Emission of amines from terrestrial vegetation

33 Pages·2015·2.4 MB·English

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doi:10.5194/bgd-12-3211-2015 s
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Thisdiscussionpaperis/hasbeenunderreviewforthejournalBiogeosciences(BG). p
e Emission of amines
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from terrestrial
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vegetation
Ideas and Perspectives: On the emission D
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c J.Sintermannand
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of amines from terrestrial vegetation in s A.Neftel
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the context of atmospheric new particle
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formation r
| Abstract Introduction
J. Sintermann and A. Neftel D Conclusions References
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AgroscopeInstituteforSustainabilityScience,Reckenholzstrasse191,8046Zurich, us Tables Figures
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Switzerland io
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(cid:74) (cid:73)
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Received:21December2014–Accepted:2February2015–Published:16February2015 a
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Correspondenceto:J.Sintermann([email protected]) r
PublishedbyCopernicusPublicationsonbehalfoftheEuropeanGeosciencesUnion. | Back Close
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Abstract D
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Inthisarticlewesummariserecentscience,whichshowshowairborneamines,specif- s
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icallymethylamines(MAs),playakeyroleinatmosphericnewparticleformation(NPF) io 12,3211–3243,2015
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by stabilising small molecule clusters. Agricultural emissions are assumed to consti- P
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5 tute the most important MA source, but given the short atmospheric residence time pe Emission of amines
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of MAs, they can hardly have a direct impact on NFP events observed in remote re- from terrestrial
gions. This leads us to the presentation of existing knowledge focussing on natural | vegetation
vegetation-relatedMAsources.HighMAcontentsaswellasemissionsbyplantshave D
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alreadybeendescribedinthe19thcentury.StrongMAemissionspredominantlyoccur c J.Sintermannand
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10 duringfloweringaspartofapollinationstrategy.Thebehaviourisspeciesspecific,but ssio A.Neftel
examples of such species are common and widespread. In addition, vegetative plant n
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tissue exhibiting high amounts of MAs might potentially lead to significant emissions, a
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andthedecompositionoforganicmaterialcouldconstituteanothersourceforairborne e TitlePage
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MAs.Thesemechanismswouldprovidesources,whichcouldbecrucialfortheamine’s
| Abstract Introduction
role in NPF, especially in remote regions. Knowledge about vegetation-related amine
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emissions is, however, very limited and thus it is also an open question how Global Dis Conclusions References
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Change and the intensified cycling of reactive nitrogen over the last 200years have us Tables Figures
altered amine emissions from vegetation with a corresponding effect on NPF. s
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(cid:74) (cid:73)
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1 Introduction e (cid:74) (cid:73)
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Amines comprise a vast range of nitrogenous organic compounds with aliphatic | Back Close
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methylamines (MA; monomethylamine=MMA, dimethylamine=DMA, trimethy- D
lamine=TMA) representing the most common (Ge et al., 2011a) and comparably isc FullScreen/Esc
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most studied airborne species. Amines have widely been identified in aerosol particu- s
late matter and wet deposition (Neff et al., 2002; Ge et al., 2011a; Healy et al., 2014; sion Printer-friendlyVersion
Wang et al., 2015). P InteractiveDiscussion
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New aerosol particle formation (NPF) from gas-phase precursors occurs frequently D
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intheatmosphere,approximatelyconstituting50to80%oftheglobalaerosolloadand c BGD
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30to50%ofcloudcondensationnuclei(Merikantoetal.,2009).Estimatesoftheglobal s
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secondary aerosol budget are highly uncertain due to uncertainties in gas-phase pre- n
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5 cursor contributions to NPF and limited mechanistic comprehension (Spracklen et al., a
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2011).WhileNPFratesobservedinthefielddonotcomplywiththeclassicalprocess- e Emission of amines
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understandinginvolvingsulphuricacid(SA)andwater(Kirkbyetal.,2011;Chenetal., from terrestrial
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2012), it has recently become increasingly clear that the ternary system of SA and vegetation
