Physiochemical Properties and Environmental Effects of Secondary Organic Aerosol PDF Download
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Author: Celia Noemi Cruz
Publisher:
ISBN:
Category : Carnegie Mellon University
Languages : en
Pages : 0
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Author: Celia Noemi Cruz
Publisher:
ISBN:
Category : Carnegie Mellon University
Languages : en
Pages : 0
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Author: Rebecca M. Harvey
Publisher:
ISBN:
Category :
Languages : en
Pages : 452
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Aerosols play important roles in atmospheric and environmental processes. Not only do they impact human health, they also affect visibility and climate. Despite recent advances made to under their sources and fate, there remains a limited understanding of the mechanisms that lead to the formation of aerosols and their ultimate fate in the atmosphere. These knowledge gaps provide the crux of the research reported herein, which has focused on identifying novel sources of atmospheric aerosol, characterizing its physical and optical properties, and rationalizing these properties using an in-depth knowledge of the molecular level mechanisms that led to its formation. Upon mowing, turfgrasses emit large amounts of green leaf volatiles which can then be oxidized by ozone to form SOA. Overall, the mowing of lawns has the potential to contribute nearly 50 μg SOA per square meter of lawn mowed. This SOA contribution is on the same order of magnitude as other predominant SOA sources (isoprene, monoterpenes, sesquiterpenes). Turfgrasses represent an interesting and potentially meaningful SOA source because they contribute to SOA and also because they cover large land areas in close proximity to oxidant sources. Another related SOA precursor is sugarcane, which is in the same family as turfgrass and is among the largest agricultural crops worldwide. Globally, the ozonolysis of sugarcane has the potential to contribute 16 Mg SOA to the atmosphere, compared to global estimates of SOA loading that range from 12-70 Tg SOA. In order to fully understand the role of atmospheric SOA on the radiative budget (and therefore climate), it is also important to understand its optical properties; its ability to absorb vs scatter light. Turfgrass and sugarcane produced SOA that was weakly absorbing while its scatter efficiency was wavelength and size-dependent. Interestingly, SOA formed under both dry (10% RH) and wet (70% RH) conditions had the same bulk chemical properties (O:C), yet significantly different optical properties, which was attributed to differences in molecular-level composition. The work presented herein represents a unique, inclusive study of SOA precursors. A complete understanding of the chemistry leading to SOA formation is used to understand its physical and optical properties and evaluate these large-scale effects of SOA from these precursors.
Author: Mehrnaz Sarrafzadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Atmospheric organic aerosols have a significant impact on climate and human health. However, our understanding of the physical and chemical properties of these aerosols is inadequate, thus their climate and health influences are poorly constrained. In this study, we investigated the secondary organic aerosol (SOA) formation from OH-initiated oxidation of -pinene. The majority of experiments were conducted in the York University smog chamber. The main objective was to identify the gas and particle phase products with an atmospheric pressure chemical ionization mass spectrometer (APCI-MS/MS). A wide variety of products were identified containing various functional groups including alcohol, aldehyde, carboxylic acid, ketone and nitrate. Following the chemical composition characterization of products, the shape, phase state and density of generated particles were determined. Images from a scanning electron microscope (SEM) revealed that SOA particles from -pinene were commonly spherical in shape, and adopted an amorphous semi-solid/liquid state. Additionally, the density was determined for SOA particles generated from -pinene/OH, nopinone/OH and nopinone/NO3 experiments for the first time using a tapered element oscillating microbalance-scanning mobility particle sizer (TEOM-SMPS) method. Our results showed a correlation between the determined particle density and the particle chemical composition of the respective system. This demonstrates that changes in particle density can be indicative of the changes in chemical composition of particles. We also investigated the chemical aging of oxidation products by exposing them to additional OH radicals or ozone. The observed changes in chemical composition of products and additional SOA mass production during OH-induced aging were attributed to further oxidation of gas phase intermediate products. The NOx dependence of SOA formation from -pinene photooxidation was investigated in the York University smog chamber and the Jlich Plant Atmosphere Chamber (JPAC). Consistent with previous NOx studies, SOA yields increased with increasing [NOx] at low-NOx conditions, whereas increasing [NOx] at high-NOx conditions suppressed the SOA yield. This increase was attributed to an increase of OH concentration. After removing the effect of [OH] on SOA yield in the JPAC, SOA yields only decreased with increasing [NOx]. Finally, the formation mechanisms of identified products were probed based on the information acquired throughout our study.
