Sequestration of precious and pollutant metals in biomass of cultured water hyacinth (Eichhornia crassipes)

Abstract

The aim of this study was to investigate the overall root/shoot allocation of metal contaminants, the amount of metal removal by absorption and adsorption within or on the external root surfaces, the dose-response of water hyacinth metal uptake, and phytotoxicity. This was examined in a single-metal tub trial, using arsenic (As), gold (Au), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), uranium (U), and zinc (Zn). Iron and Mn were also used in low-, medium-, and high-concentration treatments to test their dose effect on water hyacinth's metal uptake. Water hyacinth was generally tolerant to metallotoxicity, except for Cu and Hg. Over 80 % of the total amount of metals removed was accumulated in the roots, of which 30-52 % was adsorbed onto the root surfaces. Furthermore, 73-98 % of the total metal assimilation by water hyacinth was located in the roots. The bioconcentration factor (BCF) of Cu, Hg, Au, and Zn exceeded the recommended index of 1000, which is used in selection of phytoremediating plants, but those of U, As, and Mn did not. Nevertheless, the BCF for Mn increased with the increase of Mn concentration in water. This suggests that the use of BCF index alone, without the consideration of plant biomass and metal concentration in water, is inadequate to determine the potential of plants for phytoremediation accurately. Thus, this study confirms that water hyacinth holds potential for a broad spectrum of phytoremediation roles. However, knowing whether these metals are adsorbed on or assimilated within the plant tissues as well as knowing their allocation between roots and shoots will inform decisions how to re-treat biomass for metal recovery, or the mode of biomass reduction for safe disposal after phytoremediation.

Extending the geographic reach of the water hyacinth plant in removal of heavy metals from a temperate Northern Hemisphere river

“…Newete et al . (2016), showed that manganese accumulation increased with greater concentrations in the growth medium 31 . The initial concentrations did not vary enough within this study to fully assess this assertion.…”

“…(2015) and Newete et al . (2016) most previous work has examined removal under nutrient starving conditions, whereas in this study, there are many other nutrients present and available within the river water, as would be the case in a “real” remediation setting within any river 21 , 31 , 38 .…”

Assessment of Potential Toxic Metals in a Ramsar Wetland, Central Mexico and its Self-Depuration through Eichhornia crassipes

“…This is with the aim of protecting the plants against the harmful effects of high levels in leaves, where the photosynthetic processes take place [58,59]. Aquatic plants capable of accumulating up to 5000 mg of metals per kilogram of dry plant biomass or those with BCF > 1000 are considered as hyper-accumulators of PTMs [28,57]. In the present work, the total amount of metals accumulated by Water hyacinth plants was below 5000 mg/kg d.w.…”

“…Water hyacinths samples were washed three times with Milli-Q deionized water without a subsequent washed with deionized acidified water. According to Newete [28], the acid wash eliminates the portion of the adsorbed contaminants such as PTMs. Therefore, by omitting the acid wash, the adsorbed and absorbed portions of the contaminants remain in the plants for further analysis.…”

“…To evaluate the performance of Water hyacinth plants in the water depuration, some authors have proposed factors such as the Translocation factor (TF) and Bioaccumulation factor (BF) [17]. The importance of studying the depuration process through the BF and TF relies on the possibility to determine whether the plant has potential for using it in situ as a water depurator or not [27,28].…”