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water, together with neutralising compounds like ammonia (NH ) or amines, is a key
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10 systeminNPF(Chenetal.,2012;Almeidaetal.,2013;Kurtenetal.,2014).Aminescan u
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also form stable molecular clusters with methanesulfonic acid (Dawson et al., 2012). s
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In addition, the oxidation of organic compounds contributes to NPF (Riccobono et al., n
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2014). a
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Despite their generally low atmospheric concentrations (Ge et al., 2011a), Almeida r
15 etal. (2013)haveshownthat aminestakean important roleinNPF. Theirmainfinding | Abstract Introduction
isthatextremelysmallMAmixingratios(>3pptDMAintheircase)sufficetoefficiently
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enhance NPF rates, and that atmospheric observations of NPF rates are only consis- is
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tently explained taking amines into consideration. This is consistent with the current us Tables Figures
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mechanistic understanding. The NPF enhancement by addition of MAs is most signifi- io
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cantinsituationswithcleanair,essentiallywhenonlylittleNH ispresenttocontribute (cid:74) (cid:73)
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to SA neutralisation. p
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The indirect effect of anthropogenic aerosols represents the largest uncertainty on r
climate radiative forcing according to IPCC (2013). Almeida et al. (2013) note how the | Back Close
recent findings “show that the uncertainty is even greater than previously thought, be-
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causeextremelylowamineemissions–whichhavesubstantialanthropogenicsources is FullScreen/Esc
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and have not hitherto been considered by the IPCC – have a large influence on the s
nucleationofsulphuricacidparticles.[...]Ifamineemissionsweretospreadintopris- sio Printer-friendlyVersion
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tine regions of the boundary layer where they could switch on nucleation, substantial P InteractiveDiscussion
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increases in regional and global cloud condensation nuclei could occur”. p
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In spite of their supposedly important role for NPF, information on the atmospheric D
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abundance and emission pathways of amines remains rather scarce. Further on, we c BGD
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focus on MA as a surrogate for other airborne amines. The most important identi- s
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fied MA sources (Ge et al., 2011a) are agriculture (Schade and Crutzen, 1995; Kuhn n
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5 et al., 2011; Sintermann et al., 2014), biomass burning (Lobert et al., 1990; Andreae a
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and Merlet, 2001), and the ocean (van Neste et al., 1987; Gorzelska and Galloway, e Emission of amines
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1990; Wang and Lee, 1994; Gibb et al., 1999b; Facchini et al., 2008). Many marine al- from terrestrial
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gae produce MAs (Steiner and Hartmann, 1968; Smith, 1971, 1975) and even remote vegetation
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oceanwatercontainsMA(andtheTMA-precursortrimethylamine-N-oxide)(Gibbetal.,
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c J.Sintermannand
10 1999b, a; Gibb and Hatton, 2004). Such marine amines might represent an important u
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contributiontooceanicsecondaryaerosol(Myriokefalitakisetal.,2010).Asaminesare s
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ubiquitous in plant and animal life (Smith, 1971; Dey et al., 1997), terrestrial vegeta- n
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tion is thought to provide another, albeit very weak, source for amines, including MAs a
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(Schade and Crutzen, 1995; Ge et al., 2011a). Towards the end of the 19th century r
15 until the 1970s, some authors have described high MA abundances associated with | Abstract Introduction
tissue and the flowering of certain plant species. This kind of MA source has not yet
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been elucidated in relation to the discovered key role of amines in NPF. is
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Here,wesummarisethecurrentstateofscienceregardingtheimportanceofamines us Tables Figures
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for NPF and discuss information on the source of MAs from terrestrial vegetation in io
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order to reveal essential research targets and provide important perspectives on the (cid:74) (cid:73)
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matter.Abetterunderstandingofamineemissionpathwayswouldhelptointerpretfield p
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observationsofNPFandisultimatelyrequiredforthedescriptionofNPFinchemistry- r
transport models. | Back Close
