Characterising dissolved nitrate in precipitation using stable nitrogen and oxygen isotopes

Single event precipitation samples were collected at two sites in Newfoundland for stable isotopic analysis of nitrogen and oxygen of dissolved nitrate. Nitrate, the second largest acidifying component of rain, is formed during the oxidation of NO and NO2, collectively known as NOx as well as other nitrogen species. Both natural and anthropogenic sources exist, however fossil fuel combustion in power plants and vehicles are the main contributors of NOx to the atmosphere. Nitrogen isotopes of nitrate may give insight into the source of the atmospheric oxinitrogen species, while oxygen isotopes may provide information about the type of oxidation the NOx emissions have undergone. The isotopic signatures, in combination with chemical and meteorological data, were used to characterise the main controls of the nitrate in the precipitation.; This study has provided valuable isotopic measurements of atmospheric nitrate. To the author's knowledge, the method used in this study for isolating and processing dissolved nitrate in precipitation for stable isotopic analysis had not been previously applied to single rain events, making this study unique. As well, it has shown through the combination of isotopic and chemical data how nitrogen isotopes of precipitation nitrate are controlled by sources, while the oxygen isotopes of these compounds are controlled by atmospheric oxidation processes. (Abstract shortened by UMI.)...