Theoretical study of the cis-pinonic acid and its atmospheric hydrolysate participation in the atmospheric nucleation

Science of the Total Environment 674 (2019) 234–241

Contents lists available at ScienceDirect

Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv

Theoretical study of the cis-pinonic acid and its atmospheric hydrolysate participation in the atmospheric nucleation Xiangli Shi a, Xianwei Zhao b, Ruiming Zhang b, Fei Xu b, Jiemin Cheng a,⁎, Qingzhu Zhang b, Wenxing Wang b a b

College of Geography and Environment, Shandong Normal University, Jinan 250014, PR China Environment Research Institute, Shandong University, Jinan 250100, PR China

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• Nucleation mechanism of cis-pinonic acid was investigated. • cis-Pinonic acid may participate in new particle formation in the form of hydrolysate. • The hydrolysis reaction of cis-pinonic acid can be effectively catalyzed by sulfuric acid and nitric acid.

a r t i c l e

i n f o

Article history: Received 16 March 2019 Received in revised form 30 March 2019 Accepted 31 March 2019 Available online 01 April 2019 Editor: Pingqing Fu Keywords: cis-Pinonic acid Sulfuric acid New particle formation Computational study

a b s t r a c t cis-Pinonic acid (CPA), one of the major photooxidation products of α-pinene, is believed to contribute to the formation of aerosols formed over forested areas. In the current study, we implement quantum chemical calculation to investigate the interaction between sulfuric acid (SA) and CPA as well as the hydrolysate of CPA (HCPA) in the presence of water or ammonia in the atmosphere. The lowest free energy configurations, reactants, transition states, intermediates, and products were optimized at 298/278 K and 1 atm at the M06-2X/6-311+G(3df,3pd) level. Our results show that one CPA molecule might initially nucleate with SA molecules and subsequently participate in the formation and growth of the new particle in the form of HCPA. More than one HCPA molecule may be involved in the critical nuclei. Furthermore, the hydrolysis reaction of CPA can be effectively catalyzed by SA and nitric acid (NA) in presence of water, which significantly increases the HCPA content in the atmosphere and subsequently promotes the particle nucleation. Overall, the current study elucidates a new mechanism of atmospheric nucleation driven by CPA and its hydrolysate. © 2019 Published by Elsevier B.V.

1. Introduction ⁎ Corresponding authors. E-mail addresses: [email protected] (J. Cheng), [email protected] (Q. Zhang).

https://doi.org/10.1016/j.scitotenv.2019.03.479 0048-9697/© 2019 Published by Elsevier B.V.

New particle formation is one of primary sources of atmospheric aerosols, which can affect the radiative balance of the atmosphere,

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

weather, climate, atmospheric chemistry, air quality and public health (Zhang et al., 2012). The new particle formation has been frequently observed in boreal forests, coastal, rural, urban regions and the free troposphere (Kulmala et al., 2004; Kulmala et al., 2013). The underlying mechanism of the new particle formation at the molecular level remains poorly understood (Zhang et al., 2012). Previous studies indicate that sulfuric acid (SA), water and basic compounds drive the initial steps of atmospheric particle formation, however, their condensation explains only a small fraction of the atmospheric nanoparticle growth (Sipila et al., 2010; Riipinen et al., 2011; Riipinen et al., 2012; Zhang et al., 2012). Furthermore, oxidized organics are also considered to play important roles in both the formation and the growth of particles under ambient conditions (Metzger et al., 2010; Riipinen et al., 2012; Kulmala et al., 2013; Schobesberger et al., 2013). Controversial conclusions were reported regarding the roles of oxidized organics as well as the number of organic molecules involved in the formation of critical clusters (Zhang et al., 2009; Schobesberger et al., 2013; Beck and Hoffmann, 2016). Detailed understanding of the atmospheric nucleation processes containing organic molecules is therefore needed. Photochemical oxidation of monoterpenes leads to the formation of low-volatility products that likely contribute to particle nucleation in the atmosphere (Pathak et al., 2007; Ehn et al., 2012). These products can compete with each other to stabilize clusters in the atmosphere and the mechanism of their participation in new particle formation remains unclear (Riccobono et al., 2014; Bianchi et al., 2016; Kirkby et al., 2016; Trostl et al., 2016). α-Pinene is generated from coniferous vegetation and has become a research focus as a model to study the oxidation chemistry of a broad class of monoterpenes (Aljawhary et al., 2016; Mutzel et al., 2016; Elm et al., 2017; Witkowski and Gierczak, 2017). The highly oxygenated molecules produced by ozonolysis of α-pinene play a major role in ioninduced nucleation of pure organic particles in the absence of sulfuric acid (Kirkby et al., 2016). cis-Pinonic acid (CPA) is an important product of α-pinene reacting with ozone and biomass burning source (Cheng et al., 2011). Field measurements showed that CPA represents an important ingredient of nanoparticles over forests (O'Dowd et al., 2002). Molecular dynamic simulation and experimental composition analysis of nano-sized particles implied that only one CPA molecule and three to five SA molecules together with H2O molecules are in the critical nucleus for the CPA-SA-H2O system (Zhang et al., 2009). The dimer of CPA alone is unfavorable for new particle formation and growth due to its saturability and hy− drophobicity. The [(NH+ 4 )4(HSO4 )4] cluster appears to be limited to react with a single CPA molecule because of the adsorption of subsequent CPA molecules are much less energetically favorable (DePalma et al., 2015). And, the addition of 100-nm ammonium sulfate particles to the chamber under constant α-pinene ozonolysis conditions caused no significant decrease in CPA concentration (Ehn et al., 2014). Nevertheless, the work by Schobesberger et al. illustrated that one to four oxidized organic molecules that arise from the oxidation of monoterpenes participate in the initial steps of new particle formation and their growth between 1 and 2 nm in a controlled environment (Schobesberger et al., 2013). The hydrophobic nature of organic acids alone cannot explain the existence of only one CPA molecule in the critical nucleus. It is necessary to systematically study the nucleation processes including SA vapor and CPA in the presence or the absence of water. Adding a second CPA molecule to a CPA-SA dimer is difficult as the chemical groups of CPA are fully saturated except for the carboxyl functional group. Our recent theoretical calculation indicated that the hydration products of aldehydes are more likely to nucleate with SA in comparison with ammonia or aldehydes themselves (Shi et al., 2018). SA and organic acids can effectively act as catalysts in the hydration of aldehydes and ketones in the atmosphere and the corresponding hydration reactions rates of aldehydes are even

