phase. This drop, of 1–2 ppb S, represents a
relatively small portion of the total sulfur reacted by the end of the
experiment.
Stacked plots showing the total sulfur measured (a and b)
and modeled (c and d) under high-NO (a and c) and low-NO (b and d)
conditions. Panels (a) and (c) are for Exp. 1, and panels (b) and (d) are for Exp. 2a. Data shown in panel (b) are from
DMS-12C2 and
DMS-13C2 combined. Products
with a formula of
C2H6SO2 may be DMSO2 and/or
CH3SCH2OOH; under high-NO
conditions, they are likely to be predominantly
DMSO2. Minor products detected but not listed in the
legend due to their very low concentrations include
CH2SO2 (a sulfene or thioacid)
and CH3SO6N (likely
methanesulfonyl peroxynitrate). Note that y axes denote the changes in
concentrations of the precursor and products.
Major sulfur-containing products in Exp. 1 were SO2, particulate MSA,
and particulate sulfate, with 48 % of the product sulfur found in the
particle phase. The measured MSA : sulfate ratio (∼2.5:1) is in
broad agreement with those reported in Chen et al. (2012). Minor species
observed included dimethyl sulfoxide (DMSO), C2H6SO2 (likely
dimethyl sulfone, DMSO2), and methane sulfinic acid (MSIA), known
products from the addition channel, as well as CH2SO2 (likely a
thioacid, which may be formed as an OH oxidation product of HPMTF, Jernigan
et al., 2022a) and CH3SO6N (likely methanesulfonyl peroxynitrate,
formed from CH3S(O)2OO + NO2). No HPMTF was observed in
these experiments, which is expected given the short bimolecular RO2
lifetime.
In Exp. 2a (low-NO conditions, Fig. 2b), H2O2 was the OH precursor, and NO and
HO2 levels were sufficiently low (∼10 and 100 ppt,
respectively) enough for RO2 isomerization to dominate (τbi>10 s). HO2 generated from H2O2+ OH is
expected to promote the formation of CH3SCH2OOH from Reaction (R2);
however, we cannot distinguish CH3SCH2OOH from its isomer,
DMSO2. Product distributions are dramatically different than those
under high-NO conditions. The total sulfur products measured accounted for
nearly all (90 % (64 %–118 %)) of the reacted DMS sulfur; this
sulfur closure is good but slightly worse than in Exp. 1. The larger
uncertainty range is due to the uncertainty of the HPMTF calibration in the
I- CIMS. However, the near-sulfur closure, derived from multiple
independently calibrated instruments, combined with the HPMTF yields
(discussed in Sect. 3.3) suggest that our estimated sensitivity is
reasonably accurate, and thus our overall uncertainty of total sulfur may be
an overestimate.
Due to the long RO2 bimolecular lifetime (τbi>10 s), the dominant product is HPMTF from CH3SCH2OO isomerization;
this accounts for about half of the reacted sulfur (60 % of the measured
product sulfur). It is expected that a negligible amount (1 % or less) of
HPMTF was lost to the chamber walls under the experimental condition here
based on its estimated vapor pressure (see the Supplement). The
time series of C2H4SO3-12C2 in the I- CIMS
(C2H4SO3⚫ I-) and in the
NH4+ CIMS (C2H4SO3⚫ NH4+), shown in Fig. S2, match very well. This indicates that
there was negligible N2O5 formation from the residual NOx in
the chamber, since N2O5 is not measurable by the
NH4+ CIMS, and therefore our quantification of
HPMTF-12C2 in Exp. 2a with I- CIMS is free of N2O5
interferences. Only 3.3 % (3.1 %–5.4 %) of the reacted sulfur was
found in the aerosol by the end of the experiment.
Model–measurement comparison
The (near-)sulfur closure of the experiments, in which virtually all the
reacted sulfur was measured as products, enables a comparison with the
mechanistic model. MCM predictions for the two experiments described above
(Exp. 1 and 2a) are shown in Fig. 2c and d; individual species are also
compared in Figs. S3 and S4. Under high-NO conditions, measurements and
model predictions (Figs. 2a and c, S3) agree well for gas-phase
species and for total particulate sulfur. However, the two differ greatly in
terms of particle-phase composition: AMS measurements indicate
∼70 % of the particle-phase sulfur is MSA, with the
remainder as sulfate; by contrast, the model predicts that sulfate dominates,
with a negligible (∼0.1 %) contribution from MSA. This
suggests the mechanism may underestimate the rate of MSA formation (a result
consistent with recent studies; Wolleson de Jonge et al., 2021; Shen et al.,
2022) and/or overestimate the rate of sulfuric acid formation.
In the MCM, both MSA and sulfuric acid are formed from reactions of the
CH3S(O)2O radical:
R4CH3S(O)2O+HO2→CH3S(O)2OH+O2R5CH3S(O)2O+M→CH3+SO3.
