Person: Liu, Pengfei
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Liu
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Pengfei
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Liu, Pengfei
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Publication Synergistic Uptake by Acidic Sulfate Particles of Gaseous Mixtures of Glyoxal and Pinanediol(American Chemical Society (ACS), 2020-08-25) Qin, Yi Ming; Ye, Jianhuai; Ohno, Paul E.; Lei, Yali; Wang, Junfeng; Liu, Pengfei; Thomson, Regan J.; Martin, Scot T.; OhnoPublication Chronic effects of temperature on mortality in the Southeastern USA using satellite-based exposure metrics(Nature Publishing Group, 2016) Shi, Liuhua; Liu, Pengfei; Wang, Yan; Zanobetti, Antonella; Kosheleva, Anna; Koutrakis, Petros; Schwartz, JoelClimate change may affect human health, particularly for elderly individuals who are vulnerable to temperature changes. While many studies have investigated the acute effects of heat, only a few have dealt with the chronic ones. We have examined the effects of seasonal temperatures on survival of the elderly in the Southeastern USA, where a large fraction of subpopulation resides. We found that both seasonal mean temperature and its standard deviation (SD) affected long-term survival among the 13 million Medicare beneficiaries (aged 65+) in this region during 2000–2013. A 1 °C increase in summer mean temperature corresponded to an increase of 2.5% in death rate. Whereas, 1 °C increase in winter mean temperature was associated with a decrease of 1.5%. Increases in seasonal temperature SD also influence mortality. We decomposed seasonal mean temperature and its temperature SD into long-term geographic contrasts between ZIP codes and annual anomalies within ZIP code. Effect modifications by different subgroups were also examined to find out whether certain individuals are more vulnerable. Our findings will be critical to future efforts assessing health risks related to the future climate change.Publication Highly Viscous States Affect the Browning of Atmospheric Organic Particulate Matter(American Chemical Society, 2018) Liu, Pengfei; Li, Yong Jie; Wang, Yan; Bateman, Adam P.; Zhang, Yue; Gong, Zhaoheng; Bertram, Allan K.; Martin, ScotInitially transparent organic particulate matter (PM) can become shades of light-absorbing brown via atmospheric particle-phase chemical reactions. The production of nitrogen-containing compounds is one important pathway for browning. Semisolid or solid physical states of organic PM might, however, have sufficiently slow diffusion of reactant molecules to inhibit browning reactions. Herein, organic PM of secondary organic material (SOM) derived from toluene, a common SOM precursor in anthropogenically affected environments, was exposed to ammonia at different values of relative humidity (RH). The production of light-absorbing organonitrogen imines from ammonia exposure, detected by mass spectrometry and ultraviolet–visible spectrophotometry, was kinetically inhibited for RH < 20% for exposure times of 6 min to 24 h. By comparison, from 20% to 60% RH organonitrogen production took place, implying ammonia uptake and reaction. Correspondingly, the absorption index k across 280 to 320 nm increased from 0.012 to 0.02, indicative of PM browning. The k value across 380 to 420 nm increased from 0.001 to 0.004. The observed RH-dependent behavior of ammonia uptake and browning was well captured by a model that considered the diffusivities of both the large organic molecules that made up the PM and the small reactant molecules taken up from the gas phase into the PM. Within the model, large-molecule diffusivity was calculated based on observed SOM viscosity and evaporation. Small-molecule diffusivity was represented by the water diffusivity measured by a quartz-crystal microbalance. The model showed that the browning reaction rates at RH < 60% could be controlled by the low diffusivity of the large organic molecules from the interior region of the particle to the reactive surface region. The results of this study have implications for accurate modeling of atmospheric brown carbon production and associated influences on energy balance.Publication Cloud Activation Potentials for Atmospheric α-Pinene and β-Caryophyllene Ozonolysis Products(American Chemical Society, 2017) Gray Bé, Ariana; Upshur, Mary Alice; Liu, Pengfei; Martin, Scot; Geiger, Franz M.; Thomson, Regan J.The formation of atmospheric cloud droplets due to secondary organic aerosol (SOA) particles is important for quantifying the Earth’s radiative balance under future, possibly warmer, climates, yet is only poorly understood. While cloud activation may be parametrized using the surface tension depression that coincides with surfactant partitioning to the gas–droplet interface, the extent to which cloud activation is influenced by both the chemical structure and reactivity of