December 6, 2024 • 37 mins
Join Tim as he visits with Dr. Salehi and her PhD student, Dibya Datta, and discusses the issues we are facing concerning the use of plastics. They are convenient and helpful to farmers in many ways... holding up to various weather conditions without rot, easy to use, and cheap, but are they costing us more than we realize?
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Video Part One: https://youtu.be/RohNp3xAR4k
Video Part Two: https://youtu.be/3BilH0y5n7k
Transcript: 12-6-24 Tim's Take Episode 30 - Plastics In Our Soil.doc
#mizzou #microplastics #farming
The Missouri Agricultural Experiment Station (MOAES) extends CAFNR research to nearly 14,000 acres across the state to meet regional research and demonstration needs of agricultural producers and natural resource managers. MOAES has a storied history of major impacts in advancing science in agriculture, food and natural resources — locally, nationally and globally. These CAFNR laboratories provide research faculty with a wide variety of real-world conditions to test and develop strategies for agricultural production based on the geographical and climatic differences of our diverse state.
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Episode Transcript
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(00:00):
[♫]
(Tim Reinbott) Well, welcome to Tim's Take! And today we have a couple special guests,
Dr. Maryam Salehi, and she's in civil and environmental engineering. And her graduate
student working on... on his PhD is Dibya Kanti Datta. Welcome both of you! It's so exciting to be here
(00:25):
because you got a issue that we're going to talk about, and it's a collaboration between civil and
environmental engineering and CAFNR, and that's microplastics. (Dr. Salehi) Yeah. (Tim) But Dr.
Salehi, you ought to going to give us a little bit of overview about the use of plastics
that we have in agriculture. (Dr. Salehi) Uh... hi, Tim! Thanks for inviting us to,
(00:46):
uh... this podcast. Uh... and I'm so glad to share some information with you regarding plastic usage
and impact on agricultural soil. So you know that these days there are lots of agricultural
innovations because we have increasing world population that we need to address their,
(01:08):
uh... demand for the food. So that's why plastics have been entered to the agricultural practices.
Uh... we use plastics for different application in agriculture. Uh... one of the most common usage
of plastic in agriculture is the plastic mulch. I'm sure that many people definitely saw those
(01:30):
black or white plastics around the plants, like a strawberry... pumpkin. Uh... there are irrigation
pipes that used for, uh... you know, water conservation, and there are lots of other
applications for the plastic in the agriculture. But the major concern is that what is happening
(01:50):
to all these plastics, uh... after their use cycle or after harvesting. (Tim) Because we don't always
get them picked up, do we? (Dr. Salehi) Exactly. That's the problem. (Tim) There's always some out
there. And when you talked about there, like in our horticulture, where the food that we directly
eat, but I got to thinking about that on the way to... in today. We... we use a lot of plastics in...
(02:13):
in livestock. For example, when we make hay, we... we wrap it with... with a plastic. And this summer,
I was out in my pasture where I feed my livestock, I was shocked how much plastic is on the ground.
That I miss! When I'm pulling it off to feed the hay. We also are using it, uh... in our...
(02:35):
in our grain production. You know, plastic is everywhere when we stop and think about it! And
even in... in... in the home use! You... because you talk about like in... in our food production,
but when we buy plants, they're in plastic! (Dr. Salehi) Exactly. And we have lots of packaging
material. You know, all of those. (Tim) So what happens to all that? It just stays in the soil?
(02:57):
If... if... if we don't get it, pick it up, and do something with it, it's just going to stay in the
soil and the grass... just going to talk a little bit more about that! But let's talk a little bit
about the whole issue of plastic because there... there are some alternatives, I suppose. We could
use more organic forms of it. And I know from my own experience, like... like with hay, we used
(03:22):
to wrap it with a sisal, which is organic, but it rots! And I was so excited when we started using
plastic twine! (Dr. Salehi) Yeah, so exactly! The main, you know, the main motive for using the
plastic is that they have, uh... good properties. They are long-lasting. It's easy to use them. But
(03:43):
the main issue is that it's almost impossible to collect all of the plastic from the farmland
after we are using those. It's impossible to get them out of the soil. And gradually, you know,
year after year, we are accumulating all of this plastic in our soil. So what's happening to all
these plastics over the time? (Tim) Yeah, because they keep getting chopped up smaller and smaller
(04:05):
and smaller. (Dr. Salehi) Exactly. So that's why they get fragmented. You know, they get converted
to the smaller and smaller particles that we call them microplastics, nanoplastics. They are smaller
than 5 mm. They are tiny, so that's why it's very easy for them to get transported. For example,
if we have the rain event. So we have the storm water, they just, you know, get...
(04:29):
get into the storm water and get transported to the lake or river around the farm. Or they can,
you know, with wind, they can be transported to the surrounding environment. Or even when
they are so tiny, they can penetrate into the soil column as well. (Tim) So they could be everywhere
then. (Dr. Salehi) Exactly. (Tim) And... and they'll move off target. (Dr. Salehi) Exactly.
(04:50):
(Tim) Which is a huge issue in itself. So when did we start using so much plastic? Is that just
something gradual or... ? (Dr. Salehi) Exactly! So it started since the mid-20th century, so 1950,
around that time. And, uh... by replacing the, uh... you know, covers for the greenhouses, you
(05:12):
know, in using plastic instead of the, uh... glass for the greenhouses, and then we have the plastic
mulch, so gradually usage of plastic expanded, and we use them for different practices. One of the,
you know, major consumption of plastic is for the drip irrigation. So, uh... we can use the
(05:33):
water very efficiently when we are conducting drip irrigation, but the point is that these plastics,
uh... you know, after ground, they don't last long. So after some time, they are going to be,
uh... degraded, converted to the small particles, and they just remain in the soil. It's difficult
to recover all of those out of the soil. (Tim) I can attest to that. And now some of our research
(05:58):
is that we're burying the plastic under the ground, you know, so we can use it multiple
years, but getting that out is going to be almost impossible. So now we already have it, you know,
6 inches under the ground, so that... that... that's going to be an issue in itself. And as
we'll talk about here in a minute, it has some adverse effects. (Dr. Salehi) Definitely! You
(06:18):
know, plastic itself is going to convert it to the small pieces and distribute it into the soil
or later be transported to the, uh... water. In addition to that, there are some additives
in this plastic that they can be leeched out of the plastic into the soil, and they could
be toxic. (Tim) Oh. So that's going to make... be even a different subject just talking about
(06:38):
the... those additives that are there. You know, uh... one of the big increase I've also seen is
that when we use plastic on hoop houses and row covers, it's all plastic to... to help extend
our growing season, but even those are hard to... to... to recycle because they can... they tear.
