Seasonal cycle of seawater bromoform and dibromomethane concentrations in a coastal bay on the western Antarctic Peninsula
Seasonal cycle of seawater bromoform and dibromomethane concentrations in a coastal bay on the western Antarctic Peninsula
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DOI：
10.1029/2008gb003268
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发表时间：
2009-06-30
影响因子：
5.2
通讯作者：
Liss, Peter S.
中科院分区：
文献类型：
--
作者：
Hughes, Claire;Chuck, Adele L.;Liss, Peter S.
众所周知，海洋向空气排放溴碳气体在大气臭氧消耗中起着重要作用。本研究于2005年2月至2007年3月在南极半岛玛格丽特湾的Rothera海洋和生物时间序列（RaTS）站点定期测量了海水中溴仿（CHBr3）和二溴甲烷（CH2Br2）的浓度。CHBr3和CH2Br2浓度具有明显的季节性。最高的溴碳浓度（高达276.4 +/- 13.0 pmol CHBr3 L-1和30.0 +/- 0.4 pmol CH2Br2 L-1）与南方夏季的年度微藻华相吻合，冬季快冰下的浓度较低（高达39.5 pmol CHBr3 L-1和9.6 +/- 0.6 pmol CH2Br2 L-1）。溴碳浓度最初增加的时间与海冰退缩和微藻华的开始有关。观测到的CH2Br2/CHBr3的季节变化表明，这种关系可能用于确定溴碳源区。2005/2006年和2006/2007年夏季计算的主要正饱和度异常表明，该海湾是CHBr3和CH2Br2向大气的来源。玛格丽特湾在无冰期溴碳海气通量的估计值为84(-13至275)CHBr3 nmol m(-2) d（-1）和21(2至70)nmol CH2Br2 m(-2) d（-1）。如果这些通量率代表了每年南方夏季在南大洋大片地区发生的季节性冰边区水华，那么海洋对空气的溴碳排放可能对南极大气的化学成分产生重要影响。
Sea-to-air emissions of bromocarbon gases are known to play an important role in atmospheric ozone depletion. In this study, seawater concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) were measured regularly between February 2005 and March 2007 at the Rothera Oceanographic and Biological Time Series (RaTS) site located in Marguerite Bay on the Antarctic Peninsula. Strong seasonality in CHBr3 and CH2Br2 concentrations was observed. The highest bromocarbon concentrations (up to 276.4 +/- 13.0 pmol CHBr3 L-1 and 30.0 +/- 0.4 pmol CH2Br2 L-1) were found to coincide with the annual microalgal bloom during the austral summer, with lower concentrations (up to 39.5 pmol CHBr3 L-1 and 9.6 +/- 0.6 pmol CH2Br2 L-1) measured under the winter fast ice. The timing of the initial increase in bromocarbon concentrations was related to the sea-ice retreat and onset of the microalgal bloom. Observed seasonal variability in CH2Br2/CHBr3 suggests that this relationship may be of use in resolving bromocarbon source regions. Mainly positive saturation anomalies calculated for both the 2005/2006 and 2006/2007 summers suggest that the bay was a source of CHBr3 and CH2Br2 to the atmosphere. Estimates of bromocarbon sea-to-air flux rates from Marguerite Bay during ice-free periods are 84 (-13 to 275) CHBr3 nmol m(-2) d(-1) and 21 (2 to 70) nmol CH2Br2 m(-2) d(-1). If these flux rates are representative of the seasonal ice edge zone bloom which occurs each year over large areas of the Southern Ocean during the austral summer, sea-to-air bromocarbon emissions could have an important impact on the chemistry of the Antarctic atmosphere.