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2 The role of airborne amines in new aerosol particle formation u
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Kulmala et al. (2013) describe atmospheric NPF as a mechanism involving three- n
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regimes:(1)predominantlyneutralmolecularclusters(diameter<1.1to1.3nm)nucle- a
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ate,butfurthergrowthisinhibitedbecauseofclusterre-evaporation;(2)thesmallclus- e
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ters are efficiently stabilised by combination of SA with a base (NH /amines) (1.1 to D
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1.3to1.5to1.9nm);(3)theseactivatedclusters(>1.5to1.9nm)growmorerapidlyby c BGD
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condensation of other vapours and coagulation of clusters. The importance of amines s
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for NPF has recently been established by field (Angelino et al., 2001; Makela et al., n
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2001;Smithetal.,2010;Zhaoetal.,2011)andlaboratoryexperiments(Murphyetal., a
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2007; Berndt et al., 2010; Erupe et al., 2011; Bzdek et al., 2010; Zhao et al., 2011; Yu e Emission of amines
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et al., 2012; Zollner et al., 2012; Almeida et al., 2013; Jen et al., 2014; Kurten et al., from terrestrial
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2014), as well as from modelling studies (Kurten et al., 2008; Barsanti et al., 2009; vegetation
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Bzdek et al., 2010; Ortega et al., 2012; Loukonen et al., 2010; Nadykto et al., 2011; is
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Paasonen et al., 2012; Almeida et al., 2013; DePalma et al., 2014). On a molecular u
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level,Kurtenetal.(2014)observedhowDMAstabilisesSA,increasingthestableclus- sio
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terconcentrationbyupto6ordersofmagnitude.DMA(andtheotherMAs)isastronger
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base than NH which is one of the main reasons for its stabilisation efficiency (Ortega a
3 pe TitlePage
etal.,2012).ComparedtotheNPFratecausedbySAand2to250pptNH alone,the r
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15 enhancement is 3 to 4 orders of magnitude higher in conditions with 5 to 140ppt DMA | Abstract Introduction
and10pptNH underSAmixingratiosuptoappt(Almeidaetal.,2013).Investigating
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higherSAmixingratios(approximately1–250ppt),Jenetal.(2014)foundanincrease is
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in cluster concentration of roughly 2 orders of magnitude, caused by DMA or TMA us Tables Figures
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compared to the maximum caused by NH alone. From SA and DMA, Kurten et al. io
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20 (2014) detected NPF rates close to the collision rate between both molecules, which P (cid:74) (cid:73)
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represents the maximum possible kinetic limit. They argue that collision rate-driven p
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NPF might be observed only with a DMA concentration higher than a threshold of ap- r
proximately100timestheSAconcentration,becauseofclustercoagulationandfission | Back Close
(seeOrtegaetal.,2012).Accordingly,Almeidaetal.(2013)andJenetal.(2014)iden- D
25 tifiedbaseconcentrationsabovewhichtheenhancingeffectofthealkalinegasspecies isc FullScreen/Esc
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becomes saturated. Then, the NPF rate may proceed at its maximum, which is char- s
acteristic for each base. These base threshold concentrations were only 5 to 10ppt sio Printer-friendlyVersion
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DMA in the experiments of Almeida et al. (2013), and 20ppt DMA, 30ppt TMA, 80 to P InteractiveDiscussion
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180ppt MMA, 1.1 to 1.8ppb NH3 in the Jen et al. (2014) study. With the base exceed- pe
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ing its (SA-dependent) threshold concentration, the NPF rate solely depends on the D
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availability of SA (Kurten et al., 2014). c BGD
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Intheatmosphere, SAiscontinuouslyformed in-situviaoxidation ofsulphurdioxide s
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(Boyetal.,2005).TypicalSAmixingratioscoverarangefrom0.005to5ppt(Eiseleand n
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5 Tanner, 1993; Petäjä et al., 2009; Almeida et al., 2013). Hence, the emissions of the a
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alkaline gases determine, to a large part, the potential for NPF. In polluted air masses, e Emission of amines
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for example close to intensive agricultural activities or at urban environments, usually from terrestrial
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enough airborne NH and MAs exist (Ge et al., 2011a; Sintermann et al., 2014) to vegetation
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favourhighNPFrates.ThehighconcentrationsofexistingparticlesoftenhinderNPFby
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10 acting as coagulation sink for newly formed clusters (Kerminen et al., 2001; Dal Maso u