Reaction (R5) generates sulfur trioxide (SO3), which will quickly
hydrolyze to form sulfuric acid. SO3 can also be formed by the OH
oxidation of SO2, but this reaction would occur over 50 h of OH
exposure, much longer than the oxidation timescale in Exp. 1. Since the
measured and modeled total particulate sulfur (MSA + sulfate) agree well,
the model–measurement differences in the ratio of MSA to sulfuric acid (or
sulfate) may relate to the relative rates of these CH3S(O)2O
reactions. It is possible that the rate constant of Reaction (R4) is
underestimated in the mechanisms, but even if it is increased it to a
gas-kinetic rate (3×10-10 cm3 molec.-1 s-1),
MSA is still not predicted to dominate over sulfuric acid. Instead, the
decomposition of CH3S(O)2O (Reaction R5), which has received little
study, might be slower than the value used in the mechanism (∼0.09 s-1), leading to slower sulfuric acid formation. Alternatively,
MSA might be formed by the reaction of CH3S(O)2O with species
other than HO2, such as DMS or HCHO (Barnes et al.,
2006; Yin et al., 1990). While such reactions are unlikely to be important
in the atmosphere, they might occur in laboratory experiments, which have
relatively high concentrations of organic species. However, the kinetics of
such reactions are not well known and warrant future research.
(a) The yield of HPMTF in the abstraction channel as
a function of the bimolecular lifetime τbi of
CH3SCH2OO from the
DMS-13C2 data. The shaded area
is 1σ of the fit, which takes into account uncertainty in
both τbi (arising from
errors in [NO] and [HO2]) on the x axis, and
instrument noise on the y axis. Uncertainty in the CIMS sensitivity to HPMTF
affects the absolute measurements but not the inflection point of the curve
or the derived value of kisom. (b)
Comparison of kisom from this work
with previous determinations of
kisom at 293–298 K (Berndt
et al., 2019; Jernigan et al., 2022a; Veres et al., 2020; Wu et al., 2015;
Ye et al., 2021).
Another potential source of MSA is the oxidation of MSIA by OH
(Yin et al., 1990; Lucas and Prinn, 2002; von Glasow and Crutzen, 2004;
Wollesen de Jonge et al., 2021; Shen et al., 2022). This pathway is
currently not included in the MCM, which has MSIA reacting with OH to form
SO2 and CH3 (Fig. 1). It has been suggested (Yin et al., 1990)
that the reaction may occur via abstraction of the acidic hydrogen:
CH3S(O)OH+OH→CH3S(O)O+H2O.
As shown in Fig. 1, the resulting CH3S(O)O radical may react with
ozone to form CH3S(O)2O, which can react further to form MSA or
SO3 (Reactions R4–R5). However, inclusion of this reaction in the model
increases MSA formation only slightly, and the model–measurement discrepancy
remains large (Fig. S5). Alternatively, OH might add to MSIA (Lucas and
Prinn, 2002; Arsene et al., 2002; Shen et al., 2022), forming the
intermediate CH3SO(OH)2 that can react with O2 to produce
MSA:
R7CH3S(O)OH(MSIA)+OH→MCH3S(O)(OH)2R8CH3S(O)(OH)2+O2→CH3S(O)2(OH)+HO2.
Including these reactions into the mechanism, using the rate constant for
MSIA + OH suggested by the MCM (9×10-11 cm3 molec.-1 s-1) substantially increases the predicted MSA but at the
same time decreases the predicted SO2 concentration, worsening the
model–measurement agreement for SO2, and does not change predicted
sulfate formation, leading to an overestimate in total aerosol production
(Fig. S5). Taken together, while the OH oxidation of MSIA (Reactions R6–R8)
may contribute to MSA formation, it appears not to be the only (or major)
source for the MSA model–measurement discrepancy in the present experiments.
In the low-NO case (Figs. 2b and d, S4), measured and modeled
concentrations also broadly agree. The predicted concentration of HPMTF is
lower (by ∼30 %) than what was measured. This could be due
to the uncertainty in the sensitivity of HPMTF in the I- CIMS and/or
in the kisom value used in the model. The kisom value used, 0.09 s-1, is derived from our previous study (Ye et al., 2021); as discussed below, this
value agrees with that determined in this work. Compared to measurements,
the model also predicts somewhat higher concentrations of minor
sulfur-containing products, such as DMSO, C2H6SO2 (DMSO2+ CH3SCH2OOH), MSIA, and MTF. This could be caused by
overestimates of instruments' sensitivities, uncertainties in the rate
constants in the model, or some losses to surfaces. Nevertheless, overall
the model and measurements agree quite well, with product formation
dominated by HPMTF and little aerosol formation since low-volatility
species (MSA and sulfuric acid) are formed only as later-generation
products.
Determination of kisom
The fate of the CH3SCH2OO radical, and hence the product
distribution of DMS oxidation, relies critically on the isomerization rate
constant of the CH3SCH2OO radical (kisom). In our previous
work we determined kisom from a single reaction condition (at one value
of τbi), and the kisom value had a large uncertainty due to
the poorly constrained sensitivity of HPMTF in the CIMS. Here, we determine
kisom by examining product formation at multiple values of τbi, similar to previous measurements of isomerization rates of
terpene-derived RO2 radicals (Xu et al., 2019). MCM
modeling suggests that RO2+ RO2 reactions represent
∼1 % of the RO2 sink in the experiments, and therefore
the only bimolecular reactions considered are RO2+ NO and RO2+ HO2. HONO or NO was added to the chamber several times during the
experiment (Fig. S6), perturbing the branching of the CH3SCH2OO
radical (isomerization vs. bimolecular reactions). The total S measurements
are shown in Fig. S8. The yield of HPMTF in the abstraction channel
(Δ[HPMTF] /Δ[DMS]abs) was calculated for each
perturbation as a function of τbi after taking into account the
of loss via OH oxidation (kOH+HPMTF=2.1×10-11 cm3 molec.-1 s-1; see Sect. 3.4). The detailed calculation
is described in the Supplement (Eqs. S1–S4). Figure 3a
shows the HPMTF yield as a function of τbi. As expected, the
yield increases dramatically with τbi, and fitting these data to
Eq. S4 (given in the Supplement) enables the determination of kisom. The
best-fit value for kisom is 0.13±0.03 s-1. The uncertainty
is much smaller than in our previous determination (Ye et al., 2021) since
the fit depends only on the shape (the inflection point) of the curve and
not the absolute yield values and thus is insensitive to the uncertain
HPMTF calibration factor. Nonetheless, since the asymptotic (high τbi) value is close to 1 (1.5), our estimated calibration factor
appears to be reasonably accurate. The three data points with higher HPMTF
yields (top of Fig. 3a) were collected in the latter half of the experiment,
after HPMTF had built up in the chamber, and therefore correcting for OH
loss resulted in an increased HPMTF yield. Because of their larger
measurement uncertainties, these data points have smaller effects on the
overall fit to Eq. (S4). If the OH loss is not included, kisom=0.11±0.02 s-1 (Fig. S7).
