Laser spectrometer for high-resolution measurements of air quality and greenhouse gases

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The conversion of molecular nitrogen (N2) to ‘fixed’ nitrogen, e.g. ammonia (NH3), nitrogen oxides (NOx = NO + NO2), and nitrous oxide (N2O), has accelerated dramatically in the modern age due to industrial fertilizer production, and as an unintended consequence of high-temperature combustion. N2O is an important greenhouse gas and contributes significantly to stratospheric ozone depletion. Its atmospheric mixing ratio has been consistently increasing at a rate of 0.75 ppb per year over the last four decades, but an accurate accounting of its sources (ocean, natural and managed soils, livestock, biomass burning, industry) and sinks (photodissociation in the stratosphere) is still lacking. A laser spectrometer capable of high time resolution and high precision N2O measurements is urgently needed to support various projects within the research program. The choice of a spectrometer that can simultaneously measure CO and CO2 maximizes the applicability of the instrument, especially in the context of field measurements. The instrument will be a critical part of the suite of equipment used in laboratory studies to measure the relative yields of NOx and N2O produced through the OH-initiated oxidation of NH3. It will also be used to quantify the emissions of N2O (along with NH3 and NOx) from soil samples as a function of temperature, humidity, N content and microbial activity in chamber experiments. The capability to measure CO and CO2 simultaneously at high time resolution will be used to evaluate vehicle-specific CO/CO2 emission ratios from onroad traffic. The instrument will contribute to a network of in situ and column measurements of greenhouse gases and air quality pollutants in the Greater Toronto Area aimed at providing observational constraints at urban emission inventories. As part of the Canadian Atmospheric Laser Absorption Spectroscopy Experiment Test-bed (CALASET) project, an open-path spectrometer is being developed for balloon-based measurements of atmospheric composition. The characterization and optimization of this novel instrument, currently under construction, will be significantly improved by comparisons with side-by-side measurements from the spectrometer requested in this proposal.