Brian Barton
The Mississippi River is one of the most polluted rivers in the world, with trash and plastic pollution from across its large drainage basin ending up in the Gulf of Mexico and, ultimately, the ocean. The river carries excessively high levels of nutrients, causing a biological dead zone—known as hypoxia—to form at its mouth in the Gulf of Mexico. This is due to a combination of excess nutrients from agricultural runoff and seasonal stratification of Gulf waters. While pollution from cities and towns has decreased, human activities continue to impact the river's water quality, with toxic chemicals being introduced into the environment.
| Characteristics | Values |
|---|---|
| Type of pollution | Chemical dumping, plastic waste, agricultural runoff, sedimentation |
| Pollutants | Toxics, oil, PCBs, heavy metals, phosphorus, nitrogen |
| Causes of pollution | Human activities, poor waste management, agricultural practices, urban runoff |
| Effects of pollution | Eutrophication, hypoxia or "dead zones", loss of wildlife habitat, impaired water quality |
| Location of pollution | South of St. Cloud, Minneapolis, Gulf of Mexico, ocean |
| Efforts to reduce pollution | Clean Water Act, Mississippi River mayors' compact, litter analysis |
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What You'll Learn
Eutrophication and algal blooms
The Mississippi River is a source of eutrophication, a condition caused by nutrient enrichment, which leads to an increase in algal production. This, in turn, results in algal blooms, which have negative consequences for the environment.
Eutrophication is a process whereby excess nutrients, often from agricultural sources, stimulate plant and algae growth in water bodies. In the case of the Mississippi River, the primary source of these nutrients is agricultural runoff, which includes fertilizers, soil erosion, animal waste, and sewage. As the river flows, it carries these nutrients towards the Gulf of Mexico.
The nutrients of particular concern in the Mississippi River are nitrogen and phosphorus. While these elements are naturally occurring, human activities have led to an increase in their concentrations. Nitrogen, for example, is derived from fertilizers used in agriculture in states like Minnesota, Iowa, and Illinois, which are part of the Mississippi River Valley.
As the Mississippi River flows into the Gulf of Mexico, the water's velocity decreases, allowing sediment to settle, light to penetrate, and algae to bloom. This process has led to the endangerment of fish production in estuarine regions like the Barataria Basin. The nutrients supplied by the Mississippi River have thus raised concerns about the environmental health of coastal areas in the Gulf of Mexico.
Algal blooms, fueled by excess nitrogen and phosphorus, result in the overgrowth of algae in a short period. This algae consumes oxygen and blocks sunlight from reaching underwater plants. When the algae eventually die off, they further deplete the oxygen levels in the water, creating an environment where aquatic life cannot survive. This phenomenon is known as a "dead zone," and the largest one in the United States, covering up to 6,500 square miles, occurs every summer in the Gulf of Mexico due to nutrient pollution from the Mississippi River Basin.
To address the issues of eutrophication and algal blooms, careful industrial practices are necessary. This includes limiting the discharge of nutrients, organic matter, and chemicals from manufacturing facilities, as well as implementing measures to reduce the input of nitrogen and phosphorus into the Gulf of Mexico. Similar approaches have proven successful in the Great Lakes' recovery from eutrophication, and efforts are being made to restore wetlands along the Gulf coast to act as natural filters for the water.
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![Pollution of Illinois and Mississippi Rivers by Chicago Sewage (1907) [Leather Bound]](https://m.media-amazon.com/images/I/61FbOFgXaEL._AC_UY218_.jpg)
Agricultural runoff
Agricultural practices, such as the use of fertilizers and manure on farmland, increase the risk of nutrient loading in nearby water bodies. Nutrients like nitrogen and phosphorus are essential for plant growth, but when they are washed into rivers, they contribute to the development of hypoxic zones or "dead zones." These zones have low levels of dissolved oxygen, which can kill marine life and force mobile organisms to leave the area.
The Mississippi River Basin, in particular, drains a significant amount of farmland, making it vulnerable to agricultural runoff. In 2010, over 125 million pounds of toxics were released into waterways tributary to the Mississippi—more than half of the total released in the United States. This has led to fish consumption advisories and, at times, unsafe swimming conditions in certain sections of the river.
The problem of agricultural runoff is not unique to the Mississippi River, and it has been a concern for environmentalists and advocates for cleaner waterways across the United States. While the Environmental Protection Agency (EPA) has encouraged states to implement numerical limits on chemicals in local waterways, the lack of upstream action has been a source of tension for downstream states affected by the pollution.
To address this issue, the Department of Agriculture introduced an incentive program in 2009, known as the Mississippi River Basin Healthy Watersheds Initiative. This program provides grant money to projects proposed by farmers, environmental groups, and local governments to reduce agricultural runoff. While the results from this initiative have been promising, with a significant decrease in phosphorus and nitrogen in enrolled areas, more widespread adoption is needed to effectively combat the problem.
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Chemical dumping
The Mississippi River has been dubbed "the most tainted coastal ecosystem in the world" and "the most polluted river in the country" by scientists and conservationists. This is due to the sheer amount of pollution dumped into the river. While the river does have a relatively low flow, agricultural and chemical runoff are the leading causes of its water pollution.