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et al., 2007; Westervelt et al., 2014). In clean pristine air, however, the addition of s
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small amounts of an atmospheric base is expected to promote NPF. This much more n
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efficiently, if that base is a MA rather than NH . Thus, MA emissions in regions with a
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clean air will have a strong impact on NPF – especially when they are not coupled to r
15 larger NH3 emissions. | Abstract Introduction
In the environment, the availability of emitted MAs for NPF is constrained by their
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removal via dry and wet deposition, gas-phase oxidation – mainly by the hydroxyl rad- is
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ical – (Ge et al., 2011a; Lee and Wexler, 2013), and condensation onto pre-existing us Tables Figures
particles. The latter is an efficient removal process yielding a range of MA lifetimes sio
depending on the aerosol number-size distribution and the assumed uptake coeffi- n (cid:74) (cid:73)
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cient (defined as the fraction of molecules being permanently removed from the gas p
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phase by collision with an existing particle). Sintermann et al. (2014) roughly estimate r
a condensation sink lifetime of TMA of 0.5 and 17min for a high and lower aerosol | Back Close
burden, respectively, based on an uptake coefficient of 1. Using a chemistry-transport
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model, approximating amine emissions by scaling with those of NH (the approach is FullScreen/Esc
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taken by Schade and Crutzen, 1995), including oxidation, deposition, and the conden- s
sation sink, Yu and Luo (2014) derive atmospheric MA lifetimes. With a maximal up- sio Printer-friendlyVersion
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take coefficient of 0.03, they calculate atmospheric residence times of approximately P InteractiveDiscussion
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1h over Europe, eastern Asia, and the eastern US compared to 3 to >5h in more re- p
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moteregions.AccordingmodelledMMA/DMA/TMAconcentrationsspanapproximately D
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5/2/10pptoverIndia,2/0.5/5to5/1/10pptoverChinaandpartsofAfricaandSouth c BGD
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America, 0.2/0.1/0.5 to 2/0.5/5ppt over the major parts of the other continents to ss
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0.05/0.02/0.1 to 0.5/0.2/0.5ppt in more remote regions (excluding the polar areas). n
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ever, that emissions further away from urban areas, and hence concentrations, might e Emission of amines
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besubstantiallyunderestimated.Thiswouldbeemphasizedevenmorestronglybythe from terrestrial
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finding that the estimated agricultural amine emissions do not scale with a constant vegetation
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ratio throughout all NH emission stages (Kuhn et al., 2011; Sintermann et al., 2014).
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10 In conclusion, the short atmospheric residence time of MAs implies that only local to u
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regionalemissionsarecrucialinpromotingNPF.Emissionsintocleanairwouldspread s
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the MA potential for NPF further than in situations with higher aerosol burdens. n
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Measurements of atmospheric MAs are challenging and reports of concentrations a
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in regions away from potential urban, agricultural, or marine sources are rare. Si- r
15 multaneous observations of MAs and NH3 and NPF in remote areas would be es- | Abstract Introduction
sential to characterise the corresponding interactions. As far as we know, the only
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campaigns at comparably remote c ontinental regions have been carried out at the is
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Finnish boreal forest site Hyytiälä (Hari and Kulmala, 2005). Sellegri et al. (2005) us Tables Figures
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found 34 to 80ppt TMA (and 12ppt DMA which was below the detection limit) dur- io
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ing a short period in spring 2003, whereas Kieloaho et al. (2013) determined ambient (cid:74) (cid:73)
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DMA+ethylamine(EA)andTMA+propylamine(PA)fromMaytoOctober2011.High- ap
e (cid:74) (cid:73)
est concentrations DMA+EA and TMA+PA amounted to 157±20 and 102±60ppt, r
respectively, in September/October, which were thought to originate from litterfall- | Back Close
emissions. DMA+EA exhibited somewhat smaller concentration peaks (>50ppt)
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at the beginning of June and in July/August. Diethylamine (DEA) from unassigned is FullScreen/Esc
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sources was also measured and peaked in the summer months (15.5±0.5ppt). The s
