Department of Chemistry & Biochemistry, Florida International University, Miami, Florida 33199, USA.
Environ Sci Technol. 2010 Sep 1;44(17):6661-6. doi: 10.1021/es1010434.
Methylmercury (MeHg) is recognized as one of the major water quality concerns in the Florida Everglades. Degradation of MeHg in the water is thought to be one of the most important processes to the cycling of MeHg, but there is a lack of quantitative estimations of its effect on the distribution and cycling of MeHg in this ecosystem. Stable isotope (Me201Hg) addition method was implemented to investigate the degradation of MeHg in the Everglades. By combining these results with the field monitoring data, effects of photodegradation on MeHg distribution and its contribution to MeHg cycling were estimated. The results indicate that degradation of MeHg in Everglades water is mediated by sunlight and that UV-A and UV-B radiations are the principal driver. The spatial pattern of MeHg photodegradation potential (PPD) generally illustrated an increasing trend from north to south in the Everglades, which was opposite to the distribution of MeHg in water column. Correlation analysis shows that MeHg concentration in the water had a significant negative relation to PPD, suggesting that photodegradation could play an important role in controlling the distribution of MeHg in Everglades water. Furthermore, about 31.4% of MeHg input into the water body was removed by photodegradation, indicating its importance in the biogeochemical cycling of MeHg in the Everglades. This percent reduction is much lower than that reported for other ecosystems, which could be caused by the higher concentration of DOC in the Everglades. The relatively slower degradation of MeHg could be one of the main reasons for the high ratio of MeHg to total mercury (THg) in this ecosystem.
甲基汞（MeHg）被认为是佛罗里达州大沼泽地的主要水质问题之一。MeHg 在水中的降解被认为是其循环的最重要过程之一，但对于它对该生态系统中 MeHg 分布和循环的影响缺乏定量估计。采用稳定同位素（Me201Hg）添加法研究了大沼泽地中 MeHg 的降解。通过将这些结果与野外监测数据相结合，估计了光降解对 MeHg 分布及其对 MeHg 循环的贡献的影响。结果表明，大沼泽地水中的 MeHg 降解是由阳光介导的，其中 UV-A 和 UV-B 辐射是主要驱动力。MeHg 光降解潜力（PPD）的空间格局总体上表明从北到南呈增加趋势，这与水柱中 MeHg 的分布相反。相关分析表明，水中 MeHg 浓度与 PPD 呈显著负相关，表明光降解可能在控制大沼泽地水中 MeHg 分布方面发挥重要作用。此外，约 31.4%输入水体的 MeHg 被光降解去除，表明其在大沼泽地 MeHg 生物地球化学循环中的重要性。与其他生态系统相比，这一百分比的减少要低得多，这可能是由于大沼泽地中 DOC 的浓度较高所致。MeHg 相对较慢的降解可能是该生态系统中 MeHg 与总汞（THg）比值较高的主要原因之一。