235

greater than the rates of aldehydes reacting with OH radicals at room temperature (Tong et al., 2006; Torrent-Sucarrat et al., 2012; Long et al., 2013; Hazra et al., 2014; Rypkema et al., 2015; Huang et al., 2016). The hydrolysate of CPA is a geminal diol, which is speculated to be more hygroscopic on account of its increased oxygen functionalization (Hemming and Seinfeld, 2001). Two hydroxyl groups of the geminal diol can act as either a donor or an acceptor to form hydrogen bonds, making the molecule more feasible to combine with water and other oxygenated organic compounds as a preliminary seed for oligomers capable of condensing into SOA. Hence, CPA molecules are likely to participate in the nucleation in the form of geminal diol, of which the carboxyl group undergoes hydrolysis reaction. In order to understand whether the hydrolysate of CPA (HCPA) can participate in the atmospheric nucleation and their corresponding roles in the initial steps of particle nucleation, quantum chemical calculations were performed for the molecular interactions between SA and HCPA in the presence or absence of water. NH 3 was also considered in the nucleation occurred between SA and HCPA. The formation free energies (ΔG) were determined for the reactions involving CPA molecules as well as HCPA with SA using density functional theory (DFT) by implementing a three-consecutive-step process – the Basin Hopping Monte Carlo (BHMC) (Li and Scheraga, 1987) conformational sampling, simulated annealing (Kirkpatrick et al., 1983) optimization and subsequent geometry optimization and frequency calculations. Kinetics modeling based on quantum chemistry calculations was performed using the Atmospheric Cluster Dynamics Code (ACDC) (McGrath et al., 2012) to probe the evaporation rates of the clusters. Simulations of nuclear motion dynamics of weakly bound clusters were performed to confirm the mechanism of the nucleation. Furthermore, in order to evaluate whether HCPA can be produced in the atmosphere, we investigated the hydrolytic process of CPA and the potential atmospheric impact of SA and nitric acid (NA) on the hydrolysis of CPA in the gas phase using transition state theory. 2. Computational methods To identify the lowest free energy structures, we initially utilized BHMC simulation to generate original geometries. Subsequently, the obtained configurations were optimized using simulated annealing method to produce more structures, which were subjected to systematically manual selection for the lower-energy configurations. The selected configurations were optimized at the B3LYP/6-31g(d,p) level for energy comparison. We next carried out the circulation including simulated annealing optimization and DFT calculations until the lowest-energy configurations identified from two circulations reach an energy difference of b2 kcal/mol. Finally, the most stable configurations (within 3 kcal/mol of the identified isomer) were optimized and the frequencies were calculated at the M06-2X/6-31+G(d,p) level. Their corresponding zero-point energies (ZPEs) were determined at the M06-2X/6-311 +G(3df,3pd) level. The DFT calculations were conducted with the aid of Gaussian 09 program, revision A. (Frisch et al., 2009) Both geometry optimization and frequency calculations were performed at 298 K and 1 atm. By means of the harmonic oscillator-rigid rotor approximation, Gibbs free energies of the cluster formation were computed at 278 K and 298 K. The thermodynamic data at the M06-2X/6-311++G(3df,3pd) level were applied to complete the ACDC simulations that was put forward by McGrath et al. (2012). The time-dependent cluster concentrations were derived by integrating numerically the differential equations using the ode15s solver with MATLAB (R2017a) program. A “2 × 2 box”, where 2 is the maximum number of SA or HCPA molecules in the clusters, was simulated in the current study. The formation free energies in the ACDC simulations were obtained at 278 K and 1 atm. In the ACDC

236

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

simulations, the concentrations (a value relevant to atmospheric nucleation) of SA and HCPA were set to be 106 cm−3 and 10 parts per trillion (ppt), respectively (Barsanti and Pankow, 2004; Zhang et al., 2012; Hartonen et al., 2013; Jeon et al., 2016). The molecular dynamics simulations were performed using Amber99SB force field with the GROMACS 4.5.5 package. 50 SA, 50 HCPA and 2000 water molecules were randomly placed in a box of 10 nm × 10 nm × 10 nm. Quantum chemical calculation is particularly suitable to predict the feasibility of a reaction pathway. High-accuracy molecular orbital calculations were carried out to characterize the hydrolysis of CPA catalyzed by SA and NA. The geometrical parameters of reactants, transition states, intermediates, and products were optimized at the M06-2X/631+G(d,p) level and their corresponding vibrational frequencies were computed at the same level to determine the nature of the stationary points, ZPEs, and the thermal contributions to the free energy of activation. A larger basis set, 6-311+G(3df,2p), was employed to obtain single-point energy. Each transition state was confirmed to connect the designated reactants and products by performing an intrinsic reaction coordinate (IRC) analysis.

