Investigating Uptake and Translocation of Mercury Species by Sawgrass (Cladium jamaicense) Using a Stable Isotope Tracer Technique

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• 作者：Yuxiang Mao ; Yanbin Li ; Jennifer Richards ; Yong Cai
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：September 3, 2013
• 年：2013
• 卷：47
• 期：17
• 页码：9678-9684
• 全文大小：332K
• 年卷期：v.47,no.17(September 3, 2013)
• ISSN：1520-5851

文摘

The role of macrophytes in mercury (Hg) cycling in the Florida Everglades ecosystem has not been fully understood. In this study, a stable isotope (¹⁹⁹Hg²⁺) addition technique was used to trace the methylation, uptake, and translocation of Hg by sawgrass (Cladium jamaicense) and quantitatively evaluate the contribution of atmospheric and soil Hg to Hg in sawgrass leaves and below-ground biomass. The results showed that spiked ¹⁹⁹Hg²⁺ could be rapidly methylated to monomethylmercury (Me¹⁹⁹Hg) in the soil of the sawgrass pots. Only small portions of total Hg (THg) and monomethylmercury (MeHg) in the soil could be taken up by sawgrass, indicated by the ratios of T¹⁹⁹Hg and Me¹⁹⁹Hg (tracer) concentrations in the sawgrass below-ground biomass (BGBM) over that in the soil (6.50 卤 1.9% and 12.8 卤 3.6% for THg and MeHg, respectively). Concentrations of T¹⁹⁹Hg (tracer) and Me¹⁹⁹Hg (tracer) in sawgrass leaves only accounted for 5.50 卤 2.8% and 15.6 卤 4.0%, respectively, of that in the BGBM, implying that the fractions of mercury species transported upward by sawgrass were also small. Statistical analysis (t test) showed that sawgrass preferred MeHg over THg in both uptake and upward translocation. The majority (>90%) of THg in sawgrass leaves were estimated to be obtained from atmospheric Hg, rather than from soil, suggesting that assimilation of atmospheric Hg could increase the overall Hg stock in the Florida Everglades ecosystem. The finding about foliar uptake of Hg is especially important for a better understanding of mercury cycling in the Everglades, given the large amount of sawgrass biomass in this ecosystem.