OH and halogen atom influence on the variability of non-methane hydrocarbons in the Antarctic boundary layer

TY - JOUR

T1 - OH and halogen atom influence on the variability of non-methane hydrocarbons in the Antarctic boundary layer

AU - Read, Katie A.

AU - Lewis, Alastair C.

AU - Salmon, Rhian A.

AU - Jones, Anna E.

AU - Bauguitte, Stephane

PY - 2007/2

Y1 - 2007/2

N2 - Measurements of C-2-C-8 non-methane hydrocarbons (NMHCs) have been made in situ at Halley Base, Antarctica (75 degrees 35'S, 26 degrees 19'W) from February 2004 to February 2005 as part of the Chemistry of the Antarctic Boundary Layer and the Interface with Snow (CHABLIS) experiment. The data show long- and short-term variabilities in NMHCs controlled by the seasonal and geographic dependence of emissions and variation in atmospheric removal rates and pathways. Ethane, propane, iso-butane, n-butane and acetylene abundances followed a general OH-dependent sinusoidal seasonal cycle. The yearly averages were 186, 31, 3.2, 4.9 and 19 pptV, respectively, lower than those which were reported in some previous studies. Superimposed on a seasonal cycle was shorter-term variability that could be attributed to both synoptic airmass variability and localized loss processes due to other radical species. Hydrocarbon variability during periods of hour-to-day-long surface O-3 depletion in late winter/early spring indicated active halogen atom chemistry estimated to be in the range 1.7 x 10(3)-3.4 x 10(4) atom cm(-3) for Cl and 4.8 x 10(6)-9.6 x 10(7) atom cm(-3) for Br. Longer-term negative deviations from sinusoidal behaviour in the late August were indicative of NMHC reaction with a persistent [Cl] of 2.3 x 10(3) atom cm(-3). Maximum ethene and propene of 157 and 179 pptV, respectively, were observed in the late February/early March, consistent with increased oceanic biogenic emissions; however, their presence was significant year-round (June-August concentrations of 17.1 +/- 18.3 and 7.9 +/- 20.0 pptV, respectively).

AB - Measurements of C-2-C-8 non-methane hydrocarbons (NMHCs) have been made in situ at Halley Base, Antarctica (75 degrees 35'S, 26 degrees 19'W) from February 2004 to February 2005 as part of the Chemistry of the Antarctic Boundary Layer and the Interface with Snow (CHABLIS) experiment. The data show long- and short-term variabilities in NMHCs controlled by the seasonal and geographic dependence of emissions and variation in atmospheric removal rates and pathways. Ethane, propane, iso-butane, n-butane and acetylene abundances followed a general OH-dependent sinusoidal seasonal cycle. The yearly averages were 186, 31, 3.2, 4.9 and 19 pptV, respectively, lower than those which were reported in some previous studies. Superimposed on a seasonal cycle was shorter-term variability that could be attributed to both synoptic airmass variability and localized loss processes due to other radical species. Hydrocarbon variability during periods of hour-to-day-long surface O-3 depletion in late winter/early spring indicated active halogen atom chemistry estimated to be in the range 1.7 x 10(3)-3.4 x 10(4) atom cm(-3) for Cl and 4.8 x 10(6)-9.6 x 10(7) atom cm(-3) for Br. Longer-term negative deviations from sinusoidal behaviour in the late August were indicative of NMHC reaction with a persistent [Cl] of 2.3 x 10(3) atom cm(-3). Maximum ethene and propene of 157 and 179 pptV, respectively, were observed in the late February/early March, consistent with increased oceanic biogenic emissions; however, their presence was significant year-round (June-August concentrations of 17.1 +/- 18.3 and 7.9 +/- 20.0 pptV, respectively).

KW - VOLATILE ORGANIC-COMPOUNDS

KW - SEASONAL-VARIATIONS

KW - METHYL-CHLORIDE

KW - SURFACE SNOW

KW - SOUTH-POLE

KW - TROPOSPHERE

KW - CHEMISTRY

KW - AIR

KW - ATMOSPHERE

KW - ETHANE

U2 - 10.1111/j.1600-0889.2006.00227.x

DO - 10.1111/j.1600-0889.2006.00227.x

M3 - Article

SN - 0280-6509

VL - 59

SP - 22

EP - 38

JO - TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY

JF - TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY

IS - 1

ER -