• Engineers clean up water pollution with

    From ScienceDaily@1:317/3 to All on Wed Aug 11 21:30:42 2021
    Engineers clean up water pollution with sunlight

    Date:
    August 11, 2021
    Source:
    Michigan Technological University
    Summary:
    In addition to providing vitamin D, helping flowers grow and
    creating the perfect excuse to head to the beach, sunlight also
    helps break down chemicals in streams, lakes and rivers. Researchers
    have developed a comprehensive reactive activity model that shows
    how singlet oxygen's reaction mechanisms perform against a diverse
    group of contaminants and computes their half-life in a natural
    aquatic environment.



    FULL STORY ==========================================================================
    In addition to providing vitamin D, helping flowers grow and creating
    the perfect excuse to head to the beach, sunlight also helps break
    down chemicals in streams, lakes and rivers. Researchers from Michigan Technological University have developed a singlet oxygen model to
    calculate how particular chemicals break down in surface water.


    ========================================================================== While swimming pools use blue tiles to mimic the color of the Caribbean,
    most surface water is yellow or brown. For example, Tahquamenon Falls,
    a popular Upper Peninsula destination, is known for the caramel color of
    its chutes. That color comes from leaf and bark debris that make tannins
    -- polyphenols, or naturally occurring organic compounds in plants. It's
    this debris that absorbs sunlight and creates the singlet oxygen that
    degrades contaminants.

    Singlet Oxygen This reactive species of oxygen causes what's called photochemical transformation, a process in which light and oxidizing
    materials produce chemical reactions. But how long does it take for
    a particular chemical to break down under this sunny and vegetative
    onslaught? Understanding how many hours or days it takes a particular contaminant to break down halfway helps environmental engineers and
    scientists protect our waterways. Knowing a particular chemical's
    half-life helps resource managers estimate whether or not that chemical
    is building up in the environment.

    Daisuke Minakata, associate professor of civil, environmental and
    geospatial engineering at Michigan Tech, developed a comprehensive
    reactive activity model that shows how singlet oxygen's reaction
    mechanisms perform against a diverse group of contaminants and computes
    their half-life in a natural aquatic environment.



    ==========================================================================
    "We tested 100 different organic, structurally diverse compounds,"
    Minakata said. "If we know the reactivity between singlet oxygen
    and contaminants, we can say how long it will take to degrade one
    specific structure of a contaminant down to half the concentration."
    Minakata's collaborators are graduate students Benjamin Barrios, Benjamin Mohrhardt and Paul Doskey, professor in the College of Forest Resources
    and Environmental Science. Their research was published this summer in
    the journal Environmental Science and Technology.

    Sunshine Oxidizes and Degrades Toxic Chemicals The rate of indirect-sunlight-initiated chemical oxidation is unique to the body of
    water; each lake, river or stream has its own distinct mix of organic
    matter. And because the process does not occur in the dark, the amount
    of sunlight a water body receives also affects reactions. For example,
    singlet oxygen plays a partial role in degrading the toxins in harmful
    algal blooms and in breaking down the excess nitrogen and phosphorus
    produced by agricultural runoff.

    The reactive oxygen species also has benefits beyond our favorite lakes
    and rivers.

    "Singlet oxygen can be used for disinfection of pathogens," Minakata
    said. "It can oxidize chemicals in drinking water or wastewater
    treatments. There are many ways to use this strong chemical oxidant for
    many purposes in our lives." Moving Beyond Reactions Toward Byproducts
    With the half-life calculations established by Minakata's model, the
    research team plans to further study the byproducts produced by singlet oxygen/chemical reactions -- with an eye toward predicting whether
    the byproducts themselves will be toxic. By understanding the stages
    of degradation, Minakata and his team can develop an expanded model to
    predict the formation of sun-worn byproducts and how the interactions
    start again.

    Ultimately, a full understanding of the half-lives of the many chemicals
    that infiltrate our water sources is a step toward ensuring clean water
    for human use.

    ========================================================================== Story Source: Materials provided by
    Michigan_Technological_University. Original written by Kelley
    Christensen. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Benjamin Barrios, Benjamin Mohrhardt, Paul V. Doskey, Daisuke
    Minakata.

    Mechanistic Insight into the Reactivities of Aqueous-Phase Singlet
    Oxygen with Organic Compounds. Environmental Science & Technology,
    2021; 55 (12): 8054 DOI: 10.1021/acs.est.1c01712 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/08/210811113139.htm

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