Bronte Wells
The Chesapeake Bay has been facing a lethal overdose of pollution for over 26 years, with the three main sources of pollution being nitrogen, phosphorus, and sediment. Nitrogen occurs naturally in soil, animal waste, plant material, and the atmosphere. Phosphorus, on the other hand, enters the bay mainly through natural sources such as soil, animal waste, and plant material. However, the majority of phosphorus pollution comes from chemical fertilizers from farmland and animal operations, chemical fertilizers applied to lawns, and human waste discharged from wastewater treatment plants. Sediment, the third pollutant, includes loose particles of clay, silt, and sand that wash into the water, making it cloudy and blocking sunlight from reaching underwater plants. These pollutants enter the bay through agricultural runoff, wastewater treatment plants, air pollution, and urban and suburban runoff.
| Characteristics | Values |
|---|---|
| Main sources of pollution | Nitrogen, phosphorus, and sediment |
| Nitrogen sources | Soil, animal waste, plant material, and the atmosphere |
| Phosphorus sources | Soil, animal waste, plant material, manure, chemical fertilizers, and human waste |
| Sediment sources | Loose particles of clay, silt, and sand that wash into the water |
| Other sources of pollution | Chemical fertilizers, wastewater, septic tank discharges, air pollution, and runoff from farms, cities, and suburbs |
| Efforts to reduce pollution | Chesapeake Bay Program, Showcase Watersheds program, bans on phosphorus in lawn fertilizer, and improved farming practices |
| Impact of pollution | Reduced levels of oxygen, fish kills, algae blooms, and smothering of bottom-dwelling species |
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What You'll Learn
Nitrogen, phosphorus, and sediment pollution from agricultural runoff
Nitrogen, phosphorus, and sediment pollution are the three main pollutants affecting the Chesapeake Bay. These pollutants enter the bay through various sources, including agricultural runoff, wastewater treatment plants, air pollution, and urban and suburban runoff. While all these sources contribute to the problem, agricultural runoff is the largest source of nitrogen and phosphorus pollution in the bay.
Agricultural activities, such as the use of fertilizers and manure, are significant contributors to nitrogen and phosphorus pollution in the Chesapeake Bay. Farms in the region apply large quantities of fertilizers and manure to their fields, which can be washed into nearby waterways during rainfall or irrigation. This runoff carries high levels of nitrogen and phosphorus, which can have detrimental effects on the bay's ecosystem.
The excessive nitrogen and phosphorus from agricultural runoff fuel the growth of algae in the water. This leads to a phenomenon known as "algae blooms," where algae grow rapidly and excessively due to the abundance of nutrients. These algae blooms block sunlight from reaching underwater grasses and other aquatic plants, hindering their growth and survival. Additionally, when the algae die, they are decomposed by bacteria, which consumes the oxygen in the water. This results in the creation of "'dead zones,' areas with little to no oxygen, leading to the death of fish, crabs, oysters, and other aquatic life.
Sediment pollution, another significant issue in the Chesapeake Bay, is also partly attributed to agricultural practices. Soil erosion from farmlands can carry loose particles of clay, silt, and sand into the bay, making the water cloudy and further blocking sunlight from reaching aquatic plants. Sediment can also smother bottom-dwelling organisms like oysters and carry high concentrations of phosphorus and toxic chemicals, exacerbating the negative impacts on the bay's ecosystem.
While agriculture is a major contributor to nitrogen, phosphorus, and sediment pollution in the Chesapeake Bay, it is important to recognize that improvements are being made. Farmers are adopting better practices, such as nutrient management and implementing conservation plans, to reduce polluted runoff. These efforts are showing positive results, with reports indicating declining levels of nitrogen, phosphorus, and sediment pollution entering the bay. However, there is still much work to be done to restore the bay's health fully and address the complex challenges posed by pollution from various sources.
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Manure and chemical fertilizers from farms
Farms remain a major source of water pollution in the Chesapeake Bay. Manure and chemical fertilizers from farms are significant contributors to the Bay's poor health.
Manure is a major source of nitrogen pollution in the Chesapeake Bay. It accounts for about 40% of the nitrogen applied to fields in the watershed. When used as fertilizer, manure must be applied within a few miles of its origin due to transport challenges. While proper management can make two-thirds of the organic nitrogen in manure available to crops, it is often more difficult to manage and apply than chemical fertilizers.
Chemical fertilizers are another significant source of pollution. Excessive fertilizer use on lawns, golf courses, and other developed lands contributes to nutrient pollution in the Bay. Turf grass, the dominant crop in the Bay watershed, is the least regulated of Maryland's major crops. As a result, fertilizer nutrients can wash into nearby waters during precipitation events or seep into groundwater.
The use of manure and chemical fertilizers by farmers in the Chesapeake Bay watershed has led to high levels of nitrogen and phosphorus in the water. These nutrients fuel unnaturally high levels of algae growth, blocking sunlight from reaching underwater plants and creating "dead zones" with depleted oxygen levels that stress and suffocate aquatic life.
While efforts to minimize pollution from agriculture are showing signs of progress, there is still much work to be done. The 2015 report on the Bay's health gave the water a "C" grade, indicating that improvements are needed to restore the health of the Chesapeake Bay and its surrounding waterways.
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Septic tank discharges and wastewater treatment plants
The Chesapeake Bay watershed is home to 472 municipal and industrial wastewater treatment plants. Wastewater can include human waste, food scraps, oils, soaps, and chemicals. Before it can be released back into the environment, it needs to be treated to remove pollutants and harmful substances. Basic sewage treatment involves using bacteria to break down organic matter and chlorine or other technologies to kill harmful bacteria and reduce odour. The chlorine is then removed before the treated water is released back into surface waters. This treated wastewater is typically discharged into streams, the Bay, or other waters.
