In this laboratory-based project, the chemical transformation of biomass burning aerosol (BBA) particles will be studied. BBA are ubiquitous in the atmosphere, have a source strength of similar magnitude to fossil fuel burning, and can affect the atmosphere on local to global scales. The overall goal of this project is to obtain a comprehensive picture of the BBA life-cycle by: 1) Determination of the heterogeneous oxidation kinetics and reaction products of BBA with atmospheric trace gases; 2) Evaluation of the photochemical stability of biomolecular markers; 3) Measurement of the photosensitized heterogeneous kinetics and reaction products of BBA; and 4) Implementation of the detailed heterogeneous chemistry of BBA into atmospheric models. The heterogeneous oxidation kinetics experiments will be carried out with a chemical ionization mass spectrometer (CIMS) coupled to various flow reactors with samples in the bulk (coated wall) and aerosol phases.
Educational objectives involve undergraduate participation in research, development of new curricula, education of middle and high school students and teachers, and increasing diversity in the atmospheric sciences. Middle and high school students from local school districts, including members of underrepresented groups, will be recruited through Stony Brook University. The students will participate in an atmospheric sciences summer workshop on campus, which will involve classes, experimental demonstrations, computer simulations, and hands-on field experience such as conducting meteorological measurements and collecting aerosol particles with subsequent analysis in the laboratory. Subsequent exposure at conferences sponsored by the Collegiate Science and Technology Entry Program (C-STEP) will strengthen the students' knowledge and understanding. A summer workshop will be also be set up to educate secondary school teachers in atmospheric sciences, air pollution, and climate change. Diversity in atmospheric sciences will be further achieved by mentoring and providing research opportunities to minority and low-income students at the undergraduate level.
Biomass burning constitutes a large source of gases and aerosol particles to the atmosphere reaching emission concentrations similar to those generated by fossil fuel combustion. Biomass burning aerosol (BBA) particles affect the atmosphere on local, e.g. the urban environment, to global scales, e.g. the transport of forest fire plumes across hundreds to thousands of miles. For these reasons BBAs contribute significantly to the total concentration of particulate matter and impact the radiative budget by scattering and absorption of solar and terrestrial radiation and by changing the radiative properties of clouds. These ubiquitous atmospheric organic dominated particles interact with atmospheric trace gases acting as oxidants or radicals such as ozone (O3) or the hydroxyl radical (OH), leading to the chemical and physical transformation of BBAs. This in turn changes their role with respect to air quality, health related issues, and regional and global climate. Therefore, it is imperative to understand how these particles and oxidants interact during their transport in the atmosphere. This award supported experimental, theoretical, and model investigations into the degradation kinetics of typical organic compounds present in BBAs due to reaction with atmospheric trace gases including O3, nitrogen dioxide (NO2), nitrate radical (NO3), dinitrogen pentoxide (N2O5), and OH. The development of a custom-built chemical ionization mass spectrometer (CIMS) allowed in situ detection of these very short lived and highly reactive trace gas species, necessary to determine corresponding gas-to-particle reaction kinetics. Various flow reactors, based on previously established designs but with completely novel modifications, were created. These, in combination with CIMS allowed determination of the underlying reaction efficiency between BBA compounds and reactive trace gases. An example of an experimental setup is shown in the attached image and includes the CIMS, an aerosol flow reactor with a microwave cavity to produce OH, and an irradiated rectangular channel flow reactor. Gaseous reaction products from the reaction with OH and organic substrates were determined as well as the effect of photo-active substances present in BBA on the gas-to-particle reaction kinetics. The significance of these gaseous reaction products is that they can in turn, lead to new secondary condensed phase material thereby affecting the total atmospheric composition of gases and particles. The presence of photo-active substances significantly enhances the gas-to-particle reaction efficiency of BBAs with important implications for the chemical evolution of biomass burning plumes. Overall O3, NO3, and OH can effectively degrade BBA compounds with significant implications for aerosol source apportionment studies, air quality, and climate. The newly determined reaction kinetics from this project have been applied to atmospheric chemistry models that consider the interaction between trace gases and BBA but which until now have not achieved sufficient detail to account for reaction processes on the molecular level. These updated models now allow assessment of the most important underlying mechanisms leading to particle transformations in urban environments with poor air quality. Findings from this project will facilitate inclusion of these complex processes in regional and larger scale atmospheric models that currently lack a detailed description of gas-to-particle reaction processes. These models will then allow us to better predict atmospheric conditions and thus air quality and climate. This award also supported the academic development of undergraduate and graduate students and focused in particular on increasing the number of underrepresented minority students in atmospheric sciences. To achieve these goals, several outreach projects were undertaken including i) organization and participation of a ground level ozone workshop for K-12 teachers in high-need schools serving underrepresented minority student populations. Activities included classes and the development of laboratory experiments so K-12 teachers could study the effect of O3 on plants for implementation in class room environments; ii) development of a laboratory based atmospheric chemistry module for undergraduate students in the women in science and engineering (WISE) program; iii) sponsorship of undergraduate research projects for underrepresented minority students; and iv) development of an atmospheric science module for the yearly occurring CSTEP (Collegiate Science and Technology Entry Program) summer residential program at Stony Brook University to raise the interest of advanced middle and high school students from local high-needs school districts for atmospheric sciences. The aim of this module is to increase the students’ awareness of typical pollutants such as ozone and particulate matter which can reach high concentrations on Long Island, particularly during summer. This module consists of a class, field measurements of meteorological conditions, ozone, and particulate matter, and a laboratory component to investigate airborne particles using optical microscopes. The second attached image shows a group of high school students conducting field measurements.
