Global long-range transport and lung cancer risk from polycyclic aromatic hydrocarbons shielded by coatings of organic aerosol

Shrivastava, Manish; Lou, Sijia; Zelenyuk, Alla; Easter, Richard C.; Corley, Richard A.; Thrall, Brian D.; Rasch, Philip J.; Fast, Jerome D.; Simonich, Staci L. Massey; Shen, Huizhong; Tao, Shu

doi:10.1073/pnas.1618475114

Cited by 215 publications

(254 citation statements)

References 54 publications

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“…Further, they could disable or reduce the aerosol-induced transport of certain species, which cannot be taken up by particles after becoming highly viscous, or, conversely, enable or enhance the aerosol-induced transport of species, which were locked in before becoming highly viscous. Zelenyuk et al (2012) and Shrivastava et al (2017) suggested that long-range transport of PAHs trapped in highly viscous SOA may contribute to unexpectedly high particle-bound PAH concentrations in remote regions. In addition, there have been suggestions that PAHs may be trapped irreversibly within the soot matrix (Fernández et al, 2002), but we do not further discuss this mechanism here.…”

Section: Atmospheric Outlookmentioning

confidence: 99%

“…Unlike biogenic films, for which no RH threshold was observed, anthropogenic films exhibited increased evaporation rates above RH ∼ 20-30 %. Diffusion limitations for oxidants and organic molecules could also lead to the trapping of VOCs, such as harmful polycyclic aromatic hydrocarbons (PAHs) in the aerosol phase and protect them from oxidation, thereby facilitating their long-range transport (Shrivastava et al, 2017). In a study of evaporation rates, Abramson et al (2013) estimated the condensed-phase diffusivity (D c ) of pyrene, a PAH, contained in freshly produced α-pinene SOA as D c = 2.5×10 −17 cm 2 s −1 .…”

Section: Introductionmentioning

confidence: 99%

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Diffusivity measurements of volatile organics in levitated viscous aerosol particles

et al. 2017

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Abstract. Field measurements indicating that atmospheric secondary organic aerosol (SOA) particles can be present in a highly viscous, glassy state have spurred numerous studies addressing low diffusivities of water in glassy aerosols. The focus of these studies is on kinetic limitations of hygroscopic growth and the plasticizing effect of water. In contrast, much less is known about diffusion limitations of organic molecules and oxidants in viscous matrices. These may affect atmospheric chemistry and gas-particle partitioning of complex mixtures with constituents of different volatility. In this study, we quantify the diffusivity of a volatile organic in a viscous matrix. Evaporation of single particles generated from an aqueous solution of sucrose and small amounts of volatile tetraethylene glycol (PEG-4) is investigated in an electrodynamic balance at controlled relative humidity (RH) and temperature. The evaporative loss of PEG-4 as determined by Mie resonance spectroscopy is used in conjunction with a radially resolved diffusion model to retrieve translational diffusion coefficients of PEG-4. Comparison of the experimentally derived diffusivities with viscosity estimates for the ternary system reveals a breakdown of the Stokes-Einstein relationship, which has often been invoked to infer diffusivity from viscosity. The evaporation of PEG-4 shows pronounced RH and temperature dependencies and is severely depressed for RH 30 %, corresponding to diffusivities < 10 −14 cm 2 s −1 at temperatures < 15 • C. The temperature dependence is strong, suggesting a diffusion activation energy of about 300 kJ mol −1 . We conclude that atmospheric volatile organic compounds can be subject to severe diffusion limitations in viscous organic aerosol particles. This may enable an important long-range transport mechanism for organic material, including pollutant molecules such as polycyclic aromatic hydrocarbons (PAHs).

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Section: Atmospheric Outlookmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diffusivity measurements of volatile organics in levitated viscous aerosol particles

et al. 2017

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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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“…Perhaps, the lifetime of BrC is dependent on other factors related to aerosol oxidation and phase state, which we will discuss next. In a recent study, Shrivastava et al (2017) reported observations of an enhanced lifetime for PAHs due to the aerosol phase state during transport. The aerosol solid phase state has been shown to decrease the rate of photodegradation (Lignell et al, 2014;Hinks et al, 2015) and water diffusivity (Berkemeier et al, 2014).…”

Section: Molecular Formula Aromaticity and Brown Carbonmentioning

confidence: 99%

Molecular and physical characteristics of aerosol at a remote marine free troposphere site: Implications for atmospheric aging

Schum¹,

Zhang²,

Džepina³

et al. 2018

Preprint

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Abstract. Aerosol properties are transformed by atmospheric processes during long-range transport and play a key role in the Earth's radiative balance. To understand the molecular and physical characteristics of free tropospheric aerosol, we studied samples collected at the Pico Mountain Observatory in the North Atlantic. The observatory is located in the marine free troposphere at 2225 m above sea level, on Pico Island in the Azores archipelago. The site is ideal for the study of long-range transported free tropospheric aerosol with minimal local influence. Three aerosol samples with elevated organic carbon 5 concentrations were selected for detailed analysis. FLEXPART retroplumes indicated that two of the samples were influenced by North American wildfire emissions transported in the free troposphere and one by North American outflow mainly transported within the marine boundary layer. To determine the molecular composition of the samples, we used ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry. Thousands of molecular formulas were assigned to each of the individual samples. On average ~60 % of the molecular formulas contained only carbon, hydrogen, and oxygen 10 atoms (CHO), ~30 % contained nitrogen (CHNO), and ~10 % contained sulfur (CHOS). The molecular formula composition of the two wildfire influenced aerosol samples transported mainly in the free troposphere had relatively low average O/C ratios (0.46 ± 0.12 and 0.47 ± 0.15) despite 7 -10 days of transport time according to FLEXPART. However, the molecular composition of the North American outflow transported mainly in the boundary layer had a higher average O/C ratio (0.55 ± 0.19) with 3 days of transport time. Thus, aerosol oxidation appears to be related to environmental factors during transport and 15 not simply aging time. Meteorological conditions extracted from GFS analysis for model grids along the FLEXPART simulated transport pathways and the observed molecular chemistry were used to predict the phase state of the aerosol samples, indicating that the aerosol transported in the free troposphere was more likely to be solid and therefore less oxidized than the aerosol transported in the boundary layer. This suggests that biomass burning emissions injected into the free troposphere are longer-lived than emissions in the boundary layer. 20

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Global long-range transport and lung cancer risk from polycyclic aromatic hydrocarbons shielded by coatings of organic aerosol

Cited by 215 publications

References 54 publications

Diffusivity measurements of volatile organics in levitated viscous aerosol particles

Diffusivity measurements of volatile organics in levitated viscous aerosol particles

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

Molecular and physical characteristics of aerosol at a remote marine free troposphere site: Implications for atmospheric aging

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