Temperature effect on phase state and reactivity controls atmospheric multiphase chemistry and transport of PAHs

Mu, Qing; Shiraiwa, Manabu; Octaviani, Mega; Ma, Nan; Ding, Aijun; Su, Hang; Lammel, Gerhard; Pöschl, Ulrich; Cheng, Yafang

doi:10.1126/sciadv.aap7314

Cited by 139 publications

(164 citation statements)

References 66 publications

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“…Moreover, the phase separation has been observed in organic particles mixed with inorganic salts (You et al, 2014) and even without inorganic salts (Pöhlker et al, 2012;Riedel et al, 2016). Future simulations on equilibration timescales should consider the effects of the immiscibility Liu et al, 2013) and the phase separation (Shiraiwa et al, 2013b;Pye et al, 2017;Fowler et al, 2018) as well as composition-dependent bulk diffusivity (O'Meara et al, 2016) and the evolution of the particle phase due to reactive uptake and condensed-phase chemistry (Hosny et al, 2016). Incorporation of the particle-phase formation of oligomers and other multifunctional high molar mass compounds can lead to a reduced bulk diffusivity (Pfrang et al, 2011;Hosny et al, 2016), which may prolong the equilibration timescales.…”

Section: Discussionmentioning

confidence: 99%

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Liu

Shiraiwa

2019

Atmos. Chem. Phys.

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Secondary organic aerosols (SOA) account for a substantial fraction of air particulate matter, and SOA formation is often modeled assuming rapid establishment of gas-particle equilibrium. Here, we estimate the characteristic timescale for SOA to achieve gas-particle equilibrium under a wide range of temperatures and relative humidities using a state-of-the-art kinetic flux model. Equilibration timescales were calculated by varying particle phase state, size, mass loadings, and volatility of organic compounds in open and closed systems. Model simulations suggest that the equilibration timescale for semi-volatile compounds is on the order of seconds or minutes for most conditions in the planetary boundary layer, but it can be longer than 1 h if particles adopt glassy or amorphous solid states with high glass transition temperatures at low relative humidity. In the free troposphere with lower temperatures, it can be longer than hours or days, even at moderate or relatively high relative humidities due to kinetic limitations of bulk diffusion in highly viscous particles. The timescale of partitioning of low-volatile compounds into highly viscous particles is shorter compared to semi-volatile compounds in the closed system, as it is largely determined by condensation sink due to very slow re-evaporation with relatively quick establishment of local equilibrium between the gas phase and the near-surface bulk. The dependence of equilibration timescales on both volatility and bulk diffusivity provides critical insights into thermodynamic or kinetic treatments of SOA partitioning for accurate predictions of gas-and particle-phase concentrations of semi-volatile compounds in regional and global chemical transport models.

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Section: Discussionmentioning

confidence: 99%

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Liu

Shiraiwa

2019

Atmos. Chem. Phys.

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“…Figure 4c shows that the daytime O 3 concentrations after APEC are significantly smaller than those during APEC, indicating a weakened contribution from photochemistry after APEC. The increased amount of coating materials of BC observed after APEC compared to that during APEC was mostly likely attributed to enhanced other reactions (e.g., heterogeneous chemistry) during haze episodes (Xie et al, 2015;Yang et al, 2015;Zheng et al, 2015;Mu et al, 2018). Figure 5a2 shows that the variation in the reduction in the m NR−CM /m rBC ratio of BC-containing particles during APEC compared to that after APEC is poorly correlated with the O 3 concentration.…”

Section: Reductions In the Aging Degree Of Bcmentioning

confidence: 97%

Reduction in black carbon light absorption due to multi-pollutant emission control during APEC China 2014

Zhang

et al. 2018

Atmos. Chem. Phys.

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Abstract. Reducing black carbon (BC) emissions has been recognized as an efficient way to simultaneously improve air quality and mitigate climate change. However, the benefits of BC emission controls are not well quantified, partly due to a lack of understanding of the changes in BC light absorption as a result of emission reductions. In this work, we discuss the effects of multi-pollutant emission reductions on BC light absorption based on a field campaign study conducted before, during and after the 2014 APEC (Asia-Pacific Economic Cooperation) meeting in Beijing, China. When emission restrictions were in place during APEC, we found that the reduction in the light absorption of BC-containing particles was driven by both the decrease in BC mass concentration and the weakened light-absorption capability of BC. Compared with that before and after APEC, the daytime light absorption of BC-containing particles during APEC was reduced by ∼ 56 %, of which ∼ 48% was contributed by the decrease in BC mass concentration and the remaining ∼ 8 % was contributed by a weakening of light-absorption capability for BC. Based on single-particle soot photometer (SP2) measurements and Mie calculations, we estimated that the light-absorption capability of BC-containing particles with ∼ 80-200 nm refractory BC (rBC) cores in daytime during APEC was reduced by ∼ 6-15 % and ∼ 10-20 % compared with those before and after APEC, respectively. The decrease in BC light-absorption capability could be attributed to less coating material on BC surfaces as a result of the decreased chemical production of secondary aerosols. Compared with that before and after APEC, the mass ratio between the coating materials and rBC core (∼ 80-200 nm) during APEC decreased by ∼ 10-30 % and ∼ 31-53 %, respectively, due to reductions in coating precursor emissions, e.g., SO 2 and NO 2 . The results reveal the benefits of emission control on BC light absorption by simultaneously reducing the mass concentration and light-absorption capability of BC, implying that synergetic reduction in multiple-pollutant emissions could benefit both air quality and climate.

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“…Note that this relation is not accurate for predicting the bulk diffusivity of water and small molecules and it may also underestimate the diffusivity of organic molecules in a highly viscous matrix by a few orders of magnitudes (Champion et al, 2000;Shiraiwa et al, 2011;Power et al, 2013;Marshall et al, 2016;Bastelberger et al, 2017;Reid et al, 2018). The particle phase state, viscosity, and bulk diffusivity have been shown to affect the gas uptake and chemical transformation of organic compounds due to the kinetic limitations of bulk diffusion Abbatt et al, 2012;Zhou et al, 2013;Slade and Knopf, 2014;Arangio et al, 2015;Davies and Wilson, 2015;Wang et al, 2015;Berkemeier et al, 2016;Marshall et al, 2016;Liu et al, 2018;Pratap et al, 2018;Zhang et al, 2018), which may facilitate the long-range transport of organic compounds embedded in viscous or glassy particles (Shrivastava et al, 2017b;Mu et al, 2018). Molecular motion can be hindered in a highly viscous matrix, slowing down photochemical reactions in particles (Lignell et al, 2014;Hinks et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

et al. 2018

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Abstract. Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (T g ). We have recently developed a method to estimate T g of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol −1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol −1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the T g -scaled Arrhenius plot of fragility (viscosity vs. T g /T ) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon-Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of T g , D, the hygroscopicity parameter (κ), and the Gordon-Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2-5 orders of magnitude. Complementary measurements of viscosity and chemical composition are desired to further constrain RH-dependent viscosity in future studies.

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Temperature effect on phase state and reactivity controls atmospheric multiphase chemistry and transport of PAHs

Abstract: Atmospheric refrigerator increases the global transport and health risks of carcinogenic PAHs.

Cited by 139 publications

References 66 publications

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Reduction in black carbon light absorption due to multi-pollutant emission control during APEC China 2014

Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

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