Atmospheric Physics and Chemistry Research
Bililign Research Group

Atmospheric Physics and Chemistry Research

The research in our group centers on multiple aspects of Atmospheric Chemistry and Physics.

The work in our laboratory focuses on:

  • Bililign group spring 2016 2The study of chemical composition and optical properties of biomass burning aerosols emitted from biomass fuels in East Africa.
  • Measurement of particulate scattering, absorption, and extinction across the entire solar spectrum impact regional climate. Most current measurements are limited to a single or few wavelengths, whereas our setup allows measurement of featured absorption cross sections over a wide range of wavelengths.
  • Understanding the relationship between the change in optical properties and chemical composition due to aging is still a challenge. Changes in optical properties of soot particles due to internal mixing in the atmosphere and aging will be investigated in this project for the fuel sources in the selected region. Aging of aerosols will be simulated in our indoor smog chamber.

Facilities

In the atmosphere, biomass aerosols from fires are subject to extensive chemical processing in the atmosphere as they are exposed to sunlight, other pollutants, biogenic VOC’s and oxidants such as ozone, hydroxyl radicals, and NOx, causing the particles to evolve chemically and physically. Variations in optical properties of soot particles due to internal mixing in the atmosphere and aging remain highly uncertain, considerably hindering efforts to assess their impact on climate and weather.  The laboratory measurement of the detailed optical properties of BB aerosols as they age is extremely important in understanding aerosol climate impacts. This is done using an indoor smog chamber.

smog chamber

  • Ultra-performance liquid chromatography (UPLC) coupled in-line to both a diode array detector (DAD) and high-resolution quadrupole time-of-flight mass spectrometer equipped with an electrospray ionization source will be used to chemically characterize aerosol samples produced in our chamber experiments at UNC-Chapel Hill- Dr. Jason D. Surratt’s Lab.
  • Radiative properties of light absorbing carbon aerosols are strongly dependent on the morphological factors (shape and fractal dimensions) which change with the aging of aerosols. The optical properties of soot aerosols as they age and evolve from chain-like structures into closely packed compact clusters will be investigated using T-matrix theory using computational facilities at NCA&T-CSE Department (Dr. Kenneth Flurchick), and images are taken using JSNN facilities.

Current Activities: 

With an estimated total climate forcing of +1.1 W•m-2, black carbon (BC) and brown Carbon (BrC) are the most important of human emissions in terms of their climate forcing in the present-day atmosphere; second to CO2. BC is produced during the combustion of carbon-based fuels when oxygen is insufficient for complete combustion, which occurs during biomass burning (BB). In addition to climate forcing, recent observational and modeling efforts have shown that biomass aerosols can strongly affect a storm's lightning activity. Violent tornadoes in the Southeast and Central US during the spring are often accompanied by smoke from biomass burning in Central America. The inclusion of aerosol-cloud-radiation interactions in weather forecasts may help improve the predictability of these extreme events. This can also help improve the timeliness and accuracy of severe weather alerts within future operational forecast systems.

Newly Funded Research Activities

Through coordinated collaborative laboratory, field and modeling studies at NCAT, Howard University (HU, Colorado State University (CSU) and Aerodyne Research Inc., we will investigate a series of linked scientific questions.

  1. How does relative humidity (RH) influence the size distribution, optical properties and chemical properties of BB aerosols, and how do the optical properties of BB aerosols change in high humidity conditions in the dark?
  2. How does BB smoke influence aerosol optical properties when mixed with mineral dust?
  3. What are the physical and optical properties of aerosols produced from burning animal dung and trash? What is their contribution to aerosol loading, and what toxic species are emitted from animal dung burning?
  4. How large are the regional and global health impacts of aerosol emissions from dung, domestic-waste, and other typical African BB fuels?
  5. What is the relationship between BB cloud condensation nuclei morphological characteristics and hygroscopicity?
  6. How is the scattering enhancement factor related to intensive aerosol properties such as SSA, and does this relationship differ between laboratory and field data?

Toxicity of Complex Aerosols from Wood Burning Cook Stoves. The NCAT facility will be used to generate fresh and photo-chemically aged Biomass Burning Aerosols.

The Multiphase Heterogeneous Chemistry of SO2 under wintertime conditions

NCA&T Team was part of the Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER 2015). WINTER is an atmospheric chemistry campaign that focuses on wintertime emissions and chemical processes in the Northeastern US. The project has three goals:

(1) to characterize the chemical transformations of wintertime emissions with an equal focus on nocturnal and multiphase processes as on photochemistry;

(2) to assess the dominant mechanism of secondary aerosol formation and quantify the geographical distribution of inorganic and organic aerosol types during winter; and

(3) to provide constraints on wintertime emission inventories for urban areas, power plants and agricultural areas, and characterize the export pathways of primary pollutants to the North Atlantic.

NCA&T team (Jaime Green and Marc Fiddler) will examine the heterogeneous uptake of SO2 in the presence of non-precipitating clouds during the wintertime.  Investigations examining the modification of the mass transport, oxidation, and atmospheric lifetimes of SO2 due to winter conditions will take place.  Analysis of SO2 emissions from power plants by a comparison of SO2/CO2 and NOy/CO2 between aircraft and Air Markets Database will be investigated.

J Green WINTER
Jaime Green in the NSF-C-130 part of the WINTER campaign

 

M Fiddler WINTER
Marc Fiddler inside the NSF-C-130 part of the WINTER campaign

 

Past activities

  • Measurement of the Henry's law coefficient and first order loss rate of Isocyanic Acid (HNCO) and other pyrogenic species in the liquid phase in conjunction with HNCO and inorganic acid measurements during the California Research at the Nexus of Air Quality and Climate (CalNex 2010) and work at NCA&T used the mass Spectrometer Facility (IRC-007)
    mass spectrometer facility

 

The inability to account for the quantity of OH radical observed in the atmosphere has recently prompted an investigation into absorption of visible and near infrared light that leads to photolysis. For molecules that contain N-H and O-H bonds, vibrational overtones can have relatively intense absorption features. For some compounds, absorption due to these overtones, whose wavelengths are in the near IR and visible range of the spectrum, this can introduce enough energy into the molecule to photodissociate it. We use a combination of UV spectroscopy and CRDS to determine absolute vibrational overtone absorption cross sections. Using this data with dissociation information derived from theoretical calculations, we can determine the photolysis lifetimes (J) as a function of solar zenith angle (SZA), altitude, temperature, latitude, and longitude. We have used this method for measuring acetic and peracetic acid, and may expand this work to other relevant compounds.

NCA&T undergraduates (ASME) and EES PhD Student (now Dr. Singh) participated in the Field campaign in Boulder Colorado in the summer of 2014. 
https://www2.acom.ucar.edu/frappe 
Boulder