3. Results and discussion Recent theoretical calculations showed that DFT functional M06-2X with the 6-31+G(d) and 6-311++G(3df,3pd) basis sets is reliable for predicting the structures and free energies for atmospheric prenucleation clusters (Elm et al., 2012; Bork et al., 2014a; Bork et al., 2014b). The dependability of the M06-2X level on the geometrical parameters and energies was tested in our previous studies of aldehydes atmospheric products participation in nucleation (Shi et al., 2018). Several recent studies implemented different DFT functionals (PW91, M062X and ωB97X-D) to optimize the molecular structures of clusters and calculated the final Gibbs free energies of formation by averaging the ΔG values of different DFT functionals (Elm et al., 2015; Elm et al., 2017; Myllys et al., 2017). Although this approach is efficient to reduce the errors caused by the applied theoretical methods, it does not guarantee the derived average ΔG values approaching the real values (Xie et al., 2017; Zhang et al., 2017; Shi et al., 2018). In addition, we found that the minimum energy configurations optimized by DFT functionals (PW91, M06-2X and ωB97X-D) might be different for the same cluster (Shi et al., 2018), therefore, it is unreasonable to average the ΔG values

Fig. 1. Lowest Gibbs free energy structures of clusters calculated at the M06-2X/6-31+G(d,p) level.

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

of different minimum energy configurations. Thus, in the current study, we chose to use M06-2X to assess the final minimum energies, configurations and ΔG values.

Table 2 Gibbs free energies of formation (ΔG) for clusters composed of atmospheric precursors (sulfuric acid and aldehydes products from aldol condensation) calculated at 298 K and 1 atm. Reactions

3.1. Nucleation between SA and HCPA To investigate the possibility of HCPA participating in the SA nucleation, ΔG values were calculated for the (SA)m(HCPA)n cluster (m = 0–2 and n = 0–2). The nucleation processes of SA with CPA molecules were computed to compare with those involving SA and HCPA molecules. The identified most stable configurations and the corresponding ΔG values are presented in Fig. 1 and Table 1, respectively. The (SA)(HCPA) and (SA)(CPA) clusters were selected to elucidate the potential differences in the initial steps of the particle nucleation. As shown in Fig. 1 and Table 1, both HCPA and CPA can form three hydrogen bonds with SA, however, the ΔG value of (SA) (CPA) cluster (−12.52 kcal/mol) is lower than that of (SA)(HCPA) cluster (−10.39 kcal/mol). It infers that the formation of (SA)(CPA) cluster is more energetically favored than that of (SA)(HCPA) cluster. The formation of a (SA)(CPA)2 and a (SA)(HCPA)2 cluster by adding a second CPA or HCPA molecule to a (SA)(CPA) cluster or a (SA)(HCPA) cluster have ΔG values determined as −1.00 kcal/mol and −5.96 kcal/ mol, respectively. In a (SA)(CPA) cluster, there is no vacant electrondeficient hydrogen that allows further addition of another CPA molecule, indicating the infeasibility of the formation of a (SA)(CPA)2 cluster. This is consistent with the previous studies showing that only one CPA molecule exist in the critical nucleus (Zhang et al., 2009). However, two hydroxyl groups on the same carbon of the HCPA molecule are able to donate and to receive hydrogen atoms to form hydrogen bonds with an additional SA or HCPA molecule, indicating that more than one HCPA molecule can nucleate with a SA molecule. Calculations are further performed for the (SA)(HCPA) cluster reacting with additional SA and HCPA molecules, revealing that the corresponding ΔG values range from −5.50 to −7.02 kcal/mol (Table 1). These calculation results reveal that that more than one HCPA molecule can involve in the formation of a critical nucleus. 3.2. The roles of H2O and NH3 in the nucleation Water and base such as ammonia and amines are believed to participate in the process of new particle formation by stabilizing SA molecules during the formation of initial clusters (Benson et al., 2011; Qiu and Zhang, 2013). As water in the atmosphere is abundant and omnipresent, SA, CPA, and HCPA molecules nucleating with H2O or NH3 might occur in the realistic atmosphere. Herein, calculations were performed for such nucleation reactions and the computed lowest free energy structures and ΔG values are displayed in Fig. S2 and Table 2. The calculated geometries indicate that the number of hydrogen bonds in the (SA)(CPA)(H2O) and (SA)(HCPA)2(H2O) cluster are

237

SA + H2O ⇌ (SA)(H2O) (SA)(H2O) + CPA ⇌ (SA)(CPA)(H2O) (SA)(CPA)(H2O) + CPA ⇌ (SA)(CPA)2(H2O) (SA)(H2O) + HCPA ⇌ (SA)(HCPA)(H2O) (SA)(HCPA)(H2O) + HCPA ⇌ (SA)(HCPA)2(H2O) (SA)(HCPA)(H2O) + H2O ⇌ (SA)(HCPA)(H2O)2 (SA)(H2O)2 + HCPA ⇌ (SA)(HCPA)(H2O)2 (SA)(NH3) + HCPA ⇌ (SA)(HCPA)(NH3) (SA)(HCPA) + NH3 ⇌ (SA)(HCPA)(NH3) (SA)(NH3) + CPA ⇌ (SA)(CPA)(NH3) (SA)(CPA) + NH3 ⇌ (SA)(CPA)(NH3)

