Secondary aerosol formation from atmospheric reactions of aliphatic amines

62 Pages·2017·1.01 MB·English

Secondary aerosol formation from atmospheric reactions
of aliphatic amines
S. M. Murphy, A. Sorooshian, J. H. Kroll, N. L. Ng, P. Chhabra, C. Tong, J.
D. Surratt, E. Knipping, R. C. Flagan, J. H. Seinfeld
To cite this version:
S. M. Murphy, A. Sorooshian, J. H. Kroll, N. L. Ng, P. Chhabra, et al.. Secondary aerosol formation
from atmospheric reactions of aliphatic amines. Atmospheric Chemistry and Physics Discussions,
2007, 7 (1), pp.289-349. ￿hal-00302397￿
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Atmos. Chem. Phys. Discuss., 7, 289–349, 2007
Atmospheric
www.atmos-chem-phys-discuss.net/7/289/2007/ Chemistry ACPD
© Author(s) 2007. This work is licensed and Physics
under a Creative Commons License. Discussions 7,289–349,2007
Secondary aerosol
from atmospheric
aliphatic amines
S.M.Murphyetal.
Secondary aerosol formation from
atmospheric reactions of aliphatic amines TitlePage
Abstract Introduction
1 1 2 1 1 1
S. M. Murphy , A. Sorooshian , J. H. Kroll , N. L. Ng , P. Chhabra , C. Tong ,
Conclusions References
1 3 1 1
J. D. Surratt , E. Knipping , R. C. Flagan , and J. H. Seinfeld
Tables Figures
1DivisionofChemistryandChemicalEngineering,CaliforniaInstituteofTechnology,
Pasadena,CA91125,USA
2CurrentAddress: AerodyneResearchInc.,Billerica,MA,USA ◭ ◮
3ElectricPowerResearchInstitute,PaloAlto,CA,USA
◭ ◮
Received: 17December2006–Accepted: 17December2006–Published: 10January2007
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Correspondenceto: J.H.Seinfeld([email protected])
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InteractiveDiscussion
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Abstract
ACPD
Although aliphatic amines have been detected in both urban and rural atmospheric
aerosols, little is known about the chemistry leading to particle formation or the poten- 7,289–349,2007
tial aerosol yields from reactions of gas-phase amines. We present here the first sys-
5 tematic study of aerosol formation from the atmospheric reactions of amines. Based Secondary aerosol
on laboratory chamber experiments and theoretical calculations, we evaluate aerosol from atmospheric
formationfromreactionofOH,ozone,andnitricacidwithtrimethylamine,methylamine, aliphatic amines
triethylamine, diethylamine, ethylamine, and ethanolamine. Entropies of formation for
alkylammonium nitrate salts are estimated by molecular dynamics calculations en- S.M.Murphyetal.
abling us to estimate equilibrium constants for the reactions of amines with nitric acid.
10
Though subject to significant uncertainty, the calculated dissociation equilibrium con-
stant for diethylammonium nitrate is found to be sufficiently small to allow for its atmo- TitlePage
sphericformation,eveninthepresenceofammoniawhichcompetesforavailablenitric
Abstract Introduction
acid. Experimental chamber studies indicate that the dissociation equilibrium constant
15 for triethylammonium nitrate is of the same order of magnitude as that for ammonium Conclusions References
nitrate. All amines studied form aerosol when photooxidized in the presence of NO
x
Tables Figures
with the majority of the aerosol mass present at the peak of aerosol growth consisting
+
ofaminium(R NH )nitratesalts,whichrepartitionbacktothegasphaseastheparent
3
◭ ◮
amine is consumed. Only the two tertiary amines studied, trimethylamine and triethy-
20 lamine, are found to form significant non-salt organic aerosol when oxidized by OH or ◭ ◮
ozone; calculated organic mass yields for the experiments conducted are similar for
ozonolysis (15% and 5% respectively) and photooxidation (23% and 8% respectively). Back Close
The non-salt organic aerosol formed appears to be more stable than the nitrate salts
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and does not quickly repartition back to the gas phase.
