Abstract
Photochemistry between gas phase organic compounds, oxides of nitrogen, and ozone is expected to result in the formation of nitrogen-containing compounds of potential toxicological importance. Classes of compounds which may form include nitro-, N-nitroso-, nitrate-, and nitrite-substituted organic compounds. Many of these compounds are labile, semivolatile organic compounds in equilibrium between the gas and particulate phases in the atmosphere. The phase distribution of these potentially toxic semivolatile organic compounds can be determined using diffusion denuder sampling technology. The total concentration of N-nitroso compounds in a collected sample is determined using N-nitroso-specific denitrosation reactions followed by detection of the produced nitric oxide with a chemiluminescence detector. Denitrosation chemistry can also be used to determine nitrite compounds. Differentiation between total N-nitroso- and nitrite-containing compounds is accomplished using sulfamic acid as a nitrite-specific reagent. These sampling and analytical techniques have been used for the quantification of total N-nitroso and nitrite organic compounds in both the fine particulate (PM2.5) and gas phases in samples collected in Provo, Utah. The results indicate that the majority of the N-nitroso and nitrite organic compounds present in fine particulate matter in the studied urban area are semivolatile organic compounds which can be lost from particles during sampling. Furthermore, the concentrations of these fine particulate compounds are comparable to the concentrations of gas phase N-nitroso and nitrite organic species.