Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range

Rapid growth of organic aerosol nanoparticles over a

wide tropospheric temperature range

Dominik Stolzenburg

, Lukas Fischer

, Alexander L. Vogel

c,d,e

, Martin Heinritzi

, Meredith Schervish

, Mario Simon

Andrea C. Wagner

, Lubna Dada

, Lauri R. Ahonen

, Antonio Amorim

h,i

, Andrea Baccarini

, Paulus S. Bauer

Bernhard Baumgartner

, Anton Bergen

, Federico Bianchi

, Martin Breitenlechner

b,j,k

, Sophia Brilke

Stephany Buenrostro Mazon

, Dexian Chen

, Ant

onio Dias

d,h,i

, Danielle C. Draper

, Jonathan Duplissy

, Imad El Haddad

Henning Finkenzeller

, Carla Frege

, Claudia Fuchs

, Olga Garmash

, Hamish Gordon

d,n

, Xucheng He

, Johanna Helm

Victoria Hofbauer

, Christopher R. Hoyle

, Changhyuk Kim

p,q

, Jasper Kirkby

c,d

, Jenni Kontkanen

, Andreas K

urten

Janne Lampilahti

, Michael Lawler

, Katrianne Lehtipalo

, Markus Leiminger

, Huajun Mai

, Serge Mathot

Bernhard Mentler

, Ugo Molteni

, Wei Nie

, Tuomo Nieminen

, John B. Nowak

, Andrea Ojdanic

, Antti Onnela

Monica Passananti

, Tuukka Pet

, Lauriane L. J. Qu

ever

, Matti P. Rissanen

, Nina Sarnela

, Simon Schallhart

g,u

Christian Tauber

, Ant

onio Tom

, Robert Wagner

, Mingyi Wang

, Lena Weitz

, Daniela Wimmer

, Mao Xiao

Chao Yan

, Penglin Ye

f,t

, Qiaozhi Zha

, Urs Baltensperger

, Joachim Curtius

, Josef Dommen

, Richard C. Flagan

Markku Kulmala

g,w

, James N. Smith

, Douglas R. Worsnop

g,t

, Armin Hansel

b,x

, Neil M. Donahue

and Paul M. Winkler

a,1

Faculty of Physics, University of Vienna, 1090 Vienna, Austria;

Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck,

Austria;

Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany;

CERN, the European

Organization for Nuclear Research, 1211 Geneva, Switzerland;

Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;

Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213;

Institute for Atmospheric and Earth System Research/Physics,

Faculty of Science, University of Helsinki, 00014 Helsinki, Finland;

Centro Multidisciplinar de Astrof

ısica, University of Lisbon, 1749-016 Lisbon, Portugal;

Faculdade de Ci

encias da Universidade de Lisboa, University of Lisbon, 1749-016 Lisbon, Portugal;

John A. Paulson School of Engineering and Applied

Sciences, Harvard University, Cambridge, MA 02138;

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;

Department of Chemistry, University of California, Irvine, CA 92697;

Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder,

CO 80309;

School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom;

Institute for Atmospheric and Climate Science, ETH

Zurich, 8092 Zurich, Switzerland;

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;

Department of

Environmental Engineering, Pusan National University, 46241 Busan, Republic of Korea;

Joint International Research Laboratory of Atmospheric and Earth

System Sciences, Nanjing University, 210023 Nanjing, China;

Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland;

Aerodyne Research Inc., Billerica, MA 01821;

Finnish Meteorological Institute, 00101 Helsinki, Finland;

Institute Infante Dom Lu

ız, University of Beira

Interior, 6200 Covilh

a, Portugal;

Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing

University of Chemical Technology, Beijing, China; and

Ionicon Analytik GmbH, 6020 Innsbruck, Austria

Edited by John H. Seinfeld, California Institute of Technology, Pasadena, CA, and approved July 30, 2018 (received for review May 3, 2018)

Nucleation and growth of aerosol particles from atmospheric

vapors constitutes a major source of global cloud condensa-

tion nuclei (CCN). The fraction of newly formed particles that

reaches CCN sizes is highly sensitive to particle growth rates,

especially for particle sizes

<

10 nm, where coagulation losses

to larger aerosol particles are greatest. Recent results show that

some oxidation products from biogenic volatile organic com-

pounds are major contributors to particle formation and initial

growth. However, whether oxidized organics contribute to par-

ticle growth over the broad span of tropospheric temperatures

remains an open question, and quantitative mass balance for

organic growth has yet to be demonstrated at any temperature.

