Fertilizers' Water Pollution: Understanding The Environmental Impact

Fertilizers are a major source of water pollution, causing unhealthy conditions for aquatic life and people. They are designed to help plants grow, but when misused, they can have serious environmental consequences. Excess fertilizers are washed into waterways from hundreds of thousands of lawns and farms, polluting rivers, lakes, and bays. This is primarily due to the presence of water-soluble phosphorus, which is a key ingredient in fertilizers. When too much phosphorus enters the water, it acts as junk food for algae, causing an explosive growth known as an algal bloom. This reduces water clarity and visibility, impacting photosynthesis by aquatic plants and decreasing oxygen levels in the water, which can lead to fish kills and depleted water habitats.

Fertilizer runoff from lawns and landscaping

Nitrogen and phosphorus, essential nutrients for plant growth, are the primary culprits in fertilizer runoff. These chemicals escape into waterways, lakes, oceans, and groundwater when they are not fully absorbed by plant roots. Overfertilizing and fertilizing at the wrong time of year are common causes of fertilizer runoff. Lawns and plants often cannot absorb all the water-soluble fertilizers, leading to excess nutrients in the soil that can be easily washed away.

The impact of fertilizer runoff is exacerbated when it occurs on a large scale, such as in residential areas with thousands of lawns. The cumulative effect of excess fertilizers from multiple sources can overwhelm natural water bodies and disrupt their delicate balance. The excess nutrients act as "junk food" for algae, causing explosive growth and leading to a phenomenon known as algal blooms.

Algal blooms have far-reaching consequences. They reduce the oxygen levels in water, creating "dead zones" where fish and other aquatic life cannot survive. The decay of excessive plant growth further depletes oxygen levels, leading to "fish kills" and altering the types of plants and animals that can thrive in these waterways. Additionally, algal blooms increase the levels of toxins in the water, posing risks to human health through direct contact, drinking contaminated water, or consuming affected fish or shellfish.

To mitigate fertilizer runoff from lawns and landscaping, it is essential to apply fertilizers responsibly. This includes fertilizing only when necessary and in the recommended amounts, avoiding application before windy or rainy days, and ensuring proper storage and disposal of fertilizers. Homeowners should also consider using slow-release fertilizers, maintaining healthy lawn care practices, and incorporating native plants into their landscaping to reduce the need for excessive fertilizers.

Eutrophication of surface waters

Eutrophication is the enrichment of surface waters with plant nutrients. It is a natural process that occurs when there is an accumulation of nutrients in bodies of water, such as lakes, reservoirs, ditches, rivers, and coastal waters. While eutrophication can occur naturally, it is often accelerated by human activities, such as the use of fertilizers.

Causes of Eutrophication

The main cause of eutrophication is the excessive use of fertilizers, particularly nitrogen and phosphorus. These nutrients are essential for plant growth, but when they are present in high concentrations in water, they can have harmful effects. Nitrogen and phosphorus can enter water bodies through runoff from fertilized fields, lawns, and golf courses. In addition, untreated sewage and wastewater, as well as internal combustion of fuels, can also contribute to eutrophication by increasing nitrogen pollution.

Effects of Eutrophication

Eutrophication has several negative consequences for the environment, economy, and public health:

• Unsightly scum and odour: Algal blooms, or excessive growth of algae, can form on the surface of the water, reducing water clarity and visibility. This can decrease the recreational value of waterways and impact the aesthetic enjoyment of rivers and lakes.
• Oxygen depletion: When algae die, they are decomposed by bacteria, which consumes the oxygen dissolved in the water. This can lead to "fish kills" or the death of large numbers of fish and other aquatic organisms due to oxygen deprivation.
• Water quality issues: Eutrophication can result in the production of toxins by certain types of algae, which can be harmful to both human and aquatic health. These toxins can also increase water treatment costs.
• Economic losses: Eutrophication can lead to economic losses due to the decline in commercial and recreational fishing, reduced property values, and the cost of restoring affected water bodies.
• Navigation impediments: Dense weed growth and slime caused by eutrophication can hinder navigation in waterways.
• Loss of biodiversity: Eutrophication can cause shifts in the species composition of ecosystems, with desirable fish species being replaced by less desirable ones.

Preventing and Mitigating Eutrophication

To prevent and mitigate the impacts of eutrophication, several measures can be implemented:

• Minimize nutrient pollution: This includes proper fertilizer application, reducing runoff, and treating sewage and wastewater effectively.
• Vegetation cover: Maintaining vegetation cover can help absorb excess nutrients and prevent nutrient leaching during rainfall events.
• Rational irrigation: Improper irrigation practices can impact water quality; therefore, precision irrigation techniques should be encouraged.
• Optimize cultivation techniques: Improving weed, pest, and disease control, as well as implementing erosion control techniques, can help minimize nutrient losses.
• Agricultural planning: Implementing sustainable agricultural practices and land management techniques can reduce soil erosion and nutrient runoff into water bodies.

Algal blooms and their impact

Algal blooms, or HABs (Harmful Algal Blooms), are a result of excess nutrients in the water, which stimulates rapid and uncontrolled growth of algae and aquatic plants. Nitrogen and phosphorus are the primary nutrients responsible for this growth, and they enter waterways through various human activities, including the use of fertilizers.

