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Dec 6, 2023
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TA:
Tutorial #9: Investigating Plastic Pollution in Freshwater Systems
Instructions:
Download this worksheet to your computer, and save the file as Your Last Name_First Name_Tutorial9 Type your answers directly onto this worksheet. Upload your completed worksheet to Canvas
Assignments
Tutorial 9 as a .pdf, .doc or .docx attachment.
Learning Goals:
Interpret and analyze tabular data about plastic pollution
Articulate the differences and similarities in microplastic pollution in two different lake systems
Hypothesize the sources of plastic pollution in each system, and suggest strategies to reduce the pollution.
This tutorial is graded out of 25 marks. Point values are given in parentheses after each question
.
Resources on Canvas (optional reading, for interest only)
:
Eriksen, M., et al. (2013). Microplastic pollution in the surface waters of the Laurentian Great Lakes. Marine Pollution Bulletin 77
: 177-182.
Free, C.M., et al. (2014). High-levels of microplastic pollution in a large, remote, mountain lake. Marine Pollution Bulletin 85: 156-163.
Context: Plastic pollution is the primary form of anthropogenic debris found in marine (ocean) environments. Floating plastic debris, including microplastics, have been found in all 5 of the world’s oceans. Plastic pollution can enter waterways through drainage systems, sewage treatment overflow during high-volume rain events, or can blow into the water from the shore (Eriksen et al., 2013). Although we know quite a bit about the plastics that are floating in the oceans, there has been less research quantifying plastic pollution in freshwater systems like lakes. In
this tutorial
, you will be examining microplastic pollution in two very different lake systems: the Laurentian Great Lakes in North America, and Lake Hovsgol in the remote mountains of Mongolia. Lake Hovsgol (Figure 1) is characterized by a low population density, a lack of industry and agriculture, and no modern wastewater or sewage treatment facilities. It is one of only seventeen “ancient lakes” in the world (more than 2 million years old), and is one of the most pristine – the water can be consumed without filtering. It is the most significant drinking water reserve in Mongolia and was designated a National Park in 1992. The majority of the population lives in Hatgal (pop. 2980) in the south and Hankh (pop. 2460) in the north. Tourist camps line the southwestern shore and herding families live along primitive roads that follow the eastern and western shores (Free et al., 2014). Lake Hovsgol is similar to Lake Erie in volume, but is a tenth of its size in area.
The Laurentian Great Lakes (Figure 2) straddle the border between Canada and the United States, and are surrounded by heavily urbanized watersheds, including large cities like Chicago, Buffalo, Milwaukee, Detroit, and Toronto. The Great Lakes flow into the St Lawrence River, which flows into the Atlantic Ocean.
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Figure 1. Location of Lake Hovsgol, Mongolia.
Figure 2. Location of the Laurentian Great Lakes.
Before you start digging into the data:
1.
Make a hypothesis about which lake system (Great Lakes or Hovsgol) would have the highest level of plastic pollution. Give the reasoning for your answer. (2)
According to me, Great Lakes would have the highest level of plastic pollution. The first reason is that the Great Lakes are much larger and more heavily polluted than the Hovsgol lake. Great Lakes receives waste from the surrounding regions, which makes it likely that the plastics will end up in the lake system. Secondly, the Great Lakes system is much more accessible to than the Hovsgol Lake. The Great lakes are
surrounded by many states and countries making it accessible for the people to discard in it whereas Hovsgol is located in remote area of Mongolia.
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Part 1: The Great Lakes
The Great Lakes study is from: Eriksen, M., et al. (2013). Microplastic pollution in the surface waters of the Laurentian Great Lakes. Marine Pollution Bulletin 77
: 177-182.
On a 3-week expedition, researchers sailed Lakes Superior, Huron and Erie. Five samples were collected in Lake Superior, while 8 samples each were collected in lakes Huron and Erie (Figure 3). Samples were collected using a manta trawl with a rectangular opening 16 cm high by 61 cm wide, and a 3 m long 333 µm net. The samples were later rinsed in salt water, which floated most of the plastic to the surface for removal. Using a dissecting microscope, plastic was removed from preserved natural material, and then sorted by rinsing through Tyler sieves into 3 size classes: 0.355–0.999 mm, 1.00–4.749 mm, >4.75 mm. Individual pieces of plastic were divided into categories: fragment, foamed polystyrene, line, pellet, film; and then counted. Data from the expedition is given in
Tables 1 and 2.
Table 1. Abundance and type of particles in 3 size classes, Laurentian Great Lakes.
Table 2. Count, location and abundance of plastic pollution from 21 stations in three of the Laurentian Great Lakes.
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Figure 3. Distribution of plastic particles by count for 21 samples collected in three of the Laurentian Great Lakes.
2.
What was the most common size of plastic particles found in the Great Lakes? Give its abundance per square km. Make sure to include units in your answer. Within that category, what were the two most common type of particle? (3)
The common size of the plastic particles was 0.355-0.999 mm. The abundance of the size of particles is: 736,749.6 count/Km
2
. The common type of particles were Pellet and Fragment.
3.
Several microplastic particles in these samples were green-, blue- and purple-colored spheres (classified as
pellets), which were suspected to be microbeads from consumer products (Figure 4). What kind of consumer products contain microbeads? How do they end up in lake systems? You can do an internet search to find this answer. (2)
Consumer products that contain microbeads are personal products including body wash, facial scrubs and toothpaste. They are used in homes and beauty business, and they end up in lake through municipal sewers.