Figure 3b compares our value of kisom with previous measurements and
theoretical determinations (T= 293–298 K) (Berndt
et al., 2019; Jernigan et al., 2022a; Veres et al., 2020; Wu et al., 2015;
Ye et al., 2021). Our measured value of kisom is consistent with our
previous (single τbi) measurement (Ye
et al., 2021) though with a much reduced uncertainty and is also in broad
agreement with measured values from Berndt et al. (2019) (0.23±0.12 s-1) and
Jernigan et al. (2022) (0.1±0.05 s-1).
Reaction rates of OH with HPMTF and MTF
Here we examine the oxidation of HPMTF and MTF, two species whose chemical
fates are not well known. Both were formed only under low-NO conditions
(Exp. 2a); because of the relatively low OH concentrations of that
experiment, their concentrations increased throughout the entire experiment,
with no subsequent decay. Thus, to estimate kOH+HPMTF and
kOH+MTF, high concentrations of NO (∼70 ppb) were
introduced at the end of Experiment 2 (denoted as Exp. 2b, shown in Fig. 4a). The large amount of NO essentially terminated the production of HPMTF
and MTF and at the same time increased the OH concentration in the chamber.
The total sulfur product distribution for Exp. 2 is shown in Fig. S9. The
loss of HPMTF during this period, shown in Fig. 4b, is expected to be
dominated by OH reaction because the high level of NO precluded substantial
oxidation by O3 and NO3. Photolysis of HPMTF is also unlikely to
contribute to the observed decay: by assuming that its photolytic cross
sections are equal to the summed cross section of aldehydes and organic
peroxides taken from MCM (Khan et al., 2021), we estimate
that photolysis accounted for only 4 % of the HPMTF loss in our chamber.
Using the cross section for MTF measured by Patroescu et al. (1996), we
obtain an even lower photolysis rate, with photolysis accounting for less
than 2 % of HPMTF loss in the chamber.
(a) NO concentration measured by the
NO–NO2–NOx analyzer in Exp. 2.
At OH exposure ∼5.8 h, 70 ppb of NO was injected into the
chamber. (b) Time series of
HPMTF-12C2 and
MTF-12C2 in Exp. 2. The decay
of HPMTF and MTF was used to estimate their reaction rate coefficients with
OH.
By calculating [OH] using the decay of DMS after the addition of NO, we fit
the decay of HPMTF (Figs. 4b and S10) to derive kOH+HPMTF of 2.1 (2.0–2.2) ×10-11 cm3 molec.-1 s-1. This is in
agreement with recent measurements of Jernigan et al. (2022) (1.4 (0.27–2.4) ×10-11 cm3 molec.-1 s-1); both experimental
values are an order of magnitude higher than an earlier theoretical estimate
of the rate (1.2×10-12 cm3 molec.-1 s-1)
(Wu et al., 2015). Using this lower
value, Khan et al. (2021) estimated that photolysis loss dominates HPMTF
sink in the global marine sulfur budget, with OH oxidation only accounting
for 10 % of HPMTF loss. This higher OH rate constant suggests that OH
oxidation is in fact likely to be an important loss process for HPMTF, at
least when liquid water is not present (Fung et al.,
2022; Vermeuel et al., 2020; Novak et al., 2021).
MTF is formed predominantly as a second-generation DMS oxidation product
from CH3SCH2OOH + OH in low-NO conditions in the mechanism.
Using a similar method as kOH+HPMTF (Figs. 4b and S10), kOH+MTF is estimated to be 1.35 (1.3–1.4) ×10-11 cm3 molec.-1 s-1, which agrees with the only other measurement
of kOH+MTF, 1.11±0.22×10-11 cm3 molec.-1 s-1, by Patroescu et al. (1996).
Role of relative humidity
The experiments described above were carried out under dry conditions and
thus focus only on homogenous gas-phase chemistry; in the atmosphere,
heterogeneous and aqueous-phase processes may also be important contributors
to DMS oxidation chemistry (Hoffmann et
al., 2016). Thus, Experiments 4 and 5 were carried out at 65 % RH, under
high- and low-NO levels, respectively. These experiments were carried out
over longer timescales (higher OH exposures) than the corresponding dry
experiments to better probe multi-generational product formation.