Here, in experiments performed under atmospheric conditions in

the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the

European Organization for Nuclear Research (CERN), we show

that rapid growth of organic particles occurs over the range from

−

◦

C to 25

◦

C. The lower extent of autoxidation at reduced

temperatures is compensated by the decreased volatility of all

oxidized molecules. This is confirmed by particle-phase composi-

tion measurements, showing enhanced uptake of relatively less

oxygenated products at cold temperatures. We can reproduce the

measured growth rates using an aerosol growth model based

entirely on the experimentally measured gas-phase spectra of

oxidized organic molecules obtained from two complementary

mass spectrometers. We show that the growth rates are sen-

sitive to particle curvature, explaining widespread atmospheric

observations that particle growth rates increase in the single-

digit-nanometer size range. Our results demonstrate that organic

vapors can contribute to particle growth over a wide range of

tropospheric temperatures from molecular cluster sizes onward.

aerosols

nanoparticle growth

aerosol formation

CLOUD experiment

volatile organic compounds

he global budget of cloud condensation nuclei (CCN) signif-

icantly influences the Earth’s radiative balance, as it affects

the albedo and the lifetime of clouds. New particle formation

by gas-to-particle conversion is the largest source of CCN (1).

Especially the early steps of particle growth between 1 and

10 nm determine the survival chance of freshly formed parti-

cles and therefore their climatic relevance (2, 3). The major

vapors driving particle growth are sulfuric acid and, maybe more

importantly, low-volatility organics resulting from the oxidation

of volatile organic compounds (VOCs) (4). Monoterpenes are

an important class of atmospheric VOCs with copious emissions

from vegetation (5). They are quickly oxidized in the atmo-

sphere and, through a subsequent autoxidation process, rapidly

Author contributions: D.S., L.F., A.L.V., H.G., J. Kirkby, A. Onnela, U.B., J.C., J. Dommen,

R.C.F., M.K., D.R.W., A.H., N.M.D., and P.M.W. designed research; D.S., L.F., A.L.V., M.H.,

M. Simon, A.C.W., L.D., L.R.A., A.A., A. Baccarini, P.S.B., B.B., A. Bergen, F.B., M.B., S.B.,

S.B.M., D.C., A.D., D.C.D., J. Duplissy, I.E.H., H.F., C. Frege, C. Fuchs, O.G., H.G., X.H.,

J.H., V.H., C.R.H., C.K., J. Kirkby, J. Kontkanen, A.K., J.L., M. Lawler, K.L., M. Leiminger,

H.M., S.M., B.M., U.M., W.N., T.N., J.B.N., A. Ojdanic, A. Onnela, M.P., T.P., L.L.J.Q.,

M.P.R., N.S., S.S., C.T., A.T., R.W., M.W., L.W., D.W., M.X., C.Y., P.Y., and Q.Z. performed

research; D.S., L.F., M.B., A.H., and P.M.W. contributed new reagents/analytic tools; D.S.,

L.F., A.L.V., M.H., M. Schervish, M. Simon, A.C.W., L.D., D.C.D., M. Lawler, R.W., L.W.,

and J.N.S. analyzed data; and D.S., L.F., A.L.V., M.H., J. Kirkby, N.M.D., and P.M.W. wrote

the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This open access article is distributed under

Creative Commons Attribution-

NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND)

To whom correspondence should be addressed. Email: paul.winkler@univie.ac.at.

This article contains supporting information online at

www.pnas.org/lookup/suppl/doi:10.

1073/pnas.1807604115/-/DCSupplemental

Published online August 28, 2018.

9122–9127

PNAS

September 11, 2018

vol. 115

no. 37

www.pnas.org/cgi/doi/10.1073/pnas.1807604115

EARTH, ATMOSPHERIC,

AND PLANETARY SCIENCES

Significance

Aerosol particles can form and grow by gas-to-particle con-

version and eventually act as seeds for cloud droplets, influ-

encing global climate. Volatile organic compounds emitted

from plants are oxidized in the atmosphere, and the resulting

products drive particle growth. We measure particle growth

by oxidized biogenic vapors with a well-controlled laboratory

setup over a wide range of tropospheric temperatures. While

higher temperatures lead to increased reaction rates and con-

centrations of highly oxidized molecules, lower temperatures

allow additional, but less oxidized, species to condense. We

measure rapid growth over the full temperature range of

our study, indicating that organics play an important role in

aerosol growth throughout the troposphere. Our finding will

help to sharpen the predictions of global aerosol models.

form highly oxygenated molecules (HOMs), which constitute

a large source of low-volatility species in the atmosphere (6).

