Research

We use conventional analytical methods (spectroscopy, spectrometry, chromatography) to acquire observational datasets aimed at improving the understanding of the emissions, distribution and deposition of reactive nitrogen compounds in the environment.

In parallel, innovative instrumentation is being developed that can be validated alongside the existing technology, and then employed to answer challenging research questions about reactive nitrogen budgets.

The deployment of analytical instrumentation at field sites makes the following attributes advantageous: rugged, mobile, low maintenance, minimal use of electricity and consumables, and freedom from interference caused by atmospheric constituents or conditions. These techniques can also be used in laboratory studies to examine the specific mechanisms and rates that play important roles in the uptake and release of reactive nitrogen by surfaces.

Field Measurements


Border Air Quality Study Measurements of particulate matter (PM_2.5) and gaseous precursors at Harrow, Ontario from June–July 2007. Ground measurements of ionic species using the AIM-IC instrument. Measurements of gas-phase ammonia using the QC-TILDAS instrument.	Edinburgh Ammonia Intercomparison Study Measurements of ammonia using a variety of instruments in an agricultural field under normal grazing conditions and during application of fertilizer.	Research tower in Haliburton forest Tower based measurements of nitrogen deposition in Haliburton forest. Flux measurements of ammonia and nitrogen oxides.	CalNex Research at the nexus of air quality and climate change in California. Measurements of PM_2.5 and gaseous precursors in Bakersfield and gas-phase ammonia in Pasadena.

Analytical Techniques


Ambient Ion Monitor/Ion Chromatograph (AIM-IC) Capable of highly sensitive, continuous and simultaneous measurements of atmospheric acidic and alkaline soluble gases and aerosol constituents.	Quantum Cascade laser based Tunable Infrared Differential Absorption Spectroscpy (QC-TIDLAS) Capable of making sensitive, high time resolution measurements of ammonia in a wide variety of environments.	Chemiluminescent detection system for NO/NO₂/NO_y Makes sensitive, high time resolution measurements of atmospheric NO_x species and total reactive nitrogen oxides (NO_y).

These instruments, including supporting chemical and meteorological equipment, will be deployed in various locations such as the Forest Flux Research Station at the Borden Canadian Forces Base and the Center for Atmospheric Research Experiments (CARE) at Egbert, ON in collaboration with Environment Canada. Intensive field campaigns are also planned, the first of which will be the Border Air Quality Study in Windsor, ON during the summer of 2007. Our research will provide a complete picture of the atmospheric reactive nitrogen budget, and answer challenging questions about the transformation of reactive nitrogen in our environment.

Data Analysis

In addition to analysis of data obtained in our group, we have support from Environment Canada to analyze observations from many federal and provincial monitoring networks (e.g. NAPS, CAPMON)

Ozone in GTA
An examination of the last decade of observations of ozone and its precursors in the Greater Toronto Area has demonstrated why emission controls that have been so successful for primary pollutants have resulted in only minor reductions in photochemical ozone. This figure displays contours of predicted ozone production rates as a function of NO₂ concentration and VOC reactivity, while the shaded arrow shows the chemical space over which the atmosphere has changed in the last eight years, resulting in minimal decreases in ozone. This work (Geddes et al., 2009) has attracted significant media interest (U of T Bulletin and Varsity, Sun Media outlets, and lead story on Aug 17, 2009 Global News evening broadcasts).

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Acid Deposition in Canada
Our analysis of the chemical composition of gases, particulate matter and precipitation from CAPMON sites across Canada between 1990 and 2007 found that decreases in sulphate yielded increases in the pH of precipitation, but also altered the partitioning between HNO₃ and particulate nitrate (Cole and Murphy, submitted). The lack of routine measurements of gas phase ammonia complicates the interpretation of trends and underlines the need for the type of accurate measurements we are pursuing.

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Ground-based evaluation of OMI NO₂
Applications of remotely sensed chemical composition include evaluation of air quality models, assimilation into air quality forecast models, identification of previously unrecognized pollution hot spots or emission sources, and assessments of chronic pollutant exposure in epidemiological studies. There is interest in ascertaining to what degree observations of tropospheric columns of pollutants (e.g. NO₂) observed from space can replicate/replace data from sparse networks of traditional in situ monitors, particularly in urban areas where there is a high degree of spatial variability. One caveat is the presence of clouds, which obscure the satellite instrument’s field of view. We are assessing this by using the fractional cloud cover observed by the Ozone Monitoring Instrument (OMI) to screen the ground-based measurements, and calculate whether there is a significant selection bias in NO₂ and SO₂.