(06:59):
They rip. They... they get left behind. And it just starts growing and growing. You know,
our... like our greenhouses, we used to have glass greenhouses. And those would last 100 years! But
it's the... it's the expense. I guess, plastic is cheap. (Dr. Salehi) Yeah, definitely. It's cheap,
and it's long lasting. It can, you know, it can tolerate many environmental, you know,
(07:24):
condition with weather events, so that's why. And it's easy to use those! (Tim) Right! It's easy,
but it's not long lasting enough. (Dr. Salehi) Yeah, exactly. (Tim) All right. All right. Well,
anything else on the basics on... on just the plastics that... that... that we've seen the rise
of? And this touches all phases of agriculture, from vegetable production... livestock. You know,
(07:49):
I was just down in Missouri Bootheel last week, and a lot of the irrigation is done with plastic
of... of... of cotton and corn and soybeans. Long plastic tubes, single use, they use it one year,
and they take it up. And then, what do you do with it? Can you burn it? (Dr. Salehi) That's
the question for Dibya. (Tim) Oh, that's what Dibya will be talking about. All right! All right. What to do with all
(08:11):
this? So, but Dibya! Let's talk about that. What did I do with all this plastic? (Dibya Datta) So
again, what Dr. Salehi was talking about, like... it's really hard to collect all of them,
but whatever you can collect, like farmers, there are some ways you can, uh... firstly,
they can pile them up for re-use. But piling up, it's not a good option because, again,
(08:33):
the microplastics are... that plastic can degrade, further degrade, and, uh... move around into the,
uh... surrounding environments, can contaminate the environment further. Another option is burning
them, but burning... (Tim) That's not good, is it? (Dibya) That's not good. Definitely. Because
whenever you are burning anything that's organic, so the main problem with that, you are always,
(08:56):
uh... like releasing some gases, toxic gases, and again, some greenhouse gases. So that's
not good for the air quality around that. And some other toxic chemicals, like dioxin, they
can get released into the air and the environment and further like, harm the, uh... living beings,
(09:16):
so uh... that's a concern. Another option is recycling them. (Tim) Okay. (Dibya) But the
problem is recycling, uh... at this stage, it's still not that easily accessible, especially in
the areas, like remote areas. So it's really hard for, uh... the farmers to access those services
(09:37):
and send them. And again, sending, uh... taking those plastics to the recycling services, it's
expensive. So... (Tim) And we have different types of plastic, don't we? (Dibya) Yes. (Tim) Like this
water bottle, I believe, can be easily recycled? (Dibya) Yes. (Tim) But it's a different type of
plastic than we use in agriculture. (Dibya) Right. So when we are using plastics in agriculture,
(10:01):
there are so many types. Like, we are using mulches. We are using pipes. So many things in
there. So there are different types of plastics. And again, when they're staying longer and longer
in the agricultural field, they're getting mixed with other stuff, like sediment. You are applying
pesticides. Yes. You are applying pesticides, and there are some other environmental stuff that's
(10:22):
getting attached to those plastics. So when you send them for recycling, it's again a challenge
for the recycling facilities to recycle those plastics because they have to get rid of those
extra materials. (Tim) Ooooh. And... and... and soil, too. I mean, if they're... if they're... if
they're dirty. (Dibya) Yes. (Dr. Salehi) Exactly. (Tim) They have to be clean. And if we use them in
(10:42):
agriculture, they're not going to be clean. (Dibya) No. (Tim) Because we're having them
in the soil and... and what have you. Wow! So... but we could use alternatives, correct? Before we
start talking about how bad it is, there are some alternatives. Right? (Dibya) So the alternatives,
uh... they're like, you can use straws. (Tim) Mhm. (Dibya) You can use paper mulches. They're better
(11:07):
alternatives. They're biodegradable. Problem with them is they're still expensive, so farmers
definitely, whoever, are concerned about the cost, they definitely, uh... want to opt in for the cost
effective options. (Dr. Salehi) And something is about the performance as well. I was talking
with the farmers, and I was asking that, "Okay, why you are not using the paper mulch instead of
(11:29):
plastic mulch?" And they were, uh... talking about the performance and how long the paper
mulch will... if they are going to last until the end of the harvesting season. So maybe if we can
work more on promoting the quality of the more, you know, environmental friendly options, we can,
uh... we can encourage the farmers to use those option rather than using the plastic because,
(11:52):
in addition to the cost, performance is a concern as well. (Tim) You know, I used some paper mulch
one time. I got frustrated! Because it wasn't... I had a hard time getting it to feed to... not tear
when I was trying to put it down. And... and like you mentioned, it doesn't always last quite long
enough; whereas, our plastic lasts a little bit too long. Now, there are some plastics made from
(12:18):
cornstarch? (Dibya) Yes, cornstarch and cellulose. So uh... mostly those
are used as biodegradable plastic products... like those are used for making biodegradable
plastic. So that's another thing that's being tested for agriculture. So the thing is,
(12:38):
they're useful... biodegradable. They break down comparatively faster compared to the conventional
plastics that are produced from the petroleums and stuff. So the point is here that, biodegradable
plastics are good alternatives, but they have been tested mostly on lab scale. One problem is
(12:59):
that in agricultural field or in the natural environment, the condition might be really very
different from the lab scale because you are running the experiment under controlled, uh... conditions.
But in the agricultural field, there can be, like depending on the agricultural field, there can be
various types of soil. Their moisture capacity could be different. Their water holding capacity
(13:23):
could be different. The microbes that are living in those soils, they could be widely variable,
and uh... the sunlight the agricultural field get. So there are so many factors
in there that is really hard to simulate in the laboratory condition. So I'd say,
we don't still... don't know much how those biodegradable plastic will interact in the
(13:46):
natural environment, and it could lead to incomplete degradation of those plastics. And
if it does not degrade completely, then again, the same problems as the conventional plastics case.
(Tim) Oh, really?! (Dibya) Yeah. (Dr. Salehi) But at least we know that the impacts would be
definitely less than the synthetic plastic, so if we use the biodegradable plastic,
(14:08):
the concern is less because the impact would be less. At least they are going to get go away,
you know, earlier. (Tim) But it probably still takes some petroleum to make that biodegradable...
biodegra... (Dr. Salehi) Biodegradable. They are using some natural, uh... sources, or something
that can be degraded by microorganisms that are present in the environment. (Tim) But still may
(14:30):
take energy to make that. (Dr. Salehi) Definitely. (Tim) How often can, like this plastic be
recycled? Can I... can we recycle it forever? Or, I mean, if I take it to the recycling plant, does
it eventually start losing some of its properties? (Dr. Salehi) So I'm not sure. I haven't, you know,
work on recycling. It's out of my area. Uh... but generally, when we have the thermoplastic,
(14:53):
the plastics that they get melted with, you know, temperature, we can recycle those, you know,
generally. (Tim) You know, uh... over the weekend, I was at my daughter's, and she's a millennial.
And I said something about plastic bags. She said, "I don't use plastic bags. We use... we,
(15:13):
uh... use bags, you know, uh... " (Dr. Salehi) Reusable. (Tim) Reusable, yeah! Reusable bags and,
or... or the kids lunches go in the re... reusable containers. Yes. So that's one of
the biggest ways right there that... that we can... that we can cut down on that,
isn't it? (Dibya) Yes, definitely. Uh... for me, I started using those glass containers for
(15:36):
bringing my lunch to the office. Uh... I used to use plastics, but again, there is impact,
so I definitely avoid those. (Tim) And eventually, they will be, uh... the... the plastic containers
will eventually have to be... something has to be done to them. (Dibya) Yes. (Tim) Because it
will... so not only are we in our food production, but we're also, uh... post food production when
(15:57):
we... when we consume it ourself. Now, you've got some examples of... of where we see some... some
plastics. (Dr. Salehi) Yeah, something that we haven't discuss is the, uh... a slow release or
continual release fertilizer. And actually, some of those... some of those, they have some plastic
in their coating. So, uh... see this. These are the, uh... beads for the slow release fertilizer,
(16:24):
and in their coating, uh... there are some of those. They have some plastic. So we are adding
those to the soil to release some nutrient to the soil gradually over, you know, several months. And
after they release their nutrient, we have this coating that they call that microcapsules, so
these microcapsules is just stay in the soil, and they have some plastic as well. And the recovery
(16:49):
is almost impossible because these are just some small pieces and they distribute into the
soil. (Tim) That was one of my biggest surprises, when we started talking about this subject, that the
slow release fertilizers were... has plastic in that... in that encapsulation. That's why it's
slow... it's slow release because we're depending on that to break down. And I got thinking about it,
(17:12):
when you buy a plant at a nursery, and they've gotten some of these slow release, and I've
always looked at little empty caplets, because that's why I'm seeing, isn't it? I'm seeing the...
the plastic part that's... that's left over. So, wow. So we got to think about that even every...
in every stage of production, we got to stop and think about what we're doing! (Dr. Salehi) Yeah,
(17:33):
exactly. And you know, these are so small, so if we have a rain event or a storm, all of these
could be washed away from the farm and go to the water resources, lake, or somewhere around the
farm as well. (Tim) And that off-target pollution, that's probably... that's really where we're
looking at some issues that affects everybody. (Dr. Salehi) Mhm. Exactly. (Tim) Oh, wow. Now,
(17:55):
of course, paper mulch is an alternative to our... our plastic mulch. (Dr. Salehi) Yeah. (Tim) And...
and we... and we talked about that. Now, what... now, we also have some pots and... and such.