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InteractiveDiscussion
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1 Introduction
ACPD
Aminesareemittedintotheatmospherefromavarietyofsourcesincludingmeatcook-
ing, biomass burning, motor vehicle exhaust, industrial processes, and marine organ- 7,289–349,2007
isms. Thedominantanthropogenicsourceisemissionsfromanimalhusbandryopera-
5 tions(Table1). Whileamineemissionsfromanimalhusbandryaretypicallyreportedto Secondary aerosol
be two to three orders of magnitude less than those of ammonia (Ngwabie and Hintz, from atmospheric
2005; Schade and Crutzen, 1995), at least one study has reported gas-phase con- aliphatic amines
centrations of amines in the hundreds of ppb in areas of intense animal husbandry
(Rabaud et al., 2003). Though emission estimates vary widely, amines have been S.M.Murphyetal.
detected in marine, rural, and urban atmospheres in the gas phase, particle phase
10
and within aqueous fog and rain drops (Zhang and Anastasio, 2003). Mass spectro-
metric studies by both Murphy (1997) and Angelino (2001) have shown that molecular TitlePage
ions typically associated with amines are present in ambient particles, especially in
Abstract Introduction
air masses from agricultural regions. Tan et al.(2002) identified particle phase amines
during multiple smog events in Toronto’s winter atmosphere. Recent field studies sug- Conclusions References
15
gest that organic nitrogen species could be an appreciable fraction of organic aerosol
Tables Figures
mass (Beddows et al., 2004; Mace et al., 2003; Makela et al., 2001; McGregor and
Anastasio, 2001; Neff et al., 2002; Simoneit et al., 2003; Tan et al., 2002), although
◭ ◮
the relative importance of amines as a source of particulate organic nitrogen remains
20 unclear. ◭ ◮
During the 1970’s, interest in the gas-phase atmospheric chemistry of amines fo-
cused on carcinogenic nitrosamines formed when amines are photooxidized (Pitts et Back Close
al., 1978). It was subsequently determined that gas-phase nitrosamines photolyze
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rapidly in the troposphere and are believed to pose a minimal threat to human health.
More recently, toxicology studies have demonstrated that particulate organic nitrogen
25
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species are associated with adverse health effects (Hamoir et al., 2003). Nemmar
(2002)foundthatparticlescoatedwithaminesproducedasignificantincreasetherate InteractiveDiscussion
ofbloodclots(bynearly4times)wheninstalledinthetracheaofhamsters;incontrast,
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the effects of particles coated with carboxylic acids and unmodified polystyrene parti-
cles were not statistically significant when compared to the control group of hamsters. ACPD
Amines are oxidized in the atmosphere by both the hydroxyl radical and ozone, with
7,289–349,2007
measured rate constants suggesting that both reactions are competitive when ozone
levels are in the tens to hundreds of ppb (Tuazon et al., 1994). While many of the gas-
5
phaseoxidationpathwayshavebeenelucidated,secondaryaerosolformationresulting Secondary aerosol
fromthephotooxidationofamineshasreceivedlimitedattention. Also,becauseamines from atmospheric
arebasiccompounds,theycanformparticulatesaltsthroughreactionswithgas-phase aliphatic amines
acids present in the atmosphere (HNO , H SO ),
3 2 4
S.M.Murphyetal.
NR +HNO (g)⇄HNR NO (s) (R1)
10 3 3 3 3
2NR +H SO (g)⇄(HNR ) SO (s) (R2)
3 2 4 3 2 4 TitlePage
Reactions(R1)and(R2)areanalogoustothoseofammoniatoformammoniumsulfate Abstract Introduction
and ammonium nitrate. While the equilibria between gas-phase ammonia and nitric or
sulfuric acid to form particle-phase salts have been thoroughly investigated and the Conclusions References
thermodynamic parameters governing these reactions are well known (Mozurkewich,
15 Tables Figures
1993; Stelson and Seinfeld, 1982), similar thermodynamic parameters for amine sys-
tems were not available prior to this study.
