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首页> 外文期刊>Environmental Science & Technology >Hg L_3 XANES Study of Mercury Methylation in Shredded Eichhornia crassipes
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Hg L_3 XANES Study of Mercury Methylation in Shredded Eichhornia crassipes

机译：Hg L_3 XANES凤眼莲切丝中汞甲基化的研究

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Eichhornia crassipes (water hyacinth) is a non-native plant found in abundance in the Sacramento-San Joaquin River Delta (hereafter called Delta). This species has become a problem, clogging waterways and wetlands. Water hyacinth are also known to accumulate mercury. Recent attempts to curb its proliferation have included shredding with specialized boats. The purpose of this research is to better understand the ability of water hyacinth to phytoremediate mercury and to determine the effect of shredding and anoxic conditions on mercury speciation in plant tissue. In the field assessment, total mercury levels in sediment from the Dow Wetlands in the Delta were found to be 0.273 ± 0.070 ppm Hg, and levels in hyacinth roots and shoots from this site were 1.17 ± 0.08 ppm and 1.03 ± 0.52 ppm, respectively, indicating bioaccumulation of mercury. Plant samples collected at this site were also grown in nutrient solution with 1 ppm HgCl_2 under (1) aerobic conditions, (2) anaerobic conditions, and (3) with shredded plant material only. The greatest accumulation was found in the roots of whole plants. Plants grown in these conditions were also analyzed at Stanford Synchrotron Radiation Laboratory using Hg L_3 X-ray Absorption Near Edge Spectroscopy (XANES), a method to examine speciation that is element-specific and noninvasive. Least-squares fitting of the XANES data to methylated and inorganic mercury(ll) model compounds revealed that in plants grown live and aerobically, 5 ± 3% of the mercury was in the form of methylmercury, in a form similar to methylmercury cysteine. This percentage increased to 16 ± 4% in live plants grown anaerobically and to 22 ± 6% in shredded anaerobic plants. We conclude that shredding of the hyacinth plants and, in fact, subjection of plants to anaerobic conditions (e.g., as in normal decay, or in crowded growth conditions) increases mercury methylation. Mechanical removal of the entire plant is significantly more expensive than shredding, but it may be necessary to avoid increased biomagnification of mercury in infested areas.
机译：Eichhornia crassipes（凤眼兰）是一种非本地植物，在萨克拉曼多-圣华金河三角洲（以下称为三角洲）中大量发现。该物种已成为问题，阻塞了水路和湿地。也知道水葫芦会积聚汞。最近遏制其扩散的尝试包括用专门的船只粉碎。这项研究的目的是更好地了解水葫芦对植物进行汞修复的能力，并确定切碎和缺氧条件对植物组织中汞形成的影响。在现场评估中，发现三角洲陶氏湿地沉积物中的总汞含量为0.273±0.070 ppm Hg，该地点的风信子根和芽的汞含量分别为1.17±0.08 ppm和1.03±0.52 ppm，表明汞的生物富集。在（1）有氧条件，（2）厌氧条件和（3）仅使用切碎的植物材料的情况下，还将在此站点收集的植物样品在含有1 ppm HgCl_2的营养液中生长。在整个植物的根中发现了最大的积累。还使用Hg L_3 X射线吸收近边缘光谱法（XANES）在斯坦福同步辐射实验室对在这些条件下生长的植物进行了分析，这是一种检查特定元素且无侵害性的物种的方法。 XANES数据与甲基化和无机汞（II）模型化合物的最小二乘拟合表明，在有生命和需氧生长的植物中，5±3％的汞为甲基汞形式，类似于甲基汞半胱氨酸形式。在厌氧生长的活植物中，该百分比增加到16±4％，在切碎的厌氧植物中，该百分比增加到22±6％。我们得出的结论是，切碎风信子植物，实际上使植物经受厌氧条件（例如，在正常腐烂或拥挤的生长条件下）会增加汞的甲基化。机械去除整个植物比切碎要贵得多，但是可能有必要避免在受灾地区增加汞的生物放大倍数。

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