The Chesapeake Bay Program has been working since 1985 to reduce nutrient pollution from wastewater facilities. In 2005, states in the region began to implement a new permitting process that limited the amount of nitrogen and phosphorus that significant wastewater treatment plants could discharge. To meet these limits, facilities are being upgraded with nutrient reduction technology, including biological nutrient removal (BNR) and enhanced nutrient removal (ENR).
Septic systems are also a source of pollution in the Chesapeake Bay. These systems are responsible for a large portion of household waste in many counties in the Bay region. While septic systems can reduce nitrogen and phosphorus levels to amounts the Bay can safely absorb when functioning properly, efforts to reduce nitrogen pollution from these systems are lagging.
Nitrogen and phosphorus are both nutrients that cause harm to marine life in the Bay by fuelling unnaturally high levels of algae growth, which block sunlight from reaching underwater grasses and deplete the water of oxygen as they die off.
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Air pollution and urban/suburban runoff
While farms are the leading source of pollution entering the Chesapeake Bay, urban and suburban areas also contribute significantly to the problem. The pavement, asphalt, and other impervious surfaces found in cities act as both conduits and sources of pollution. Rather than being absorbed by soil or vegetation, rainwater and snowmelt that fall on roadways and other hard surfaces tend to flow rapidly toward gutters and urban streams. In the process, that water picks up nitrogen, phosphorus, and a range of oils, salts, heavy metals, pharmaceuticals, and other pollutants. The rapid flow also means that urban stream banks tend to erode rapidly and yield large amounts of sediment pollution.
Air pollution emitted by cars and trucks, industries, gas-powered lawn tools, and other sources contributes about one-third of the total nitrogen load entering Chesapeake waterways. This air pollution can come from any location within the Bay’s “airshed,” which measures about 570,000 square miles and stretches to Canada, Ohio, and South Carolina. Power plants, factories, and motor vehicles continuously burn fossil fuels that fill the air with nitrogen and chemical contaminants.
Nitrogen and phosphorus are the two nutrients of concern in the Chesapeake Bay area. Excessive amounts of these nutrients cause algal blooms and dead zones in the Bay. They can come from natural sources, like soil, plant material, and wild animal waste, but they also come from lawn fertilizers, septic systems, and livestock manure. In one suburban Baltimore watershed, researchers found that 56% of the nutrients in a local stream came from lawn fertilizer.
To reduce nutrient pollution, states including New York and New Jersey have recently banned phosphorus in lawn fertilizer, imposed buffer zones around water bodies, and taken other steps to limit fertilizer runoff from lawns. Minnesota was the first state to ban phosphorus in lawn fertilizer, beginning in 2002. A follow-up survey found this to be one method of reducing nutrient pollution that was popular with consumers and cost-nothing.
There are also ways to counter stormwater runoff in cities and suburbs. The most effective approaches are to limit the development of new impervious surfaces, preserve forested landscapes, enhance the permeability of urban soils, and expand green spaces in cities. Beyond that, the use of infiltration strips, sand filters, rain gardens, green roofs, and other infrastructure can help.
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Poor fertilizer usage and management
Fertilizer usage on turf grass is a particular concern. Turf grass is Maryland's biggest crop, with approximately 1.3 million acres planted statewide. However, it is the least regulated of the state's major crops. When turf grass is covered with excessive fertilizer, the nutrients can wash into nearby waters during rainfall or snowmelt, contributing to water pollution.
Agricultural practices, including the use of chemical fertilizers, manure, and chicken litter, are significant sources of nitrogen and phosphorus pollution in the Chesapeake Bay watershed. While efforts to minimize pollution from agriculture have shown improvements, manure and fertilizer remain the sources of half of the nitrogen and phosphorus entering the Bay. Better agricultural practices and management changes are necessary to reduce the environmental impact of farms on the watershed.
The type of fertilizer used also plays a role in pollution. Chemical fertilizers applied to lawns, golf courses, and other developed lands contribute to phosphorus pollution. Additionally, the use of phosphorus in fertilizers, whether organic or synthetic, intended for established turf grass should be banned, as it is a leading cause of recurring poor water quality in the Bay and its tributaries.
To address poor fertilizer usage and management, it is crucial to implement guidelines that align with water quality restoration goals. This includes limiting the amount of nitrogen in fertilizers and ensuring a portion of it is slow-release to reduce runoff. Proper fertilizer usage on lawns is also essential, such as avoiding over-application and refraining from applying it to dormant lawns or frozen ground. By improving fertilizer usage and management practices, we can reduce nutrient pollution and work towards achieving a clean and sustainable Chesapeake Bay.
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Frequently asked questions
The three main sources of Chesapeake Bay soil pollution are nitrogen, phosphorus, and sediment. Nitrogen and phosphorus are both nutrients, which cause harm to marine life by creating algae blooms. While nitrogen occurs naturally in soil, animal waste, plant material, and the atmosphere, phosphorus mostly comes from natural sources such as soil, animal waste, and plant material.
Nitrogen and phosphorus enter the water in high amounts and cause algae to grow too quickly. These "algae blooms" block sunlight from reaching underwater plants, which need it to survive. When the algae die, they are decomposed by bacteria that consume the oxygen in the water, creating areas of little-to-no oxygen called dead zones.
To reduce soil pollution, states in the Chesapeake Bay region will have to target all the watershed's sources of nutrient pollution. This includes limiting the nutrients in fertilizers, banning phosphorus from fertilizers, and requiring an upper limit on the amount of nitrogen in fertilizers.