the individual molecules comprising this surfactant pool is largely unknown. We report herein considerable differences in the surface tension depression of aqueous pendant droplets that contain synthetically prepared ozonolysis products derived from α-pinene and β-caryophyllene, the most abundant of the monoterpenes and sesquiterpenes, respectively, that are emitted over the planet’s vast forest ecosystems. Oxidation products derived from β-caryophyllene were found to exhibit significantly higher surface activity than those prepared from α-pinene, with the critical supersaturation required for cloud droplet activation reduced by 50% for β-caryophyllene aldehyde at 1 mM. These considerable reductions in the critical supersaturation were found to coincide with free energies of adsorption that exceed ∼25 kJ/mol, or just one hydrogen bond equivalent, depending on the ammonium sulfate and oxidation product concentration in the solution. Additional experiments showed that aldehyde-containing oxidation products exist in equilibrium with hydrated forms in aqueous solution, which may modulate their bulk solubility and surface activity. Equilibration time scales on the order of 10–5 to 10–4 s calculated for micrometer-sized aerosol particles indicate instantaneous surface tension depression in the activation processes leading to cloud formation in the atmosphere. Our findings highlight the underlying importance of molecular structure and reactivity when considering cloud condensation activity in the presence of SOA particles.Publication Impacts of Temperature and its Variability on Mortality in New England(2015) Shi, Liuhua; Kloog, Itai; Zanobetti, Antonella; Liu, Pengfei; Schwartz, JoelRapid buildup of greenhouse gases is expected to increase the Earth surface mean temperature, with unclear effects on temperature variability1–3. This adds urgency to better understand the direct effects of the changing climate on human health. However, the effects of prolonged exposures to temperatures, which are important for understanding the public health burden, are unclear. Here we demonstrate that long-term survival was significantly associated with both seasonal mean values and standard deviations (SDs) of temperature among the Medicare population (aged 65+) in New England, and break that down into long-term contrasts between ZIP codes and annual anomalies. A rise in summer mean temperature of 1 °C was associated with 1.0% higher death rate whereas an increase in winter mean temperature corresponded to 0.6% lower mortality. Increases in temperature SDs for both summer and winter were harmful. The increased mortality in warmer summers was entirely due to anomalies, while it was long term average differences in summer SD across ZIP codes that drove the increased risk. For future climate scenarios, seasonal mean temperatures may in part account for the public health burden, but excess public health risk of climate change may also stem from changes of within season temperature variability.Publication Enhanced aerosol particle growth sustained by high continental chlorine emission in India(Springer Science and Business Media LLC, 2021-01-25) Gunthe, Sachin S.; Liu, Pengfei; Panda, Upasana; Raj, Subha S.; Sharma, Amit; Darbyshire, Eoghan; Reyes-Villegas, Ernesto; Allan, James; Chen, Ying; Wang, Xuan; Song, Shaojie; Pöhlker, Mira L.; Shi, Liuhua; Wang, Yu; Kommula, Snehitha M.; Liu, Tianjia; Ravikrishna, R.; McFiggans, Gordon; Mickley, Loretta; Martin, Scot; Pöschl, Ulrich; Andreae, Meinrat O.; Coe, Hugh; CoeMany cities in India experience severe deterioration of air quality in winter. Particulate matter is a key atmospheric pollutant that impacts millions of people. In particular, high levels of particulate matter reduce visibility, which has severely damaged the economy and endangered human lives. But the underlying chemical mechanisms and physical processes responsible for initiating haze and fog formation remain poorly understood. Here we present the measurement results of chemical composition of particulate matter in Delhi and Chennai. We find persistently high chloride in Delhi, and episodically high chloride in Chennai. These measurements, combined with thermodynamic modeling, suggest that in the presence of excess ammonia in Delhi, high local emission of hydrochloric acid partition into aerosol water. The highly water-absorbing and soluble chloride in the aqueous phase substantially enhances aerosol water uptake through co-condensation, which sustains particle growth leading to haze and fog formation. We therefore suggest that high local concentration of gas-phase hydrochloric acid, possibly emitted from plastic-contained waste burning and industry causes some 50% of the reduced visibility. Our work implies that identification and regulation of gaseous hydrochloric acid emissions could be critical to improve visibility and human health in India.