Let's take a look at those. (Dr. Salehi) So, these are the plastic pots that they are used for the,
uh... nurseries. (Tim) Everybody uses those! (Dr. Salehi) Yes! So, but there
are some options. We can use the biodegradable version of this. Uh... I'm sure... oh! This
(18:20):
one! This one. (Dibya) This is organic pots. (Dr. Salehi) Yeah... yeah. We can just use these instead
of this plastic one to reduce the impact of, you know, plastics. (Tim) And those go directly
in the ground. (Dr. Salehi) Exactly. (Tim) Sure. (Dibya) And... and we have this straws
here. (Dr. Salehi) So, and these are some irrigation pipes that they use. (Tim) Yeah,
(18:40):
there's so much of every stage of... of production we see a lot. So even if we're really good about
eating our fruits and our vegetables, we'll probably have a huge plastic impact, don't
we? (Dr. Salehi) Yeah. (Tim) I mean... I mean really, really we do. (Dibya) There is a chance,
uh... because, uh... again, Dr. Salehi was saying, like those plastics break down into smaller
(19:03):
particles that we know as micro and nanoplastics. So, uh... to comprehend like how small they are,
nanoplastic, it's like one nanometer is a millionth of a millimeter, right? So,
so small. (Tim) We're talking about a millionth of a millimeter! (Dibya) Yes. (Tim) That's pretty
small. (Dibya) Yes, that's really small. It's, uh... probably comparable to some of the nutrient
(19:26):
ions that plants can absorb. (Tim) Well, so it's... it's the same size as like potassium or
nitrogen. (Dibya) Ah, that I don't know actually. (Tim) Well, I mean that some of our... our nutrients in...
in the form, wow! So, plants could take them up, couldn't they? (Dibya) Through their root,
it's possible. There has been, uh... studies going on, and they're trying to understand
better like if plants can take up microplastics and nanoplastics. And it's much more likely
(19:52):
that nanoplastics can get absorbed... absorbed through the roots. (Dr. Salehi) But generally,
plastic when they are a smaller, their risk and their associated, you know, toxic impact is
increasing because when they are small, they can, uh... they can move easily. You know,
because they are very small, they can penetrate into the soil column, or they can just wash the
(20:14):
off with the storm. (Dibya) Off with the water or just when there is wind. Uh... just wind can blow
them away so far. (Tim) So we got in the wind at the nanoplastics? Wow. (Dr. Salehi) Or even
microplastics. (Dibya) Yes, microplastics. (Tim) Well, you know, when I think about,
uh... my lunch bag, I say, "Well, I'm recycling bags I get from the grocery store." Plastic bags.
(20:39):
But I only use them once, or maybe twice, but then they start tearing, so I... (Dibya) You can... you
just throw them. (Tim) Right. (Dibya) So it's just contributing to more plastic waste. (Tim) Yes,
it is. So you really got to be careful about what you're doing. (Dr. Salehi) Yeah, reusable bags are
very good options for, you know, grocery. (Tim) I'm sorry. What are those? (Dr. Salehi) They're
reusable bags. (Tim) Oh, reusable bags, yes! Which are often made out of plant materials.
(21:03):
(Dr. Salehi) Yeah. (Dibya) Yeah, or cotton bags maybe. Those can be a good alternative. (Tim) And when
they're wore out, they can be recycled or... or... or turned back into the environment some
way because... because... because they are. And plastics, of course, they're petroleum,
and they have a petroleum carbon footprint to make them too because you have... so it's a...
it's a... it's a big... big, uh... issue. All right. Well, anything else we want to talk about
(21:28):
the basics before we really dive into... into what contaminants that the plastics contain?
(Dibya) Just one thing I can talk about like, uh... food safety as I was saying.
Uh... plants, there has been studies going on, like if plants can, uh... absorb micro, uh... micro
(21:51):
or nanoplastic from soil. So, uh... I had the opportunity to work on a study with Dr. Salehi
where, uh... it was not on agriculture directly. That was, uh... with storm water. But we saw that
as the plastics age, especially microplastics, they can absorb a heavy metals on their surfaces,
like lead, zinc, copper. So if any plant end up ab... absorbing micro or nanoplastics,
(22:19):
there is a risk it can... not only micro or nanoplastic is getting into our food... our
fruits, our vegetables, there could be other heavy metals or other contaminants if they're absorbed
to the plastic surfaces that's getting into our food. (Tim) Or if we're eating root crops
that... that could be growing into the... into the plastic. So we'll pick that up after our break.
(22:41):
(Tim Reinbott) All right. So we've talked about microplastics and nanoplastics,
which are 1 millionth of a millimeter. (Dibya Datta) Mhm. (Tim) It's a lot of
zeros before the decimal point. Had to... had to figure that up. So, but a study came
out last year that showed that bottled water can have nanoplastics in it. So we can consume these
(23:02):
nanoplastics? (Dr. Maryam Salehi) Yeah, actually one of the... one of the topic that we are
studying in our lab is about the contamination of the microplastic in the drinking water, you know,
because they could come up in the drinking water, even tap water. There are several other studies that
show that they are in the tap water, so that's why when we are discussing about the contamination in
(23:23):
the farmland, the concern is that... one of the concern is that this plastic could be transported
to our drinking water resources and then eventually come up in our tap water. (Tim) Right!
Because we either get our water from impoundments, which is... which can be... water could be drained
in it from farms and what have you, or from subsurface, but again, the man... the... the
(23:47):
nanoplastics are moving through the soil. So they could get taken up that way, and then they wind up
in the... in the... (Dibya) Groundwater? (Tim) Yes! Exactly! And that winds up in our... in
our water system and in us. So some of us, uh... have well water, so it's... we're shallow wells.
Some of us are getting water from different sources, so it's not that difficult to imagine
(24:13):
we are getting these nanoplastics into us! (Dr. Salehi) Exactly. (Tim) And like you said earlier,
they can have heavy metals... (Dibya) Uh... like they can absorb heavy metals if there is any heavy
metal in the agricultural field. (Tim) Right. (Dibya) Yeah. (Tim) So you know, when we use our
arsenics and what have you in our pesticides, they could pick all that back up, couldn't
they? (Dr. Salehi) Yeah, and you know, any organic contaminant. You know, we are using herbicide,
(24:37):
pesticides in the farm. They can accumulate those on their surface, and when they get transported to
other environment, they can have those on their surface as well. (Tim) Oh, wow. So they're...
they're... they're carriers really, aren't they? (Dr. Salehi) Exactly. (Tim) They're carriers of
the environment that they're in. (Dibya) Yeah. (Dr. Salehi) Yeah. (Tim) They're...
they're really an indication of that. And so, do they have any compounds themselves that they
(25:03):
might release into the environment? (Dr. Salehi) Yeah, you know, when they processing the plastics,
they are adding some additives. For example, plasticizer or other sort of, you know,
antioxidants... (Dibya) Stabilizers. (Dr. Salehi) Stabilizer. Lots... lots of, you know,
additives are added to them because they want to, uh... facilitate their processing, and when they,
(25:25):
uh... disintegrate and degrade in the farm, they can leech those contaminant out into the
environment. (Tim) Oh, wow. (Dibya) Like two of the common, uh... is... there is Bisphenol A,
and there is phthalates. These are more commonly used as additives in plastics to,
uh... improve their properties, or uh... to make them last longer. And this, uh... phthalates and
(25:51):
Bisphenol A, they're really harmful for human being. Like they can mess up with your hormones
and reproductive system, so... (Dr. Salehi) But there are some regulations for that, so I'm not
sure how is the regulation for addition of those to the plastics, but generally, uh... there are
some additives that they can leech out. (Tim) But there were some, uh... plastics that got banned
(26:15):
additives because... (Dr. Salehi) Yes! Yeah! (Tim) Because of the... the human hormones that
they were mimicking. (Dr. Salehi) Exactly! Some of these are banned. Yeah. (Tim) But those are
probably still out there. Those plastics could... could... could very well be out there, still...
still carrying those... those compounds. Wow! What else do we need to do then? I mean, what...
I mean, we talked about alternatives. (Dr. Salehi) Yeah, one thing that we can do is that if we are
(26:37):
applying plastic mulch, we do our best to recover them from the soil, you know, as much as possible.
