Allan Bertram

We focus on chemical and physical processes important in the atmosphere. Of special interest are atmospheric aerosol particles and the role they play in urban air pollution, climate change and atmospheric chemistry. Ultimately our goal is to better understand the role of human activity on the Earth'­s atmosphere.

Atmospheric aerosol particles, which range in size from 10 to 10,000 nanometers, can effect Earths climate by scattering or absorbing solar radiation and by modifying the nucleation and reflectivity of clouds. For example, a recent analysis suggests that a large portion of Arctic warming may be attributed to atmospheric soot, a type of atmospheric aerosol. Poorly understood from a scientific standpoint, atmospheric aerosols constitute one of the largest uncertainties in predicting future climate change. Aerosol particles also negatively affect air quality and are largely responsible for visibility reduction in urban environments. Elevated levels of aerosol particles are also strongly correlated with increased cardio-pulmonary morbidity, according to epidemiological studies.

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Heterogeneous atmospheric chemistry

Over the past two decades, laboratory, fieldwork, and modeling studies have conclusively shown that interactions between gas-phase species and atmospheric aerosol particles (termed heterogeneous atmospheric chemistry) can significantly influence the chemistry of the atmosphere. One of the goals of our research is to identify key heterogeneous reactions that are important in the atmosphere. Atmospheric heterogeneous reactions are simulated and probed in the laboratory using aerosol reaction chambers, flow tube reactors, and state-of-the-art analytical techniques. From the laboratory data we determine fundamental kinetics and mechanisms of these reactions for incorporation into atmospheric models.

Aerosol mass spectrometry (field studies)

To assess the impact of Asian particulate pollution on Western Canada as well as general trends in background aerosol, a state-of-the-art single particle mass spectrometer designed and built at UBC is being deployed at Environment Canada'­s Whistler High Elevation site, located at the peak of Whistler Mountain, BC. This site offers the rare opportunity of nearly year-round measurements of tropospheric air unaffected by local background. This project is a collaboration with researchers at UBC (Allan Bertram and Ian McKendry), Environment Canada (Anne Marie MacDonald and Richard Leaitch) and Pacific Northwest National Laboratory (Daniel Cziczo).

Kinetics and mechanisms of ice nucleation in the atmosphere (laboratory studies)

Ice clouds in the troposphere play a key role in the Earths climate system by strongly influencing the Earth­s radiative properties. These clouds form when ice nucleates on or in aerosol particles in the troposphere. Another area of research in our group focuses on understanding the mechanisms and determining the kinetics of these processes. Results from this project should provide building blocks for accurately representing ice clouds in climate models.

Ice nucleation (computer simulations)

The ice nucleation studies in our laboratory have also led to a collaboration with Gren Patey (UBC) involving computer simulations to better understand and predict ice nucleation on a molecular level. Currently we are investigating ice nucleation on mineral dust surfaces containing defects such as steps, edges, and cracks using these simulations.

Hygroscopic properties and phase transitions of atmospheric aerosols

Atmospheric aerosol particles can undergo several types of phase transitions. Two types of atmospherically relevant phase transitions are deliquescence and efflorescence. We are currently studying these phase transitions for a range of atmospheric conditions to incorporate into atmospheric models. A wide range of instruments are being used for these studies including optical microscopy, FTIR microscopy and an electrodynamic balance.

Viscosity of atmospheric particles

The viscosity of aerosol particles is a fundamental property that is currently poorly quantified. However, information on the viscosity of these particles is required for accurate predictions of particle growth, mass and removal, all of which are closely connected to air quality and climate predictions. To quantify the viscosities of aerosol particles, we developed two new techniques, namely a bead mobility technique and a poke-flow technique combined with fluid simulations. Using these techniques, we determine the viscosities of aerosol particles as a function of relative humidity. Moreover, we apply this new data to predictions of air quality, visibility, and climate.

Ice nuclei (field studies)

Ice nucleation studies extend to field sites in Canada and abroad. Several projects involve collaborative work as part of the Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments (NETCARE). In France, the BIODETECT 2014 summer campaign focused on aerosols from biological origin (bacteria, fungi, pollen). Aerosol particles from these field sites are collected and characterized for their ice nucleation ability, INP concentrations, and composition.

For more information on specific projects please see the Bertram Group Homepage

Bertram Group Homepage