Lorax Environmental Services Ltd., Vancouver, British Columbia V6J 3H9, Canada.
Environ Sci Technol. 2011 Apr 1;45(7):2605-12. doi: 10.1021/es103604p. Epub 2011 Feb 28.
The biogeochemical mechanisms of Se exchange between water and sediments in two contrasting lentic environments were assessed through examination of Se speciation in the water column, porewater, and sediment. High-resolution (7 mm) vertical profiles of <0.45 μm Se species across the sediment-water interface demonstrate that the behavior of dissolved Se(VI), Se(IV), and organo-Se are closely linked to redox conditions as revealed by porewater profiles of redox-sensitive species (dissolved O2, NO3-, Fe, Mn, SO4(2-), and ΣH2S). At both sites Se(VI) is removed from solution in suboxic near-surface porewaters demonstrating that the sediments are serving as diffusive sinks for Se. X-ray absorption near edge spectroscopy (XANES) of sediments suggests that elemental Se and organo-Se represent the dominant sedimentary sinks for dissolved Se. Dissolved Se(IV) and organo-Se are released to porewaters in the near-surface sediments resulting in the diffusive transport of these species into the water column, where between-site differences in the depths of release can be linked to differences in redox zonation. The presence or absence of emergent vegetation is proposed to present a dominant control on sedimentary redox conditions as well as on the recycling and persistence of reduced Se species in bottom waters.
通过考察水柱、孔隙水和沉积物中硒的形态，评估了两种对比性静水环境中硒在水-沉积物之间交换的生物地球化学机制。在整个水-沉积物界面上，对 <0.45 μm 硒形态进行了高分辨率（7mm）的垂直剖面分析，结果表明，溶解态硒（VI）、硒（IV）和有机硒的行为与氧化还原条件密切相关，这可以通过孔隙水中氧化还原敏感物质（溶解氧、硝酸盐、铁、锰、硫酸盐和总硫化氢）的剖面反映出来。在两个地点，亚缺氧近表面孔隙水中都有硒（VI）从溶液中去除，这表明沉积物是硒的扩散汇。沉积物的 X 射线吸收近边光谱（XANES）分析表明，元素硒和有机硒是溶解态硒的主要沉积物汇。溶解态硒（IV）和有机硒被释放到近表面沉积物的孔隙水中，导致这些物质通过扩散进入水柱，而释放点之间的深度差异可与氧化还原分带的差异联系起来。有或没有挺水植被被认为是控制沉积物氧化还原条件以及底部水中还原态硒物质再循环和持久性的主要因素。
