Fate and Occurrence of Microplastics in Agricultural Runoff

Malayna Wingert Author

07/30/2020 Added

23 Plays

Description

Discusses the mobilization of microplastics on field plots containing biosolids and manure as soil fertilizers.

Searchable Transcript

Search:

[00:00:01.292]Hello everyone my name is Malayna Wingert
[00:00:04.200]and I am majoring in Biological Systems Engineering
[00:00:07.715]I am apart of the
[00:00:09.175]Summer Nebraska Engineering Research Program
[00:00:11.000]this summer and I am working with Dr. Shannon Bartelt Hunt
[00:00:14.340]and her graduate student
[00:00:16.220]The project we are working on this summer is
[00:00:18.043]The Fate and Occurrence of Microplastics
[00:00:20.543]in Agricultural Runoff
[00:00:22.970]First let's talk about what microplastics are
[00:00:26.460]Microplastics are plastic particles
[00:00:28.382]less than 5 mm wide
[00:00:30.557]There are two main types of microplastics
[00:00:33.360]Primary and Secondary
[00:00:34.816]We will be focusing mostly on secondary
[00:00:37.203]in our experiment
[00:00:39.821]These are specific examples of microplastic's dangers
[00:00:45.712]Their small size
[00:00:46.922]Ability to deplete the soil
[00:00:48.604]contaminating additives
[00:00:50.234]and ability to transport into the food web
[00:00:52.686]are all reasons why microplastics
[00:00:54.715]are a problem today
[00:00:58.160]Some of the main sources of microplastics
[00:01:00.429]include atmospheric deposition
[00:01:02.269]and fertilizer application.
[00:01:04.996]During atmospheric deposition
[00:01:07.540]microplastics are deposited onto the land
[00:01:09.474]from the atmosphere
[00:01:10.928]They are able to do this
[00:01:12.460]because of their small size
[00:01:13.271]and the open layout of agricultural fields.
[00:01:17.134]Biosolids are a fertilizer that comes from
[00:01:19.452]Wastewater treatment plant's discharge or sludge
[00:01:23.250]Wastewater treatment plants
[00:01:24.592]can remove up to 99% of microplastics
[00:01:26.925]from domestic wastewater
[00:01:28.629]industry waste
[00:01:29.471]and storm water runoff that enters the plant
[00:01:32.169]These microplastics are then concentrated
[00:01:34.369]into sludge and applied directly
[00:01:36.226]onto agricultural fields.
[00:01:38.209]The nutrients from these fertilizers
[00:01:40.189]is used by crops but microplastics still remain
[00:01:42.771]in the soil.
[00:01:45.252]In our project biosolids and manure
[00:01:47.532]were applied to our test plots
[00:01:49.352]to study the quantity of microplastics
[00:01:52.246]these fertilizers contribute to the soil
[00:01:55.566]Motivations of our research include
[00:01:58.606]the lack of research of microplastics
[00:02:00.846]in agroecosystems.
[00:02:03.154]We want to close the gap on this topic.
[00:02:07.411]For this year's project our objectives are
[00:02:10.506]How are microplastics mobilized in agricultural soils
[00:02:13.986]What features of microplastics affect mobilization?
[00:02:17.576]And what microplastic characteristics
[00:02:19.806]are most common in runoff or horizontal movement?
[00:02:25.234]In order to investigate these objectives
[00:02:27.714]we set up 6 test plots at Roger's Memorial Farm
[00:02:30.443]outside of Lincoln, Nebraska.
[00:02:32.933]Of the 6 plots
[00:02:34.630]2 were applied with biosolids
[00:02:36.462]2 were applied with manure
[00:02:38.193]and 2 were kept as controls
[00:02:41.752]The plots that had fertilizer
[00:02:43.642]had enough fertilizer to meet a
[00:02:45.012]one year nitrogen requirement for corn
[00:02:47.248]and this is about 177 kg
[00:02:51.413]The test plots were constructed with metal buffers
[00:02:54.122]around them to direct runoff from each plot
[00:02:56.642]into the runoff pipe
[00:02:57.982]and then into the collection tank
[00:02:59.792]which allowed us to collect samples
[00:03:01.442]after the storm event
[00:03:05.052]Here is our test plot
[00:03:06.508]The trough that we dug into the ground
[00:03:08.918]our runoff pipe and the collection tank
[00:03:12.568]For sampling,
[00:03:13.559]I will be showing you the sampling dates
[00:03:15.288]and results from last year
[00:03:16.898]as these are the expected results for this year
[00:03:19.278]We have sampled only once this year
[00:03:21.173]and have not tested the results as of now
[00:03:24.129]Six storm events were sampled last year
[00:03:26.121]from July to October
[00:03:28.301]This is in addition to 9 sampling dates
[00:03:30.181]the summer previous
[00:03:33.471]Samples were collected for storm events
[00:03:35.018]when rainfall was greater than
[00:03:36.219]3/4 of an inch
[00:03:38.989]To sample, the collection tanks have
[00:03:40.878]a metal bucket that collects water
[00:03:43.048]These buckets are stirred to get particles
[00:03:44.987]off of the bottom
[00:03:46.417]Then a glass container is dipped into the water
[00:03:49.167]and collects the sample
[00:03:50.884]One sample is taken from each plot
[00:03:53.694]The samples are then taken
[00:03:54.944]into the lab to be analyzed
[00:03:57.038]To analyze the runoff samples
[00:03:58.751]there are a few steps
[00:04:00.161]First the samples are covered with aluminum foil
[00:04:02.361]and placed into an oven
[00:04:03.561]to dry at 70 degrees Celcius
