EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Open Access Atmos. Chem. Phys. Discuss., 13, 14115–14140,Atmospheric 2013 Atmospheric www.atmos-chem-phys-discuss.net/13/14115/2013/Chemistry Chemistry doi:10.5194/acpd-13-14115-2013 © Author(s) 2013. CC Attribution 3.0 License.and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric This discussion paper is/hasMeasurement been under review for the journal AtmosphericMeasurement Chemistry and Physics (ACP). Please referTechniques to the corresponding final paper in ACP ifTechniques available. Discussions Open Access Identification and quantification of Open Access Biogeosciences Biogeosciences particle growth channels during newDiscussions Open Access particle formation Open Access Climate Climate of the Past of the Past M. R. Pennington1, B. R. Bzdek1, J. W. DePalma1, J. N. Smith2,3, Discussions A.-M. Kortelainen3, L. Hildebrandt Ruiz2,*, T. Petäjä4, M. Kulmala4, Open Access Open Access D. R. Worsnop4, and M. V. Johnston1 Earth System Earth System 1 Dynamics Dynamics Department of Chemistry and Biochemistry, University of Delaware, Newark,Discussions DE 19716, USA 2Atmospheric Chemistry Division, National Center for Atmospheric Research, 1850 Table Open Access Mesa Dr., Boulder, CO 80305,Geoscientific USA Geoscientific Open Access 3Department of Applied Physics, University of Eastern Finland, Kuopio, 70211, Finland 4 Instrumentation Instrumentation Department of Physical Sciences,Methods University and of Helsinki, 00014, Helsinki,Methods Finland and * now at: Department of ChemicalData Engineering, Systems University of Texas at Austin,Data Systems Austin, TX 78712, USA Discussions Open Access Open Access Geoscientific Received: 5 March 2013 – Accepted:Geoscientific 13 May 2013 – Published: 30 May 2013 Model Development Model Development Correspondence to: M. V. Johnston ([email protected]) Discussions Published by Copernicus Publications on behalf of the European Geosciences Union. Open Access Open Access Hydrology and Hydrology and Earth System14115 Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract Open Access Open Access Solid Earth Atmospheric new particle formationSolid Earth (NPF) is a key source of ambient ultrafine parti- cles that may contribute substantially to the global production of cloudDiscussions condensation nuclei (CCN). While NPF is driven by atmospheric nucleation, its impact on CCN con- 5 centration depends strongly on atmosphericOpen Access growth mechanisms since the growthOpen Access rate must exceed the loss rate due to scavenging in order for the particles to reach the The Cryosphere The Cryosphere CCN size range. In this work, chemical composition measurements ofDiscussions 20 nm diame- ter particles during NPF in Hyytiälä, Finland, in March–April 2011 permit identification and quantitative assessment of important growth channels. In this work we show that: 10 (A) sulfuric acid, a key species associated with atmospheric nucleation, accounts for less than half of particle mass growth during this time period; (B) the sulfate content of a growing particle during NPF is quantitatively explained by condensation of gas phase sulfuric acid molecules, in other words sulfuric acid uptake is collision limited; (C) sul- furic acid condensation substantially impacts the chemical composition of preexisting 15 nanoparticles before new particles have grown to a size sufficient to be measured; (D) ammonium and sulfate concentrations are highly correlated, indicating that ammonia uptake is driven by sulfuric acid uptake; (E) sulfate neutralization by ammonium does not reach the predicted thermodynamic endpoint, suggesting that a kinetic barrier ex- ists for ammonia uptake; (F) carbonaceous matter accounts for more than half of the 20 particle mass growth and its oxygen-to-carbon ratio (∼ 0.5) is characteristic of freshly formed secondary organic aerosol; and (G) differences in the overall growth rate from one formation event to another are caused by variations in the growth rates of all major chemical species, not just one individual species. 