Department of Chemical Engineering and Applied Chemistry , University of Toronto , 200 College Street , Toronto , M5S 3E5 , Canada.
Department of Civil and Mineral Engineering , University of Toronto , 35 St George St. , Toronto , M5S 1A4 , Canada.
Environ Sci Technol. 2018 Aug 7;52(15):8365-8372. doi: 10.1021/acs.est.8b01876. Epub 2018 Jul 9.
Radioactive strontium (Sr) is a common groundwater contaminant at many nuclear sites. Its natural retention in groundwater-fed wetlands is an attractive remediation strategy. However, at present, the biogeochemical mechanisms controlling Sr transport at the sediment-water interface are poorly understood. In this field study, Sr fate was investigated in two wetlands with contrasting vegetation and hydrologic regimes. The marsh was an open-water wetland with constant water table and no emergent vegetation. The swamp was vegetated with fluctuating water levels and a thick mat of submerged cattail litter in the water column. High-resolution porewater Sr concentrations and solid-phase sediment Sr species revealed distinct profiles between the two wetlands. The marsh exhibited a strongly reduced environment and sharp concentration peaks at the sediment-water interface. In contrast, the smaller concentration gradients of the swamp resulted in a reduced flux of Sr to the surface water. The organic fraction of the sediment dominated Sr retention compared to the inorganic iron and manganese oxides. However, the marsh had a significant fraction of recalcitrant Sr presumably due to its incorporation into sulfur and/or carbonate minerals. These results suggest that vegetated wetlands with fluctuating hydrologic regimes could act as efficient sinks for Sr pollution.
放射性锶（Sr）是许多核设施中常见的地下水污染物。其在地下水补给湿地中的自然滞留是一种有吸引力的修复策略。然而，目前，控制沉积物-水界面上 Sr 迁移的生物地球化学机制还知之甚少。在这项实地研究中，研究了两种具有不同植被和水文条件的湿地中 Sr 的命运。沼泽是一个具有稳定地下水位和无挺水植被的开阔水面湿地。沼泽则有波动的水位和水中厚厚的菰属植物碎屑垫。高分辨率的孔隙水 Sr 浓度和固相沉积物 Sr 形态揭示了两种湿地之间的明显差异。沼泽表现出强烈的还原环境和在沉积物-水界面处的浓度峰值。相比之下，沼泽较小的浓度梯度导致 Sr 向地表水的通量减少。与无机铁和锰氧化物相比，沉积物中的有机部分对 Sr 的保持起主要作用。然而，沼泽中存在大量难以降解的 Sr，可能是由于其被纳入硫和/或碳酸盐矿物中。这些结果表明，具有波动水文条件的植被湿地可能成为 Sr 污染的有效汇。