[00:04:05.981]Here is the jar with aluminum foil
[00:04:08.911]Then the samples go through a
[00:04:10.511]density separation phase
[00:04:12.881]A zinc bromide solution is prepared
[00:04:14.436]and added to each jar
[00:04:16.356]The jar are then sonicated for one hour
[00:04:19.007]Sonication is using sound energy
[00:04:21.345]to agitate particles
[00:04:22.785]in this case it was to prevent clumping
[00:04:24.836]or aggregation
[00:04:27.287]To seperate by density the jars
[00:04:29.177]were left to settle and seperate for 24 hours
[00:04:32.667]the top layer was pipetted
[00:04:34.397]and then filtered
[00:04:35.657]When the filters are analyzed
[00:04:37.619]the parameters recorded included
[00:04:39.379]the total microplastic count
[00:04:40.869]morphology and size
[00:04:43.189]Samples are primarily analyzed under
[00:04:44.989]UV light as it causes the polymer
[00:04:46.969]particles to give off a blue color
[00:04:49.113]as you can see in this photo
[00:04:53.439]These are 3 of the 4 major morphologies
[00:04:55.349]we are looking for
[00:04:56.709]The other includes microbeads
[00:05:05.560]These two bar graphs show the microplastic
[00:05:07.454]concentration for liquid
[00:05:09.412]on the top of the collection tank
[00:05:11.745]and mixed or the bottom
[00:05:14.777]Blue denoted an experimental plot
[00:05:16.985]which is a plot that is applied with biosolids
[00:05:19.775]And the gray denotes the control
[00:05:21.933]As you can see the microplastic
[00:05:23.623]concentrations vary anywhere from
[00:05:25.223]20 to 160 microplastics per liter
[00:05:29.134]At every sampling date for both types
[00:05:31.284]of samples
[00:05:32.083]the plots with applied biosolids
[00:05:34.288]always had a higher microplastic concentration
[00:05:37.876]Additionally, average concentration of
[00:05:40.136]microplastics in the mixed samples
[00:05:42.463]is often higher than the liquid samples
[00:05:44.691]Showing that these microplastics
[00:05:46.328]are more likely to settle into sediments
[00:05:48.501]once the runoff velocity slows down
[00:05:50.754]Also, due to this finding
[00:05:52.160]this year we only be taking mixed samples
[00:05:56.645]As you can see from the pie charts
[00:05:58.193]morphology was fairly uniform
[00:06:00.286]Showing that the shape of microplastics
[00:06:02.426]primarily found in the agricultural environment
[00:06:04.936]are either fibers or fragments
[00:06:07.511]Of these fibers approximately
[00:06:09.271]83% were shorter than 2 millimeters
[00:06:11.626]And this shows a tendency for smaller
[00:06:13.526]microplastics to be transported
[00:06:15.835]This makes sense as they are smaller
[00:06:17.638]and it takes less energy to transport them
[00:06:19.648]away from their source area
[00:06:21.918]Shown in the red and blue pie chart here
[00:06:24.174]is a contribution of microplastics from biosolids
[00:06:27.811]this is considered to be the difference
[00:06:29.320]between the number of microplastics
[00:06:30.767]in the experimental and control plots
[00:06:34.531]By comparing this number
[00:06:35.589]to the total microplastics in biosolids
[00:06:38.858]We can look at the fate of microplastics
[00:06:41.898]from biosolids which is shown in the pie chart
[00:06:45.918]The red section denotes the percentage
[00:06:48.888]of microplastics that were transferred
[00:06:50.981]from biosolids into runoff
[00:06:53.172]and this is approximately 17%
[00:06:56.351]The rest denoted in blue represents
[00:06:58.311]the percent of microplastics
[00:07:00.004]that stayed in the biosolids
[00:07:04.403]In conclusion
[00:07:05.453]in the agricultural environment
[00:07:07.063]biosolids do show to produce increased
[00:07:09.679]levels of microplastics in runoff
[00:07:12.653]Further the microplastics transported
[00:07:15.306]are primarily smaller
[00:07:16.606]fragment and fiber morphologies
[00:07:18.826]that then settle with sediments
[00:07:20.486]once runoff velocity decreases
[00:07:23.402]In response to last year's results
[00:07:24.962]we plan to further study
[00:07:26.407]the background levels of microplastics
[00:07:29.734]in controls
[00:07:31.443]This year we have made a few changes
[00:07:34.285]As I mentioned above
[00:07:35.495]samples taken are going to be
[00:07:37.305]all mixed samples
[00:07:38.790]Also we added 2 more plots
[00:07:40.610]where manure is the fertilizer for those two
[00:07:45.705]Also this year our plots had crops in them
[00:07:48.282]this may contribute differently to our samples
[00:07:51.640]Because of this
[00:07:52.580]we will be taking a stem from the milo
[00:07:54.540]plants that reside there to see if any
[00:07:56.700]microplastics have stuck to the outside
[00:07:59.731]of them
[00:08:00.860]I also want to mention that
[00:08:02.005]support for this work
[00:08:02.919]in part
[00:08:03.359]was provided by the College of Engineering's
[00:08:05.659]Dean's Office
[00:08:06.859]and Engineering Graduate Programs
[00:08:08.299]at the University of Nebraska Lincoln
[00:08:10.379]through the Summer Nebraska Engineering
[00:08:11.669]Research Program
[00:08:14.564]Thank you!

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Fate and Occurrence of Microplastics in Agricultural Runoff

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments