Halocarbon and pigment profiles in the waters of the Amundsen and Ross Seas, Antarctica

Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters, and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130ºW) and Ross Sea (158ºW- 160ºE). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Saturation anomalies for the surface water and brine (in sea ice) were determined for the two indicator halocarbons bromoform and chloriodomethane. For bromoform, the surface water anomalies varied between -83 and 11%, whereas chloroiodomethane anomalies varied between -6 and 1,200%. The saturation anomalies for brine varied between -56 to 120% for bromoform and 91 to 22,000% for chloroiodomethane, indicating that sea ice could be a possible source both to the atmosphere and the surface waters. Polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments.

目前学界对南极海域中挥发性卤代有机化合物（halocarbons）的分布特征及其与生物物理变量的关联尚未明晰。2007-2008年南极夏季（12月至次年1月）期间，研究人员在阿蒙森海（100°W~130°W）与罗斯海（158°W~160°E）海域测定了卤代烃与色素的浓度；此外还同步检测了大气、积雪与海冰中的卤代烃含量。研究发现，卤代烃的分布在很大程度上受海冰调控，远洋生物群落对其分布的影响则相对微弱。与冰间湖开阔水域及罗斯海底层水体相比，覆冰区域表层混合层中天然生成的卤代烃浓度显著升高；相较于表层海水，海冰卤水内的卤代烃浓度同样更高。积雪培养实验证实了卤代烃存在另一潜在来源。阿蒙森海与罗斯海的卤代烃分布差异显著，这主要源于二者迥异的海洋学环境背景。针对碘代卤代烃，研究仅在罗斯海海域发现其与代表普林藻属（Phaeocystis）的色素含量存在较弱相关性。研究针对两种指示性卤代烃——三溴甲烷（bromoform）与氯碘甲烷（chloriodomethane），测定了表层海水及海冰卤水的饱和异常值：其中三溴甲烷的表层海水饱和异常值介于-83%至11%之间，氯碘甲烷的饱和异常值范围为-6%至1200%；海冰卤水的饱和异常值则为三溴甲烷-56%~120%、氯碘甲烷91%~22000%，这表明海冰可能是大气与表层海水卤代烃的潜在来源之一。极地海域对全球卤代烃收支平衡具有显著影响，因此全球尺度的卤代烃评估需将极地海域纳入考量范畴。