Posted on 11/08/2019 8:00:33 AM PST by LesbianThespianGymnasticMidget
Study explores removal mechanisms, microbial impacts and lifetimes of select microplastics on the ocean surface
Florida Atlantic University
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A schematic figure of plastic photo-dissolution and plastic dissolved organic carbon (DOC) biodegradation. Credit: Lee Ann DeLeo
Trillions of plastic fragments are afloat at sea, which cause large “garbage patches” to form in rotating ocean currents called subtropical gyres. As a result, impacts on ocean life are increasing and affecting organisms from large mammals to bacteria at the base of the ocean food web. Despite this immense accumulation of plastics at sea, it only accounts for 1 to 2 percent of plastic debris inputs to the ocean. The fate of this missing plastic and its impact on marine life remains largely unknown.
It appears that sunlight-driven photoreactions could be an important sink of buoyant plastics at sea. Sunlight also may have a role in reducing plastics to sizes below those captured by oceanic studies. This theory could partly explain how more than 98 percent of the plastics entering the oceans go missing every year. However, direct, experimental evidence for the photochemical degradation of marine plastics remains rare.
A team of scientists from Florida Atlantic University’s Harbor Branch Oceanographic Institute, East China Normal University and Northeastern University conducted a unique study to help elucidate the mystery of missing plastic fragments at sea. Their work provides novel insight regarding the removal mechanisms and potential lifetimes of a select few microplastics.
For the study, published in the Journal of Hazardous Materials, researchers selected plastic polymers prevalently found on the ocean surface and irradiated them using a solar simulator system. The samples were irradiated under simulated sunlight for approximately two months to capture the kinetics of plastic dissolution. Twenty-four hours was the equivalent of about one solar day of photochemical exposure in the subtropical ocean gyre surface waters. To assess the physical and chemical photodegradation of these plastics, researchers used optical microscopy, electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy.
Results showed that simulated sunlight increased the amount of dissolved carbon in the water and made those tiny plastic particles tinier. It also fragmented, oxidized and altered the color of the irradiated polymers. Rates of removal depended upon polymer chemistry. Engineered polymer solutions (recycled plastics) degraded more rapidly than polypropylene (e.g. consumer packaging) and polyethylene (e.g. plastic bags, plastic films, and containers including bottles), which were the most photo-resistant polymers studied.
Based on the linear extrapolation of plastic mass loss, engineered polymer solutions (2.7 years) and the North Pacific Gyre (2.8 years) samples had the shortest lifetimes, followed by polypropylene (4.3 years), polyethylene (33 years), and standard polyethylene (49 years), used for crates, trays, bottles for milk and fruit juices, and caps for food packaging.
“For the most photoreactive microplastics such as expanded polystyrene and polypropylene, sunlight may rapidly remove these polymers from ocean waters. Other, less photodegradable microplastics such as polyethylene, may take decades to centuries to degrade even if they remain at the sea surface,” said Shiye Zhao, Ph.D., senior author and a post-doc researcher working in the laboratory of Tracy Mincer, Ph.D., an assistant professor of biology/biogeochemistry at FAU’s Harbor Branch and Harriet L. Wilkes Honors College. “In addition, as these plastics dissolve at sea, they release biologically active organic compounds, which are measured as total dissolved organic carbon, a major byproduct of sunlight-driven plastic photodegradation.”
Zhao and collaborators also checked the biolability of plastic-derived dissolved organic carbon upon marine microbes. These dissolved organics seem to be broadly biodegradable and a drop in the ocean compared to natural biolabile marine dissolved organic carbon. However, some of these organics or their co-leachates may inhibit microbial activity. The dissolved organic carbon released as most plastics photodegraded was readily utilized by marine bacteria.
“The potential that plastics are releasing bio-inhibitory compounds during photodegradation in the ocean could impact microbial community productivity and structure, with unknown consequences for the biogeochemistry and ecology of the ocean,” said Zhao. “One of four polymers in our study had a negative effect on bacteria. More work is needed to determine whether the release of bioinhibitory compounds from photodegrading plastics is a common or rare phenomenon.”
