Characterization and Quantification of the Oxides of Sulfur and Nitrogen and Associated Compounds in Their Gaseous, Aerosol, and Dissolved States

摘要

The needs and problems associated with the characterization and quantification of the oxides of sulfur and nitrogen and associated compounds in their gaseous, aerosol, and dissolved states are discussed. Illustrations are given of the techniques in present usage for the determination of the substances of interest to investigators concerned with the effects of air pollutants on the terrestrial ecosystem. The value and utility of the newer techniques employing real time continuous instrumentation are presented and compared with the more traditional approaches utilizing sampling collection. A plea is made to provide resources for data reduction especially in order to obtain constructive utilization of continuous instrumentation. It is asserted that real time instrumentation is best utilized during campaign measurement programs where short time resolution is required and that collection techniques still have a place, especially in long term monitoring efforts. Special attention was directed at, and the problems highlighted that are associated with, the utilization of the real time instruments available for the flame photometric determination of the oxides of sulfur and the chemiluminescent measurement of the oxides of nitrogen. The newer methods proposed for their use in the determination of sulfate and nitric acid respectively are presented. The difficulties associated with the determination of nitrate are enunciated and attention focused on the problems of obtaining a sample due to the variation of the vapor pressure of gaseous nitric acid and ammonia above solid ammonium nitrate which is in association with an acidic aerosol containing sulfate. The utility of measurements of the composition of rainwater is discussed in light of its application to determine the mechanisms through which rain derives its chemical composition. (ERA citation 05:029585)