The Clean Water Act (CWA) regulates both point source pollution and non-point source pollution through ambient water quality standards. However, regulating non-point source pollution, such as agricultural runoff, is much more challenging and ineffective. This is evident in the case of the Mississippi River, where current agricultural practices lead to nutrient loading and eutrophication.
Industrial facilities have also contributed significantly to the chemical pollution of the Mississippi River. For example, Roquette America Inc. was identified as the biggest polluter in Iowa, dumping 1.7 million pounds of toxic chemicals into the Mississippi River. Additionally, the Tyson Foods plant in Sedalia, Missouri, released 410,724 pounds of toxins into Little Muddy Creek.
The consequences of this chemical dumping are severe. These toxic chemicals are linked to cancer, developmental disorders, and reproductive disorders. Furthermore, the Mississippi River is a source of drinking water for half a million people, putting their health at risk.
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Sedimentation and silt
The Mississippi River carries roughly 550 million metric tonnes (500 million tons) of sediment into the Gulf of Mexico each year. This sediment, composed of sand and mud, is foundational to the Mississippi River Delta, which has formed over the last 7,000 years. The river's sediment is derived from its 3,250,000-square-km (1,250,000-square-mi) basin and has contributed to the expansion of Louisiana's coastline.
The natural processes that built the Mississippi River Delta did not capture all the sediment carried by the river. Before human intervention, between 30 to 70 percent of the sediment was retained to shape the delta, while the rest was transported to the deeper waters of the Gulf of Mexico. The implementation of flood protection levees has further altered the natural cycle, causing sediment to be lost into the deep waters instead of nourishing the marshes and wetlands.
Leveeing has disrupted the natural cycle of sediment accumulation and land formation. While some sediment escapes at the ends of the levees, much of the valuable mud and sand bypasses the marshes that depend on it for sustenance and restoration. This diversion of sediment contributes to Louisiana's land loss crisis, as the marshes and wetlands are deprived of the essential material necessary for their regeneration.
To address the land loss crisis and restore the health of the Mississippi River Delta and coastal Louisiana, efforts are being made to maximize the capture and utilization of sediment for coastal restoration. By employing a combination of marsh creation and sediment diversion projects, there is a possibility to recapture enough sediment to sustain the deltaic coastline and mitigate the effects of land loss.
The Mississippi River's sedimentation and silt have significant implications for the region's ecology and geography. The river's ability to transport and deposit sediment has shaped the landscape over millennia, contributing to the formation of new land and the expansion of coastlines. However, human interventions, such as leveeing, have disrupted these natural processes, leading to sediment loss and subsequent environmental challenges.
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Plastic pollution
The Mississippi River is a significant source of plastic pollution in the ocean. As the drainage system for 40% of the continental United States, plastic waste and other litter enter the river through storm drains and smaller waterways. The river then carries this pollution into the Gulf of Mexico and, ultimately, the ocean.
While the Mississippi River is a major contributor to plastic pollution in the ocean, it is not the only culprit. It is estimated that around 90% of plastics in the ocean come from just 10 rivers, nine of which are located in Asia. These rivers are located alongside large human populations with poor waste management systems, contributing to the growing problem of plastic pollution in our oceans.
Agricultural runoff is one of the leading causes of water pollution in the Mississippi River. Current agricultural practices lead to nutrient loading and eutrophication, which can have detrimental effects on the environment and ecosystem health. The Mississippi River provides drinking water to more than 20 million people and 50 cities, so ensuring the quality and safety of the water is crucial.
In recent years, there have been efforts to address the problem of plastic pollution in the Mississippi River. The Mississippi River Cities and Towns Initiative (MRCTI) is a coalition of mayors from across the Mississippi River Basin who have partnered with organizations like the United Nations Environment Programme (UNEP) and the National Geographic Society to combat plastic pollution. They have implemented initiatives to promote education and outreach, improve waste management systems, and collect data on the presence of plastic waste within the watershed.
One such initiative is the Mississippi River Plastic Pollution Initiative, which began in Spring 2021 with data collection in three pilot locations: Baton Rouge, Louisiana; St. Louis, Missouri; and St. Paul, Minnesota. During this initiative, citizen scientists helped to survey over 111 kilometers (69 miles) squared area along the Mississippi River corridor, using the Marine Debris Tracker app developed by the University of Georgia. The findings from this initiative have provided valuable information to support existing stormwater programs and improve waste management systems.
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Frequently asked questions
The Mississippi River is one of the most polluted rivers in the world. It carries trash, plastic, and chemical dumping into the ocean. The river's drainage basin covers 41% of the United States, and water from these areas eventually flows into the ocean.
The main sources of pollution in the Mississippi River are agricultural and urban runoff, sedimentation, and chemical dumping. The river also receives pollution from its tributaries.
The Mississippi River contributes to the formation of a hypoxic zone or ""dead zone" in the Gulf of Mexico. This area has very low oxygen levels due to excess nutrients and seasonal stratification of waters, leading to the death of marine life.
Efforts to reduce pollution in the Mississippi River include the Clean Water Act, which regulates point source and non-point source pollution. Mayors of cities along the river have also committed to reducing plastic and trash. Additionally, new technologies and consumer advocacy are being used to address plastic pollution.