Results from Exp. 4 (in which 50–100 ppb NO was maintained in the chamber)
are shown in Fig. 5a. The overall product distribution is similar to that
under dry conditions (Fig. 2a), with SO2, MSA, and sulfate being the
major reaction products. The modeled product distribution shown in Fig. S11a is largely the same as that in the dry experiment (Fig. 2c), as water
does not play a role in the gas-phase oxidation mechanism shown in Fig. 1.
Even though this experiment was carried out over longer timescales, the
measured sulfur closure is quite good, 107 % (99 %–171 %) of the
reacted DMS at the end of the experiment.
Results from the high-humidity (65 % RH) DMS oxidation
experiments. (a) Product formation under high-NO conditions (Exp. 4). (b)
Product formation under low-NO conditions (Exp. 5). Because of instrument
downtime, no data were collected for the first 4 h of equivalent OH
exposure. (c) Comparison of major species between the low-RH (Exp. 1) and
high-RH experiment (Exp. 4) under high-NO conditions. (d) Comparison of major
species between the low-RH (Exp. 2) and high-RH experiment (Exp. 5) under
low-NO conditions. Changes in product concentrations are plotted against
changes in DMS concentration over the initial 6 h of OH exposure, when
data from both the dry and high-RH experiments were available.
Figure 5c compares the evolving concentrations of major product species
under high- and low-RH conditions, presented as change in product
concentration relative to change in DMS concentration, over the initial OH
exposure (corresponding to that of Exp. 1). Over these timescales, species
such as DMSO, SO2, and MSA showed a relatively small effect of RH. By
contrast, almost no C2H6SO2 (likely DMSO2) was measured
in the gas phase under high-RH conditions. Within the timescale of the experiments, our
measurements do not suggest conversion of MSA to sulfate in the aerosol
phase, as predicted in some modeling studies (Fung et al., 2022; Chen et
al., 2018). This difference may arise from low particle-phase OH
concentrations in our experiments.
Figure 5b shows products from Exp. 5 (65% RH, low-NO conditions, τbi>1 s). As in the low-RH, long-τbi case (Exp. 2a,
Fig. 2b), HPMTF and SO2 are the dominant measured products, and
little aerosol formation is observed. One minor new product, with formula
SO6, was detected in the I- CIMS in this experiment; it is likely
an adduct (i.e., O3⚫ SO3⚫ I-) or a
fragment formed in the instrument, but the parent species is unknown. In
contrast to the high-NO experiment (Exp. 4), sulfur closure was markedly
worse than under dry conditions. In the first 6 h of equivalent OH
exposure (the timescale of the dry experiment), only 74 % (53 %–97%) of the reacted sulfur was detected as products. This sulfur closure
degraded still further as the experiment proceeded and was only 23 %
(18 %–31 %) at the end of the experiment. Here, I- CIMS
sensitivities derived from the dry calibration were used for species
quantification and therefore may underestimate the concentration under high-RH conditions (Lee et al., 2014; Veres et al., 2020).
However, these differences would have to be dramatic (by factor of 5 or
more) to account for all the reacted sulfur, and therefore such calibration
errors are unlikely to explain the decreased sulfur closure.
Figure 5d shows differences for key product species formed in the long-τbi experiments under the high- and low-RH conditions, again over the
timescales of the dry experiment (the first 6 h of equivalent OH
exposure). Over these timescales, the initial yields of DMSO,
C2H6SO2, and HPMTF are not substantially different in the
humid and dry cases. SO2 concentrations were lower under humid
conditions but with an absolute difference of only ∼2 ppb.
Thus the production rates of these species are not affected dramatically by
RH level. Instead the poor sulfur closure at high-RH conditions suggests that extra
losses over longer timescales may be most likely by uptake to surfaces. The low
aerosol concentration towards the end of the experiment (due to particle
wall loss over the long experimental time, ∼17 h) could lead
to substantial chamber wall loss of low-volatility products, which would
contribute to this gap in measured sulfur. Such surface losses are likely
exacerbated at high-RH conditions, due to uptake into the aqueous phase. The initial
aerosol liquid water content (LWC) in the high-RH experiment was
10–100 µg m3, orders of magnitude lower than LWC in maritime clouds (Wallace and Hobbs, 2006). Therefore, such losses may play an
even more important role in the real atmosphere. Indeed, studies have
suggested that uptake to cloud water may be an important sink of gas-phase
HPMTF. Using in situ measurements, Vermeuel et al. (2020) and Novak et al. (2021) have shown that
HPMTF is lost to clouds and aerosols effectively in the marine boundary
layer. Similarly, using a global model, Fung et al. (2022) found that including cloud uptake into a global model substantially
decreases the global burden of HPMTF, by up to 86 %. This uptake of water-soluble
intermediate species (e.g., MSIA, DMSO2, and HPMTF) into cloud droplets
may then contribute to the condensed-phase production of MSA and sulfate
(Hoffmann et al., 2021; Novak et al., 2021), but such processes are not
accessed in the present chamber experiment.