observation of NPF events was only moderately correlated to the occurrence of the sio Printer-friendlyVersion
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measured amines. As shown by Hellén et al. (2014), the amines were generally more P InteractiveDiscussion
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abundant at the boreal forest site than in the urban environment of Helsinki during the p
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same period. It appears striking that the prevailing amine concentrations at the bo- D
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real forest exceed the threshold values given by Almeida et al. (2013) and Jen et al. c BGD
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(2014) at which the maximum NPF rate could occur. Schade and Crutzen (1995) es- ss
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timated an average MA:NH emission ratio of 0.7% from agricultural sources, which n
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5 areassumedtodominatetheanthropogenicMAsourceandlikewise,Sintermannetal. a
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(2014) measured a maximum TMA emission ratio o f 1%. By contrast, simultaneous e Emission of amines
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measurements of MAs and NH at a coastal-rural site, with potential marine source from terrestrial
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influence, indicated time averaged concentration ratios DMA:NH =1.6 to 3.5% and vegetation
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TMA:NH =0.75to3.9%(Freshouretal.,2014).Inanotherstudyattworuralforested D
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10 areas,theMA:NH3 ratiodidnotexceed1%,butcorrelationwithisopreneledtospec- cus J.SinAte.rNmeaftnenl and
ulationaboutavegetationsource(Youetal.,2014).Despitehighmeasurementuncer- s
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tainties (Freshour et al., 2014), such elevated MA concentrations and higher ratios to n
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NH in comparatively remote situation compared with agricultural environments, could a
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point towards vegetation as another source for MAs. r
| Abstract Introduction
3 Vegetation as a potentially significant source for gas-phase amines D Conclusions References
15 is
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Ithasbeenobservedthatadiversegroupofseveralplantspeciesexhibitsexceptionally us Tables Figures
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high amounts of MAs associated (a) either generally with their vegetative tissue (e.g. io
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(cid:74) (cid:73)
foliage), or (b) with blossoms during flowering (Smith, 1971, 1975). These species are P
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MAreservoirsrepresentingstrongpotentialMAemitters.Wicke(1862)wasamongthe e (cid:74) (cid:73)
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firsttodescribetheemissionofTMAfromplants.HeobservedtheoccurrenceofTMA
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incondensedtranspirationofChenopodiumvulvaria,knownforitsfish-likesmellwhich
ischaracteristicofTMA.Remarkably,hesawsomekindof“fog”emergingwhenexpos- Dis FullScreen/Esc
ingaHCl-coatedglassrodtotheairclosetotheplant.Hemightindeedhavebeenthe c
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firstscientisttowitnesstheeffectsofNPFfromTMAneutralisingtheacid.Atthattimeit ssio Printer-friendlyVersion
had been known that also pears (Pyrus communis), hawthorn (Crataegus monogyna), n
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andtherowan(Sorbusaucuparia)containTMAintheirblossoms(Wicke,1862).Later, a
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theextremelyhighTMAcontentofChenopodiumvulvariawasestablishedbyCromwell e
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(1950)andCromwellandRichards(1966),whofollowedtheworksofPowerandChes- D
nut(1925);Vickery(1925);KleinandSteiner(1928);SteinerandLöffler(1929);Vickery isc BGD
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(1932), among others. By then, the range of higher plants with a high MA content in s
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foliage or blossoms had been extended to a few more species. Further on, Stein von n
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5 Kamienski (1957a, b, 1958) and Steiner (1966) provided measurements comprising a
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the identification of MAs in foliage and especially blossoms of various plants (trees, e Emission of amines
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bushes, herbs), a larger number of fungi, and even some lichen and moss, demon- from terrestrial
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strating that enrichment of volatile amines is widespread among some families (like vegetation
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Araceae, Caprifoliaceae, Cornaceae, Rosaceae, Umbelliferae) and almost not found
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10 in other families (Labiatae, Papilionaceae) (Smith, 1971). Volatile amine abundance u
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is highly species-specific and may depend on phenology and site (Stein von Kamien- s
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ski,1957a;Steiner,1966;Smith,1971).Smith(1971)reviewedthestateofknowledge n
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aboutaminesandplantsatthattime.MMA,DMA,andTMAhavecommonlybeenfound a
