Global concentrations of selected halocarbons, 1988-1992

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:50585

Wang, J L.C.

During a period of 5 years, 1988 to 1992, 15 field sampling trips have been completed in an effort to continue monitoring background atmospheric concentration of 6 man-made halocarbons, i.e., CCl{sub 2}F{sub 2} (CFC-12), CCl{sub 3}F (CFC-11), CCl{sub 2}FCClF{sub 2} (CFC-113), CH{sub 3}CCl{sub 3}, CCl{sub 4}, and C{sub 2}Cl{sub 4}. Approximately 70 to 90 flask air samples were collected 3 to 4 times a year from remote surface locations in the Pacific, ranging between latitudes 72{degrees}N and 47{degrees}S. The samples were analyzed in the laboratory at University of California, Irvine employing cryogenic sample preconcentration, gas chromatographic separation and electron capture detection. Diluted air mixtures made from pure halocarbons were rigorously formulated to the part per trillion by volume levels (x10{sup {minus}12}) and were employed to calibrate the absolute halocarbon concentrations of a whole air sample used as a working standard in the sample analysis. The absolute calibrations performed on three chlorofluorocarbons (CFCs) yielded winter-1992 averaged global concentrations of 80, 498, and 266 pptv for CFC-11, CFC-12, and CFC-113, respectively. Among the halocarbons measured CFC-11, CFC-12, and CFC-113 have been studied in detail including the changes in their temporal trends, north-to-south gradients, rates of increase, etc, at a time when their emissions have been slowly cut back as required by the Montreal Protocol and its amendments. In general, the background concentrations of these CFCs all showed a substantial decrease in their rate of growth in the atmosphere in recent years compared to earlier years. The rates of increase for winter 1992 are 3, 9, and 2.5 pptv/yr compared to 11, 20, and 8 in 1988, for CFC-11, CFC-12, and CFC-113, respectively. Seasonal variation in global concentrations for a hydroxy-radical reactive species, tetrachloroethylene (CCl{sub 2}{double_bond}CCl{sub 2}) has also been studied.

• Research Organization: California Univ., Irvine, CA (United States)
• OSTI ID: 50585
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CHLOROFLUOROCARBONS
ECOLOGICAL CONCENTRATION
FREONS
GLOBAL ASPECTS