Bargagli Roberto, Agnorelli Chiara, Borghini Francesca, Monaci Fabrizio
Dipartimento di Scienze Ambientàli, Università di Siena, Via P.A. Mattioli, 4; 53100 Siena, Italy.
Environ Sci Technol. 2005 Nov 1;39(21):8150-5. doi: 10.1021/es0507315.
Mercury emitted by anthropogenic and natural sources occurs in the atmosphere mostly in the gaseous elemental form, which has a long lifetime in tropical and temperate regions. Once deposited in terrestrial and aquatic ecosystems the metal is partly re-emitted into the air, thus assuming the characteristics of global pollutants such as persistent volatile chemicals. In polar regions, during and after the sunrise, the photochemically driven oxidation of gaseous Hg by reactive halogens may result in areas of greatly enhanced Hg deposition. Mercury concentrations in soils, lichens, and mosses collected in a stretch between 74 degrees 30' S and 76 degrees 00' S, in ice-free coastal areas of Victoria Land facing the Terra Nova Bay coastal polynya, were higher than typical Antarctic baselines. The finding of enhanced Hg bioaccumulation in Antarctic terrestrial ecosystems facing a coastal polynya strongly supports recent speculations on the role of ice crystals ("frost flowers") growing in polynyas as a dominant source of sea salt aerosols and bromine compounds, which are involved in springtime mercury depletion events (MDEs). These results raise concern aboutthe possible environmental effects of changes in regional climate and sea ice coverage, and on the possible role of Antarctica as a sink in the mercury cycle.
人为源和自然源排放的汞在大气中大多以气态单质形式存在，在热带和温带地区具有较长的存留时间。一旦汞沉积到陆地和水生生态系统中，部分会再次排放到空气中，从而呈现出持久性挥发性化学物质等全球污染物的特征。在极地地区，日出期间及之后，气态汞被活性卤素光化学驱动氧化可能导致汞沉积大幅增加的区域。在面向特拉诺瓦湾沿岸冰间湖的维多利亚地无冰沿海地区，南纬74°30′至76°00′之间采集的土壤、地衣和苔藓中的汞浓度高于典型的南极基线。在面临沿海冰间湖的南极陆地生态系统中发现汞生物累积增强，这有力地支持了近期有关在冰间湖中生长的冰晶（“霜花”）作为海盐气溶胶和溴化合物主要来源所起作用的推测，这些物质参与了春季汞损耗事件（MDEs）。这些结果引发了人们对区域气候和海冰覆盖变化可能产生的环境影响以及南极洲在汞循环中作为汇的可能作用的担忧。
