Methane fluxes were calculated from measurements carried out at a temperate upland forest in Central Ontario using the eddy covariance method over five months in the summer and fall seasons of 2011. Measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) which simultaneously measured methane (CH4), carbon dioxide (CO2), and water at 10 Hz sampling rates. Observed methane fluxes showed net uptake of methane over the measurement period with an average uptake flux value (±standard deviation of the mean) of -2.7±0.13 nmol m-2 s-1. Methane fluxes showed a diurnal pattern of increased uptake during the day and increasing uptake with seasonal progression. There was also a significant correlation in methane fluxes with soil water content and wind speed. Comparison of the FGGA measurements to those using a static chamber method and canister sampling showed close agreement in flux and mixing ratio values respectively.

Carbon dioxide is taken up by crops during production and released back to the atmosphere at different geographical locations through respiration of consumed crop commodities. In this study, spatially distributed county-level US cropland net primary productivity, harvested biomass, changes in soil carbon, and human and livestock consumption data were integrated into the prior terrestrial biosphere flux generated by the Boreal Ecosystem Productivity Simulator (BEPS). A global time-dependent Bayesian synthesis inversion with a nested focus on North America was carried out based on CO2 observations at 210 stations. Overall, the inverted annual North American CO2 sink weakened by 6.5% over the period from 2002 to 2007 compared to simulations disregarding US crop statistical data. The US Midwest is found to be the major sink of 0.36±0.13 PgC yr-1 whereas the large sink in the US Southeast forests weakened to 0.16±0.12 PgC yr-1 partly due to local CO2 sources from crop consumption.

Methane fluxes were calculated from measurements carried out at a temperate upland forest in Central Ontario using the eddy covariance method over five months in the summer and fall seasons of 2011. Measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) which simultaneously measured methane (CH4), carbon dioxide (CO2), and water at 10 Hz sampling rates. Observed methane fluxes showed net uptake of methane over the measurement period with an average uptake flux value (±standard deviation of the mean) of -2.7±0.13 nmol m-2 s-1. Methane fluxes showed a diurnal pattern of increased uptake during the day and increasing uptake with seasonal progression. There was also a significant correlation in methane fluxes with soil water content and wind speed. Comparison of the FGGA measurements to those using a static chamber method and canister sampling showed close agreement in flux and mixing ratio values respectively.

Carbon dioxide is taken up by crops during production and released back to the atmosphere at different geographical locations through respiration of consumed crop commodities. In this study, spatially distributed county-level US cropland net primary productivity, harvested biomass, changes in soil carbon, and human and livestock consumption data were integrated into the prior terrestrial biosphere flux generated by the Boreal Ecosystem Productivity Simulator (BEPS). A global time-dependent Bayesian synthesis inversion with a nested focus on North America was carried out based on CO2 observations at 210 stations. Overall, the inverted annual North American CO2 sink weakened by 6.5% over the period from 2002 to 2007 compared to simulations disregarding US crop statistical data. The US Midwest is found to be the major sink of 0.36±0.13 PgC yr-1 whereas the large sink in the US Southeast forests weakened to 0.16±0.12 PgC yr-1 partly due to local CO2 sources from crop consumption.

The isotopic composition of water in the atmosphere is influenced by how the water evaporated, how it was transported, and how it formed in the cloud before falling. Because these processes are temperature dependent, the isotopic ratios stored in glacial ice and other proxy sources have been used as an indicator of pre-instrumental climate. There is uncertainty, however, as to whether isotopic ratios should be interpreted as a proxy of local temperature, or as a broader indicator of changes in how the vapor was transported. To better understand these processes, the NASA GISS general circulation model (GCM) was used to examine two different types of controls on the isotopic composition of moisture. The first control was the large-scale circulation of the atmosphere. Over Europe, it was found that δ18O is strongly controlled by a Northern Annular Mode-like pattern, detected in both the GCM and for Europe’s high-quality precipitation δ18O data. Over the southwest Yukon, it was found that higher δ18O was associated with moisture transport from the south, which led to a re-interpretation of the large mid-19th century δ18O shift seen in the ice cores from Mt. Logan. The second type of control was microphysical, relating to the way precipitation interacts with vapor after it has formed. Using a GCM sensitivity experiment, the effects of ‘post-condensation exchange’ were found to depend primarily on the proportion between the amount of upstream precipitation that fell as rain and the amount that fell as snow, and at low latitudes, on the strength of atmospheric moisture recycling. This led to a partitioning of the well-observed correlation between temperature and precipitation δ18O into its initial and post-condensation components, and a GCM-based interpretation of satellite measurements of the isotopic composition of water vapor in the troposphere.