We take them out of the soil and send them to the recycling facility or even the landfill,
but we need to make sure that we are taking those out of our soil. Uh... we use, you know,
if possible, we use the biodegradable plastic mulch, or even better if we use the organic,
(27:02):
you know, options. We use the straw or wood chip or something that is organic rather than adding
some synthetic material to our farm. (Tim) Now, you all have developed a filter for this though,
haven't you? (Dr. Salehi) Yes! Actually, recently. Yeah, we had a project that we compilated. It was
a filter to remove the microplastic from the tap water. (Tim) And were you finding a lot of
(27:26):
microplastics in our tap water? (Dr. Salehi) Yeah, actually we can. It was just simulated
experimenting in the lab, but nowadays, one of my student is testing the, uh... tap water for
plastic we found. Uh... some plastic is just a preliminary, uh... data, but uh... yeah. You know,
because our water treatment plants generally designed to remove the conventional contaminant,
(27:52):
not the micro or nanoplastic. And even through the distribution system, uh... because some of
these water infrastructure, they are plastic themselves, so they can release some plastic
into the water as well. So there are some sources that are contributing... or even in our home, for
example, in my home, we are using the PEX pipes. So there... yeah, so there are some, you know,
(28:16):
sources that possibly could contaminate, uh... the tap water with plastic. But there are, you know,
there are research to be done. You know, there are lots of unknown in this area, so definitely
some research should be conducted in this area to confirm it.(Tim) Oh, sure! Sure. Plastics are
used in everything! It's very difficult. Even like your boxes that... that you brought your samples
(28:40):
in are plastic. (Dr. Salehi) Yeah. (Tim) And, uh... so probably the future is... is going to be
that we... we're better at recycling our plastics, using alternatives to plastics, and maybe making
the plastics out of non-petroleum. (Dr. Salehi) Exactly. Just biobased. (Tim) So do you think our
(29:02):
biobased, would they have any of the contaminants too that we see, and... you know, stickers
and what have you, or... ? (Dr. Salehi) So... biobased, the main thing is that we are not using
the synthetic or synthetic plastic, just regular plastic, that they are lasting for a long time in
the environment. For biobased, they are designed to be... to degrade faster. So they are going to
(29:25):
disintegrate in the environment, so we are not accumulating them for a long time. (Tim) And break
down into their basic products (carbon, hydrogen, oxygen)? That's... that's what we... that we hope;
whereas, our real petroleum plastics never really do, do they? (Dr. Salehi) It will take a long
time. Yeah. (Tim) Much long... much longer than my life... than our lifespan. (Dr. Salehi) Exactly...
(29:47):
yeah. (Tim) You know, uh... my, uh... daughters and I were talking about, uh... looking... looking
at the past and blaming our ancestors for this or that. I told them that I think plastic is
going to be what our generation gets judged on. You know, how could we have done that? Not...
(30:08):
not using res... not using renewables. I... I remember, uh... most... most drinks that you
bought when I was growing up was in glass. (Dr. Salehi) Yeah. (Tim) And glass, as we know, can be
recycled very easily. And we thought it was great when we got plastic! It was lighter and, you know,
we just throw away! It was easier to... to... to use. But that's came at... at a cost. (Dibya) Yes.
(30:32):
Definitely. (Tim) And I think the biggest surprise is what the plastics can latch on to,
and it contaminate us with that. (Dibya) Yeah. And there are so many different types of plastic,
so we are yet to know like, what their effects are on our body. Like, we only know so much about
(30:57):
it. (Dr. Salehi) Yeah, there... there's limited research in the health consequences, you know,
negative health consequences of plastic. So definitely, there are a lot to investigate...
(Tim) They call it more planetary... planetary health. You know, how our whole as a... as a...
as a society. (Dr. Salehi) Yeah. (Tim) Can any of our issues that we have with our own health,
(31:19):
can that be traced back to some of the plastics that... that... that we have? (Dr. Salehi) I
guess they should... they should conduct more research. (Tim) Yeah that's something that...
that's probably they need to look at then. Oh, wow. Anything else that we... that we're
concerned with that... that... that we should know about plastic? (Dibya) So, uh... if we,
uh... get back to the agricultural field, some of the things plastic can do through the agricultural
(31:40):
lands that, uh... farmers could be more concerned about is the long-lasting fertility issues. So if
plastic gets accumulated, since they're breaking down, firstly they can block the pores, or because
of the existence of plastic in the soil, it can alter the soil structure. So... (Tim) Oh,
(32:00):
shoot! Haven't thought about that part yet. Yes! (Dibya) So, uh... eventually because of the
change in soil structure, uh... the water holding capacity, uh... the moisture content of the soil,
that can get changed, and that can eventually affect the crop growth. And the more and more
plastics farmers keep using on their lands, the more plastics get accumulated over time,
(32:26):
and that can create a problem with the fertility issues. Uh... the longer there are plastics
in there... (Dr. Salehi) Could happen in many years... yeah. (Dibya) ...many years,
uh... the fertility might reduce. So the quality of, uh... crops they grow, the vegetables and
fruits we get, might not be as good as we used to get. (Tim) Because... so, does plastic have
(32:48):
a... a charge to it? Like a plus? A minus? (Dr. Salehi) Negative, yeah. (Tim) So it's a negative charge. So it can act a lot like a soil particle then, and... but it's not. (Dibya) No. (Tim) Oh,
wow. And... and like you said, plugging the... the... the, uh... particles up, that...
the soil structure. (Dr. Salehi) Yeah, it can influence the water flow through the soil and
(33:09):
water retention. (Dibya) Plastic surfaces are mostly negative. We found... (Tim) They attract
cations. (Dibya) Yes. They can... (Dr. Salehi) But you know, cations like, you know, metals. You
know, met... heavy metals. They have positively, you know, positive charge, so they can attach to
the negative charge. And there are other sort of, you know, interaction. And something about
plastic is that when they are degrading in the environment, their surface charge could change,
(33:31):
you know. Or... you know, for example, when they are in the, uh... you know, there are
some moisture, there is possibility that some microorganisms grow on the surface of the plastic,
so their surface charge could vary when they are on the farm. So that could influence their
interaction with other contaminant. (Tim) Right. And... and also this negative charge makes it when
(33:56):
they repel, and they can move through the soil a lot easier. (Dibya) Yes. (Tim) Deeper and deeper
and deeper into the soil, into the water, into the groundwater. That's why we start seeing some those
issues. (Dibya) And, uh... when we were studying microplastics, uh... one thing we found that as
they age, the negative charge on their surface increase. (Tim) Oh, really? (Dr. Salehi) Yeah,
the aging was photodegradation. So when they expose to the solar radiation and they age,
(34:19):
they become more negative. Yeah. (Tim) Which could compound that effect then. (Dibya) So could be,
uh... possibly there could be more electrostatic attraction. Positive charges are getting more
attracted to their surfaces. So like heavy metals, cations. (Dr. Salehi) Yeah. But there are other,
you know, other sorts of interactions as well. This is just electrostatic. There are other sorts
(34:41):
of interaction as well that could influence their contaminant transport. (Tim) Oh, wow. Yeah, so
we can... we can have some... some... some issues here then, can't we? I think this... this has been
fantastic about bringing awareness to it, and... and how it affects every part of our life. And...
(35:01):
and some basic steps that... that... that... that we can do. (Dibya) Yes. (Tim) That we can really,
really do. (Dibya) And there are definitely some places we can think about replacing plastic. You
were talking about hay. So it's much convenient to cover them with plastic, uh... if you're using,
uh... those hay or silage as a, uh... feed for your livestock. So I know that's convenient,
(35:27):
and farmers are opting in for probably a cost effective option, but if you build a silo,
that's more, uh... that's like, more expensive, but again, that's long-lasting. (Tim) Right. So
some things, uh... there is a tradeoff between opting in for a cost effective option or spending
(35:51):
more and going for a long-lasting, sustainable option. So... (Tim) Yeah, we're going to have
to stop and think about this different ways. You know, one of the things first came to my mind is
year 'round... Missouri's great because we're in the bullseye that we can have year 'round grazing.
Where you don't feed as much hay. You don't feed as much hay. You don't have to have as much
(36:11):
plastics, and... and that sort of thing. So there is those type of options too. Just changing how
we... how we look at... at our food production. (Dibya) Yes. (Tim) All right. Well, thank you
all so much. This has been very interesting. I think we've opened a lot of eyes. There's been
some things that I hadn't really thought about. You know, how... how plastics can move through
(36:34):
the soil. How they can... since they're negative, they can attach to our... to our... our cations.
Not only the heavy metals, but maybe some of the ones that we want for our plant's growth... plant
growth, like potassium, for example. That... that... that... that's really important. And
how it keeps getting smaller and smaller and smaller and can wind up in our drinking water,
(36:55):
in our food, and probably, we don't know quite where it can wind up at yet, have we? Because
we haven't looked there yet. (Dr. Salehi) Yeah. (Dibya) There's so much to study. (Tim) And you
may not... you might be a little afraid to look at it. [laughter] So, all right. Well,
thank you all so much! Uh... good luck on your, uh... dissertation. Seems like you've done a
(37:16):
great job so far, and... and you got a lot to do, and a very exciting subject. And... and,
Dr. Salehi, it's been fantastic to work with you, and continue as... as we're working on this,
uh... that we can come up with some alternatives and maybe how to manage our plastics in our... in
our life. So... (Dr. Salehi) Yeah, thanks for inviting us. (Tim) You're welcome.