ΔG (kcal/mol) −3.76 −9.92 0.75 −7.13 −6.28 −0.28 −5.36 −9.36 −6.35 −9.28 −4.15

greater than those in the (SA)(HCPA)(H2O) and (SA)(CPA)2(H2O) cluster, respectively. As listed in Table 2, the calculations suggest that the following favorability of product formation, (SA)(CPA)(H2O) (−9.92 kcal/mol) N (SA)(HCPA)(H2O) (−7.13 kcal/mol), formed from a (SA) (H2O) reacting with a CPA or a HCPA molecule. However, the formation of a (SA)(HCPA)2(H2O) cluster from a HCPA and a (SA)(HCPA)(H2O) is much favored over the formation of a (SA)(CPA)2(H2O) cluster from a CPA and a (SA)(CPA)(H2O), which have ΔG values of −6.28 kcal/mol and 0.75 kcal/mol, respectively. Further calculations were performed for reactions involving more water molecules. The Gibbs free energy associated with the formation of a (SA)(HCPA)(H2O)2 from a (SA)(H2O)2 reacting with a HCPA (−5.36 kcal/mol) is less negative than those formation of a (SA)(HCPA)(H2O) from a (SA)(H2O) and a HCPA (−7.13 kcal/mol) and the formation of a (SA)(HCPA) from a SA and a HCPA (−10.39 kcal/mol). Overall, the calculation results indicate that HCPA molecules are less likely to participate in the initial steps of nucleation with the increase of water molecules in the systems. As shown in Fig. S2, both the formation of (SA)(CPA)(NH3) and the (SA)(HCPA)(NH3) cluster involve a proton transferring from SA to NH3. Furthermore, it is more energetically feasible to form a (SA) (HCPA)(NH3) cluster from a (SA)(NH3) with a HCPA or a (SA)(HCPA) with a NH3 than to generate a (SA)(CPA)(NH3) cluster from a (SA) (NH3) with a CPA or a (SA)(CPA) with a NH3, respectively (Table 2). Overall, our calculations illustrate that HCPA molecules are possible to participate in the initial steps of new particle formation and growth in the presence of water or ammonia.

Table 1 Gibbs free energies of formation (ΔG) for clusters composed of atmospheric precursors (sulfuric acid, other common nucleation candidates and aldehydes) calculated at 298 K and 1 atm. Reactions SA + NH3 ⇌ (SA)(NH3) SA + HOOC(CH2)2COOH ⇌ (SA)(HOOC(CH2)2COOH) SA + CPA ⇌ (SA)(CPA) (SA)(CPA) + CPA ⇌ (SA)(CPA)2 CPA + CPA ⇌ (CPA)2 SA + HCPA ⇌ (SA)(HCPA) SA + SA ⇌ (SA)2 (SA)(HCPA) + SA ⇌ (SA)2(HCPA) (SA)(HCPA) + HCPA ⇌ (SA)(HCPA)2 (SA)(HCPA)2 + SA ⇌ (SA)2(HCPA)2 (SA)2(HCPA) + HCPA ⇌ (SA)2(HCPA)2

ΔG (kcal/mol) −7.38 −11.33 −12.52 −1.00 −8.37 −10.39 −10.21 −7.02 −5.96 −6.56 −5.50

Fig. 2. Calculated evaporation rates of (SA)m(HCPA)n on the SA–HCPA grid at 278 K.

238

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

3.3. ACDC modeling of the (SA)m(HCPA)n evaporation rates We employed ACDC to obtain the evaporation rates of the initially sectional (SA)m(HCPA)n (m = 1–2 and n = 1–2) clusters and (SA)2 (HCPA)2 was treated as the maximal cluster in consideration of the computation cost. The evaporation rates for (SA)m(HCPA)n on the SAHCPA grid at 278 K are presented in Fig. 2. The evaporation rates are on the order of 10 s−1 for the clusters (SA)(HCPA) and (SA)2 and on the order of 104 s−1 for the clusters (SA)2(HCPA) and (SA)(HCPA)2, implying that HCPA molecules have significant impact on the stability of SA. However, the evaporation rates of the (SA)m(HCPA)n clusters are

still slightly higher than those of amine or other organics (Elm et al., 2017; Xie et al., 2017). Moreover, the HCPA dimer is more volatile in comparison with the SA dimer or (SA)(HCPA). The fact that the dimers of organic acids alone are unfavorable for new particle formation is also observed experimentally by another study (Zhang et al., 2009). 3.4. Molecular dynamic simulation of nucleation The snapshots of the SA-HCPA-H2O system at different simulation times are shown in Fig. 3. In order to explicitly display the distribution of SA and HCPA, we did not highlight the water molecules in the

Fig. 3. The distribution of molecules in a system consisting of 50 HCPA, 50 SA, and 2000 water molecules at different simulation times.

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

3.5. The hydrolysis of CPA SA and organic acid exert catalysis in the gas-phase hydrolysis of formaldehyde, glyoxal, alkyl formate and ketene occurring at the temperature range 200–298 K (Noziere and Riemer, 2003; Jogunola et al., 2010; Torrent-Sucarrat et al., 2012; Long et al., 2013; Hazra et al., 2014; Louie et al., 2015). The efficiency of water molecules catalyzing this gas-phase hydrolysis is negligible according to the previous studies (Hazra et al., 2013; Long et al., 2013). In order to understand the generation of HCPA in the atmosphere, we performed calculations to characterize the hydrolysis process of CPA under the catalysis of SA and NA. The profiles of the potential energy surfaces were investigated in detail. In the SA or NA assisted reactions, the simultaneous collision of three molecules is extremely improbable, thus, it is most likely that one reactant firstly forms a complex with water followed by the reaction with another reactant. In this work, we investigate the SA⋯H2O or NA⋯H2O complexes reacting with one CPA molecule. The possible mechanism is as follows: SA þ H2 O→SA⋯H2 O

ð1Þ

SA⋯H2 O þ CPA→Products

ð2Þ

4. Conclusions DFT methods were implemented to characterize the mechanism of CPA and HCPA reacting with SA to form clusters in the atmospheric particle generation process and the possibility of HCPA existing in the atmosphere. Geometries and ΔG values were calculated at 298 K (or 278 K) and 1 atm. This study elucidates a significant mechanism for the new particle formation involving partial monoterpenes oxidation products containing carbonyl groups from forests. The thermodynamics and dynamics analysis reveal that more than one HCPA molecule likely participate in the formation of critical nuclei and contribute to particle growth by stabilizing SA. Combining with our previous study (Shi et al., 2018), the current study infers that geminal diols generated from carbonyl compounds contribute to atmospheric particles formation and growth. The molecular dynamic simulation also indicates that HCPA can form stable complexes with pure SA molecules in the presence of water. Besides participating in the new particle formation, SA also catalyzes the hydrolysis of CPA to produce HCPA, which further promotes the nucleation. In conclusion, one or two SA molecules may create a critical nucleus with the aid of HCPA molecules and other vapors. The evaporation rates for clusters including HCPA in our study are not low enough compared with those of amine and some other

