Environmental hazards of fluoride in volcanic ash from the ongoing Eyjafjallajökull eruption, Iceland

火山喷发可以将大量从岩浆中脱气的硫、氯和氟转移到大气以及陆地和水生环境中，有可能在不同的时间和空间尺度上造成重大扰动。富含氟的喷发造成了特别的担忧，因为氟以氟化物的形式排放，在环境中具有高度的反应性，如果浓度升高，对植物、动物和人类都是有毒的。1783年冰岛拉基火山喷发给该国造成了巨大的经济损失和人口结构变化，这是火山引起的氟化物污染的一个戏剧性例子。将火山氟化物排放返回地面的一种特别有效的方法是通过火山灰尘埃。众所周知，有些火山喷发产生的火山灰含有很高浓度的氟化物，很容易溶于水。这是喷发出的烟柱中的气体和火山灰发生反应的结果。一般来说，火山氟对火山灰的环境危害是通过测量火山灰沉积物的厚度和测量与火山灰相关的水溶性氟的浓度来评估的。然而，最近的证据表明，在火山灰中，氟也以难于溶于水的化合物的形式存在。这表明，氟很可能在一系列环境条件下释放，因此，必须考虑到，以便评估富氟火山喷发造成的进入和潜在的环境危害。控制火山灰上氟化物的数量和这种氟化物在不同溶解度的水池中的分布的因素很少受到限制，还有待进一步的研究。此外，还需要更多地了解火山氟在受火山灰沉积影响的环境隔间(土壤、水)中的行为。这类研究的结果将加强我们评估和预测富氟喷发造成的环境和健康危害的能力，从而有助于在火山危机期间和之后进行风险评估和管理。埃亚菲亚德拉火山于4月13日开始持续活动，正在产生持续的气体和细粒火山灰。在撰写本报告时(4月21日)，火山灰已经在火山口以南约20公里的居民区和农业区积聚了10厘米的沉积物。最新的初步分析表明，该火山现在产生的火山灰的水溶性氟浓度高达800毫克/公斤，使艾亚菲亚德拉火山灰成为有史以来氟含量最高的火山灰物质之一。由于火山喷发没有明显的缓和迹象，迫切需要评估艾亚菲亚德拉火山灰烬对环境造成的潜在危害，并收集必要的数据，以便深入了解上述问题。在重大的环境淋溶和再活化之前，快速的现场反应对于灰分的取样和表征至关重要。我们建议立即前往冰岛，对受影响地区的火山灰、土壤、植被和地表水进行仔细的地球化学调查。将在现场对氟化物污染进行初步评估。对样本的进一步实验室分析将提供对火山灰上氟化物的存在方式以及暴露在环境介质中时其释放和扩散的新见解。该项目产生的独特数据将为火山灰中的火山氟化物的潜在环境危害提供新的见解，并将显著提高我们向处理火山危机(包括正在进行的埃亚菲亚德拉火山喷发)的风险管理人员提供信息的能力。

Volcanic eruptions can transfer large quantities of sulphur, chlorine and fluorine degassed from magmas to the atmosphere and to terrestrial and aquatic environments, with the potential to result in significant perturbations at various temporal and spatial scales. Fluorine-rich eruptions create particular concerns because the fluorine, which is emitted as fluoride, is highly reactive in the environment, and in elevated concentrations, is toxic for plants, animals, and humans. A dramatic illustration of volcano-induced fluoride pollution is the 1783 eruption of Laki in Iceland, which resulted in substantial economic damage and demographic change in the country. A particularly efficient way of returning volcanic fluoride emissions to the ground is via ash fallout. It is well established that some eruptions produced ash with very high concentrations of fluoride readily soluble in water. This results from reactions between gas and ash in the eruptive plume. In general, the environmental hazards of volcanic fluoride on ash is assessed by surveying the thickness of the ash deposits and by measuring the concentration of water-soluble fluoride associated with the ash. However, recent evidence indicates that fluoride is also present in ash in the forms of poorly water-soluble compounds. This suggests that fluoride is likely to be released under a range of environmental conditions and therefore, must be considered in order to assess the entry and potential environmental hazards posed by fluoride-rich volcanic eruptions. The factors governing the amount of fluoride on ash and the distribution of this fluoride in pools with variable solubility are poorly constrained and await further investigations. In addition, increased knowledge on the behaviour of volcanic fluoride in the environmental compartments (soil, water) affected by ash deposition is also required. The results of such studies will enhance our capacity to assess and predict the environmental and health hazards posed by fluoride-rich eruptions, thereby contributing to risk assessment and management practices, during and in the aftermath of a volcanic crisis. The ongoing activity of Eyjafjallajökull volcano which started on April 13th is producing a sustained plume of gases and fine-grained ash. At the time of writing (21 April), ash has accumulated in deposits >10 cm in residential and farming areas ~20 km south from the crater. The most recent preliminary analyses indicate that the volcano is now producing ash with water-soluble fluoride concentrations up to 800 mg/kg, placing the Eyjafjallajökull ash amongst the most fluoride-rich ash material ever documented. With the eruption showing no clear signs of easing off, there is an urgent need to assess the potential environmental hazards posed by the Eyjafjallajökull ash, and to collect the essential data needed to gain insights into the issues outlined above. A rapid field response is essential to sample and characterise ash before significant environmental leaching and remobilisation. We propose to travel to Iceland immediately to conduct a careful geochemical survey of ash, soil, vegetation and surface water in the affected areas. A preliminary assessment of fluoride contamination will be obtained in the field. Further laboratory analyses of the samples will provide new insights into the modes of occurrence of fluoride on ash and on its release and dispersion upon exposure to environmental agents. The unique data generated from the project will provide new insights into the potential environmental hazards of volcanic fluoride in ash, and will significantly improve our capability to inform risk managers dealing with volcanic crises, including the ongoing Eyjafjallajökull eruption.