SERIAL GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC MEASUREMENTS OF SOME VOLATILE ORGANIC-COMPOUNDS IN THE ARCTIC ATMOSPHERE DURING THE 1992 POLAR SUNRISE EXPERIMENT

Variations of selected volatile organic compounds (11 halocarbons, 3 h ydrocarbons, and acetone) in Arctic air were measured with an automate d GC/MS at Alert, Canada, as a part of the 1992 Polar Sunrise Experime nt. During the springtime ozone depletion, several volatile organic co mpounds (VOCs) correlated significantly with ozone. In particular, tri chloroethylene had a strong positive correlation (R = 0.90), while bro moform (R = -0.87) and acetone (R = -0.90) were negatively correlated. Isopentane (R = 0.77), n-butane (R = 0.77), and tetrachloroethylene ( R = 0.66) were also positively correlated with ozone. These findings s uggest that the ozone depletion at Alert, including its small-scale fl uctuations, is caused by the advection of air masses in which reaction s by Cl and Br atoms rapidly consumed chloroethylenes and alkanes conc urrently and destroyed ozone while the air was over the ocean. In wint er, however, slightly negative correlations of ozone with trichloroeth ylene (R = -0.51) and tetrachloroethylene (R = -0.40) were found, whic h may be caused by the vertical mixing of surface and free tropospheri c air.