Investigation into the mechanisms of size-resolved particle dry deposition across three environments

2022 Summer.Includes bibliographical references.Airborne particulate matter, or aerosols, have significant impacts on radiative forcing through both their direct - scattering and absorbing light - and indirect effects- acting as cloud condensation nuclei and altering the lifetime of clouds. The magnitude of these effects is largely determined by particle lifetime, which is defined by their rate of removal through wet and dry deposition. Dry deposition, specifically of accumulation mode aerosols (0.1 – 1 µ), is one of the largest sources of uncertainty in global models. The processes that influence deposition are poorly constrained and few comprehensive measurements are available to improve our understanding. Characterizing these mechanisms is vital for predicting spatial and temporal trends in particle dry deposition and lifetime. While there have been improvements in quantifying and understanding dry deposition, large gaps in our knowledge still exist that make predicting the impacts of aerosols on Earth's climate difficult. To improve understanding of the underlying mechanisms that determine the rate of particle deposition in an environment this dissertation reports size-resolved dry deposition measurements from three distinct environment types. First, we report measurements from a test house which identify dilution and deposition as the most important factors influencing particle concentrations indoors. This analysis also shows that deposition indoor is governed by the same fundamental process that we consider for outdoor environments. Second, we present particle flux and deposition measurements from a Ponderosa pine forest over four seasons where significant enhancement in deposition during the wintertime was observed. This is attributable to changes in interception, caused by changes in plant physiology and surface structure during the winter that leads to an increase in their ability to uptake particles. Finally, we show particle and black carbon deposition from a low Arctic tundra during snow-cover that are elevated compared to predictions of dry deposition in that region. Incorporating interception into the model parameterizations improved model measurement agreement and provides evidence to suggest that surface structure and microroughness impact deposition even when there is snow-cover

Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures.

It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on measured size distributions of PM (0.001-20 μm), along with estimated exposures and respiratory-tract deposition. Number concentrations were highest for sub-10 nm particles during cooking using a propane-fueled stovetop. During some cooking activities, calculated PM2.5 mass concentrations (assuming a density of 1 g cm-3) exceeded 250 μg m-3, and exposure during the postcooking decay phase exceeded that of the cooking period itself. The modeled PM respiratory deposition for an adult residing in the test house kitchen for 12 h varied from 7 μg on a day with no indoor activities to 68 μg during a simulated day (including breakfast, lunch, and dinner preparation interspersed by cleaning activities) and rose to 149 μg during a simulated Thanksgiving day

Progress Toward the Total Synthesis of Cryptocaryol A

Cryptocaryol A is a stereochemically complex natural product with potential anticancer properties. A convergent, stereoselective, and concise (11-step) total synthesis has been devised, and progress toward the completion of this synthesis is reported. The stereocenters have been installed using a combination of asymmetric allylation using Leighton\u27s reagent and internal stereorelay. Key steps include an asymmetric bis-allylation, terminus differentiation via ring-closing metathesis, a chemoselective alkene oxidation using ozone, and a boron aldol reaction with 1,5-anti stereoinduction

Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures.

It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on measured size distributions of PM (0.001-20 μm), along with estimated exposures and respiratory-tract deposition. Number concentrations were highest for sub-10 nm particles during cooking using a propane-fueled stovetop. During some cooking activities, calculated PM2.5 mass concentrations (assuming a density of 1 g cm-3) exceeded 250 μg m-3, and exposure during the postcooking decay phase exceeded that of the cooking period itself. The modeled PM respiratory deposition for an adult residing in the test house kitchen for 12 h varied from 7 μg on a day with no indoor activities to 68 μg during a simulated day (including breakfast, lunch, and dinner preparation interspersed by cleaning activities) and rose to 149 μg during a simulated Thanksgiving day

Indoor emissions of total and fluorescent supermicron particles during HOMEChem.

Inhalation of particulate matter is associated with adverse health outcomes. The fluorescent portion of supermicron particulate matter has been used as a proxy for bioaerosols. The sources and emission rates of fluorescent particles in residential environments are not well-understood. Using an ultraviolet aerodynamic particle sizer (UVAPS), emissions of total and fluorescent supermicron particles from common human activities were investigated during the HOMEChem campaign, a test-house investigation of the chemistry of indoor environments. Human occupancy and activities, including cooking and mopping, were found to be considerable sources of indoor supermicron fluorescent particles, which enhanced the indoor particle concentrations by two orders of magnitude above baseline levels. The estimated total (fluorescent) mass emission rates for the activities tested were in the range of 4-30 (1-11) mg per person meal for cooking and 0.1-4.9 (0.05-4.7) mg/h for occupancy and mopping. Model calculations indicate that, once released, the dominant fate of coarse particles (2.5-10 micrometer in diameter) was deposition onto indoor surfaces, allowing for the possibility of subsequent resuspension and consequent exposures over durations much longer than the ventilation time scale. Indoor coarse particle deposition would also contribute to soiling of indoor surfaces