Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland.
Nat Commun. 2024 Nov 7;15(1):9623. doi: 10.1038/s41467-024-53974-z.
Arsenic, a toxic element from both anthropogenic and natural sources, reaches surface environments through atmospheric cycling and dry and wet deposition. Biomethylation volatilizes arsenic into the atmosphere and deposition cycles it back to the surface, affecting soil-plant systems. Chemical speciation of deposited arsenic is important for understanding further processing in soils and bioavailability. However, the range of atmospheric transport and source signature of arsenic species remain understudied. Here we report significant levels of methylated arsenic in precipitation, cloud water and aerosols collected under free tropospheric conditions at Pic du Midi Observatory (France) indicating long-range transport, which is crucial for atmospheric budgets. Through chemical analyses and moisture source diagnostics, we identify terrestrial and marine sources for distinct arsenic species. Estimated atmospheric deposition fluxes of methylated arsenic are similar to reported methylation rates in soils, highlighting atmospheric deposition as a significant, overlooked source of potentially bioavailable methylated arsenic species impacting plant uptake in soils.
砷是一种有毒元素，无论是人为来源还是自然来源，都通过大气循环以及干湿沉降到达地表环境。生物甲基化将砷挥发到大气中，并通过沉积循环将其带回地表，从而影响土壤-植物系统。沉积砷的化学形态对于理解其在土壤中的进一步转化和生物可利用性很重要。然而，大气传输的范围和砷形态的源特征仍有待研究。本研究报告了在法国皮丘米迪多观测站（Pic du Midi Observatory）的自由对流层条件下收集的降水、云水中和气溶胶中有显著水平的甲基化砷，这表明存在长距离传输，这对大气预算至关重要。通过化学分析和水汽源诊断，我们确定了不同砷形态的陆地和海洋来源。估算的大气甲基化砷沉积通量与土壤中报道的甲基化速率相似，这突出表明大气沉积是一种重要的、被忽视的潜在生物可利用的甲基化砷形态的来源，该来源会影响土壤中植物的吸收。
