AsianScientist (Jan. 25, 2018) – Researchers at the RIKEN Center for Sustainable Resource Science (CSRS) in Japan have demonstrated that that moss can remove lead from polluted water and soil. They published their findings in the journal PLOS One.
Lead-contaminated water is a serious environmental concern that has recently proved to be disastrous when left untreated. Compounding the problem, the typical way to remove lead or other heavy metals from water requires fossil fuels and a tremendous amount of energy. As an alternative to these typical processes, phytoremediation is a method that uses photosynthesizing organisms to clean up soil or water contamination.
In the present study, the CSRS researchers began their search for a phytoremediation-based removal method by studying Funaria hygrometrica, a moss that is known to grow well in sites contaminated with metals like copper, zinc and lead.
“We found that the moss can function as an excellent lead absorbent when in the protonema stage of development,” said first author Dr. Misao Itouga of the CSRS. “This valuable ability means that moss protonema will likely make exceptional wastewater cleaners in mining and chemical industries.”
To characterize the metal-absorbing ability of the moss, the team first prepared solutions with varying concentrations of 15 different metals and exposed them to F. hygrometrica. After 22 hours of exposure, mass-spectrometer analysis showed that the moss cells had absorbed lead up to 74 percent of their dry weight, which is much higher than any of the other metals.
Knowing where the lead accumulates is important for understanding how it occurs and for developing more efficient phytoremediation methods. The researchers found that within the moss protonema cells, more that 85 percent of the lead had accumulated in the cell walls, with smaller amounts being found in organelle membranes and inside the chloroplasts, where photosynthesis occurs.
The team also observed that the cell walls absorbed lead even after being removed from living moss. Further analysis using two-dimensional nuclear magnetic resonance indicated that polygalacturonic acid in the cell walls was responsible for absorbing the lead.
“We compared F. hygrometrica data with those from land plants and seaweeds and found that the presence of polygalacturonic acid in the cell wall is one of the characteristics that separated this type of moss from other plants,” said Itouga.
They next determined that the protonema cells absorbed lead well at pH values between 3 and 9, which is important because the acidity of metal-polluted water can vary.
“Our findings show that F. hygrometrica is a useful bio-material for recovering lead from aqueous solutions and will contribute to the Sustainable Development Goals set by the United Nations, specifically, the Life on Land goal,” said group leader Professor Hitoshi Sakakibara of CSRS. “We are currently exploring opportunities to work with recycling-oriented companies.”
The article can be found at: Itouga et al. (2017) Protonema of the Moss Funaria hygrometrica Can Function as a Lead (Pb) Adsorbent.
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Source: RIKEN; Photo: Pixabay.
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