Impact of Algal Blooms

The uncontrolled growth of algae has several impacts:

• Reduction in Water Quality: Algal blooms reduce the clarity and visibility of the water, reducing light penetration and hindering photosynthesis by aquatic plants. This, in turn, affects the oxygen levels in the water, creating low-oxygen conditions that can lead to "fish kills" and deplete the water habitat.
• Eutrophication: The excessive growth of algae and aquatic plants leads to eutrophication, an increase in organic matter within a water body. This process further reduces oxygen levels and compromises water quality and biodiversity.
• Toxicity: Certain types of algae produce toxins that can be harmful to humans, animals, and the environment. These toxins can contaminate drinking water sources, leading to various health issues, including skin rashes, throat irritation, and gastroenteritis. They can also affect plant structures and inhibit essential physiological processes.
• Economic Impact: Algal blooms can have economic implications for industries such as fishing and tourism. They can lead to fishing catch declines, recreational closures, and reduced property values in affected areas.
• Oxygen Depletion: As algal blooms decay, they consume oxygen in the water, creating anoxic conditions that can suffocate other organisms in the ecosystem.
• Gas Emissions: The decay of algal blooms can release harmful gases like methane and hydrogen sulfide, which can have negative environmental and health impacts.

Pollution from improper fertilizer application

Fertilizers are a major source of water pollution, with improper application leading to a range of environmental, economic, and public health issues. The chemicals in fertilizers, when washed into waterways, cause a process called eutrophication, which is the enrichment of surface waters with plant nutrients. This leads to an increase in algae and other aquatic plant life, which can be harmful to aquatic ecosystems and human health.

How Improper Fertilizer Application Causes Water Pollution

During rain storms, water running off lawns and fields can pick up excess fertilizer on the ground and carry it into local streams, rivers, lakes, and bays. This is especially true in areas with a lot of hard surfaces like rooftops, sidewalks, and roads, as the runoff carries pollutants, including nitrogen and phosphorus, into waterways. Fertilizer that finds its way into these water bodies fuels the rapid and harmful growth of algae and other aquatic plants.

The Impact of Improper Fertilizer Application

The growth of algae and aquatic plants can be so explosive that it creates an algal "bloom," discoloring the water and reducing water clarity and visibility. This excessive growth causes an unhealthy increase in organic matter within a water body, a process called eutrophication. Eutrophication from synthetic fertilizer pollution has costly impacts on the environment, economy, and public health.

As the excessive plant growth dies, it uses up oxygen in the water, leading to "fish kills" where large numbers of fish die due to low oxygen levels. Eutrophication can also lead to the replacement of desirable fish species with less desirable ones, as well as the production of toxins by certain types of algae, which can be harmful to fish, shellfish, plants, and even humans.

Preventing Pollution from Improper Fertilizer Application

To prevent water pollution from improper fertilizer application, it is important to apply fertilizers only when needed, during the proper season, and in the correct amounts. Avoid applying fertilizer near waterways, driveways, sidewalks, and storm drains. Use a mulching mower on lawns and keep leaves, grass clippings, and soil out of streets and gutters. It is also important to clean up after pets, as pet waste contains phosphorus, which contributes to eutrophication.

The role of agriculture in water pollution

Agriculture is the single largest user of freshwater resources, using a global average of 70% of all surface water supplies. The sector is both a cause and a victim of water pollution. While agricultural practices discharge pollutants and sediments into surface and/or groundwater, they are also affected by the use of wastewater and polluted surface and groundwater, which contaminate crops and transmit diseases to farmworkers and consumers.

Causes of Water Pollution

Agriculture is responsible for the discharge of agrochemicals, organic matter, drug residues, sediments, and saline drainage into water bodies. The use of pesticides and chemical fertilizers in crop production, for example, has led to the contamination of lakes and coastal waters, impacting biodiversity and fisheries.

The growth in crop production has been achieved mainly through the intensive use of inputs such as pesticides and chemical fertilizers. The global market for pesticides is worth more than USD 35 billion per year, with some countries experiencing double-digit growth in the intensity of pesticide use.

Effects of Water Pollution

Water pollution poses risks to aquatic ecosystems, human health, and productive activities. For instance, high levels of nitrates in water can cause "blue baby syndrome", a potentially fatal illness in infants. Eutrophication, caused by the accumulation of nutrients in lakes and coastal waters, impacts biodiversity and fisheries.

In the United States, agriculture is the main source of pollution in rivers and streams, the second main source in wetlands, and the third main source in lakes. Similarly, in China, agriculture is responsible for a large share of surface-water pollution and is almost exclusively responsible for groundwater pollution by nitrogen.

Addressing Water Pollution

The right policies and incentives can encourage more sustainable and healthy diets, thereby moderating increases in food demand. Financial incentives such as taxes and subsidies on food and coupons for consumers can positively influence dietary behavior. Additionally, reducing food losses and waste can minimize the waste of resources and associated environmental impacts.

On-farm practices in crop production, livestock, and aquaculture are crucial for preventing pollution. In crop production, management measures such as limiting and optimizing the type, amount, and timing of fertilizer and pesticide applications can reduce the risk of water pollution. Establishing protection zones along surface watercourses, within farms, and in buffer zones around farms can also effectively reduce pollution migration into water bodies.

Agriculture plays a significant role in water pollution, and addressing this issue requires a combination of policy interventions, economic incentives, and on-farm practices. By implementing sustainable practices and reducing the use of pollutants, it is possible to mitigate the harmful impacts of agricultural activities on water resources.

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