Mauro J B N, Guimarães J R D, Hintelmann H, Watras C J, Haack E A, Coelho-Souza S A
Laboratório de Traçadones, IBCCF, Bloco G/CCS/Ilha do Fundão, Universidade Federal do Rio de Janeiro, CEP: 21949-900, Rio de Janeiro (RJ), Brasil.
Anal Bioanal Chem. 2002 Nov;374(6):983-9. doi: 10.1007/s00216-002-1534-1. Epub 2002 Oct 8.
Comparative tests of net mercury methylation potentials, with cultivated and macrophyte-associated periphyton and using stable ((200)HgCl(2) and CH(3)(199)HgCl) and labeled ((203)HgCl(2)) mercury, have been conducted in the Everglades nutrient removal area (Florida, USA) and in a tropical coastal Brazilian lake (RJ, Brazil). More methylmercury was formed by macrophyte-associated (up to 17% of added (203)Hg(II)) than cultivated (up to 1.6%) periphyton and methylmercury formation was lower in periphyton exposed to light (0.2%). High methylation was also observed for samples incubated with stable mercury isotopes (1.5-7.7% of added (200)Hg(II)), confirming the results obtained with labeled mercury. Simultaneous addition of (200)HgCl(2) and CH(3)(199)HgCl indicated that CH(3)(199)HgCl had no inhibitory effect on Hg methylation. The elevated methylation potentials observed in macrophytes, because of their root-associated periphyton, might contribute significantly to the high levels of methylmercury observed in Everglades biota. Comparative mercury methylation tests were also conducted in the water of a stratified temperate lake (Wisconsin, USA). Similar trends were observed for both stable and radioisotopes, with increasing mercury methylation along the depth profile. The highest levels (0.9% (203)Hg(II) and 0.8% (200)Hg(II)) were obtained below the oxic/anoxic boundary, where sulfide starts to increase, probably as a result of the intense activity of sulfate-reducing bacteria in the anoxic layer.
在美国佛罗里达州大沼泽地营养物去除区和巴西里约热内卢的一个热带沿海湖泊中，利用稳定态汞（(200)HgCl(2)和CH(3)(199)HgCl）以及标记汞（(203)HgCl(2)），对养殖的附生植物和与大型植物相关的附生植物的净汞甲基化潜力进行了对比试验。与大型植物相关的附生植物形成的甲基汞更多（高达添加(203)Hg(II)的17%），而养殖的附生植物形成的甲基汞较少（高达1.6%），且暴露在光照下的附生植物中甲基汞的形成更低（0.2%）。在用稳定汞同位素培养的样品中也观察到了较高的甲基化率（占添加(200)Hg(II)的1.5 - 7.7%），这证实了用标记汞获得的结果。同时添加(200)HgCl(2)和CH(3)(199)HgCl表明CH(3)(199)HgCl对汞甲基化没有抑制作用。由于大型植物根部的附生植物，在大型植物中观察到的甲基化潜力升高，这可能是大沼泽地生物群中甲基汞含量高的重要原因。还在美国威斯康星州一个分层温带湖泊的水中进行了汞甲基化对比试验。对于稳定同位素和放射性同位素，都观察到了类似的趋势，随着深度增加汞甲基化率上升。在有氧/缺氧边界以下获得了最高水平（(203)Hg(II)为0.9%，(200)Hg(II)为0.8%），在该边界处硫化物开始增加，这可能是由于缺氧层中硫酸盐还原菌的强烈活动所致。
