Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Science

First Advisor

Bililign, Solomon

Abstract

A recent study of biomass fires and some field measurements have revealed that isocyanic acid can reach levels as high as 600 ppbv near fires and up to 200 pptv in ambient air. After the solubility was measured for the first time, it was then possible for any potential human health effects of HNCO to be evaluated. HNCO is highly soluble in the human body given that the physiological pH is 7.4, and there exists an increased risk for atherosclerosis, cataracts, and rheumatoid arthritis via protein carbamylation. Based on preliminary experimental results conducted at a pH of 3.0 ± 0.1 and room temperature (T = 25 ± 1°C), Henry's coefficient was found to be 21.1 ± 2.7 M/atm with the first order loss rate k = (6.3 ± 1.6) x 10-4 s-1 (in solution). This solubility measurement made it possible for HNCO atmospheric sensitivity and in-cloud lifetimes to be estimated using a numerical cloud box model. It is revealed that it is essential for the cloud pH to be calculated at every timestep rather than prescribing a constant pH value. The model shows that the elevation, liquid water content, droplet size, and gas-phase nitric and isocyanic acid concentrations are critical in characterizing HNCO in clouds and the -cloud lifetime of HNCO which is estimated to range from approximately 6.156 ± 0.007 to 82.435 ± 0.188 hours. It is also noteworthy to mention that the lower liquid water content of a cloud such as fog or haze (approximately .05 g/m3 ), the better the chance of reducing the HNCO concentration. We also demonstrate that the idea of making a numerical cloud chemistry estimate with a static pH leads to completely inaccurate results. A dynamic cloud acidity calculation is determined to be essential. This solubility measurement made it possible for HNCO atmospheric sensitivity and in-cloud lifetimes to be estimated using a numerical cloud box model. It is revealed that it is essential for the cloud pH to be calculated at every timestep rather than prescribing a constant pH value. The model shows that the elevation, liquid water content, droplet size, and gas-phase nitric and isocyanic acid concentrations are critical in characterizing HNCO in clouds and the -cloud lifetime of HNCO which is estimated to range from approximately 6.156 ± 0.007 to 82.435 ± 0.188 hours. It is also noteworthy to mention that the lower liquid water content of a cloud such as fog or haze (approximately .05 g/m3 ), the better the chance of reducing the HNCO concentration. We also demonstrate that the idea of making a numerical cloud chemistry estimate with a static pH leads to completely inaccurate results. A dynamic cloud acidity calculation is determined to be essential. This solubility measurement made it possible for HNCO atmospheric sensitivity and in-cloud lifetimes to be estimated using a numerical cloud box model. It is revealed that it is essential for the cloud pH to be calculated at every timestep rather than prescribing a constant pH value. The model shows that the elevation, liquid water content, droplet size, and gas-phase nitric and isocyanic acid concentrations are critical in characterizing HNCO in clouds and the -cloud lifetime of HNCO which is estimated to range from approximately 6.156 ± 0.007 to 82.435 ± 0.188 hours. It is also noteworthy to mention that the lower liquid water content of a cloud such as fog or haze (approximately .05 g/m3 ), the better the chance of reducing the HNCO concentration. We also demonstrate that the idea of making a numerical cloud chemistry estimate with a static pH leads to completely inaccurate results. A dynamic cloud acidity calculation is determined to be essential. This solubility measurement made it possible for HNCO atmospheric sensitivity and in-cloud lifetimes to be estimated using a numerical cloud box model. It is revealed that it is essential for the cloud pH to be calculated at every timestep rather than prescribing a constant pH value. The model shows that the elevation, liquid water content, droplet size, and gas-phase nitric and isocyanic acid concentrations are critical in characterizing HNCO in clouds and the -cloud lifetime of HNCO which is estimated to range from approximately 6.156 ± 0.007 to 82.435 ± 0.188 hours. It is also noteworthy to mention that the lower liquid water content of a cloud such as fog or haze (approximately .05 g/m3 ), the better the chance of reducing the HNCO concentration. We also demonstrate that the idea of making a numerical cloud chemistry estimate with a static pH leads to completely inaccurate results. A dynamic cloud acidity calculation is determined to be essential.

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