Atmospheric Volatile Hydrocarbon Composition at Five Remote Sites in Northwestern North Carolina

摘要

The results of a study to measure the volatile hydrocarbon composition of the atmosphere at several sites in the southern Appalachian Mountains of northwestern North Carolina are presented. Ambient air was sampled repeatedly at five geographically and botanically different remote sites from September 1981 to October 1982. In addition, limited sampling was done in and just outside the town of Boone, NC. Samples were collected in stainless steel canisters and analyzed for C-2 to C-12 hydrocarbons by gas chromatography with flame ionization detection. The nonmethane total hydrocarbon concentrations at the remote sites ranged from 32 to 132 ppbC. The range of identified paraffins, olefins, and aromatics concentrations was 7 to 65 ppbC, 1 to 8 ppbC, and 2 to 20 ppbC, respectively. Isoprene and alpha-pinene made up a small portion of NMTHC, ranging from less than 0.05 to 13 ppbC and less than 0.05 to 9 ppbC, respectively. Unknown peaks eluting mostly in the post-C-9 region of the chromatogram were a significant portion of the NMTHC, ranging from 13 to 108 ppbC. The identity and source of the unknown compounds are not well understood, although some of them are probably biogenic. Isoprene and alpha-pinene displayed a distinct seasonal variation related to ambient temperature; whereas, acetylene and the sum of paraffins, olefins, and aromatics showed no seasonal variation.