1 Introduction 25 Atmospheric new particle formation (NPF), the process whereby gaseous precursors nucleate to form clusters on the order of one nanometer and then grow rapidly to larger 14116 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | sizes, can significantly impact cloud condensation nuclei (CCN) levels (Kerminen et al., 2005; Kuang et al., 2010; Merikanto et al., 2009) and thereby influence precipitation patterns (Lee and Feingold, 2010) and climate (Rosenfeld et al., 2008) through chang- ing cloud albedo (Charlson et al., 1992; Lohmann and Feichter, 2005). With respect 5 to human health, NPF produces a large number of nanoparticles and because of their small size they can deposit throughout the respiratory tract or enter the bloodstream (Oberdörster et al., 2005). Exposure to elevated nanoparticle concentrations is asso- ciated with higher incidences of adverse cardiopulmonary effects (Gong et al., 2008; Knibbs et al., 2011; Maudgalya et al., 2008). In urban environments, nanoparticles 10 arising from secondary sources can account for over 50 % of the nanoparticle number concentration (Klems et al., 2011). In fact, anthropogenic pollution has been suggested to enhance the formation of nanoparticles over forested environments (Zhang et al., 2009). Despite the importance of nanoparticles to climate and human health, the ex- act mechanisms governing NPF are poorly understood (Bzdek and Johnston, 2010; 15 Kulmala et al., 2004). Atmospheric NPF is a two-step process involving (1) the nucleation of small particles or clusters at a critical size and (2) spontaneous growth of the critical nucleus to larger sizes (Kulmala et al., 2000, 2013; Zhang et al., 2012). Much effort has been devoted to understanding the atmospheric nucleation process. Nucleation is thought to occur 20 mainly by the formation of uncharged clusters in the atmosphere (Kulmala et al., 2007) and involves sulfuric acid (Sipila et al., 2010; Young et al., 2008; Weber et al., 1997), water, ammonia (Ball et al., 1999; Benson et al., 2009; Korhonen et al., 1999), amines (Berndt et al., 2010; Yu et al., 2012; Zollner et al., 2012) and possibly organic con- densable species (Metzger et al., 2010) such as organic acids (Zhang et al., 2004b; 25 Hou et al., 2013). Indeed, organic species such as amines are likely involved during nucleation, as sulfuric acid and ammonia are insufficient to explain nucleation (Kirkby et al., 2011). Nonetheless, sulfuric acid appears to be the key chemical component, as the nucleation rate in both laboratory and field measurements frequently depends 14117 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | on the sulfuric acid concentration (Kuang et al., 2008; Metzger et al., 2010; Nieminen et al., 2009). While much progress has been made in understanding the mechanisms underlying nucleation, the chemical mechanisms governing particle growth are less certain (Riip- 5 inen et al., 2012). For a nucleated nanoparticle to become climatically relevant, it must grow at a rate that is much higher than the rate at which it is lost due to scavenging (Riipinen et al., 2007; Kuang et al., 2010). It has been shown that expected growth rates based on gas phase sulfuric acid concentrations usually do not match measured growth rates during ambient NPF, suggesting that other chemical species contribute 10 to growth (Kuang et al., 2010; Smith et al., 2008; Stolzenburg et al., 2005). Chemi- cal composition measurements in the 10–30 nm size range have implicated a variety of molecular species including sulfate, nitrate, ammonium and organics (Smith et al., 2005, 2008, 2010). Several potential growth channels have been suggested, especially concerning growth by aminium salts (Barsanti et al., 2009; Smith et al., 2010; Wang 15 et al., 2010a,b) and by organic matter (Donahue et al., 2011; Monge et al., 2012; Per- raud et al., 2012). However, the extent to which other chemical species contribute to growth is not known, in part because few instruments can provide quantitative chemical composition measurements in the nanoparticle size regime (Bzdek et al., 2012a). This work utilizes 20 the Nano Aerosol Mass Spectrometer (NAMS), a single particle mass spectrometer that provides a quantitative measure of particle composition in the 10–30 nm size range (Wang and Johnston, 2006; Wang et al., 2006; Pennington and Johnston, 2012) to de- termine quantitatively the contributions of certain chemical species to particle growth during NPF in the remote boreal forest environment. A quantitative understanding of 25 the contributions of various chemical species to particle growth is necessary in order to accurately assess the impact of NPF on CCN levels and climate. 14118 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 Methods 2.1 Nano Aerosol Mass Spectrometer (NAMS) Data presented in this work were obtained with NAMS. Ambient air was sampled to the NAMS from a height of ∼ 4 m through a 1.27 cm (O.D.) length of copper tubing at a flow −1 5 rate of