Samples in the study included post-consumer microplastics from recycled plastics like a shampoo bottle and a disposable lunch box (polyethylene, polypropylene, and expanded polystyrene), as well as standard polyethylene, and plastic-fragments collected from the surface waters of the North Pacific Gyre. A total of 480 cleaned pieces of each polymer type were randomly selected, weighed and divided into two groups.
Looks like I was not giving Africa its due.
At least the plastic is breaking down due to UV and is not a semi permanent problem.
The problem with all the biodegradable plastics is the people polluting the most can afford the more expensive packaging the least.
We should reduce pollutants to harmless chemicals before sending them into the oceans.
Years ago, when I lived in a beautiful old mansion on a beautiful river in a historic area, I had to replace my septic tank. The plumber told me that in olden times, the toilet waste was just piped untreated into the river and that the pipes were still in place, that he could re-connect them and save me the cost of replacing the septic tank. I was outraged at the very idea. I fired him and hired another plumber to replace the septic tank.
I have no sympathy for environmentalist whackos! I have had some extremely unpleasant dealings with them!
But I am a true environmentalist, as are most, maybe all, of the Freepers who post here on FR--and unlike the mentally ill whacko fools!
I am also a true liberal, as are most, maybe all, of the Freepers who post here on FR--and unlike the mentally ill fools who love to call themselves liberal but who in fact are the opposite.
I'm sure that you are a true environmentalist and a true liberal also, Boog. Otherwise you wouldn't be a Freeper--you'd be posting on...what's that site that's so left-wing nutcase...? I can't remember.
Why, pray tell, are we DUMPING plastics in the ocean?
That would take all the fun out of the liberal drama queen's rant...
That's still there, under the plastic...
“we need to dump more stuff into the oceans...”
For the good old days. Big smelly belly dump barges full of trash, garbage, and horse droppings headed out to sea followed by a dense cloud of noisey seagulls.
So tossing plastic in the ocean is the best thing we can do for the environment? Neat! Off to the shore now ...
The silly notion that the earth is a self destructive organism is advanced by those seeking control over their neighbors. They are the ones seeking the destruction of the planet.
Oh my lord. I love to travel, willing to go almost anywehere provided it’s safe. But I have no desire and will not set foot in India. Sorry Indian freepers, nothing personal. I’ve just seen too many pics like the one posted.
You win the thread prize!
“I don’t know whether incineration would reduce it to harmless chemicals.”
There’s bound to be biproducts, but considering the advances we have made in “scrubber” technology for smokestacks, I bet it could be made pretty negligible.
You got your work cut out for you. The Chinese, Indians and Africans always win this event. Being from a civilized country you really don’t have a chance to even make the prelims.
You would not make it out of this heat:
https://www.youtube.com/watch?v=y2teSx5xiRk
fill that marianna trench... in nature’s own trash compacter
Those who dine in high school cafeterias have long suspected this.
The sea has a bunch of oil leaking into it all the time and always has. Oil naturally leaks out of the ground.
The sea has a way of dealing with all of this oil.
It uses the same method on plastic.
Why would this be puzzling?
Good luck getting them to do anything about it.
"Now throw all trash and garbage over the side. Sweepers."
One problem with that, though. Some plastics do not break down into their chemical components, but break down into smaller and smaller fragments. If the tiniest fragments become concentrated enough in an area it can affect any filter-feeding organisms near the bottom of the food chain (coral, clams/oysters, sardines, menhaden, etc.). They can literally starve to death with full bellies, because there is no nutrition to be had from the plastic.
When the bottom of the food chain is disrupted it affects the higher orders' feeding. Not a good thing.
I suppose it depends on the quantity.
For me, everything is about PPM. I see our planet’s holistic ecosystem as a big HVAC system. Those are designed with particular parameters in mind. It’s why you want one size for a 1.000 sq ft house, and another for a 3,000 sq ft house. I think the earth’s “HVAC” system is operating at a fraction of its capacity regarding the human race’s impact and influence. We are like a single mouse huddled in the corner of that 3,000 sq ft house. The HVAC can handle our extra body heat. :)
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