• Scientists demonstrate that some tropica

    From ScienceDaily@1:317/3 to All on Wed Apr 13 22:30:46 2022
    Scientists demonstrate that some tropical plants have potential to
    remove toxic heavy metals from the soil

    Date:
    April 13, 2022
    Source:
    Nanyang Technological University
    Summary:
    A team of researchers has demonstrated that some plant species
    could help to remove toxic heavy metals and metalloids from
    contaminated soil.



    FULL STORY ==========================================================================
    A team of researchers from Nanyang Technological University, Singapore
    (NTU Singapore) and Singapore's National Parks Board (NParks), has
    demonstrated that some plant species could help to remove toxic heavy
    metals and metalloids from contaminated soil.


    ========================================================================== Phytoremediation is the use of plants to extract and store contaminants
    from soil. As a first step to determine if candidate plants had phytoremediation abilities, the team examined samples of them for levels
    of heavy metals and metalloids. A high concentration detected suggested
    an ability to absorb the pollutants.

    The study by the Singapore research team discovered that there are
    existing tropical plants which could potentially play a role in the
    remediation of contaminated lands. The plants examined in the study are
    widely available and include species that are native or naturalised to Singapore. They could thus, be introduced and removed from plots of land
    with minimal impact to ecosystems and could lead to the development of
    a sustainable and environmentally friendly way of managing contaminants
    in soil.

    The findings were published in the scientific peer-reviewed journal Environmental Pollution in February.

    Professor Lam Yeng Ming, Chair of NTU's School of Materials Science
    and Engineering, who co-led the study, said: "In a small nation like
    Singapore, land may be repurposed to support new development plans, so
    it is important that we have a green and sustainable way to remediate
    land that is contaminated. We set out to uncover how to better make
    use of tropical plants to do phytoremediation and through advanced characterisation techniques, we showed how some of these tropical plant
    species can be an environmentally friendly and literally a "green"
    way to remove contaminants in soil.

    Phytoremediation also has benefits of cost effectiveness, simplicity
    of management, aesthetic advantages, and long-term applicability and sustainability. The strategy prevents erosion and metal leaching by
    stabilising or accumulating heavy metals, so that helps reduce the risk
    of contaminant spread." The team conducted a field survey and collected
    soil and plant samples between March 2019 and January 2020. A total of 46
    plant species were studied as potential candidates for phytoremediation.



    ========================================================================== Among them, 12 plant species, which include the commonly seen Cow Grass (Axonopus compressus), hyperaccumulators like the Brake Fern (Pteris
    vittata) and the Indian Pennywort (Centella asiatica), were effective
    for the accumulation of several types of heavy metals and metalloids.

    The elements investigated in the study were heavy metals and metalloids
    that are potentially toxic to humans and animals, such as cadmium,
    arsenic, lead, and chromium. They occur naturally in soils, but rarely
    at toxic levels.

    However, they can accumulate and reach higher levels over a long period of time, as heavy metal particles from air pollution (e.g. vehicle emissions, construction activities) tend to accumulate and remain in the top layers
    of soil.

    Other factors that could result in high levels of heavy metals in soil
    include the use of synthetic products such as pesticides, paints,
    batteries, industrial waste, and land application of industrial or
    domestic sludge.

    To assess whether the levels of heavy metal were dangerous, the team used
    the Dutch Standard, which provides values for the acceptable threshold
    of environmental pollutants in soils. This mode of assessment has also
    been adopted by Singapore's government agencies.

    Associate Professor Tan Swee Ngin, from the Academic Group of Natural
    Sciences and Science Education at NTU's National Institute of Education,
    who was the study's co-author, said: "Our results revealed there were
    regions where levels of heavy metals and metalloids were relatively high
    and could affect the environment and the health of flora and fauna in Singapore. This would call for preventive actions, such as our method of
    using plants to remove these toxic materials, to be employed to minimise
    heavy metal contamination." The NParks researchers involved in the
    study are from its Centre for Urban Greenery and Ecology. They include
    Dr Subhadip Ghosh, Senior Researcher and Mr Mohamed Lokman Mohd Yusof,
    Senior Research Executive.



    ==========================================================================
    The development of this plant-based solution to improve soil quality
    is part of the University's efforts to mitigate our impact on the
    environment, that is aligned with the NTU 2025 strategic plan, which aims
    to develop sustainable solutions to address some of humanity's pressing
    grand challenges.

    Team's findings expand potential of environmentally friendly methods Phytoremediation could serve as a more environmentally friendly
    alternative to existing industrial options to remove the heavy metals
    from polluted soil, which include methods such as soil washing and acid leaching. These methods can be costly and may utilise harsh chemicals
    to remove pollutants from soil.

    Heavy machinery to conduct excavation and transportation of soil is also usually required in such processes and these procedures may negatively
    affect the environment by affecting soil health and fertility. These
    methods also run a high risk of exposing humans or animals to the
    heavy metals.

    However, phytoremediation is a slow and long-term commitment and requires prudent management in the removal and disposal of the contaminated
    plant samples. Using different types of efficient plants to carry out phytoremediation in polluted soils, and with enough growth cycles through repeated planting, can ultimately lead to reductions in the level of
    heavy metals and metalloids in the soil.

    The joint research team is currently testing the plants on plots of land
    in Singapore that have high concentrations of heavy metals to better
    determine the effectiveness of the plants in an urban setting.

    They are also testing the usage of other inorganic particles that are incorporated into plants and that can both help in the plant growth and
    improve the uptake of these contaminants by the plants. This will reduce
    the time taken for the absorption of the heavy metals and hence speed
    up the remediation time.


    ========================================================================== Story Source: Materials provided by
    Nanyang_Technological_University. Note: Content may be edited for style
    and length.


    ========================================================================== Journal Reference:
    1. Yamin Wang, Swee Ngin Tan, Mohamed Lokman Mohd Yusof, Subhadip
    Ghosh,
    Yeng Ming Lam. Assessment of heavy metal and metalloid levels and
    screening potential of tropical plant species for phytoremediation
    in Singapore. Environmental Pollution, 2022; 295: 118681 DOI:
    10.1016/ j.envpol.2021.118681 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220413104203.htm

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