◭ ◮
There have been a limited number of laboratory chamber experiments in which
aerosolresultingfromaminephotooxidationwasobserved(Angelinoetal.,2001;Pitts ◭ ◮
et al., 1978). Aerosol yields, the relative importance of acid-base chemistry, and the
20
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oxidative pathways leading to particle formation remain poorly understood. The goal
of the present work is to use controlled laboratory chamber studies to evaluate the FullScreen/Esc
aerosol forming potential, by acid-base reactions, photooxidation and ozonolysis, of
aliphatic amines known to be present in the atmosphere. The amines studied (with
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abbreviationused)are: trimethylamine(TMA),methylamine(MA),triethylamine(TEA),
25
diethylamine (DEA), ethylamine (EA), and ethanolamine (MEA). InteractiveDiscussion
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2 Experimental
ACPD
3
Allexperiments(Table2)werecarriedoutintheCaltechdual28m FEPTefloncham-
bers (Cocker et al., 2001; Keywood et al., 2004). The chambers are surrounded by 7,289–349,2007
banks of black lights (276GE350BL) output from which is in the ultraviolet predomi-
5 nantly between 300 and 400 nm, with a maximum at 354 nm. Ports allow for the intro- Secondary aerosol
duction of clean, dry (<10% RH) air, gas-phase reagents, inorganic seed aerosol, and from atmospheric
formeasurementofNO,NOx,O3,RH,temperature,andparticulatemass,size,number aliphatic amines
o o
concentration, and chemistry. Temperature is held at 20 C, increasing to 25 C during
photooxidation experiments using the black lights. Commercial monitors (Horiba) are S.M.Murphyetal.
used to measure O (by UV absorption) and NO/NO (NO conversion to NO by acti-
10 3 x x
vated carbon, followed by NO + O chemiluminescence). Both amines and nitric acid
3
(whenadded)wereinjectedintothechamberbypassingastreamofdry,cleanairover TitlePage
a known volume of high purity liquid phase compound. The purity and source of the
Abstract Introduction
amines used in this study are: trimethylamine (45% solution in H O, Fluka), methy-
2
lamine (40 wt.% solution in H O, Sigma-Aldrich ), triethylamine (>99.5% purity, Sigma Conclusions References
15 2
Aldrich),diethylamine(>99.5%purity,SigmaAldrich), ethylamine(70wt.%solutionin
Tables Figures
H O,Aldrich),ethanolamine,(≥99%purity,SigmaAldrich). Gas-phaseconcentrations
2
ofaminesandnitricacidwerenotdirectlymeasuredandwereinsteadestimatedbased
◭ ◮
onthevolumeofliquidphaseamineinjected;theseconcentrationsrepresentthemax-
20 imum possible within the chamber in the absence of wall loss. ◭ ◮
“Seed”aerosolwasgeneratedbyatomizingasolutionof0.015Mammoniumsulfate
or 0.75 M ammonium nitrate. Particle-phase measurements were made by an Aero- Back Close
dyne Time of Flight Aerosol Mass Spectrometer (cToF-AMS), a Particle-Into-Liquid
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SamplerCoupledtoIonChromatography(PILS-IC),andadifferentialmobilityanalyzer
(DMA,TSI3760). Duringexperimentnumber20(Table2),chamberparticleswerecol-
25
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lected onto a Teflon (PALL Life Sciences, 47-mm diameter, 1.0-µm pore size) filter for
analysisbymassspectrometryusingbothMatrixAssistedLaserDesorptionIonization InteractiveDiscussion
(MALDI)andelectrosprayionization(ESI)todeterminehowspectrafromtheseioniza-
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tion techniques compared to the electron impact ionization spectra of the cToF-AMS.
Details of the extraction and analysis methodology used for the Teflon filter are given ACPD
in Surratt et al. (2006).
7,289–349,2007
2.1 PILS-IC
Secondary aerosol
The PILS-IC (particle-into-liquid sampler coupled with ion chromatography) is a quan-
5 from atmospheric
titative technique for measuring water-soluble ions, including inorganic, organic acid,
aliphatic amines
and amine ions in aerosol particles. The PILS-IC used in this study (Sorooshian et al.,
2006) is based on the prototype design (Weber et al., 2001) with key modifications, S.M.Murphyetal.
including integration of a liquid sample fraction collector and real-time control of the
steam injection tip temperature. Chamber air is sampled through a 1 µm cut-size im-
10
pactorandasetofthreedenuders(URGandSunsetLaboratories)toremoveinorganic TitlePage
(basicandacidic)andorganicgasesthatwouldotherwisebiasaerosolmeasurements.