Atmospheric ammonia contributes to a number of environmental problems, but many questions regarding the behaviour of ammonia in the atmosphere remain. Field studies were performed to investigate the gas-particle partitioning of ammonia, the surface-atmosphere exchange, and to compare measurements with an online chemical transport model and offline thermodynamic models. A state-of-the-art instrument, Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS), with a novel sampling technique was used to measure ammonia. The detection limit of the instrument was found to be 690 ppt at 1 Hz and 42 ppt when averaged to 5 minutes. The uncertainty in the measurement is 10 % based on calibration from a permeation tube source. Laboratory and field tests show the ammonia time response to be slower at lower mixing ratios, and when the ambient relative humidity is high. Observations from the first field campaign discussed, the Border Air Quality and Meteorology Study (BAQS-Met), were compared to a chemical transport model AURAMS (A Unified Regional Air quality Modeling System). The model was often biased low in ammonia and ammonium and predicted an incorrect diurnal profile. Observations suggest a coupling between gas-particle and surface-atmosphere equilibria whereby a large atmospheric condensation sink induces emission of ammonia from the surface. A simple approach at representing the ammonia bi-direction flux more closely matched the observations, indicating that a fully coupled bi-directional flux parameterization in chemical transport models is necessary to accurately predict atmospheric ammonia. A suite of instrumentation during the CalNex 2010 field campaign allowed for in-depth analysis of gas-particle partitioning and estimation of aerosol pH. Observations were compared to predictions from the thermodynamic equilibrium models ISORROPIA and E-AIM. Deviations form equilibrium were found during periods of high levels of aerosol nitrate and positive net charge. The gas-particle partitioning was found to be very sensitive to aerosol pH.

The isotopic composition of water in the atmosphere is influenced by how the water evaporated, how it was transported, and how it formed in the cloud before falling. Because these processes are temperature dependent, the isotopic ratios stored in glacial ice and other proxy sources have been used as an indicator of pre-instrumental climate. There is uncertainty, however, as to whether isotopic ratios should be interpreted as a proxy of local temperature, or as a broader indicator of changes in how the vapor was transported. To better understand these processes, the NASA GISS general circulation model (GCM) was used to examine two different types of controls on the isotopic composition of moisture. The first control was the large-scale circulation of the atmosphere. Over Europe, it was found that δ18O is strongly controlled by a Northern Annular Mode-like pattern, detected in both the GCM and for Europe’s high-quality precipitation δ18O data. Over the southwest Yukon, it was found that higher δ18O was associated with moisture transport from the south, which led to a re-interpretation of the large mid-19th century δ18O shift seen in the ice cores from Mt. Logan. The second type of control was microphysical, relating to the way precipitation interacts with vapor after it has formed. Using a GCM sensitivity experiment, the effects of ‘post-condensation exchange’ were found to depend primarily on the proportion between the amount of upstream precipitation that fell as rain and the amount that fell as snow, and at low latitudes, on the strength of atmospheric moisture recycling. This led to a partitioning of the well-observed correlation between temperature and precipitation δ18O into its initial and post-condensation components, and a GCM-based interpretation of satellite measurements of the isotopic composition of water vapor in the troposphere.