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intheamine-enrichedvegetation.TableA1(Appendix)summarisesspeciesassociated r
15 with MAs found in the literature. Some examples of higher plant species, which are | Abstract Introduction
widespread in Europe, include: Castanea sativa, Cornus sanguinea, Crataegos laevi-
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gata,Crataegusmonogyna,Mercurialisannua,Mercurialisperennis,Pyruscommunis, is
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Sorbus aucuparia, among others. us Tables Figures
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ItisnotentirelyclearwhichpathwaysleadtoMAcreationwithinsuchplants(Steiner, io
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1966; Smith, 1971). In principle, formation pathways are the decarboxylation of amino (cid:74) (cid:73)
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acids and transamination from aldehydes (Cromwell and Richards, 1966; Steiner, p
e (cid:74) (cid:73)
1966; Steiner et al., 1967; Smith, 1971, 1975; Wink and Hartmann, 1981; Dey et al., r
1997; Farquhar et al., 1983; Bagni and Tassoni, 2001; Dudareva et al., 2013). Most | Back Close
measurementsaddressedtheMAcontentwithinthetissueofvegetationpartssuchas
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fruiting bodies, foliage, and especially blossoms. However, the MAs are also released is FullScreen/Esc
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intothegasphase.Oftenthecharacteristicsmellwasobserved,indicatingthatamines s
were also being emitted from the living plant. In fact, many plants use the chemical sio Printer-friendlyVersion
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mimicryeffectofaminoidfragrances,resemblingexcrementsanddecay,inordertoat- P InteractiveDiscussion
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tract dung and carrion insects, such as flies and beetles, for pollination. The scents in- p
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volveacomplexcompositionofmanydifferentvolatileswithvariousnitrogen-containing D
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compounds (Dobson, 2006; Abrol, 2012; Woodcock et al., 2014). It has been recog- c BGD
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nised that MA volatilisation from blossoms plays an important role in that pollination s
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mechanism (Smith, 1971). It might also be that amines serve as antioxidants (Larson, n
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5 1988). a
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At least 15 different amines have been identified as floral scent compounds, and e Emission of amines
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generally the quality and quantity of scents varies spatially and temporally, from plant from terrestrial
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toplant,andbetweenspecies(DudarevaandPichersky,2006;KnudsenandGershen- vegetation
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zon,2006).Theblossomsareusually,butnotnecessarily,ofwhite,green,orred-brown
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10 colour and often exhibit the characteristic amine odour (Stein von Kamienski, 1957a). u
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One example of plants using MAs as part of a pollination strategy is the hawthorn s
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(here: Crataegus monogyna and Crataegus laevigata). Hawthorn shows the charac- n
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teristic scent of TMA (El-Sayed, 2014). It is striking that already in medieval times a
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hawthorn branches were a symbol of the Black Death, since the hawthorn’s fragrance r
15 mimics decay (Vickery, 1995). | Abstract Introduction
Our own dynamic chamber measurements using Chemical Ionisation Mass Spec-
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trometry (CIMS) highlight strong TMA emissions from freshly cut twigs with blossoms is
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ofCrataeguslaevigataandCornussanguinea(Fig.1).Thesemeasurementsoriginally us Tables Figures
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hadanexplorativeintention,butwetentativelyderiveemissionestimates.HighestTMA io
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emissions from the approximately 45 Crataegus laevigata blossoms were in the range (cid:74) (cid:73)
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0.019–0.038nmols and peaked between 0.011 and 0.022nmols for Cornus san- p
e (cid:74) (cid:73)
guinea (5 umbels). 1000 (as an arbitrary number) blossoms or 100 umbels, respec- r
−1
tively, would thus have emitted up to 0.84 and 0.44nmols . As a comparison, the | Back Close
TMA emissions from 1 square meter covered with a mix of farm animal excrements,
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as a very strong TMA source, have been determined to be of the order of 10nmols−1 is FullScreen/Esc
25 c
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(Sintermann et al., 2014). It is striking that the NH volatilisation from the blossoms s
is much lower than that of TMA, implying that in th3e absence of another significant sio Printer-friendlyVersion
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NH source (like agriculture), vegetation-related MA emissions might be an important P InteractiveDiscussion
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pathway providing atmospheric bases available for NPF. p
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