Recent studies have shown that HOMs from the ozonolysis of

the predominant monoterpene

-pinene are able to form (7) and

efficiently grow particles from cluster sizes onward (8). Model

simulations suggest that they are major contributors to parti-

cle formation on a global scale (9). Moreover, the impact of

HOMs on initial particle growth might explain the observa-

tions of increasing growth rates with particle size between 1 and

10 nm during particle-formation events (10) by a multicompo-

nent Kelvin effect (8, 11), also known as nano-K

ohler theory

(12). This is because HOMs span a wide range of volatilities (13),

and, with increasing particle size, more and more low-volatility

species can contribute to the growth process.

In contrast to sulfuric acid plus ammonia or amines, where

growth proceeds close to the kinetic limit (14), growth driven by

organics is governed by the resulting volatilities of the wide vari-

ety of oxidation products. Therefore, temperature likely plays a

decisive role, as the saturation concentration has a steep expo-

nential temperature dependence as described by the Clausius–

Clapeyron relation. Additionally, a recent study has shown that

temperature crucially influences the chemical composition of the

initially formed molecular clusters in

-pinene ozonolysis (15).

Therefore, the contribution of biogenic organics to new parti-

cle formation might be strongly sensitive to temperature. This,

in turn, may significantly influence the importance of new par-

ticle formation at high altitudes (16) and in outflow regions of

deep-convective clouds—for example, over the Amazon Basin

(17–19).

Here, we investigate in the Cosmics Leaving Outdoor

Droplets (CLOUD) chamber (20) the effect of tempera-

ture on the production of oxygenated molecules and subse-

quent particle growth from dark

-pinene ozonolysis at three

different temperatures (

−

◦

C, 5

◦

C, and 25

◦

C) for various pre-

cursor concentrations. The resulting volatility distributions are

inferred by combining two types of chemical ionization (CI) high-

resolution time of flight mass spectrometers (TOF-MS) (21, 22)

using complementary ionization techniques to obtain a detailed

representation of the gaseous oxidation products. Together

with the precision measurement of particle growth rates (23)

and analysis of the particle-phase composition (24), this allows

identification of the underlying processes and their temper-

ature dependence responsible for initial growth in biogenic

ozonolysis systems (see

Materials and Methods

for details about

the experimental setup and measurement procedures).

Results

Observed Gas-Phase Composition and Volatility Distribution.

measured gas-phase composition with a nitrate-CI atmospheric

pressure interface (APi)-TOF-MS (nitrate-CI) (21) and a proton

transfer reaction (PTR)-TOF-MS (PTR3) (22) to obtain a more

detailed overview of the neutral gas-phase species present dur-

ing the

-pinene ozonolysis experiments. We obtained overlap

for peaks observed in both instruments (

SI Appendix

, Fig. S3

)

and show a combined mass-defect plot of both instruments for

three representative experiments at three different temperatures

SI Appendix

, Fig. S4

. The PTR3 introduces

200 previously

undetected molecular ion signals, not only HOMs, which are

usually specified by their high oxygen to carbon ratio (O:C

0.7 for monomers), but mostly compounds toward lower oxida-

tion states. For molecules with identified chemical composition,

a volatility can be assigned according to the number of oxy-

gen atoms

and the number of carbon atoms

within the

molecule (

SI Appendix

As volatilities of organic compounds observed in the atmo-

sphere vary by

10 orders of magnitude and the combined mass

spectra contain

∼

500 different molecules, it is convenient to

simplify considerations of gas-to-particle partitioning by group-

ing compounds together within a volatility basis set (VBS) (13,

25). Within this framework, the volatility bins are separated

by one decade in

∗

at 300 K, and for other temperatures,

the binned distribution is shifted toward lower saturation mass

concentrations. The saturation mass concentration of oxidized

organics should follow the Clausius–Clapeyron relation at a con-

stant evaporation enthalpy

∆

vap

, which in turn is linked to

∗

at 300 K (13) (

SI Appendix

Fig. 1 shows the resulting binned volatility distribution of all

observed organic gas-phase compounds for three representative

experiments. We averaged observed gas-phase concentrations

Fig. 1.

Volatility distributions for representative experiments with similar

-pinene ozonolysis rate: 25

◦

C (

), 5

◦

C (

), and

−

◦

C (

). The green and

blue bars show summed molecular ions observed in the nitrate-CI and PTR3,

respectively. The highest and lowest bin are overflow bins. Volatility bins

are defined at 300 K, shifted, and widened according to their corresponding

temperature. The resulting saturation mass concentration is defined on the

axis, while log

300K

is specified by white numbers. Additionally, the bins

in supersaturation with

1 are found left of the indicating arrow.

ELVOC, extremely low-volatility organic compound; IVOC, intermediate-

volatility organic compound; LVOC, low-volatility organic compound; SVOC,

semi-volatile organic compound.

Stolzenburg et al.

PNAS

September 11, 2018

vol. 115

no. 37

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