E

snapshots. At t = 0 ps, SA and HCPA are scattered and are not subject to accumulation. At t = 250 ps, SA and HCPA show a trend towards convergence. The nucleation between SA and HCPA becomes more evident with simulation time increasing. After 4000 ps, SA and HCPA form a stable cluster larger than 3 nm in diameter and the water molecules are mainly distributed on the periphery of this cluster. As displayed in these snapshots, both SA and HCPA are evenly distributed in the nucleation process. Furthermore, the phenomenon is not observed that multiple SA and one HCPA reacting with water molecules to form the critical nucleus. As reported by the previous APi-TOF measurements, the case that pure SA clustered with more than four molecules in the presence of water is nearly nonexistent (Riccobono et al., 2014; Bianchi et al., 2016). The clusters of critical nuclear scales are formed by multiple SA and more than one HCPA with water molecules in our molecular dynamic simulation, which is consistent with the above thermodynamic analysis. Furthermore, these clusters undergo subsequent growth by coagulating with additional SA, HCPA and water molecules.

239

NA þ H2 O→HNO3 ⋯H2 O

ð3Þ

NA⋯H2 O þ CPA→Products

ð4Þ

The energy profiles in the presence or absence of SA and NA are displayed in Fig. 4 and the corresponding geometrical configurations of the transition states are listed in Fig. S3. In the eight-membered transition state (TS2 and TS3), SA (or NA) and water both act as the hydrogen donor and acceptor. A hydrogen atom of the water is transferred to the SA while a hydrogen atom of SA or NA is transferred to the CPA, yielding (SA)(HCPA) and (NA)(HCPA) complexes as the primary products. Hence, SA and NA molecule in the final product are not the original ones. The most noteworthy differences are the potential barriers of TS2 and TS3 in comparison with that of TS1. With the existence of SA, the potential barrier of the CPA hydrolysis is decreased from 37.35 kcal/mol to 4.18 kcal/mol. Similarly, the activation energies of hydrolysis reaction are decreased for NA. It implies that the catalysis of SA and NA on the CPA hydrolysis could greatly increase the content of HCPA in the atmosphere. The CPA molecule, as an organic acid, may also catalyze its hydrolysis by the participation of a second CPA molecule.

E

or

Fig. 4. The schematic energy profiles of the CPA hydrolysis catalyzed by SA and NA. ΔH is calculated at 0 K.

240

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241

organics, inferring that other stabilizing compounds such as water, ammonium salt, and organic salt are likely involved in the process of nucleation with SA. In addition, the hydrolysis of CPA is a reversible process and its hydrolysate is unstable. Thus, it remains unclear that how long HCPA molecules can exist in the clusters containing SA. Future studies are needed to elucidate the contribution of HCPA molecules in the atmosphere to the nucleation under conditions with different humidity levels and the corresponding nucleation mechanisms in the presence of other vapors. And, the importance of this pathway in the atmosphere compared with all the other competing processes (such as nucleation from sulfuric acid and ammonia, sulfuric acid assisted nucleation of highly oxygenated molecules, and condensation of pinonic acid onto existing organic particles) requires further study. Acknowledgment The work is financially supported by China Postdoctoral Science Foundation (No. 2018M640651), NSFC (National Natural Science Foundation of China, project Nos. 21337001, 21677089, 21477066), Open Foundation of State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences (No. SKLECRA2016OFP09) and Fundamental Research Funds of Shandong University (project Nos. 2017JC033, 2016WLJH51). We thank Jonas Elm et al. for providing us with the Atmospheric Cluster Dynamics Code (ACDC). Appendix A. Supplementary data Gibbs free energies, minimum-energy structures and their Cartesian coordinates calculated using M06-2X/6-311+G(3df,3pd) are available. The material is available free of charge via the Internet at http://www. elsevier.com/. Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2019.03.479. References Aljawhary, D., Zhao, R., Lee, A.K., Wang, C., Abbatt, J.P., 2016. Kinetics, mechanism, and secondary organic aerosol yield of aqueous phase photo-oxidation of alpha-pinene oxidation products. J. Phys. Chem. A 120, 1395–1407. Barsanti, K.C., Pankow, J.F., 2004. Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—part 1: aldehydes and ketones. Atmos. Environ. 38, 4371–4382. Beck, M., Hoffmann, T., 2016. A detailed MS n study for the molecular identification of a dimer formed from oxidation of pinene. Atmos. Environ. 130, 120–126. Benson, D.R., Yu, J.H., Markovich, A., Lee, S.H., 2011. Ternary homogeneous nucleation of H2SO4, NH3, and H2O under conditions relevant to the lower troposphere. Atmos. Chem. Phys. 11, 4755–4766. Bianchi, F., Trostl, J., Junninen, H., Frege, C., Henne, S., Hoyle, C.R., Molteni, U., Herrmann, E., Adamov, A., Bukowiecki, N., Chen, X., Duplissy, J., Gysel, M., Hutterli, M., Kangasluoma, J., Kontkanen, J., Kuerten, A., Manninen, H.E., Muench, S., Perakyla, O., Petaja, T., Rondo, L., Williamson, C., Weingartner, E., Curtius, J., Worsnop, D.R., Kulmala, M., Dommen, J., Baltensperger, U., 2016. New particle formation in the free troposphere: a question of chemistry and timing. Science 352, 1109–1112. Bork, N., Du, L., Kjaergaard, H.G., 2014a. Identification and characterization of the HCIDMS gas phase molecular complex via infrared spectroscopy and electronic structure calculations. J. Phys. Chem. A 118, 1384–1389. Bork, N., Du, L., Reiman, H., Kurten, T., Kjaergaard, H.G., 2014b. Benchmarking ab initio binding energies of hydrogen-bonded molecular clusters based on FTIR spectroscopy. J. Phys. Chem. A 118, 5316–5322. Cheng, Y., Brook, J.R., Li, S.-M., Leithead, A., 2011. Seasonal variation in the biogenic secondary organic aerosol tracer cis-pinonic acid: enhancement due to emissions from regional and local biomass burning. Atmos. Environ. 45, 7105–7112. DePalma, J.W., Wang, J., Wexler, A.S., Johnston, M.V., 2015. Growth of ammonium bisulfate clusters by adsorption of oxygenated organic molecules. J. Phys. Chem. A 119, 11191–11198. Ehn, M., Kleist, E., Junninen, H., Petäjä, T., Lönn, G., Schobesberger, S., Dal Maso, M., Trimborn, A., Kulmala, M., Worsnop, D.R., Wahner, A., Wildt, J., Mentel, T.F., 2012. Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air. Atmos. Chem. Phys. 12, 5113–5127. Ehn, M., Thornton, J.A., Kleist, E., Sipila, M., Junninen, H., Pullinen, I., Springer, M., Rubach, F., Tillmann, R., Lee, B., Lopez-Hilfiker, F., Andres, S., Acir, I.H., Rissanen, M., Jokinen, T., Schobesberger, S., Kangasluoma, J., Kontkanen, J., Nieminen, T., Kurten, T., Nielsen, L.B., Jorgensen, S., Kjaergaard, H.G., Canagaratna, M., Maso, M.D., Berndt, T., Petaja, T., Wahner, A., Kerminen, V.M., Kulmala, M., Worsnop, D.R., Wildt, J., Mentel, T.F., 2014. A large source of low-volatility secondary organic aerosol. Nature 506, 476–479.