Author: Yue Zhang
Publisher: American Chemical Society
ISBN: 0841299293
Category : Science
Languages : en
Pages : 176
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Book Description
The uncertainties in the aerosol effects on radiative forcing limit our knowledge of climate change, presenting us with an important research challenge. Aerosols in Atmospheric Chemistry introduces basic concepts about the characterization, formation, and impacts of ambient aerosol particles as an introduction to graduate students new to the field. Each chapter also provides an up-to-date synopsis of the latest knowledge of aerosol particles in atmospheric chemistry.
Author: Hayder Abdul-Razzak
Publisher: BoD – Books on Demand
ISBN: 9535107283
Category : Science
Languages : en
Pages : 494
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Book Description
The book is divided into two sections. The first section presents characterization of atmospheric aerosols and their impact on regional climate from East Asia to the Pacific. Ground-based, air-born, and satellite data were collected and analyzed. Detailed information about measurement techniques and atmospheric conditions were provided as well. In the second section, authors provide detailed information about the organic and inorganic constituents of atmospheric aerosols. They discuss the chemical and physical processes, temporal and spatial distribution, emissions, formation, and transportation of aerosol particles. In addition, new measurement techniques are introduced. This book hopes to serve as a useful resource to resolve some of the issues associated with the complex nature of the interaction between atmospheric aerosols and climatology.
Author: Quentin Gerald James Malloy
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 414
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Author: Mallory Lynn Hinks
Publisher:
ISBN: 9780355307016
Category :
Languages : en
Pages : 153
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Book Description
Atmospheric aerosols represent one of the greatest uncertainties in predicting the Earth's future climate. Secondary organic aerosols (SOA) are particularly complicated because they are highly susceptible to change upon exposure to different conditions, such as varying temperatures and relative humidities (RHs), sunlight, and different atmospheric pollutants. The goal of this work was to increase our understanding of the contribution of SOA to the Earth's radiation budget by exploring how different environmental conditions can affect aerosol properties and processes.The first project investigated the effect of viscosity on photochemical kinetics of probe molecules embedded in laboratory-generated SOA. Temperature and RH of the system were varied independently to adjust the viscosity of the SOA and the samples were irradiated. At lower temperatures and humidities both systems exhibited lower photoreaction rates, suggesting that increased viscosity hinders the motion of the molecules in the SOA slowing down their photochemical reactions. This means that molecules trapped inside SOA in cold, dry parts of the atmosphere will photodegrade slower than in warm and humid areas.The next stage of this work was to study the effect of RH on the mass loading and composition of SOA formed from toluene photooxidation. When the RH was increased from 0% to 75%, the yield of toluene SOA made under low NOx conditions decreased by an order of magnitude. High resolution mass spectrometry revealed a significant reduction in the fraction of oligomers present in the SOA made under humid conditions compared to dry conditions. These results suggest that water vapor suppresses oligomer formation in low NOx toluene SOA, reducing aerosol yield. This means that concentrations of toluene SOA in the atmosphere will be dependent on the RH and NOx concentrations.The last stage of this work investigated the interaction between SOA and ammonia. SOA made from toluene, n-hexadecane, or limonene in a chamber was exposed to gaseous ammonia while the mass loading and composition was monitored. These experiments indicated that ammonia could be taken up into SOA, leaving less ammonia in the atmosphere to neutralize atmospheric acids. This leads to a reduction of inorganic aerosols in the atmosphere.
Author: Rekha Kale
Publisher: Scitus Academics LLC
ISBN: 9781681171326
Category : Aerosols
Languages : en
Pages : 0
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Book Description
Atmospheric Aerosols is a vital problem in current environmental research due to its importance in atmospheric optics, energetics, radiative transfer studies, chemistry, climate, biology and public health. Aerosols can influence the energy balance of the terrestrial atmosphere, the hydrological cycle, atmospheric dynamics and monsoon circulations. Because of the heterogeneous aerosol field with large spatial and temporal variability and reduction in uncertainties in aerosol quantification is a challenging task in atmospheric sciences. Keeping this in view the present study aims to assess the impact of aerosols on coastal Indian station Visakhapatnam and the adjoining Bay of Bengal. An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or not. Examples of natural aerosols are fog, forest exudates and geyser steam.