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Figure 4. Colour variation among pellet particles <1 mm
4.
Using the information in Table 2, calculate the average abundance of plastic pollution in each of the Great Lakes sampled by making your own table in Excel. (1)
Superior
huron
Erie
12645
12645
12645
3542
1229
4686
1277
1694
8511
2616
2213
57122
6875
6541
6056
5352
9112
456
466305
0
280947
5391
3766.25
105673
In a new Excel sheet, in Row 1 of columns A, B, and C, input the name of each of the Great Lakes studied.
For each lake, input the abundance at each sampling location into cells in the column.
In an empty cell at the bottom of the column, type “ =AVERAGE(
” and then select the cells you want to calculate the average for, followed by “
)
”. Your formula should look something like “=AVERAGE(A1:A5)”, and the result will be the average abundance for that lake.
Select all the cells in your table by dragging a box around them, and click on Format as a Table
. Choose your table style and click the box “
My table has headers
”.
With your whole table still selected, click on Edit
Copy
, and then Paste your table in the space below.
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According to your table, what is the average abundance of plastic pollution in each lake? Make sure to include units. (3)
Lake Superior: 5391 count/Km^2
Lake Huron: 3766.25 count/Km^2
Lake Erie: 105673 count/Km^2
5.
In which lake of the three sampled was the largest average abundance of plastic found? Suggest why that might be the case. (Hint: examine Figure 2 to help you answer this question). (1)
Lake Erie has the largest abundance of plastics. It has proximity to Detroit and Cleveland and the waste products of these cities are dumped into them
6.
Of the three lakes sampled, Lake Superior has the lowest population; but the abundance of plastics found there was greater than in Lake Huron, which has a larger population. What factor(s) may account for this finding? (Hint: examine Figure 3 to help you answer this question). (1)
There are 200 rivers enter Lake Superior and thus makes it have more plastic waste than Lake Huron. Lake
Huron is a smaller lake and thus has fewer rivers flowing into it. Part 2: Lake Hovsgol
The Lake Hovsgol study is from: Free, C.M., et al. (2014). High-levels of microplastic pollution in a large, remote, mountain lake. Marine Pollution Bulletin 85: 156-163.
Researchers surveyed and collected anthropogenic debris from Lake Hovsgol shorelines. They also collected samples from the lake using the same equipment and methods as in the Great Lakes study (Figure 5). Samples were rinsed and sorted into the same size classes: 0.355–0.999 mm, 1.00–4.749 mm, and >4.75 mm. Plastic particles within each size classification were counted and categorized as fragment, foam, line/fiber, pellet, or film (Table 3).
Table 3. Average density (particles/km
2
) and proportion of microplastics by type and size in Lake Hovsgol (not including shoreline debris).
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Figure 5. Density of pelagic (in the lake) microplastics and shoreline macroplastics relative to wave energy and pollution
sources. (A) Location of Lake Hovsgol in northern Mongolia. (B) Density of macroplastic debris in the shoreline surveys
(purple, g/km) and microplastic debris in the pelagic surveys (red, particles/km
2
); symbols graduated by density. Potential
sources for pollution include towns (black circles), tourist camps (black triangles), roads (solid black lines), and rivers (solid
blue lines). Dashed line indicates the park boundary.
7.
What was the most common size of plastic particles found in Lake Hovsgol? Give its abundance per square
km. Within that category, what were the two most common type of particle? (3)
The common size of the plastic particle is 0.333-0.999. Abundance of plastic pollution in Lake Hovosgl is 1200 particles per Km. The most common type of particles are fragment and line/fiber. 8.
Compare your answer to #7 with your answer to #2. What do you think accounts for the similarities/differences between the types of plastics found in Lake Hovsgol vs. the Great Lakes? (2)
Lake Hovosgl is contaminated with microplastics than the Lake Huron and Superior. No microbeads or pellets were found because the herding families around the Lake used less of cleaning products. 9.
The total average abundance of plastic pollution in Lake Hovsgol is given in Table 3. What is it? (1)
The Table indicates an average of 20.264 particles of plastic pollution per square Km of water
10.
Compare the average abundance of plastic pollution in Lake Hovsgol to the three Great Lakes sampled by Eriksen et al. Do these results match your hypothesis from the beginning of tutorial (Question #1)? (2)
Yes, this does match the hypothesis. The great Lakes have an average of 113672.8 microplastics per square Km, while Hovsgal has 20264 microplastics per square Km.
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11.
Give two possible reasons why, despite being a remote mountain lake, Lake Hovsgol would exhibit such high levels of plastic pollution. (2)
This could be due to:
1
). Maybe the Tourism activities
in the area surrounding the lake generate plastic waste.
2). The waste management by the people living around the lake would contribute to higher levels of plastic
pollution.
12.
Suggest a strategy or policy for reducing plastic pollution in each of these lake systems (there may be a different strategy/policy for each lake system). (2)
The Strategy for reducing the plastic pollution in lake systems could include-
1)
Reducing single use plastics and encouraging recycling. 2)
Increase public awareness about proper waste disposal through outreach Programs. Footnote
: The 2013 study by Eriksen and colleagues was the first time that researchers had documented microbeads in the Great Lakes. This research resulted in the Microbead-Free Waters Act, which became US federal
law in 2015 and banned the use of microbeads in cosmetics.
Canada enacted similar legislation in 2017, with the Microbeads in Toiletries Regulations. Holland EVSC 100 2022
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