Conclusions
In this study, we conducted a series of chamber experiments to investigate
the total product distribution from DMS oxidation at different RO2
fates and relative humidities. Under dry conditions, good sulfur closure was
obtained, suggesting most of the sulfur-containing product species were
accounted for. Under high-NO conditions (τbi<0.1 s),
major products are SO2, MSA, and sulfate, whereas under low-NO
conditions (τbi>10 s), HPMTF formed from RO2
isomerization makes up about half of the product sulfur, with very little
MSA or sulfate formation. Comparisons between measurements and MCM
predictions show relatively good agreement for most species and total
aerosol formation. However, under high-NO conditions, the model predicts
much more sulfate and less MSA than was measured; this might indicate errors
in the kinetics of the reactions that lead to rapid (first-generation) MSA
or sulfate formation. This work also provides new measurements of the rate
constants (at 295 K) of key reactions in the DMS oxidation mechanism,
including kisom (0.13±0.03 s-1), kHPMTF+OH (2.1×10-11 cm3 molec.-1 s-1), and kMTF+OH (1.35×10-11 cm3 molec.-1 s-1). Our measured value of
kHPMTF+OH, which is consistent with that of Jernigan et al. (2022a), suggests
that OH is a more important gas-phase sink of HPMTF than photolysis. Lastly,
results from high-RH conditions suggest heterogeneous losses of at least
some of the products, indicating that uptake into the atmospheric aqueous
phase (e.g., cloud droplets) may be an important sink as well.
Taken together, our results show that RO2 fate has a controlling
influence on the distribution of sulfur-containing products from DMS
oxidation. In particular, the formation of HPMTF from RO2 isomerization
suppresses (or at least delays) the gas-phase formation of SO2,
sulfate, and MSA. Additional studies are needed to constrain the
temperature dependence of kisom to predict the formation of HPMTF (and
other products) in warmer or colder environments, as well as to characterize
the full multiphase product distribution under higher-RH conditions. In
addition, experiments carried out over longer oxidation timescales and with
different oxidants are needed to better understand the amount and rate of
aerosol formation over days of oxidation. A related need is improved
constraints on the atmospheric fate of HPMTF and other key reaction
intermediates (e.g., DMSO, MSIA), including rates and products of gas-phase
oxidation, aqueous-phase oxidation, and photolysis, as well as rates of
physical loss (deposition and uptake).
Code and data availability
Chamber data and species concentrations for all experiments and model outputs have been archived and are available via the Kroll Group publication website at http://krollgroup.mit.edu/publications.html (Kroll Group, 2022). The F0AM model used in this work is publicly available at https://github.com/AirChem/F0AM/releases/tag/v3.2 (Wolfe, 2019; Wolfe et al., 2016), and the latest release is available at https://zenodo.org/record/6984581 (Wolfe et al., 2022).
The supplement related to this article is available online at: https://doi.org/10.5194/acp-22-16003-2022-supplement.
Author contributions
QY, MBG, JEK, FM, AZ, YL, and JRR collected the data. QY and MBG analyzed the
data. MBG performed box model simulations. QY and JHK wrote the manuscript.
MC, FNK, CLH, and JHK provided project guidance. All authors were involved in
helpful discussion and contributed to the manuscript.
Competing interests
At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.
Disclaimer
Publisher’s note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Acknowledgements
The authors thank Timothy Bertram, Gordon Novak,
and Chris Jernigan at the University of Wisconsin–Madison for insightful
discussions.
Financial support
This work was supported by the U.S. Department of Energy
Biological and Environmental Research program (grant no. DE-SC0018934) and the
Harvard Global Institute.
Review statement
This paper was edited by Sergey A. Nizkorodov and reviewed by three anonymous referees.
References
Arsene, C., Barnes, I., Becker, K. H., Schneider, W. F., Wallington, T. T.,
Mihalopoulos, N., and Patroescu-Klotz, I. V.: Formation of methane sulfinic
acid in the gas-phase OH-radical initiated oxidation of dimethyl
sulfoxide, Environ. Sci. Technol, 36, 5155–5163, 2002.
Barnes, I., Becker, K. H., and Patroescu, I.: The tropospheric oxidation of
dimethy sulfide: a new source of carbonyl sulfide, Geophys. Res. Lett.,
21, 2389–2392, 1994.Barnes, I., Hjorth, J., and Mihalapoulos, N.: Dimethyl sulfide and dimethyl
sulfoxide and their oxidation in the atmosphere, Chem. Rev., 106,
940–975, 10.1021/cr020529+, 2006.Berndt, T., Scholz, W., Mentler, B., Fischer, L., Hoffmann, E. H., Tilgner,
A., Hyttinen, N., Prisle, N. L., Hansel, A., and Herrmann, H.: Fast Peroxy
Radical Isomerization and OH Recycling in the Reaction of OH Radicals with
Dimethyl Sulfide, J. Phys. Chem. Lett., 10, 6478–6483,
10.1021/acs.jpclett.9b02567, 2019.
Charlson, R. J., Lovelock, J. E., Andreae, M. O., and Warren, S. G.: Oceanic
phytoplankton, atmospheric sulphur, cloud albedo and climate, Nature, 326,
665–661, 1987.Chen, Q., Sherwen, T., Evans, M., and Alexander, B.: DMS oxidation and sulfur aerosol formation in the marine troposphere: a focus on reactive halogen and multiphase chemistry, Atmos. Chem. Phys., 18, 13617–13637, 10.5194/acp-18-13617-2018, 2018.Chen, T. and Jang, M.: Chamber simulation of photooxidation of dimethyl sulfide and isoprene in the presence of NOx, Atmos. Chem. Phys., 12, 10257–10269, 10.5194/acp-12-10257-2012, 2012.