Abstract Introduction
Sample air mixes with steam in a condensation chamber where rapid adiabatic mixing
produces a high water supersaturation. Droplets grow sufficiently large to be collected
Conclusions References
by inertial impaction before being delivered to vials held on a rotating carousel. The
15
contents of the vials are subsequently analyzed off-line using a dual IC system (ICS- Tables Figures
2000with25µLsampleloop,DionexInc.) forsimultaneousanionandcationanalysis.
Data for the following ions are reported: acetate, formate, nitrate, sulfate ammo- ◭ ◮
nium, methylammonium, dimethylammonium, trimethylammonium, ethylammonium,
◭ ◮
diethylammonium, and triethylammonium. The PILS-IC technique cannot be used to
20
speciate many of the organic compounds that make up the total aerosol mass since Back Close
these are not sufficiently ionic in water to have affinity for the IC columns used (an-
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ion: Dionex AS-11 column 2×250 mm, ASRS Ultra II 2-mm suppressor, potassium
hydroxide eluent; cation: CS12A column 2×250mm, CSRS Ultra II 2-mm suppressor,
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methanesulfonicacideluent);nevertheless,alloftheaminesaltsformedintheexperi-
25
ments reported here were successfully speciated. It should be noted that ammonium,
InteractiveDiscussion
methylammonium,andethylammoniumco-elute;additionalco-elutingpairsarediethy-
lammonium:trimethylammonium and potassium:dimethylammonium. While potassium
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was never expected to be present and ammonium formation was not anticipated for
many of the experiments, background levels of these species in the IC baseline noise ACPD
did interfere with quantification of co-eluting species. The limit of detection (LOD) for
each ion (NH+, NO−, acetate, formate, and the six aforementioned amine species) is 7,289–349,2007
4 3
defined in this study as the air-equivalent concentration of the lowest concentration
5
standardthatisdistinctfrombaselinenoiseintheICplusthreetimesthestandardde- Secondary aerosol
viation(n=3)ofthismeasurement. TheLOD’sfortheionsmeasuredusingthePILS-IC from atmospheric
techniqueforthisstudyareallbelow0.1µgm−3,withtheexceptionsoftrimethylamine aliphatic amines
and triethylamine, which have LOD’s of 0.60 and 0.89µgm−3, respectively. In all ex-
S.M.Murphyetal.
periments, chamber air containing gas-phase amine and nitric acid (when added) was
10
run through a particle filter and sampled by the PILS-IC; none of the amines was ever
detected in these filtered vials, confirming that the carbon denuder was able to com-
TitlePage
pletely remove gas-phase species and that the PILS-IC signal is entirely a result of
aerosol-phase compounds.
Abstract Introduction
2.2 Aerodyne cTof-AMS Conclusions References
15
The design parameters and capabilities of the cToF-AMS instrument are described Tables Figures
in detail elsewhere (Drewnick et al., 2004a; 2004b). Briefly, chamber air enters the
instrumentthrougha100µmcriticalorificeataflowrateof1.4cm3 s−1. Particleswitha ◭ ◮
vacuumaerodynamicdiameterbetweenroughly50and800nmareefficientlyfocused
◭ ◮
by an aerodynamic lens, passed through a 1% chopper, and then impacted onto a
20
tungsten vaporizer. The chopper can be operated in three modes: (1) completely Back Close
blocking the beam to gather background mass spectra; (2) out of the beam’s path
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to collect ensemble average mass spectra over all particles sizes; (3) chopping the
beam to create size-resolved mass spectra. The vaporizer is set at ∼550 ◦C to ensure
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complete volatilization of the aerosol. Once vaporized, molecules undergo electron
25
impact ionization at 70eV and are orthogonally pulsed every 19µs into the time of
InteractiveDiscussion
flight mass analyzer. The resolution of the mass analyzer is ∼800 (M/∆M). For all
mass spectra shown in this work the ion signal is represented as sticks, the height
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of which represent the raw ion signal integrated over 1 amu bins. These stick mass
spectra are divided into different chemical species based on the methodology of Allan ACPD
et al. (2003), with exceptions noted in the text. The limits of detection, calculated as
threetimesthestandarddeviationofthenoiseforparticlefilteredairare<0.05µgm−3 7,289–349,2007
for all species measured.
