By: Anna S.
Although humans live in terrestrial ecosystems, it is important to remember that the ocean covers 70% of the Earth’s surface (National Ocean Service). The ocean provides beautiful coasts and modes of transportation, but it is heavily degraded due to many sources of pollution, including factories and sewage treatment plants that directly dump chemicals into it. In addition, oceans are contaminated because of nonpoint source pollution, a process that involves an extensive amount of nondirect sources getting to the ocean. One way in which seemingly random or irrelevant substances can reach the ocean is through runoff, which occurs when rain runs through farmlands, construction sites, city roads, and other areas and ultimately empties out into the ocean (Virginia Department of Environmental Quality). Runoff continues to be a widespread pollutant, as its vast connections between bodies of water can cause it to be formed in almost any setting.
The Mississippi River empties out into the Gulf of Mexico, which is a marginal sea in the Atlantic Ocean. Photo from: Scitable
As most rivers empty out into oceans, nonpoint source pollutants, such as fertilizers and chemical waste, have a clear route to these large bodies of water. According to National Geographic, runoff has a clear path to the ocean because of impervious surfaces which cannot absorb water, such as roads and sidewalks. On its way to the ocean, runoff “picks up litter, petroleum, chemicals, fertilizers, and other toxic substances.” The gathering of these materials occurs after it rains, as rain water can collect runoff. Together, these substances pass through more surfaces (such as oil in parking lots, spilled gas at gas stations, fertilizers in farmlands) that may contain toxic chemicals.
However, there are many methods that can be implemented in many different aspects to control ocean pollution. When it comes to construction sites, for example, runoff can be prevented from getting to a river in the first place, which can be done by limiting the amount of ground that is being broken into. The Environmental Protection Agency (EPA) recommends that ground is only broken into if it absolutely needs to be. They also advise that construction is done in phases so that it is easier to control runoff for each area of building, as a precaution to limit sedimentation in runoff. Additionally, it is recommended that construction workers use sediment traps and diversion ditches, which are temporary channels that serve as places where runoff can collect and stay. These are commonly used along slopes. Slope protection, which is the placement of small fences along a slope in 10 to 20 feet intervals, can also be used slowing and catching runoff.
Sediment trap filled with runoff that otherwise would have made its way to a nearby river. Photo from: Small Business
Slope protection barriers stopping runoff from making its way down slopes. Photo from: Small Business
To further prevent rain from collecting toxic chemicals on its way to the ocean, the path that rain takes to the ocean can be stopped altogether through the implementation of green roofs, which are urban rooftop surfaces made up of growth media and plants that absorb rainwater. Green roofs can prevent the total volume of stormwater and lower the peak rates of runoff (Penn State). This means that rainwater can be contained, which reduces the volume of runoff to the ocean, therefore limiting pollution altogether. Absorbent surfaces can also prevent rainwater from entering the stormwater system, a network in which rainwater makes its way through different bodies of water, eventually ending up in the ocean. To learn more about green roofs, check out Ava's article, How Green Roofs Can Combat Climate Change
An extravagant green roof located in Moesgaard Museum, Højbjerg, Denmark.
Photo from: Architectural Digest
Runoff is a huge factor in nonpoint source pollution that has a direct effect on the ocean, but this pollution problem can be prevented. As discussed, there are methods that can control the amount of nonpoint source pollution that occurs, including sediment traps, slope protection, green roofs, and more. In some cases, it does not take that much effort to prevent runoff. Simple actions such as using fertilizer properly (in the correct amounts and at the right time of the year) or covering bare soil with vegetation can help prevent nonpoint source pollution in the ocean (FairFax County). Water covers most of our planet, so it is important to help keep it clean. It is a home to marine life and an important part of the ecosystem. Runoff cannot empty out into our oceans because marine life is already filled with plastic and oil. Drainage of toxic substances worsens ocean pollution and makes it harder for the Earth’s aquatic life to thrive. Therefore, everyone must do their part in keeping the world’s water clean by eliminating the potential for nonpoint source pollution in the first place, through land conservation. Bodies of water should never be treated like trash cans for chemical waste; runoff control can prevent them from being used in this way.
Discussion Questions:
What are some day to day pollutants that enter runoff?
Should certain buildings (apartment complexes, buildings belonging to large institutions, etc) be required to have green roofs?