(37:37):
All right! Well, this is it for Tim's Take, and we'll talk to you next time.
[♫]
[♫]
(Tim Reinbott) Well, welcome to Tim's Take! And today we have a couple special guests,
Dr. Maryam Salehi, and she's in civil and environmental engineering. And her graduate
student working on... on his PhD is Dibya Kanti Datta. Welcome both of you! It's so exciting to be here
(00:25):
because you got a issue that we're going to talk about, and it's a collaboration between civil and
environmental engineering and CAFNR, and that's microplastics. (Dr. Salehi) Yeah. (Tim) But Dr.
Salehi, you ought to going to give us a little bit of overview about the use of plastics
that we have in agriculture. (Dr. Salehi) Uh... hi, Tim! Thanks for inviting us to,
(00:46):
uh... this podcast. Uh... and I'm so glad to share some information with you regarding plastic usage
and impact on agricultural soil. So you know that these days there are lots of agricultural
innovations because we have increasing world population that we need to address their,
(01:08):
uh... demand for the food. So that's why plastics have been entered to the agricultural practices.
Uh... we use plastics for different application in agriculture. Uh... one of the most common usage
of plastic in agriculture is the plastic mulch. I'm sure that many people definitely saw those
(01:30):
black or white plastics around the plants, like a strawberry... pumpkin. Uh... there are irrigation
pipes that used for, uh... you know, water conservation, and there are lots of other
applications for the plastic in the agriculture. But the major concern is that what is happening
(01:50):
to all these plastics, uh... after their use cycle or after harvesting. (Tim) Because we don't always
get them picked up, do we? (Dr. Salehi) Exactly. That's the problem. (Tim) There's always some out
there. And when you talked about there, like in our horticulture, where the food that we directly
eat, but I got to thinking about that on the way to... in today. We... we use a lot of plastics in...
(02:13):
in livestock. For example, when we make hay, we... we wrap it with... with a plastic. And this summer,
I was out in my pasture where I feed my livestock, I was shocked how much plastic is on the ground.
That I miss! When I'm pulling it off to feed the hay. We also are using it, uh... in our...
(02:35):
in our grain production. You know, plastic is everywhere when we stop and think about it! And
even in... in... in the home use! You... because you talk about like in... in our food production,
but when we buy plants, they're in plastic! (Dr. Salehi) Exactly. And we have lots of packaging
material. You know, all of those. (Tim) So what happens to all that? It just stays in the soil?
(02:57):
If... if... if we don't get it, pick it up, and do something with it, it's just going to stay in the
soil and the grass... just going to talk a little bit more about that! But let's talk a little bit
about the whole issue of plastic because there... there are some alternatives, I suppose. We could
use more organic forms of it. And I know from my own experience, like... like with hay, we used
(03:22):
to wrap it with a sisal, which is organic, but it rots! And I was so excited when we started using
plastic twine! (Dr. Salehi) Yeah, so exactly! The main, you know, the main motive for using the
plastic is that they have, uh... good properties. They are long-lasting. It's easy to use them. But
(03:43):
the main issue is that it's almost impossible to collect all of the plastic from the farmland
after we are using those. It's impossible to get them out of the soil. And gradually, you know,
year after year, we are accumulating all of this plastic in our soil. So what's happening to all
these plastics over the time? (Tim) Yeah, because they keep getting chopped up smaller and smaller
(04:05):
and smaller. (Dr. Salehi) Exactly. So that's why they get fragmented. You know, they get converted
to the smaller and smaller particles that we call them microplastics, nanoplastics. They are smaller
than 5 mm. They are tiny, so that's why it's very easy for them to get transported. For example,
if we have the rain event. So we have the storm water, they just, you know, get...
(04:29):
get into the storm water and get transported to the lake or river around the farm. Or they can,
you know, with wind, they can be transported to the surrounding environment. Or even when
they are so tiny, they can penetrate into the soil column as well. (Tim) So they could be everywhere
then. (Dr. Salehi) Exactly. (Tim) And... and they'll move off target. (Dr. Salehi) Exactly.
(04:50):
(Tim) Which is a huge issue in itself. So when did we start using so much plastic? Is that just
something gradual or... ? (Dr. Salehi) Exactly! So it started since the mid-20th century, so 1950,
around that time. And, uh... by replacing the, uh... you know, covers for the greenhouses, you
(05:12):
know, in using plastic instead of the, uh... glass for the greenhouses, and then we have the plastic
mulch, so gradually usage of plastic expanded, and we use them for different practices. One of the,
you know, major consumption of plastic is for the drip irrigation. So, uh... we can use the
(05:33):
water very efficiently when we are conducting drip irrigation, but the point is that these plastics,
uh... you know, after ground, they don't last long. So after some time, they are going to be,
uh... degraded, converted to the small particles, and they just remain in the soil. It's difficult
to recover all of those out of the soil. (Tim) I can attest to that. And now some of our research
(05:58):
is that we're burying the plastic under the ground, you know, so we can use it multiple
years, but getting that out is going to be almost impossible. So now we already have it, you know,
6 inches under the ground, so that... that... that's going to be an issue in itself. And as
we'll talk about here in a minute, it has some adverse effects. (Dr. Salehi) Definitely! You
(06:18):
know, plastic itself is going to convert it to the small pieces and distribute it into the soil
or later be transported to the, uh... water. In addition to that, there are some additives
in this plastic that they can be leeched out of the plastic into the soil, and they could
be toxic. (Tim) Oh. So that's going to make... be even a different subject just talking about
(06:38):
the... those additives that are there. You know, uh... one of the big increase I've also seen is
that when we use plastic on hoop houses and row covers, it's all plastic to... to help extend
our growing season, but even those are hard to... to... to recycle because they can... they tear.