5
Secondary aerosol
2.3 Effective density from atmospheric
aliphatic amines
Calculating the density of aerosol particles is important for two reasons. First, multi-
plying the aerosol volume measured by the DMA by the material density allows one S.M.Murphyetal.
to calculate aerosol mass yields. (The cToF-AMS cannot be used to directly quan-
tify aerosol mass because the fraction of particles that bounce off of the vaporizer is
10
unknown and the PILS-IC does not measure the mass of non-ionic species) Second, TitlePage
changes in the density give an indication of alterations in particle morphology during
Abstract Introduction
secondary aerosol formation.
The effective density (ρ ) is a function of the vacuum aerodynamic diameter (d )
eff va Conclusions References
measured by the cToF-AMS and the mobility diameter (d ) measured by the DMA
15 m
(DeCarlo et al., 2004), Tables Figures
d C (d )
ρ = vaρ = ρ c ve (1) ◭ ◮
eff d o mδ3χχ C (d )
m t v c m
◭ ◮
where ρ is unit density (1g cm−3), C is the slip correction factor, d is the volume
o c ve
equivalentdiameter,δ istheinternalvoidfraction,χ isthedynamicshapefactorinthe Back Close
t
transition regime, and χ is the dynamic shape factor in the free molecular regime.
20 v FullScreen/Esc
AsdescribedinBahreinietal.(2005)andDecarloetal.(2004),theeffectivedensity
is equivalent to the material density if the shape factor and slip correction factor are
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unity and the internal void fraction is zero. These assumptions are probably slightly
incorrect for amine salts and amine oxidation products, given that ammonium nitrate
InteractiveDiscussion
particles have an effective density 20 percent less than the material density of ammo-
25
niumnitratewhenρeff iscalculatedusingsimultaneouscToF-AMSandDMAmeasure- EGU
296
ments (Jayne et al., 2000). Indeed the effective densities calculated in this way for
the aminium nitrates are less than the literature values. While there is no need to use ACPD
effectivedensitiestocalculatethemassofpuresalts(thePILS-ICisablequantitatively
measure these), it is necessary to use effective densities (as an approximation of the 7,289–349,2007
material density) to calculate the mass of aerosol formed during photooxidation and
5
ozonolysis because non-ionic species are present. Secondary aerosol
To calculate the effective density, one represents the DMA volume distribution, nor- from atmospheric
mally expressed as dV/dlog (d ), as dV/dlog (ρ d ) and adjusts ρ until this dis- aliphatic amines
m eff m eff
tribution (with peak height normalized to 1) aligns in diameter space with the mass
S.M.Murphyetal.
distribution from the cToF-AMS, dM/dlog (d ) (peak height also normalized to 1). The
10 va
twodistributionsalignwhenthecorrecteffectivedensityisusedbecauseρ d =d ρ .
eff m va o
Figure1ashowsthecalculatedeffectivedensityoftriethylammoniumnitrate(TEAN)is
1.1±0.1gcm−3 whiletheeffectivedensityoftheaerosolformedfromphotolysisofTEA TitlePage
(mixed TEAN and products from TEA oxidation) has an effective density of unity.
Abstract Introduction
2.4 Oxidation experiments Conclusions References
15
Three types of amine oxidation experiments were conducted in this study: (1) Pho- Tables Figures
tooxidation in the absence of NO , (2) Photooxidation in the presence of NO , and (3)
x x
dark ozonolysis. Hydrogen peroxide (H O ) was used as the OH radical precursor for ◭ ◮
2 2
alloftheNO -freephotooxidationexperimentsandmanyofthehighNO experiments
x x ◭ ◮
(seeTable2fordetails). H O isintroducedbybubbling5Lmin−1 ofhumidifiedroom-
20 2 2
temperatureairfor2.5hthrougha50%H O solution(Aldrich),throughaparticlefilter Back Close
2 2
to avoid the introduction of droplets, and finally into the chamber. The mixing ratio
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of H O achieved using this method has been previously estimated to be between 3
2 2
and 5ppm (Kroll et al., 2006). To minimize potential uptake of H O by the aerosol,
2 2
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all experiments were carried out under dry (RH<10%) conditions. To determine if the
25
presence of hydrogen peroxide significantly affected the particle-phase chemistry, nu-
InteractiveDiscussion
meroushighNO photooxidationexperimentswereconductedintheabsenceofH O ,
x 2 2
somewiththegas-phaseamineandNOx alone,andotherswherepropenewasadded EGU
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