Selenium in Volcanic Environments (SELVES)

硒（Se）是一种天然存在的类金属，少量就有营养价值，但浓度仅为推荐剂量的两倍就会中毒。英国土壤通常缺乏硒，需要补充，但在火山地区和覆盖磷酸盐或富有机质页岩的土壤中，硒可能过量存在，对健康构成重大挑战。硒在光伏、玻璃生产、肥料和电池中至关重要；预计到2050年，硒需求将增长5-10倍。火山是环境中硒（及其化学“孪生兄弟”硫）的主要自然来源。由于其极端的挥发性，硒富集于火山气体和气溶胶以及热液流体中，硒沉积在斑岩中，并作为副产物与铜一起开采。到目前为止，由于火山气体中硒的采样和火山岩中硒的精确分析所涉及的技术挑战，我们对火山硒的定量认识非常有限。我们建议开展一套新的硒地球化学研究（以及其他对环境重要的痕量挥发性金属），利用最近使用无人飞行器对高温气体进行采样的发展；以及新的、精确的硒测量分析方案。我们手头已经有了一系列合适的样本，这些样本来自于研究人员在最近的一系列玄武岩爆发中收集的各种熔岩和气体/气溶胶样本（热点：2021年，拉帕尔马，坎布雷Vieja； 2018年，美国基拉韦厄火山，2018年，冰岛Fagradalsfjall；俯冲带：瓦努阿图，Ambrym火山，2018年；智利，维拉里卡，2018年）。我们将量化每次火山喷发释放出的硒和硫的流量，并对其进行控制；并确定硒以何种化学、生物可利用的形式通过火山喷发被输送到地表环境。这些目标的成功实现为更大规模、综合性、高影响的研究提供了基础，这些研究的重点是通过火山活动向地表环境输送的重金属（如汞、铊和铅以及硒）、它们的环境命运、生物吸收，包括现代和地球历史上植物对硒和硫的吸收以及向地下水的吸收所产生的竞争效应。该研究为改进斑岩型矿床中硒的热液分配模式和硒资源的可持续高效利用奠定了基础。该项目探索了一个广泛主题的前沿，通过健康、环境和经济的联系，影响了NERC的职权范围。

Selenium (Se) is a naturally-occurring metalloid that is nutritionally-required in small amounts but can become toxic at concentrations only twice recommended doses. UK soils are typically Se-deficient and require supplementation, but in volcanic regions and in soils overlying phosphate or organic-rich shales Se may be present in excess, representing a significant health challenge. Selenium is of critical importance in photovoltaics, glass production, fertilisers and batteries; Se demand is projected to rise 5-10 times by 2050. Volcanoes dominate the natural sources of Se (and its chemical 'twin', sulfur) to the environment. Due to its extreme volatility Se is enriched in volcanic gases and aerosol and in hydrothermal fluids, from which Se is deposited in porphyries and mined as a by-product with copper. Up to now, due to the technical challenges involved with sampling Se in volcanic gases and analysing it precisely in volcanic rocks, our quantitative understanding of volcanic Se is extremely limited. We propose the launch of a set of new studies of Se geochemistry (and that of other environmentally-important trace volatile metals) which take advantage of the recent development of using unoccupied aerial vehicles to sample high temperature gases; and new, precise analytical protocols for Se measurements. We have a range of suitable samples in hand already, from a diverse suite of samples of lavas, and gas/aerosol, collected by the investigators during recent explosive basaltic eruptions in a range of settings (hotspot: Cumbre Vieja, La Palma, 2021; Kilauea, USA, 2018, Fagradalsfjall, Iceland, 2021; subduction zone: Ambrym Volcano, Vanuatu, 2018; and Villarrica, Chile, 2018). We will quantify the flux of outgassing Se from each eruption, along with sulfur, and the controls on it; and establish in what chemical, bioavailable form Se is delivered to the surface environment via eruptions. The successful achievement of these objectives provides the basis for larger, integrative, high impact studies focussed on heavy metals (e.g. mercury, thallium and lead, as well as Se) delivered to the surface environment by volcanic activity, their environmental fate, biological uptake, including the competing effects of Se and S uptake by plants and incorporation into groundwater, both in the modern-day and in the history of our planet. This study lays the groundwork for improved hydrothermal models of Se partitioning into porphyry deposits and sustainable and efficient Se ore resource utilisation. This project explores the frontiers of a wide-ranging topic with impacts across the NERC remit through the nexus of health, environment and economy.