(06:59):
They rip. They... they get left behind. And it just starts growing and growing. You know,
our... like our greenhouses, we used to have glass greenhouses. And those would last 100 years! But
it's the... it's the expense. I guess, plastic is cheap. (Dr. Salehi) Yeah, definitely. It's cheap,
and it's long lasting. It can, you know, it can tolerate many environmental, you know,
(07:24):
condition with weather events, so that's why. And it's easy to use those! (Tim) Right! It's easy,
but it's not long lasting enough. (Dr. Salehi) Yeah, exactly. (Tim) All right. All right. Well,
anything else on the basics on... on just the plastics that... that... that we've seen the rise
of? And this touches all phases of agriculture, from vegetable production... livestock. You know,
(07:49):
I was just down in Missouri Bootheel last week, and a lot of the irrigation is done with plastic
of... of... of cotton and corn and soybeans. Long plastic tubes, single use, they use it one year,
and they take it up. And then, what do you do with it? Can you burn it? (Dr. Salehi) That's
the question for Dibya. (Tim) Oh, that's what Dibya will be talking about. All right! All right. What to do with all
(08:11):
this? So, but Dibya! Let's talk about that. What did I do with all this plastic? (Dibya Datta) So
again, what Dr. Salehi was talking about, like... it's really hard to collect all of them,
but whatever you can collect, like farmers, there are some ways you can, uh... firstly,
they can pile them up for re-use. But piling up, it's not a good option because, again,
(08:33):
the microplastics are... that plastic can degrade, further degrade, and, uh... move around into the,
uh... surrounding environments, can contaminate the environment further. Another option is burning
them, but burning... (Tim) That's not good, is it? (Dibya) That's not good. Definitely. Because
whenever you are burning anything that's organic, so the main problem with that, you are always,
(08:56):
uh... like releasing some gases, toxic gases, and again, some greenhouse gases. So that's
not good for the air quality around that. And some other toxic chemicals, like dioxin, they
can get released into the air and the environment and further like, harm the, uh... living beings,
(09:16):
so uh... that's a concern. Another option is recycling them. (Tim) Okay. (Dibya) But the
problem is recycling, uh... at this stage, it's still not that easily accessible, especially in
the areas, like remote areas. So it's really hard for, uh... the farmers to access those services
(09:37):
and send them. And again, sending, uh... taking those plastics to the recycling services, it's
expensive. So... (Tim) And we have different types of plastic, don't we? (Dibya) Yes. (Tim) Like this
water bottle, I believe, can be easily recycled? (Dibya) Yes. (Tim) But it's a different type of
plastic than we use in agriculture. (Dibya) Right. So when we are using plastics in agriculture,
(10:01):
there are so many types. Like, we are using mulches. We are using pipes. So many things in
there. So there are different types of plastics. And again, when they're staying longer and longer
in the agricultural field, they're getting mixed with other stuff, like sediment. You are applying
pesticides. Yes. You are applying pesticides, and there are some other environmental stuff that's
(10:22):
getting attached to those plastics. So when you send them for recycling, it's again a challenge
for the recycling facilities to recycle those plastics because they have to get rid of those
extra materials. (Tim) Ooooh. And... and... and soil, too. I mean, if they're... if they're... if
they're dirty. (Dibya) Yes. (Dr. Salehi) Exactly. (Tim) They have to be clean. And if we use them in
(10:42):
agriculture, they're not going to be clean. (Dibya) No. (Tim) Because we're having them
in the soil and... and what have you. Wow! So... but we could use alternatives, correct? Before we
start talking about how bad it is, there are some alternatives. Right? (Dibya) So the alternatives,
uh... they're like, you can use straws. (Tim) Mhm. (Dibya) You can use paper mulches. They're better
(11:07):
alternatives. They're biodegradable. Problem with them is they're still expensive, so farmers
definitely, whoever, are concerned about the cost, they definitely, uh... want to opt in for the cost
effective options. (Dr. Salehi) And something is about the performance as well. I was talking
with the farmers, and I was asking that, "Okay, why you are not using the paper mulch instead of
(11:29):
plastic mulch?" And they were, uh... talking about the performance and how long the paper
mulch will... if they are going to last until the end of the harvesting season. So maybe if we can
work more on promoting the quality of the more, you know, environmental friendly options, we can,
uh... we can encourage the farmers to use those option rather than using the plastic because,
(11:52):
in addition to the cost, performance is a concern as well. (Tim) You know, I used some paper mulch
one time. I got frustrated! Because it wasn't... I had a hard time getting it to feed to... not tear
when I was trying to put it down. And... and like you mentioned, it doesn't always last quite long
enough; whereas, our plastic lasts a little bit too long. Now, there are some plastics made from
(12:18):
cornstarch? (Dibya) Yes, cornstarch and cellulose. So uh... mostly those
are used as biodegradable plastic products... like those are used for making biodegradable
plastic. So that's another thing that's being tested for agriculture. So the thing is,
(12:38):
they're useful... biodegradable. They break down comparatively faster compared to the conventional
plastics that are produced from the petroleums and stuff. So the point is here that, biodegradable
plastics are good alternatives, but they have been tested mostly on lab scale. One problem is
(12:59):
that in agricultural field or in the natural environment, the condition might be really very
different from the lab scale because you are running the experiment under controlled, uh... conditions.
But in the agricultural field, there can be, like depending on the agricultural field, there can be
various types of soil. Their moisture capacity could be different. Their water holding capacity
(13:23):
could be different. The microbes that are living in those soils, they could be widely variable,
and uh... the sunlight the agricultural field get. So there are so many factors
in there that is really hard to simulate in the laboratory condition. So I'd say,
we don't still... don't know much how those biodegradable plastic will interact in the
(13:46):
natural environment, and it could lead to incomplete degradation of those plastics. And
if it does not degrade completely, then again, the same problems as the conventional plastics case.
(Tim) Oh, really?! (Dibya) Yeah. (Dr. Salehi) But at least we know that the impacts would be
definitely less than the synthetic plastic, so if we use the biodegradable plastic,
(14:08):
the concern is less because the impact would be less. At least they are going to get go away,
you know, earlier. (Tim) But it probably still takes some petroleum to make that biodegradable...
biodegra... (Dr. Salehi) Biodegradable. They are using some natural, uh... sources, or something
that can be degraded by microorganisms that are present in the environment. (Tim) But still may
(14:30):
take energy to make that. (Dr. Salehi) Definitely. (Tim) How often can, like this plastic be
recycled? Can I... can we recycle it forever? Or, I mean, if I take it to the recycling plant, does
it eventually start losing some of its properties? (Dr. Salehi) So I'm not sure. I haven't, you know,
work on recycling. It's out of my area. Uh... but generally, when we have the thermoplastic,
(14:53):
the plastics that they get melted with, you know, temperature, we can recycle those, you know,
generally. (Tim) You know, uh... over the weekend, I was at my daughter's, and she's a millennial.
And I said something about plastic bags. She said, "I don't use plastic bags. We use... we,
(15:13):
uh... use bags, you know, uh... " (Dr. Salehi) Reusable. (Tim) Reusable, yeah! Reusable bags and,
or... or the kids lunches go in the re... reusable containers. Yes. So that's one of
the biggest ways right there that... that we can... that we can cut down on that,
isn't it? (Dibya) Yes, definitely. Uh... for me, I started using those glass containers for
(15:36):
bringing my lunch to the office. Uh... I used to use plastics, but again, there is impact,
so I definitely avoid those. (Tim) And eventually, they will be, uh... the... the plastic containers
will eventually have to be... something has to be done to them. (Dibya) Yes. (Tim) Because it
will... so not only are we in our food production, but we're also, uh... post food production when
(15:57):
we... when we consume it ourself. Now, you've got some examples of... of where we see some... some
plastics. (Dr. Salehi) Yeah, something that we haven't discuss is the, uh... a slow release or
continual release fertilizer. And actually, some of those... some of those, they have some plastic
in their coating. So, uh... see this. These are the, uh... beads for the slow release fertilizer,
(16:24):
and in their coating, uh... there are some of those. They have some plastic. So we are adding
those to the soil to release some nutrient to the soil gradually over, you know, several months. And
after they release their nutrient, we have this coating that they call that microcapsules, so
these microcapsules is just stay in the soil, and they have some plastic as well. And the recovery
(16:49):
is almost impossible because these are just some small pieces and they distribute into the
soil. (Tim) That was one of my biggest surprises, when we started talking about this subject, that the
slow release fertilizers were... has plastic in that... in that encapsulation. That's why it's
slow... it's slow release because we're depending on that to break down. And I got thinking about it,
(17:12):
when you buy a plant at a nursery, and they've gotten some of these slow release, and I've
always looked at little empty caplets, because that's why I'm seeing, isn't it? I'm seeing the...
the plastic part that's... that's left over. So, wow. So we got to think about that even every...
in every stage of production, we got to stop and think about what we're doing! (Dr. Salehi) Yeah,
(17:33):
exactly. And you know, these are so small, so if we have a rain event or a storm, all of these
could be washed away from the farm and go to the water resources, lake, or somewhere around the
farm as well. (Tim) And that off-target pollution, that's probably... that's really where we're
looking at some issues that affects everybody. (Dr. Salehi) Mhm. Exactly. (Tim) Oh, wow. Now,
(17:55):
of course, paper mulch is an alternative to our... our plastic mulch. (Dr. Salehi) Yeah. (Tim) And...
and we... and we talked about that. Now, what... now, we also have some pots and... and such.