Chin, M., Jacob, D. J., Gardner, G. M., Foreman-fowler, M. S., Spiro, P. A., and Savoie, D. L.: A global three-dimensional model of tropospheric sulfate,
J. Geophys. Res., 101, 18667–18690, 1996.
Crounse, J. D., Nielsen, L. B., Jørgensen, S., Kjaergaard, H. G., and
Wennberg, P. O.: Autoxidation of organic compounds in the atmosphere, J.
Phys. Chem. Lett., 4, 3513–3520, 2013.Decarlo, P. F., Kimmel, J. R., Trimborn, A., Northway, M. J., Jayne, J. T., Aiken, A. C., Gonin, M., Fuhrer, K., Horvath, T., Docherty, K. S., Worsnop, D. R., and Jimenez, J. L.: Aerosol Mass Spectrometer, Anal. Chem., 78, 8281–8289, 10.1021/ac061249n, 2006.Fung, K. M., Heald, C. L., Kroll, J. H., Wang, S., Jo, D. S., Gettelman, A., Lu, Z., Liu, X., Zaveri, R. A., Apel, E. C., Blake, D. R., Jimenez, J.-L., Campuzano-Jost, P., Veres, P. R., Bates, T. S., Shilling, J. E., and Zawadowicz, M.: Exploring dimethyl sulfide (DMS) oxidation and implications for global aerosol radiative forcing, Atmos. Chem. Phys., 22, 1549–1573, 10.5194/acp-22-1549-2022, 2022.Hodshire, A. L., Campuzano-Jost, P., Kodros, J. K., Croft, B., Nault, B. A., Schroder, J. C., Jimenez, J. L., and Pierce, J. R.: The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings, Atmos. Chem. Phys., 19, 3137–3160, 10.5194/acp-19-3137-2019, 2019.Hoffmann, E. H., Tilgner, A., Schrödner, R., Bräuer, P., Wolke, R., and Herrmann, H.: An advanced modeling study on the impacts and atmospheric
implications of multiphase dimethyl sulfide chemistry, P. Natl. Acad.
Sci. USA, 113, 11776–11781, 10.1073/pnas.1606320113, 2016.Hoffmann, E. H., Heinold, B., Kubin, A., Tegen, I., and Herrmann, H.: The
Importance of the Representation of DMS Oxidation in Global
Chemistry-Climate Simulations, Geophys. Res. Lett., 48, e2021GL094068, 10.1029/2021GL094068, 2021.Huang, D. D., Li, Y. J., Lee, B. P., and Chan, C. K.: Analysis of Organic
Sulfur Compounds in Atmospheric Aerosols at the HKUST Supersite in Hong Kong
Using HR-ToF-AMS, Environ. Sci. Technol., 49, 3672–3679,
10.1021/es5056269, 2015.Huijnen, V., Williams, J., van Weele, M., van Noije, T., Krol, M., Dentener, F., Segers, A., Houweling, S., Peters, W., de Laat, J., Boersma, F., Bergamaschi, P., van Velthoven, P., Le Sager, P., Eskes, H., Alkemade, F., Scheele, R., Nédélec, P., and Pätz, H.-W.: The global chemistry transport model TM5: description and evaluation of the tropospheric chemistry version 3.0, Geosci. Model Dev., 3, 445–473, 10.5194/gmd-3-445-2010, 2010.
Hunter, J. F., Carrasquillo, A. J., Daumit, K. E., and Kroll, J. H.:
Secondary Organic Aerosol Formation from Acyclic, Monocyclic, and Polycyclic
Alkanes, Environ. Sci. Technol., 48, 10227–10234, 2014.
Jenkin, M. E., Saunders, S. M., and Pilling, M. J.: The tropospheric
degradation of volatile organic compounds: a protocol for mechanism
development, Atmos. Environ., 31, 81–104, 1997.Jernigan, C. M., Fite, C. H., Vereecken, L., Berkelhammer, M. B., Rollins,
A. W., Rickly, P. S., Novelli, A., Taraborrelli, D., Holmes, C. D., and
Bertram, T. H.: Efficient production of carbonyl sulfide in the low-NOx
oxidation of dimethyl sulfide, Geophys. Res. Lett., 49, 10.1029/2021GL096838, 2022a.
Jernigan, C. M., Christopher, D. C., and Timothy H. B.: Reactive Uptake of
Hydroperoxymethyl Thioformate to Sodium Chloride and Sodium Iodide Aerosol
Particles, J. Phys. Chem. A, 126, 4476–4481, 2022b.
Khan, M. A. H., Bannan, T. J., Holland, R., Shallcross, D. E., Archibald, A.
T., Matthews, E., Back, A., Allan, J., Coe, H., Artaxo, P., and Percival, C.
