Total Mercury Distribution and Volatilization in Microcosms with and Without the Aquatic Macrophyte Eichhornia Crassipes

摘要

Mercury (Hg) is one of the most toxic pollutants and spreads in the environment according to its affinity to several compartments. Aquatic macrophytes, such as Eichhornia crassipes, are known as sites for accumulation of Hg and methylmercury formation. The objective of this research was to observe Hg distribution among air, water and whole plants of the macrophyte E. crassipes for 17 days. The distribution of a single 203Hg spike was evaluated by gamma spectrometry. Two experiments, with and without macrophytes, were made, and the compartments analyzed for the presence of Hg were air, 0.2-μm filtered water, suspended and settled particles, roots, leafs, petioles and adsorption on the desiccators walls. 203Hg was detected in all analyzed compartments, and the highest total Hg concentrations were found in the roots and particles of the incubations with and without macrophytes that retained in average 68 and 34 % of added Hg, respectively. On the other hand, the lowest concentrations were found in air for both incubations, with higher volatilization (up to 2.5 % of added Hg) in the absence of macrophytes. The lower Hg values in leafs and petioles suggest this plant has mechanisms of Hg retention in the roots. Results suggest this macrophyte promotes changes in the Hg cycle since it attracts most Hg present in water and particulate to its roots and settled particles underneath and also reduces Hg volatilization.