Let's take a look at those. (Dr. Salehi) So, these are the plastic pots that they are used for the,
uh... nurseries. (Tim) Everybody uses those! (Dr. Salehi) Yes! So, but there
are some options. We can use the biodegradable version of this. Uh... I'm sure... oh! This
(18:20):
one! This one. (Dibya) This is organic pots. (Dr. Salehi) Yeah... yeah. We can just use these instead
of this plastic one to reduce the impact of, you know, plastics. (Tim) And those go directly
in the ground. (Dr. Salehi) Exactly. (Tim) Sure. (Dibya) And... and we have this straws
here. (Dr. Salehi) So, and these are some irrigation pipes that they use. (Tim) Yeah,
(18:40):
there's so much of every stage of... of production we see a lot. So even if we're really good about
eating our fruits and our vegetables, we'll probably have a huge plastic impact, don't
we? (Dr. Salehi) Yeah. (Tim) I mean... I mean really, really we do. (Dibya) There is a chance,
uh... because, uh... again, Dr. Salehi was saying, like those plastics break down into smaller
(19:03):
particles that we know as micro and nanoplastics. So, uh... to comprehend like how small they are,
nanoplastic, it's like one nanometer is a millionth of a millimeter, right? So,
so small. (Tim) We're talking about a millionth of a millimeter! (Dibya) Yes. (Tim) That's pretty
small. (Dibya) Yes, that's really small. It's, uh... probably comparable to some of the nutrient
(19:26):
ions that plants can absorb. (Tim) Well, so it's... it's the same size as like potassium or
nitrogen. (Dibya) Ah, that I don't know actually. (Tim) Well, I mean that some of our... our nutrients in...
in the form, wow! So, plants could take them up, couldn't they? (Dibya) Through their root,
it's possible. There has been, uh... studies going on, and they're trying to understand
better like if plants can take up microplastics and nanoplastics. And it's much more likely
(19:52):
that nanoplastics can get absorbed... absorbed through the roots. (Dr. Salehi) But generally,
plastic when they are a smaller, their risk and their associated, you know, toxic impact is
increasing because when they are small, they can, uh... they can move easily. You know,
because they are very small, they can penetrate into the soil column, or they can just wash the
(20:14):
off with the storm. (Dibya) Off with the water or just when there is wind. Uh... just wind can blow
them away so far. (Tim) So we got in the wind at the nanoplastics? Wow. (Dr. Salehi) Or even
microplastics. (Dibya) Yes, microplastics. (Tim) Well, you know, when I think about,
uh... my lunch bag, I say, "Well, I'm recycling bags I get from the grocery store." Plastic bags.
(20:39):
But I only use them once, or maybe twice, but then they start tearing, so I... (Dibya) You can... you
just throw them. (Tim) Right. (Dibya) So it's just contributing to more plastic waste. (Tim) Yes,
it is. So you really got to be careful about what you're doing. (Dr. Salehi) Yeah, reusable bags are
very good options for, you know, grocery. (Tim) I'm sorry. What are those? (Dr. Salehi) They're
reusable bags. (Tim) Oh, reusable bags, yes! Which are often made out of plant materials.
(21:03):
(Dr. Salehi) Yeah. (Dibya) Yeah, or cotton bags maybe. Those can be a good alternative. (Tim) And when
they're wore out, they can be recycled or... or... or turned back into the environment some
way because... because... because they are. And plastics, of course, they're petroleum,
and they have a petroleum carbon footprint to make them too because you have... so it's a...
it's a... it's a big... big, uh... issue. All right. Well, anything else we want to talk about
(21:28):
the basics before we really dive into... into what contaminants that the plastics contain?
(Dibya) Just one thing I can talk about like, uh... food safety as I was saying.
Uh... plants, there has been studies going on, like if plants can, uh... absorb micro, uh... micro
(21:51):
or nanoplastic from soil. So, uh... I had the opportunity to work on a study with Dr. Salehi
where, uh... it was not on agriculture directly. That was, uh... with storm water. But we saw that
as the plastics age, especially microplastics, they can absorb a heavy metals on their surfaces,
like lead, zinc, copper. So if any plant end up ab... absorbing micro or nanoplastics,
(22:19):
there is a risk it can... not only micro or nanoplastic is getting into our food... our
fruits, our vegetables, there could be other heavy metals or other contaminants if they're absorbed
to the plastic surfaces that's getting into our food. (Tim) Or if we're eating root crops
that... that could be growing into the... into the plastic. So we'll pick that up after our break.
(22:41):
(Tim Reinbott) All right. So we've talked about microplastics and nanoplastics,
which are 1 millionth of a millimeter. (Dibya Datta) Mhm. (Tim) It's a lot of
zeros before the decimal point. Had to... had to figure that up. So, but a study came
out last year that showed that bottled water can have nanoplastics in it. So we can consume these
(23:02):
nanoplastics? (Dr. Maryam Salehi) Yeah, actually one of the... one of the topic that we are
studying in our lab is about the contamination of the microplastic in the drinking water, you know,
because they could come up in the drinking water, even tap water. There are several other studies that
show that they are in the tap water, so that's why when we are discussing about the contamination in
(23:23):
the farmland, the concern is that... one of the concern is that this plastic could be transported
to our drinking water resources and then eventually come up in our tap water. (Tim) Right!
Because we either get our water from impoundments, which is... which can be... water could be drained
in it from farms and what have you, or from subsurface, but again, the man... the... the
(23:47):
nanoplastics are moving through the soil. So they could get taken up that way, and then they wind up
in the... in the... (Dibya) Groundwater? (Tim) Yes! Exactly! And that winds up in our... in
our water system and in us. So some of us, uh... have well water, so it's... we're shallow wells.
Some of us are getting water from different sources, so it's not that difficult to imagine
(24:13):
we are getting these nanoplastics into us! (Dr. Salehi) Exactly. (Tim) And like you said earlier,
they can have heavy metals... (Dibya) Uh... like they can absorb heavy metals if there is any heavy
metal in the agricultural field. (Tim) Right. (Dibya) Yeah. (Tim) So you know, when we use our
arsenics and what have you in our pesticides, they could pick all that back up, couldn't
they? (Dr. Salehi) Yeah, and you know, any organic contaminant. You know, we are using herbicide,
(24:37):
pesticides in the farm. They can accumulate those on their surface, and when they get transported to
other environment, they can have those on their surface as well. (Tim) Oh, wow. So they're...
they're... they're carriers really, aren't they? (Dr. Salehi) Exactly. (Tim) They're carriers of
the environment that they're in. (Dibya) Yeah. (Dr. Salehi) Yeah. (Tim) They're...
they're really an indication of that. And so, do they have any compounds themselves that they
(25:03):
might release into the environment? (Dr. Salehi) Yeah, you know, when they processing the plastics,
they are adding some additives. For example, plasticizer or other sort of, you know,
antioxidants... (Dibya) Stabilizers. (Dr. Salehi) Stabilizer. Lots... lots of, you know,
additives are added to them because they want to, uh... facilitate their processing, and when they,
(25:25):
uh... disintegrate and degrade in the farm, they can leech those contaminant out into the
environment. (Tim) Oh, wow. (Dibya) Like two of the common, uh... is... there is Bisphenol A,
and there is phthalates. These are more commonly used as additives in plastics to,
uh... improve their properties, or uh... to make them last longer. And this, uh... phthalates and
(25:51):
Bisphenol A, they're really harmful for human being. Like they can mess up with your hormones
and reproductive system, so... (Dr. Salehi) But there are some regulations for that, so I'm not
sure how is the regulation for addition of those to the plastics, but generally, uh... there are
some additives that they can leech out. (Tim) But there were some, uh... plastics that got banned
(26:15):
additives because... (Dr. Salehi) Yes! Yeah! (Tim) Because of the... the human hormones that
they were mimicking. (Dr. Salehi) Exactly! Some of these are banned. Yeah. (Tim) But those are
probably still out there. Those plastics could... could... could very well be out there, still...
still carrying those... those compounds. Wow! What else do we need to do then? I mean, what...
I mean, we talked about alternatives. (Dr. Salehi) Yeah, one thing that we can do is that if we are
(26:37):
applying plastic mulch, we do our best to recover them from the soil, you know, as much as possible.