Elm, J., Bilde, M., Mikkelsen, K.V., 2012. Assessment of density functional theory in predicting structures and free energies of reaction of atmospheric prenucleation clusters. J. Chem. Theory Comput. 8, 2071–2077. Elm, J., Myllys, N., Hyttinen, N., Kurten, T., 2015. Computational study of the clustering of a cyclohexene autoxidation product C6H8O7 with itself and sulfuric acid. J. Phys. Chem. A 119, 8414–8421. Elm, J., Myllys, N., Olenius, T., Halonen, R., Kurten, T., Vehkamaki, H., 2017. Formation of atmospheric molecular clusters consisting of sulfuric acid and C8H12O6 tricarboxylic acid. Phys. Chem. Chem. Phys. 19, 4877–4886. Frisch, M., Trucks, G., Schlegel, H.B., Scuseria, G., Robb, M., Cheeseman, J., Scalmani, G., Barone, V., Mennucci, B., Petersson, G.A., 2009. Gaussian 09, Revision A. 02. Gaussian. Inc. Hartonen, K., Parshintsev, J., Vilja, V.-P., Tiala, H., Knuuti, S., Lai, C.K., Riekkola, M.-L., 2013. Gas chromatographic vapor pressure determination of atmospherically relevant oxidation products of β-caryophyllene and α-pinene. Atmos. Environ. 81, 330–338. Hazra, M.K., Francisco, J.S., Sinha, A., 2013. Gas phase hydrolysis of formaldehyde to form methanediol: impact of formic acid catalysis. J. Phys. Chem. A 117, 11704–11710. Hazra, M.K., Francisco, J.S., Sinha, A., 2014. Hydrolysis of glyoxal in water-restricted environments: formation of organic aerosol precursors through formic acid catalysis. J. Phys. Chem. A 118, 4095–4105. Hemming, B.L., Seinfeld, J.H., 2001. On the hygroscopic behavior of atmospheric organic aerosols. Ind. Eng. Chem. Res. 40, 4162–4171. Huang, M.-q., Cai, S.-y., Liao, Y.-m., Zhao, W.-x., Hu, C.-j., Wang, Z.-y., Zhang, W.-j., 2016. Theoretical studies on mechanism and rate constant of gas phase hydrolysis of glyoxal catalyzed by sulfuric acid. Chin. J. Chem. Phys. 29, 335–343. Jeon, S.H., Lee, J.Y., Jung, C.H., Kim, Y.P., 2016. Seasonal variation of the concentrations of pinic acid and cis-pinonic acid in the atmosphere over Seoul. J. Korea. Soc. Atmos. Environ. 32, 208–215. Jogunola, O., Salmi, T., Eranen, M., Mikkola, J.P., 2010. Qualitative treatment of catalytic hydrolysis of alkyl formates. Appl. Catal. A Gen. 384, 36–44. Kirkby, J., Duplissy, J., Sengupta, K., Frege, C., Gordon, H., Williamson, C., Heinritzi, M., Simon, M., Yan, C., Almeida, J., Trostl, J., Nieminen, T., Ortega, I.K., Wagner, R., Adamov, A., Amorim, A., Bernhammer, A.K., Bianchi, F., Breitenlechner, M., Brilke, S., Chen, X., Craven, J., Dias, A., Ehrhart, S., Flagan, R.C., Franchin, A., Fuchs, C., Guida, R., Hakala, J., Hoyle, C.R., Jokinen, T., Junninen, H., Kangasluoma, J., Kim, J., Krapf, M., Kurten, A., Laaksonen, A., Lehtipalo, K., Makhmutov, V., Mathot, S., Molteni, U., Onnela, A., Perakyla, O., Piel, F., Petaja, T., Praplan, A.P., Pringle, K., Rap, A., Richards, N.A., Riipinen, I., Rissanen, M.P., Rondo, L., Sarnela, N., Schobesberger, S., Scott, C.E., Seinfeld, J.H., Sipila, M., Steiner, G., Stozhkov, Y., Stratmann, F., Tome, A., Virtanen, A., Vogel, A.L., Wagner, A.C., Wagner, P.E., Weingartner, E., Wimmer, D., Winkler, P.M., Ye, P., Zhang, X., Hansel, A., Dommen, J., Donahue, N.M., Worsnop, D.R., Baltensperger, U., Kulmala, M., Carslaw, K.S., Curtius, J., 2016. Ion-induced nucleation of pure biogenic particles. Nature 533, 521–526. Kirkpatrick, S., Gelatt, C.D., Vecchi, M.P., 1983. Optimization by simulated annealing. 220, 671–680. Kulmala, M., Vehkamäki, H., Petäjä, T., Dal Maso, M., Lauri, A., Kerminen, V.M., Birmili, W., McMurry, P.H., 2004. Formation and growth rates of ultrafine atmospheric particles: a review of observations. J. Aerosol Sci. 35, 143–176. Kulmala, M., Kontkanen, J., Junninen, H., Lehtipalo, K., Manninen, H.E., Nieminen, T., Petaja, T., Sipila, M., Schobesberger, S., Rantala, P., Franchin, A., Jokinen, T., Jarvinen, E., Aijala, M., Kangasluoma, J., Hakala, J., Aalto, P.P., Paasonen, P., Mikkila, J., Vanhanen, J., Aalto, J., Hakola, H., Makkonen, U., Ruuskanen, T., Mauldin 3rd, R.L., Duplissy, J., Vehkamaki, H., Back, J., Kortelainen, A., Riipinen, I., Kurten, T., Johnston, M.V., Smith, J.N., Ehn, M., Mentel, T.F., Lehtinen, K.E., Laaksonen, A., Kerminen, V.M., Worsnop, D.R., 2013. Direct observations of atmospheric aerosol nucleation. Science 339, 943–946. Li, Z.Q., Scheraga, H.A., 1987. Monte-Carlo-minimization approach to the multipleminima problem in protein folding. Proc. Natl. Acad. Sci. U. S. A. 84, 6611–6615. Long, B., Tan, X.F., Chang, C.R., Zhao, W.X., Long, Z.W., Ren, D.S., Zhang, W.J., 2013. Theoretical studies on gas-phase reactions of sulfuric acid catalyzed hydrolysis of formaldehyde and formaldehyde with sulfuric acid and H2SO4⋯H2O complex. J. Phys. Chem. A 117, 5106–5116. Louie, M.K., Francisco, J.S., Verdicchio, M., Klippenstein, S.J., Sinha, A., 2015. Hydrolysis of ketene catalyzed by formic acid: modification of reaction mechanism, energetics, and kinetics with organic acid catalysis. J. Phys. Chem. A 119, 4347–4357. McGrath, M.J., Olenius, T., Ortega, I.K., Loukonen, V., Paasonen, P., Kurtén, T., Kulmala, M., Vehkamäki, H., 2012. Atmospheric cluster dynamics code: a flexible method for solution of the birth-death equations. Atmos. Chem. Phys. 12, 2345–2355. Metzger, A., Verheggen, B., Dommen, J., Duplissy, J., Prevot, A.S.H., Weingartner, E., Riipinen, I., Kulmala, M., Spracklen, D.V., Carslaw, K.S., Baltensperger, U., 2010. Evidence for the role of organics in aerosol particle formation under atmospheric conditions. Proc. Natl. Acad. Sci. U. S. A. 107, 6646–6651. Mutzel, A., Rodigast, M., Iinuma, Y., Böge, O., Herrmann, H., 2016. Monoterpene SOA– contribution of first-generation oxidation products to formation and chemical composition. Atmos. Environ. 130, 136–144. Myllys, N., Olenius, T., Kurten, T., Vehkamaki, H., Riipinen, I., Elm, J., 2017. Effect of bisulfate, ammonia, and ammonium on the clustering of organic acids and sulfuric acid. J. Phys. Chem. A 121, 4812–4824. Noziere, B., Riemer, D.D., 2003. The chemical processing of gas-phase carbonyl compounds by sulfuric acid aerosols-2,4-pentanedione. Atmos. Environ. 37, 841–851. O'Dowd, C.D., Aalto, P., Hmeri, K., Kulmala, M., Hoffmann, T., 2002. Aerosol formation: atmospheric particles from organic vapours. Nature 416, 497–498. Pathak, R.K., Stanier, C.O., Donahue, N.M., Pandis, S.N., 2007. Ozonolysis of α-pinene at atmospherically relevant concentrations: temperature dependence of aerosol mass fractions (yields). J. Geophys. Res. 112.

