Sources and Sinks

Lesson

Purpose and Context

When scientists talk about pollution, they often use the term “source” to describe where a pollutant is coming from and the term “sink” to describe where or in what the pollutant ends up, is stored, or accumulates. To help remember these terms, you can think of a faucet and kitchen sink – the faucet is the source of water, and the basin under the faucet is the sink where the water ends up in. A source could be a certain activity, product, region, or type of infrastructure like a pipeline or factory that releases a pollutant into the environment. A sink could be any physical or biological component of an ecosystem, for example, the air, soil, a body of water, or a certain plant or animal that takes in a pollutant.

It’s important to know how plastics get into and travel around the environment and how the pollution is impacting wildlife, so that we can design better solutions to protect habitats and organisms in them. 

Scientist have been studying habitats and ecosystems throughout the world to research where plastics are ending up. They are finding plastics everywhere they look – streams, rivers, lakes, and oceans,  the atmosphere, our soils, mountain glaciers, icecaps, and even compost [1, 2]. The size, shape, and the density of each piece of plastic pollution each impact how it gets transported, where it ends up, and which organisms are affected by it. We need a diverse set of solutions to address the many forms of plastic pollution and their various impacts on animals, plants, and habitats. 

We’ve assembled ten photos that depict some of the sources and sinks of plastic pollution, and a couple of prompts to help guide your and your student’s analysis of the images.

Sources

[1] Zalasiewicz, Jan, Waters, Colin N., Ivar do Sul, Juliana, Corcoran, Patricia L., Barnosky, Anthony D., Cearreta, Alejandro, Edgeworth, Matt, Galuszka, Agnieszka, Jeandel, Catherine, Leinfelder, Reinhold, McNeill, J.R., Steffen, Will, Summerhayes, Colin, Wagreich, Michael, Williams, Mark, Wolfe, Alexander P., Yonan, Yasmin, The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene. Anthropocene http://dx.doi.org/10.1016/j.ancene.2016.01.002

[2] https://www.unep.org/news-and-stories/story/plastic-planet-how-tiny-plastic-particles-are-polluting-our-soil

Instructions

Prepare

Familiarize yourself with the image cards, using either the PDF (Sources and Sinks – Image Cards – PDF) or the Google Slides (Sources and Sinks – Image Cards – Google Slides). Each image depicts an aspect of the sources or sinks of plastic in the environment. Most images also include a description or information to understand the image. Print out the Image Cards and cut the printouts along the dotted lines, or upload the Image Cards onto your Learning Management System (LMS) for students to access digitally. 

In class

1. Students brainstorm, research, discuss, and note down their thoughts on the Sources and Sinks Student Worksheet Google Doc using the two prompts provided: 

• What is the image showing? Describe the situation or information shown.
• What question(s) does this image spark in your mind? 

2. Discussion Ideas

• How does the presence of plastic change the physical components of an ecosystem? Do you think it can influence the biological cycles within an ecosystem? How so?
• Is plastic litter a point-source or nonpoint-source of pollution? Do any of the image cards depict or suggest point-sources of plastic pollution? Do any of the image cards depict or suggest nonpoint-sources of plastic pollution?
• As a class, draw a diagram summarizing the sources and sinks of plastic pollution depicted in the image cards.
• Pick a plastic item shown or described in the image cards. In your group, discuss a possible solution to prevent that specific item from getting into the environment in the first place. (Tip: Think about why we use that product or item in the first place, and what we could do instead to avoid using that kind of plastic item. What sort of alternative products, systems, or strategies would need to be created, engineered or designed?)

Tips and Suggestions

• Suggested learning format: Students work in small groups. Each group is assigned a subset of images to analyze. Then groups share their interpretation and questions with the whole class. Educator facilitates further discussion.
• Some of these images are quite graphic. Many organisms are harmed by plastic pollution, but we can each do our part by limiting our use, making sure we don’t litter, and informing others about the problem. Let students know that they are already helping out by learning about this today.

Associated Standards

NGSS

• MS-LS 2-4 Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.

AP Environmental Science

• 8.1 Sources of Pollution STB-3.A.2 Nonpoint-sources of pollution are diffused and can therefore be difficult to identify, such as pesticide spraying or urban runoff.
• 8.2 Human Impacts on Ecosystems STB-3.B.8 Litter that reaches aquatic ecosystems, besides being unsightly, can create intestinal blockage and choking hazards for wildlife and introduce toxic substances to the food chain.

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