J.: Impacts of Hydroperoxymethyl Thioformate on the Global Marine Sulfur
Budget, ACS Earth Sp. Chem., 5, 2577–2586, 2021.Kloster, S., Feichter, J., Maier-Reimer, E., Six, K. D., Stier, P., and Wetzel, P.: DMS cycle in the marine ocean-atmosphere system – a global model study, Biogeosciences, 3, 29–51, 10.5194/bg-3-29-2006, 2006.Krechmer, E. J., Lopez-Hilfiker, F., Koss, A., Hutterli, M., Stoermer, C.,
Deming, B., Kimmel, J., Warneke, C., Holzinger, R., Jayne, J., Worsnop, D.,
Fuhrer, K., Gonin, M., and Gouw, J. De: Evaluation of a New Reagent-Ion
Source and Focusing Ion- Molecule Reactor for Use in
Proton-Transfer-Reaction Mass Spectrometry, Anal. Chem., 90, 12011–12018,
10.1021/acs.analchem.8b02641, 2018.Kroll Group: Chamber data and species concentrations, http://krollgroup.mit.edu/publications.html, last access: 2022.Lamarque, J.-F., Emmons, L. K., Hess, P. G., Kinnison, D. E., Tilmes, S., Vitt, F., Heald, C. L., Holland, E. A., Lauritzen, P. H., Neu, J., Orlando, J. J., Rasch, P. J., and Tyndall, G. K.: CAM-chem: description and evaluation of interactive atmospheric chemistry in the Community Earth System Model, Geosci. Model Dev., 5, 369–411, 10.5194/gmd-5-369-2012, 2012.Lucas, D. D. and Prinn, R. G.: Mechanistic studies of dimethylsulfide
oxidation products using an observationally constrained model, J. Geophys. Res.-Atmos., 107, ACH-12, 10.1029/2001JD000843, 2002.Lana, A., Bell, T. G., Simo, R., Vallina, S. M., Ballabrera-Poy, J., Kettle,
A. J., Dachs, J., Bopp, L., Saltzman, E. S., Stefels, J., Johnson, J. E.,
and Liss, P. S.: An updated climatology of surface dimethlysulfide
concentrationsand emission fluxes in the global ocean, Global Biogeochem.
Cycles, 25, GB1004, 10.1029/2010GB003850, 2011.Lee, B. H., Lopez-Hilfiker, F. D., Mohr, C., Kurtén, T., Worsnop, D. R., and Thornton, J. A.: An iodide-adduct high-resolution time-of-flight
chemical-ionization mass spectrometer: Application to atmospheric inorganic
and organic compounds, Environ. Sci. Technol., 48, 6309–6317,
10.1021/es500362a, 2014.
McManus, J. B., Kebabian, P. L., and Zahniser, M.S.: Astigmatic mirror
multipass absorption cells for long-path-length spectroscopy, Appl.
Optics, 34, 3336–3348, 1995.McManus, J. B., Zahniser, M. S., Nelson, D. D., McGovern, R. M., Agnese, M., and Brown, W. F.: Compact Quantum Cascade Laser Instrument for High Precision
Trace Gas Measurements, in: Optical Instrumentation for Energy and
Environmental Applications (p. EThC2), Optica Publishing Group, 10.1364/E2.2011.EThC2, 2011.
Mihalopoulos, N., Barnes, I., and Becker, K. H.: Infrared absorption spectra
and integrated band intensities for gaseous methanesulphonic acid (MSA),
Atmos. Environ., 25, 807–812, 1992.Novak, G. A., Fite, C. H., Holmes, C. D., Veres, P. R., Neuman, J. A.,
Faloona, I., Thornton, J. A., Wolfe, G. M., Vermeuel, M. P., Jernigan, C.
M., Peischl, J., Ryerson, T. B., Thompson, C. R., Bourgeois, I., Warneke,
C., Gkatzelis, G. I., Coggon, M. M., Sekimoto, K., Bui, T. P., Dean-Day, J.,
Diskin, G. S., DiGangi, J. P., Nowak, J. B., Moore, R. H., Wiggins, E. B.,
Winstead, E. L., Robinson, C., Thornhill, K. L., Sanchez, K. J., Hall, S.
R., Ullmann, K., Dollner, M., Weinzierl, B., Blake, D. R., and Bertram, T.
H.: Rapid cloud removal of dimethyl sulfide oxidation products limits
SO2 and cloud condensation nuclei production in the marine atmosphere,
P. Natl. Acad. Sci., 118, e2110472118, 10.1073/PNAS.2110472118,
2021.Patroescu, I. V., Barnes, I., and Becker, K. H.: FTIR kinetic and mechanistic
study of the atmospheric chemistry of methyl thiolformate, J. Phys. Chem.,
100, 17207–17217, 10.1021/jp961452u, 1996.Rap, A., Scott, C. E., Spracklen, D. V., Bellouin, N., Forster, P. M.,
Carslaw, K. S., Schmidt, A., and Mann, G.: Natural aerosol direct and
indirect radiative effects, Geophys. Res. Lett., 40, 3297–3301,
10.1002/grl.50441, 2013.Saunders, S. M., Jenkin, M. E., Derwent, R. G., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 161–180, 10.5194/acp-3-161-2003, 2003.
Shen, J., Scholz, W., He, X. C., Zhou, P., Marie, G., Wang, M., Marten, R.,
Surdu, M., Rörup, B., Baalbaki, R. and Amorim, A, Ataei,
F., Bell, D. M., Bertozzi, B., Brasseur, Z., Caudillo, L., Chen, D., Chu,
B., Dada, L., Duplissy, J., Finkenzeller, H., Granzin, M., Guida, R.,
Heinritzi, M., Hofbauer, V., Iyer, S., Kemppainen, D., Kong, W., Krechmer,
J. E., Kürten, A., Lamkaddam, H., Lee. C. P., Lopez, B., Mahfouz, N. G.,
Manninen, H. E., Massabò, D., Mauldin, R. L., Mentler, B., Müller,
T., Pfeifer, J., Phillppov, M., Piedehierro, A. A., Roldin, P.,
Schobesberger, S., Simon, M., Stolzenburg, D., Tham, Y. J., Tomé, A.,
Umo, N. S., Wang, D., Wang, Y., Weber, S. K., Welti, A., Wollesen de Jonge,
R., Wu, Y., Zauner-Wieczorek, M., Zust, F., Baltensperger, U., Curtius, J.,
Flagan, R. C., Hansel, A., Möhler, O., Petäjä,
T., Volkamer, R., Kulmala, M., Lehtipalo, K., Rissanen, M., Kirkby, J.,
El-Haddad, I., Bianchi, F., Silipä, M., Donahue, N. M., and Worsnop, D.