Atmospheric ammonia contributes to a number of environmental problems, but many questions regarding the behaviour of ammonia in the atmosphere remain. Field studies were performed to investigate the gas-particle partitioning of ammonia, the surface-atmosphere exchange, and to compare measurements with an online chemical transport model and offline thermodynamic models. A state-of-the-art instrument, Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS), with a novel sampling technique was used to measure ammonia. The detection limit of the instrument was found to be 690 ppt at 1 Hz and 42 ppt when averaged to 5 minutes. The uncertainty in the measurement is 10 % based on calibration from a permeation tube source. Laboratory and field tests show the ammonia time response to be slower at lower mixing ratios, and when the ambient relative humidity is high. Observations from the first field campaign discussed, the Border Air Quality and Meteorology Study (BAQS-Met), were compared to a chemical transport model AURAMS (A Unified Regional Air quality Modeling System). The model was often biased low in ammonia and ammonium and predicted an incorrect diurnal profile. Observations suggest a coupling between gas-particle and surface-atmosphere equilibria whereby a large atmospheric condensation sink induces emission of ammonia from the surface. A simple approach at representing the ammonia bi-direction flux more closely matched the observations, indicating that a fully coupled bi-directional flux parameterization in chemical transport models is necessary to accurately predict atmospheric ammonia. A suite of instrumentation during the CalNex 2010 field campaign allowed for in-depth analysis of gas-particle partitioning and estimation of aerosol pH. Observations were compared to predictions from the thermodynamic equilibrium models ISORROPIA and E-AIM. Deviations form equilibrium were found during periods of high levels of aerosol nitrate and positive net charge. The gas-particle partitioning was found to be very sensitive to aerosol pH.

The role of weather and climate variability on the health of Aboriginal people in Fort Albany and Toronto, Ontario, Canada is explored through four complementary research studies. The first study examined past temperature trends of Fort Albany (using climate records of Moosonee) and Toronto. Temperature variability was found to be greater in Moosonee than in Toronto, and day to day temperature minimum (Tmin) threshold exceedances of 5 degrees Celsius was found to have significantly declined in both Toronto and Fort Albany. The second study explored the effects of climate change on a rural First Nation group in Fort Albany. Observed environmental changes include changes in the timing of seasons, spring melt and ice freeze-up; warmer seasons, an increase in extreme and unpredictable weather, and changes in animal patterns. These changes have affected subsistence harvesting activities and community infrastructure, which have lead to increased health risks, though many community members have exhibited resiliency and adaptation. The third study compared current health status between an urban Aboriginal and non-Aboriginal group. Urban Aboriginal participants were found to be at greater risk to psychological distress and seasonal affective disorder (SAD) than non-Aboriginal participants. Moreover, those who self-rated their health as poor/fair were more likely to exhibit psychological distress than those who self-rated their health as good/very good/excellent. The fourth study compared the effects of weather and seasonal change among a rural First Nation group, an urban Aboriginal group and an urban non-Aboriginal group. Urban Aboriginal participants were most affected by weather while rural Aboriginal (i.e. First Nation) participants were least affected by weather. These studies demonstrate that both urban and rural Aboriginal groups may be at risk to climate change and weather-related changes; though specific implications may differ due to different lifestyles and capacities to adapt to environmental conditions.

This study describes two projects involving recent research on atmospheric ammonia. The first project investigates differences in modelling techniques of aerosol acidity using data from two recent field campaigns. Our results show that allowing or disallowing gas-particle partitioning in the Extended Aerosol Inorganic Model (E-AIM) changed the average modelled aerosol activity of H+ from one campaign by seven orders of magnitude and that disallowing gas-particle partitioning may not accurately represent the chemical state of the aerosols. The second project investigates the interference of reduced nitrogen in commercial chemiluminescent nitrogen oxide monitors with molybdenum oxide catalytic converters. This phenomenon is strongly dependent on the temperature of the catalytic converter. Our results show these instruments can have high conversion efficiencies of gaseous NH3 and NH4+ salts to NO at typical reported converter temperatures, but conversion efficiency varies between instruments and may be the result of uncertainty in reported converter temperature.