X. Shi et al. / Science of the Total Environment 674 (2019) 234–241 Qiu, C., Zhang, R., 2013. Multiphase chemistry of atmospheric amines. Phys. Chem. Chem. Phys. 15, 5738–5752. Riccobono, F., Schobesberger, S., Scott, C.E., Dommen, J., Ortega, I.K., Rondo, L., Almeida, J., Amorim, A., Bianchi, F., Breitenlechner, M., David, A., Downard, A., Dunne, E.M., Duplissy, J., Ehrhart, S., Flagan, R.C., Franchin, A., Hansel, A., Junninen, H., Kajos, M., Keskinen, H., Kupc, A., Kurten, A., Kvashin, A.N., Laaksonen, A., Lehtipalo, K., Makhmutov, V., Mathot, S., Nieminen, T., Onnela, A., Petaja, T., Praplan, A.P., Santos, F.D., Schallhart, S., Seinfeld, J.H., Sipila, M., Spracklen, D.V., Stozhkov, Y., Stratmann, F., Tome, A., Tsagkogeorgas, G., Vaattovaara, P., Viisanen, Y., Vrtala, A., Wagner, P.E., Weingartner, E., Wex, H., Wimmer, D., Carslaw, K.S., Curtius, J., Donahue, N.M., Kirkby, J., Kulmala, M., Worsnop, D.R., Baltensperger, U., 2014. Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles. Science 344, 717–721. Riipinen, I., Pierce, J.R., Yli-Juuti, T., Nieminen, T., Häkkinen, S., Ehn, M., Junninen, H., Lehtipalo, K., Petäjä, T., Slowik, J., Chang, R., Shantz, N.C., Abbatt, J., Leaitch, W.R., Kerminen, V.M., Worsnop, D.R., Pandis, S.N., Donahue, N.M., Kulmala, M., 2011. Organic condensation: a vital link connecting aerosol formation to cloud condensation nuclei (CCN) concentrations. Atmos. Chem. Phys. 11, 3865–3878. Riipinen, I., Yli-Juuti, T., Pierce, J.R., Petäjä, T., Worsnop, D.R., Kulmala, M., Donahue, N.M., 2012. The contribution of organics to atmospheric nanoparticle growth. Nat. Geosci. 5, 453–458. Rypkema, H.A., Sinha, A., Francisco, J.S., 2015. Carboxylic acid catalyzed hydration of acetaldehyde. J. Phys. Chem. A 119, 4581–4588. Schobesberger, S., Junninen, H., Bianchi, F., Lonn, G., Ehn, M., Lehtipalo, K., Dommen, J., Ehrhart, S., Ortega, I.K., Franchin, A., Nieminen, T., Riccobono, F., Hutterli, M., Duplissy, J., Almeida, J., Amorim, A., Breitenlechner, M., Downard, A.J., Dunne, E.M., Flagan, R.C., Kajos, M., Keskinen, H., Kirkby, J., Kupc, A., Kurten, A., Kurten, T., Laaksonen, A., Mathot, S., Onnela, A., Praplan, A.P., Rondo, L., Santos, F.D., Schallhart, S., Schnitzhofer, R., Sipila, M., Tome, A., Tsagkogeorgas, G., Vehkamaki, H., Wimmer, D., Baltensperger, U., Carslaw, K.S., Curtius, J., Hansel, A., Petaja, T., Kulmala, M., Donahue, N.M., Worsnop, D.R., 2013. Molecular understanding of atmospheric particle formation from sulfuric acid and large oxidized organic molecules. Proc. Natl. Acad. Sci. U. S. A. 110, 17223–17228. Shi, X., Zhang, R., Sun, Y., Xu, F., Zhang, Q., Wang, W., 2018. A density functional theory study of aldehydes and their atmospheric products participating in nucleation. Phys. Chem. Chem. Phys. 20, 1005–1011.