We take them out of the soil and send them to the recycling facility or even the landfill,
but we need to make sure that we are taking those out of our soil. Uh... we use, you know,
if possible, we use the biodegradable plastic mulch, or even better if we use the organic,
(27:02):
you know, options. We use the straw or wood chip or something that is organic rather than adding
some synthetic material to our farm. (Tim) Now, you all have developed a filter for this though,
haven't you? (Dr. Salehi) Yes! Actually, recently. Yeah, we had a project that we compilated. It was
a filter to remove the microplastic from the tap water. (Tim) And were you finding a lot of
(27:26):
microplastics in our tap water? (Dr. Salehi) Yeah, actually we can. It was just simulated
experimenting in the lab, but nowadays, one of my student is testing the, uh... tap water for
plastic we found. Uh... some plastic is just a preliminary, uh... data, but uh... yeah. You know,
because our water treatment plants generally designed to remove the conventional contaminant,
(27:52):
not the micro or nanoplastic. And even through the distribution system, uh... because some of
these water infrastructure, they are plastic themselves, so they can release some plastic
into the water as well. So there are some sources that are contributing... or even in our home, for
example, in my home, we are using the PEX pipes. So there... yeah, so there are some, you know,
(28:16):
sources that possibly could contaminate, uh... the tap water with plastic. But there are, you know,
there are research to be done. You know, there are lots of unknown in this area, so definitely
some research should be conducted in this area to confirm it.(Tim) Oh, sure! Sure. Plastics are
used in everything! It's very difficult. Even like your boxes that... that you brought your samples
(28:40):
in are plastic. (Dr. Salehi) Yeah. (Tim) And, uh... so probably the future is... is going to be
that we... we're better at recycling our plastics, using alternatives to plastics, and maybe making
the plastics out of non-petroleum. (Dr. Salehi) Exactly. Just biobased. (Tim) So do you think our
(29:02):
biobased, would they have any of the contaminants too that we see, and... you know, stickers
and what have you, or... ? (Dr. Salehi) So... biobased, the main thing is that we are not using
the synthetic or synthetic plastic, just regular plastic, that they are lasting for a long time in
the environment. For biobased, they are designed to be... to degrade faster. So they are going to
(29:25):
disintegrate in the environment, so we are not accumulating them for a long time. (Tim) And break
down into their basic products (carbon, hydrogen, oxygen)? That's... that's what we... that we hope;
whereas, our real petroleum plastics never really do, do they? (Dr. Salehi) It will take a long
time. Yeah. (Tim) Much long... much longer than my life... than our lifespan. (Dr. Salehi) Exactly...
(29:47):
yeah. (Tim) You know, uh... my, uh... daughters and I were talking about, uh... looking... looking
at the past and blaming our ancestors for this or that. I told them that I think plastic is
going to be what our generation gets judged on. You know, how could we have done that? Not...
(30:08):
not using res... not using renewables. I... I remember, uh... most... most drinks that you
bought when I was growing up was in glass. (Dr. Salehi) Yeah. (Tim) And glass, as we know, can be
recycled very easily. And we thought it was great when we got plastic! It was lighter and, you know,
we just throw away! It was easier to... to... to use. But that's came at... at a cost. (Dibya) Yes.
(30:32):
Definitely. (Tim) And I think the biggest surprise is what the plastics can latch on to,
and it contaminate us with that. (Dibya) Yeah. And there are so many different types of plastic,
so we are yet to know like, what their effects are on our body. Like, we only know so much about
(30:57):
it. (Dr. Salehi) Yeah, there... there's limited research in the health consequences, you know,
negative health consequences of plastic. So definitely, there are a lot to investigate...
(Tim) They call it more planetary... planetary health. You know, how our whole as a... as a...
as a society. (Dr. Salehi) Yeah. (Tim) Can any of our issues that we have with our own health,
(31:19):
can that be traced back to some of the plastics that... that... that we have? (Dr. Salehi) I
guess they should... they should conduct more research. (Tim) Yeah that's something that...
that's probably they need to look at then. Oh, wow. Anything else that we... that we're
concerned with that... that... that we should know about plastic? (Dibya) So, uh... if we,
uh... get back to the agricultural field, some of the things plastic can do through the agricultural
(31:40):
lands that, uh... farmers could be more concerned about is the long-lasting fertility issues. So if
plastic gets accumulated, since they're breaking down, firstly they can block the pores, or because
of the existence of plastic in the soil, it can alter the soil structure. So... (Tim) Oh,
(32:00):
shoot! Haven't thought about that part yet. Yes! (Dibya) So, uh... eventually because of the
change in soil structure, uh... the water holding capacity, uh... the moisture content of the soil,
that can get changed, and that can eventually affect the crop growth. And the more and more
plastics farmers keep using on their lands, the more plastics get accumulated over time,
(32:26):
and that can create a problem with the fertility issues. Uh... the longer there are plastics
in there... (Dr. Salehi) Could happen in many years... yeah. (Dibya) ...many years,
uh... the fertility might reduce. So the quality of, uh... crops they grow, the vegetables and
fruits we get, might not be as good as we used to get. (Tim) Because... so, does plastic have
(32:48):
a... a charge to it? Like a plus? A minus? (Dr. Salehi) Negative, yeah. (Tim) So it's a negative charge. So it can act a lot like a soil particle then, and... but it's not. (Dibya) No. (Tim) Oh,
wow. And... and like you said, plugging the... the... the, uh... particles up, that...
the soil structure. (Dr. Salehi) Yeah, it can influence the water flow through the soil and
(33:09):
water retention. (Dibya) Plastic surfaces are mostly negative. We found... (Tim) They attract
cations. (Dibya) Yes. They can... (Dr. Salehi) But you know, cations like, you know, metals. You
know, met... heavy metals. They have positively, you know, positive charge, so they can attach to
the negative charge. And there are other sort of, you know, interaction. And something about
plastic is that when they are degrading in the environment, their surface charge could change,
(33:31):
you know. Or... you know, for example, when they are in the, uh... you know, there are
some moisture, there is possibility that some microorganisms grow on the surface of the plastic,
so their surface charge could vary when they are on the farm. So that could influence their
interaction with other contaminant. (Tim) Right. And... and also this negative charge makes it when
(33:56):
they repel, and they can move through the soil a lot easier. (Dibya) Yes. (Tim) Deeper and deeper
and deeper into the soil, into the water, into the groundwater. That's why we start seeing some those
issues. (Dibya) And, uh... when we were studying microplastics, uh... one thing we found that as
they age, the negative charge on their surface increase. (Tim) Oh, really? (Dr. Salehi) Yeah,
the aging was photodegradation. So when they expose to the solar radiation and they age,
(34:19):
they become more negative. Yeah. (Tim) Which could compound that effect then. (Dibya) So could be,
uh... possibly there could be more electrostatic attraction. Positive charges are getting more
attracted to their surfaces. So like heavy metals, cations. (Dr. Salehi) Yeah. But there are other,
you know, other sorts of interactions as well. This is just electrostatic. There are other sorts
(34:41):
of interaction as well that could influence their contaminant transport. (Tim) Oh, wow. Yeah, so
we can... we can have some... some... some issues here then, can't we? I think this... this has been
fantastic about bringing awareness to it, and... and how it affects every part of our life. And...
(35:01):
and some basic steps that... that... that... that we can do. (Dibya) Yes. (Tim) That we can really,
really do. (Dibya) And there are definitely some places we can think about replacing plastic. You
were talking about hay. So it's much convenient to cover them with plastic, uh... if you're using,
uh... those hay or silage as a, uh... feed for your livestock. So I know that's convenient,
(35:27):
and farmers are opting in for probably a cost effective option, but if you build a silo,
that's more, uh... that's like, more expensive, but again, that's long-lasting. (Tim) Right. So
some things, uh... there is a tradeoff between opting in for a cost effective option or spending
(35:51):
more and going for a long-lasting, sustainable option. So... (Tim) Yeah, we're going to have
to stop and think about this different ways. You know, one of the things first came to my mind is
year 'round... Missouri's great because we're in the bullseye that we can have year 'round grazing.
Where you don't feed as much hay. You don't feed as much hay. You don't have to have as much
(36:11):
plastics, and... and that sort of thing. So there is those type of options too. Just changing how
we... how we look at... at our food production. (Dibya) Yes. (Tim) All right. Well, thank you
all so much. This has been very interesting. I think we've opened a lot of eyes. There's been
some things that I hadn't really thought about. You know, how... how plastics can move through
(36:34):
the soil. How they can... since they're negative, they can attach to our... to our... our cations.
Not only the heavy metals, but maybe some of the ones that we want for our plant's growth... plant
growth, like potassium, for example. That... that... that... that's really important. And
how it keeps getting smaller and smaller and smaller and can wind up in our drinking water,
(36:55):
in our food, and probably, we don't know quite where it can wind up at yet, have we? Because
we haven't looked there yet. (Dr. Salehi) Yeah. (Dibya) There's so much to study. (Tim) And you
may not... you might be a little afraid to look at it. [laughter] So, all right. Well,
thank you all so much! Uh... good luck on your, uh... dissertation. Seems like you've done a
(37:16):
great job so far, and... and you got a lot to do, and a very exciting subject. And... and,
Dr. Salehi, it's been fantastic to work with you, and continue as... as we're working on this,
uh... that we can come up with some alternatives and maybe how to manage our plastics in our... in
our life. So... (Dr. Salehi) Yeah, thanks for inviting us. (Tim) You're welcome.
(37:37):
All right! Well, this is it for Tim's Take, and we'll talk to you next time.
[♫]
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