Author: Jae Young Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The presence of anthropogenic organic compounds in atmospheric aerosols has the potential to contribute to global climate change by altering the hygroscopic behavior and surface tension of the aerosols. Since the hygroscopicity and surface tension of aerosols are related to their sizes, albedos, and tendencies to form clouds, characterizing these two key parameters is important in understanding the effect of atmospheric aerosols on global climate change. Although real atmospheric aerosols are composed of complex mixtures of inorganic and/or organic compounds, the hygroscopicity and surface tension of various aerosol mixtures are still poorly understood. Laboratory experiments were designed to provide a better understanding of the physicochemical properties of various dicarboxylic acid mixtures. Dicarboxylic acids are frequently measured water-soluble organic compounds in atmospheric aerosols. The major focus was on whether the water uptake or surface tension altering property of one organic solute was affected by the presence of another compound in solution. First, to understand the hygroscopicity of dicarboxylic acid aerosol mixtures, water vapor pressure was measured at 12 °C over aqueous bulk solutions containing dicarboxylic acids using both a quadrupole mass spectrometer and a Baratron pressure transducer. Our water vapor pressure measurements for mixtures were compared with predictions made using Zdanovskii-Stokes-Robinson (ZSR) method and the modified UNIQUAC Functional-group Activity Coefficients (UNIFAC) model. Second, to understand the surface tension of dicarboxylic acid aerosol mixtures, surface tension was measured at 20 °C over dicarboxylic acid solutions using a tensiometer. The surface tension of two-, three-, and four-dicarboxylic acid solutions was measured to see how the overall surface tension depends on the number of dicarboxylic acids added to the solution. Our surface tension measurements were then utilized in Kohler's equation to examine the atmospheric impact of the organic aerosol mixtures. Due to surface tension-lowering effects, aerosols containing organic compounds can be more easily activated into cloud droplets. Lastly, the surface tension of solutions containing dicarboxylic acids plus a second category of water-soluble compounds was measured at 20 °C. Ammonium sulfate, D-glucose, and humic acid sodium salts were chosen to represent other categories of water-soluble compounds. Taken together, our results suggest that the physicochemical properties of organic aerosol mixtures cannot be accurately predicted using a linear combination of single component properties. Instead, the interactions between various components must be included for better predictions of physicochemical properties. More studies are needed to accurately quantify and model aerosol effects on global climate changes.
Author: Crystal Glen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Secondary organic aerosols (SOA) comprise a substantial fraction of the total global aerosol budget. While laboratory studies involving smog chambers have advanced our understanding of the formation mechanisms responsible for SOA, our knowledge of the processes leading to SOA production under ambient gaseous and particulate concentrations as well as the impact these aerosol types have on climate is poorly understood. Although the majority of atmospheric aerosols scatter radiation either directly or indirectly by serving as cloud condensation nuclei, soot is thought to have a significant warming effect through absorption. Like inorganic salts, soot may undergo atmospheric transformation through the vapor condensation of non-volatile gaseous species which will alter both its chemical and physical properties. Typical smog chamber studies investigating the formation and growth of SOA as well as the soot aging process are temporally limited by the initial gaseous concentrations injected into the chamber environment. Furthermore, data interpretation from such experiments is generally restricted to the singular gaseous species under investigation. This dissertation discusses the use of a new aerosol chamber designed to study the formation and growth of SOA and soot aging under atmospherically relevant conditions. The Ambient Aerosol Chamber for Evolution Studies (AACES) was deployed at three field sites where size and hygroscopic growth factor (HGF) of ammonium sulfate seed particles was monitored over time to examine the formation and growth of SOA. Similar studies investigating the soot aging process were also conducted in Houston, TX. It is shown that during the ambient growth of ammonium sulfate seed particles, as particle size increases, hygroscopic growth factors decrease considerably resulting in a significant organic mass fraction in the particle phase concluding an experiment. Observations of soot aging show an increase in measured size, HGF, mass and single scattering albedo. Ambient growth rate comparisons with chamber growth yielded similar trends verifying the use of AACES to study aerosol aging. Based on the results from this study, it is recommended that AACES be employed in future studies involving the production and growth of SOA and soot aging under ambient conditions in order to bridge the gaps in our current scientific knowledge.