241

Sipila, M., Berndt, T., Petaja, T., Brus, D., Vanhanen, J., Stratmann, F., Patokoski, J., Mauldin 3rd, R.L., Hyvarinen, A.P., Lihavainen, H., Kulmala, M., 2010. The role of sulfuric acid in atmospheric nucleation. Science 327, 1243–1246. Tong, C., Blanco, M., Goddard, W.A., Seinfeld, J.H., 2006. Secondary organic aerosol formation by heterogeneous reactions of aldehydes and ketones: a quantum mechanical study. Environ. Sci. Technol. 40, 2333–2338. Torrent-Sucarrat, M., Francisco, J.S., Anglada, J.M., 2012. Sulfuric acid as autocatalyst in the formation of sulfuric acid. J. Am. Chem. Soc. 134, 20632–20644. Trostl, J., Chuang, W.K., Gordon, H., Heinritzi, M., Yan, C., Molteni, U., Ahlm, L., Frege, C., Bianchi, F., Wagner, R., Simon, M., Lehtipalo, K., Williamson, C., Craven, J.S., Duplissy, J., Adamov, A., Almeida, J., Bernhammer, A.K., Breitenlechner, M., Brilke, S., Dias, A., Ehrhart, S., Flagan, R.C., Franchin, A., Fuchs, C., Guida, R., Gysel, M., Hansel, A., Hoyle, C.R., Jokinen, T., Junninen, H., Kangasluoma, J., Keskinen, H., Kim, J., Krapf, M., Kurten, A., Laaksonen, A., Lawler, M., Leiminger, M., Mathot, S., Mohler, O., Nieminen, T., Onnela, A., Petaja, T., Piel, F.M., Miettinen, P., Rissanen, M.P., Rondo, L., Sarnela, N., Schobesberger, S., Sengupta, K., Sipila, M., Smith, J.N., Steiner, G., Tome, A., Virtanen, A., Wagner, A.C., Weingartner, E., Wimmer, D., Winkler, P.M., Ye, P., Carslaw, K.S., Curtius, J., Dommen, J., Kirkby, J., Kulmala, M., Riipinen, I., Worsnop, D.R., Donahue, N.M., Baltensperger, U., 2016. The role of low-volatility organic compounds in initial particle growth in the atmosphere. Nature 533, 527–531. Witkowski, B., Gierczak, T., 2017. cis-Pinonic acid oxidation by hydroxyl radicals in the aqueous phase under acidic and basic conditions: kinetics and mechanism. Environ. Sci. Technol. 51, 9765–9773. Xie, H.B., Elm, J., Halonen, R., Myllys, N., Kurten, T., Kulmala, M., Vehkamaki, H., 2017. Atmospheric fate of monoethanolamine: enhancing new particle formation of sulfuric acid as an important removal process. Environ. Sci. Technol. 51, 8422–8431. Zhang, R., Wang, L., Khalizov, A.F., Zhao, J., Zheng, J., McGraw, R.L., Molina, L.T., 2009. Formation of nanoparticles of blue haze enhanced by anthropogenic pollution. Proc. Natl. Acad. Sci. U. S. A. 106, 17650–17654. Zhang, R., Khalizov, A., Wang, L., Hu, M., Xu, W., 2012. Nucleation and growth of nanoparticles in the atmosphere. Chem. Rev. 112, 1957–2011. Zhang, H., Kupiainen-Määttä, O., Zhang, X., Molinero, V., Zhang, Y., Li, Z., 2017. The enhancement mechanism of glycolic acid on the formation of atmospheric sulfuric acid–ammonia molecular clusters. J. Chem. Phys. 146, 184308.