Investigation of Air Pollutants Near the Great Lakes in Ontario and Along the Coast of California

This dissertation is of two parts. In the first part, carbonyls were measured in Ridgetown, Ontario using an automated HPLC-DNPH system during the BAQS-Met study in 2007. Median concentrations for formaldehyde, acetaldehyde, acetone, propanal, MEK and butanal were observed to be 1.5, 0.67, 1.9, 0.072, 0.22 and 0.041 ppb respectively. The highest carbonyl concentrations were observed with trans-boundary transport associated with airmasses that passed over Michigan and Illinois and could have originated from the Ohio Valley. Local ozone sensitivity was established using the HCHO/NO2 ratio and this area was found to be sensitive to both VOCs and NOx. Carbonyls accounted for 35% of O3 formation estimated using the MIR scale. Lake breeze events had no significant impact on carbonyl concentrations in this location.

In the second part of this dissertation, aerosol concentrations and composition were obtained along the coast of California using a High-Resolution Time-of-Flight aerosol mass spectrometer (HR-AMS) onboard RV Atlantis during CalNex in 2010. Measured submicron aerosols were dominated by particulate sulfate and particulate organic matter (pOM), which accounted for 86% of all measured submicron aerosol mass. High aerosol concentrations were associated with land breezes from polluted cities while low concentrations were observed with sea breezes.

For the first time, a method is proposed to establish non-refractory particulate chloride (NR p-Cl) in ambient air that is enriched with sea salt chloride. This method involves the subtraction of refractory chloride signal (RF HxCl+), which was estimated using the HxCl+ (total chloride signal) to Na35Cl+ ratio in artificially generated sea spray aerosols. Also for the first time, a method is proposed to determine percentage chloride depletion in ambient aerosols using HR-AMS measurements of Na+ and Na35Cl+. Using this proposed method, study-wide median chloride depletion in submicron aerosols was determined to be 78%. For NR p-Cl, increasing concentrations were observed with increasing RH and pH and decreasing temperature. Finally, pOM in sea spray aerosols was observed to be dominated by hydrocarbons (55%) and oxygenated hydrocarbon classes (37%); this pOM was found to be positively correlated with seawater DMS.