Phytoaccumulation of Trace Elements by Wetland Plants: I. Duckweed

Abstract

There has been much interest recently in the use of constructed wetlands for the removal of toxic trace elements from wastewaters. Wetland plants play an important role in the trace elements removal process. It is not known, however, which wetland plant species absorb specific trace elements at the fastest rates. Such knowledge is essential to maximize the efficiency of trace element removal by wetlands. In this study, we investigated the potential of duckweed (Lemna minor L.) to accumulate Cd, Cr, Cu, Ni, Pb, and Se when supplied individually in a nutrient solution at a series of concentrations ranged from 0.1 to 10 mg L−1. The results show that under experimental conditions, duckweed proved to be a good accumulator of Cd, Se, and Cu, a moderate accumulator of Cr, and a poor accumulator of Ni and Pb. The highest concentrations of each trace element accumulated in duckweed tissues were 13.3 g Cd kg−1, 4.27 g Se kg−1, 3.36 g Cu kg−1, 2.87 g Cr kg−1, 1.79 g Ni kg−1, and 0.63 g Pb kg−1. Duckweed exhibited some symptoms of toxicity (e.g., reduced growth, chlorosis) at higher levels of element supply (except for Cr). The toxicity effect of each trace element on plant growth was, in descending order of damage, Cu > Se > Pb > Cd > Ni > Cr. We conclude that duckweed shows promise for the removal of Cd, Se, and Cu from contaminated wastewater since it accumulates high concentrations of these elements. Further, the growth rates and harvest potential make duckweed a good species for phytoremediation activities.

The accumulation of metal (Co, Cr, Cu, Mn and Zn) in freshwater Ulva (Chlorophyta) and its habitat

“…However, the BCF values were very low for Co (1.35 and 3.46). Based on the criteria given by Zayed et al (1998), the BCF value over 1.000 is generally considered to be proof that the plant will be useful for phytoremediation. This study resulted in BCF values above 10 3 for Mn, Zn, Cr (only for Ulva from the lake), and Cu (only for Ulva from the river), indicating that freshwater Ulva are good hyperaccumulators of Mn and Zn, irrespective of the type of aquatic ecosystem for thalli development.…”

“…The BCFs were calculated as described by Zayed et al (1998) based on the concentration of a given element in water, sediment and plant tissues. The BCF was calculated as follows: BCF = the mean concentration of the metal in the plant tissue (lg g -1 dry weight)/the mean concentration of the metal in the water (lg mL -1 ) or the sediment (lg g -1 dry weight).…”

Phytofiltration of Arsenic and Cadmium From the Water Environment UsingMicranthemum Umbrosum(J.F. Gmel) S.F. Blake As A Hyperaccumulator

“…In general, a plant with a BCF of more than 1000 is considered a hyperaccumulator. A plant with a BCF of 1 to less than 1000 is considered an accumulator, and with a BCF of less than 1 as an excluder (Zayed et al 1998). In addition, A plant is defined to be a hyper-accumulator if it can concentrate the pollutants in any above ground tissue of dry weight; which varies according to the pollutant involved: >1000 mg/kg for Ni, Cu, Co, Cr or Pb; >10,000 mg/kg for Zn or Mn (Morel et al 2006).…”

Potential of macrophytes for removing atrazine from aqueous solution

“…Lemna gibba is a small, floating aquatic monocotyledon, that grows fast and adapts easily to various environmental conditions, whose phenology characteristics can facilitate the phytoremediation. It is widely distributed in the world, where it plays an important role in extracting and accumulating metallic ion from the waters (Zayed et al, 1998).…”