R.: High Gas-Phase Methanesulfonic Acid Production in the OH-Initiated
Oxidation of Dimethyl Sulfide at Low Temperatures, Environ. Sci. Technol.,
56, 13931–13944, 2022.Veres, P. R., Andrew Neuman, J., Bertram, T. H., Assaf, E., Wolfe, G. M.,
Williamson, C. J., Weinzierl, B., Tilmes, S., Thompson, C. R., Thames, A.
B., Schroder, J. C., Saiz-Lopez, A., Rollins, A. W., Roberts, J. M., Price,
D., Peischl, J., Nault, B. A., Møller, K. H., Miller, D. O., Meinardi,
S., Li, Q., Lamarque, J. F., Kupc, A., Kjaergaard, H. G., Kinnison, D.,
Jimenez, J. L., Jernigan, C. M., Hornbrook, R. S., Hills, A., Dollner, M.,
Day, D. A., Cuevas, C. A., Campuzano-Jost, P., Burkholder, J., Paul Bui, T.,
Brune, W. H., Brown, S. S., Brock, C. A., Bourgeois, I., Blake, D. R., Apel,
E. C., and Ryerson, T. B.: Global airborne sampling reveals a previously
unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere,
P. Natl. Acad. Sci. USA, 117, 4505–4510,
10.1073/pnas.1919344117, 2020.
Vermeuel, M. P., Novak, G. A., Jernigan, C. M., and Bertram, T. H.: Diel
profile of hydroperoxymethyl thioformate: Evidence for surface deposition
and multiphase chemistry, Environ. Sci. Technol, 54, 12521–12529,
2020.von Glasow, R. and Crutzen, P. J.: Model study of multiphase DMS oxidation with a focus on halogens, Atmos. Chem. Phys., 4, 589–608, 10.5194/acp-4-589-2004, 2004.
Wallace, J. M. and Hobbs, P. V.: Atmospheric science: an introductory
survey, U. K. Elsevier Inc., ISBN 9780127329512, 2006.Wolfe, G.: F0AM model, https://github.com/AirChem/F0AM/releases/tag/v3.2, last access: 2019.Wolfe, G. M., Marvin, M. R., Roberts, S. J., Travis, K. R., and Liao, J.: The Framework for 0-D Atmospheric Modeling (F0AM) v3.1, Geosci. Model Dev., 9, 3309–3319, 10.5194/gmd-9-3309-2016, 2016.Wolfe, G., Haskins, J., and srobe: AirChem/F0AM: v4.2.2 (v4.2.2), Zenodo [code], 10.5281/zenodo.6984581, 2022.Wollesen de Jonge, R., Elm, J., Rosati, B., Christiansen, S., Hyttinen, N., Lüdemann, D., Bilde, M., and Roldin, P.: Secondary aerosol formation from dimethyl sulfide – improved mechanistic understanding based on smog chamber experiments and modelling, Atmos. Chem. Phys., 21, 9955–9976, 10.5194/acp-21-9955-2021, 2021.Wu, R., Wang, S., and Wang, L.: New mechanism for the atmospheric oxidation
of dimethyl sulfide. The importance of intramolecular hydrogen shift in a
CH3SCH2OO radical, J. Phys. Chem. A, 119, 112–117,
10.1021/jp511616j, 2015.Xu, L., Møller, K. H., Crounse, J. D., Otkjær, R. V., Kjaergaard, H.
G., and Wennberg, P. O.: Unimolecular reactions of peroxy radicals formed in
the oxidation of α-Pinene and β-Pinene by hydroxyl radicals,
J. Phys. Chem. A, 123, 1661–1674, 10.1021/acs.jpca.8b11726, 2019.
Ye, Q., Goss, M. B., Isaacman-Vanwertz, G., Zaytsev, A., Massoli, P., Lim,
C., Croteau, P., Canagaratna, M., Knopf, D. A., Keutsch, F. N., Heald, C. L., and Kroll, J. H.: Organic Sulfur Products and Peroxy Radical Isomerization
in the OH Oxidation of Dimethyl Sulfide, ACS Earth Sp. Chem., 5,
2013–2020, 10.1021/acsearthspacechem.1c00108, 2021.
Yin, F., Grosjean, D., and Seinfeld, J. H.: Photooxidation of Dimethyl
Sulfide and Dimethyl Disulfide. I: Mechanism Development, J. Atmos. Chem., 11, 309–365, 1990.Zaytsev, A., Breitenlechner, M., Koss, A. R., Lim, C. Y., Rowe, J. C., Kroll, J. H., and Keutsch, F. N.: Using collision-induced dissociation to constrain sensitivity of ammonia chemical ionization mass spectrometry (NH4+ CIMS) to oxygenated volatile organic compounds, Atmos. Meas. Tech., 12, 1861–1870, 10.5194/amt-12-1861-2019, 2019.