River Basins: Pollution's Impact And The Way Forward

Water pollution is a pressing issue that jeopardizes human health and the environment. It occurs when harmful substances contaminate a body of water, degrading water quality and rendering it toxic. While water pollution can come from a single source, such as a factory drain, it often results from human infrastructure around a river, with contaminants entering the river at many points along its length.

Agricultural activities are a significant source of water pollution, as fertilizers, pesticides, and animal waste wash into waterways, causing nutrient pollution. This, in turn, can lead to algal blooms, which suffocate plants and animals, creating dead zones devoid of life. Industrial processes also contribute to water pollution, with chemical waste and oil being discharged into rivers. These pollutants can immediately kill fish and other animals or enter the food chain, accumulating to toxic levels.

The effects of water pollution are far-reaching. It can cause illnesses and even death, with unsafe water killing more people each year than war and violence combined. Water pollution also disrupts aquatic ecosystems, reducing biodiversity and affecting the life cycles of insects and other organisms.

To address water pollution, it is crucial to consider both the sources of pollution and the type of water body affected, whether it is groundwater, surface water, or ocean water. Preventative measures include proper disposal of chemicals and waste, maintaining vehicles to prevent leaks, and reducing plastic consumption.

Nitrogen pollution

Effects of Nitrogen Pollution on Water Bodies

Impact on Human Health

Global Impact

According to a study published in Nature Communications, nitrogen pollution is expected to affect one-third of global river basins by 2025. This will result in a severe lack of water, affecting up to 3 billion people. Regions in the US, South China, Central Europe, and Africa are projected to become hotspots of water scarcity due to excess nitrogen.

Addressing Nitrogen Pollution

To address the issue of nitrogen pollution in river basins, it is crucial to consider both water quantity and quality. Policymakers and water resource managers need to urgently address water quality as a matter of priority. Additionally, there is a need to reduce nitrogen emissions from motor vehicles, energy production, and agriculture, as these are significant contributors to nitrogen pollution in water bodies.

Eutrophication

Causes of Eutrophication

Effects of Eutrophication

• It induces cyanobacteria formation, hypoxia, and the release of bloom toxins, which can accumulate in aquatic organisms and humans and cause illnesses, toxicities, and even death.
• It leads to oxygen depletion and fish mortality, creating "dead zones" devoid of life.
• It disturbs the physicochemical parameters of water bodies, impacting the conservation ecology and diversity of other biotic assemblages.

Mitigation of Eutrophication

To mitigate eutrophication, an integrated and adaptive approach is necessary, addressing water quality, water quantity, soil, groundwater, and surface water. This involves:

• Optimizing nutrient uptake efficiency
• Enhancing nutrient retention and recirculation
• Implementing nutrient discharge and effect-oriented measures
• Utilizing smart monitoring, smart modelling, smart measures, and smart governance

Additionally, microbial and ecological remediations, such as constructed wetlands, can be applied to control point and non-point pollution sources effectively and eco-friendly.

Industrial waste

The production of all kinds of industrial goods generates wastewater that can be contaminated with toxic substances. In Europe, there have been strict limits for decades that industries must observe when discharging wastewater into public networks. Therefore, wastewater must be treated or clarified before it can be discharged into the sewage system or rivers. However, in emerging countries such as China, India, Africa, or South America, environmental policy has not yet reached this stage, and the illegal discharge of wastewater from industry into rivers and lakes is part of everyday life.

The discharge of residual pollution into public waters has serious consequences. Many of the hazardous substances from industry are difficult to biodegrade and therefore accumulate in water sediments. The consequence of this industrial waste water pollution is that fish, crustaceans, and other creatures become ill, and some die. Through cracks in the ground, the polluted water from rivers and the contaminants from the water sediments get into the groundwater and thus into the drinking water.

There are many types of water pollution, and the main industrial waste of water pollution includes:

• Petroleum products: used as fuel or lubricating oil and produced during the manufacture of plastics.
• Heavy metals: such as copper, lead, and selenium, they come mainly from industry, in the manufacture of cars, in mines, or exhaust air systems.
• Hazardous wastes: highly flammable and corrosive, they come mainly from construction and demolition, manufacturing and trade, and from waste treatment processes (secondary wastes).
• Sediments: due to the discharge of polluted industrial wastewater, non-degradable toxins accumulate in aquatic sediments for years and slowly enter the groundwater or are stirred up into the water during floods or dredging.
• Per- and polyfluorinated alkyl compounds (PFAS): They mainly come from the textile industry, hard chrome plating, and extinguishing agents. PFAS are not completely degradable in nature and accumulate in the fatty tissue or mother's milk of mammals.

Oil pollution

The density of oil and water determines whether the oil will float or sink in a river. Oil usually floats because it is less dense than water. However, very heavy oils with a density of 1.01 g/cc would float in the ocean but sink in a river. When spilled oil sinks, it can be challenging to clean up, as it may pool at the bottom of the river.

The movement of oil spills in rivers is generally downstream and can be influenced by wind and the presence of dams or locks. Oil tends to collect along the banks, where it can be harmful to plants and animals that ingest the contaminated vegetation. Oil can also interact with sediment carried by rivers, causing it to settle at the bottom, particularly near the river mouth.

To address oil pollution in river basins, it is essential to have effective prevention measures and response strategies. This includes proper maintenance of pipelines and facilities that handle oil and other chemicals. Additionally, technologies such as absorbent sponges and filtering systems can be deployed to contain and clean up oil spills in rivers.

Overall, oil pollution in river basins poses a significant threat to the environment and human health. It is crucial to prioritize prevention, preparedness, and effective response strategies to mitigate the impacts of oil spills in these fragile ecosystems.

Water temperature changes

Elevated water temperatures decrease oxygen levels, which can kill fish and alter food chain composition, reduce species biodiversity, and foster the invasion of new thermophilic species. The elevated temperature typically decreases the level of dissolved oxygen in the water, harming aquatic animals such as fish, amphibians, and other aquatic organisms. Thermal pollution may also increase the metabolic rate of aquatic animals, resulting in these organisms consuming more food in a shorter time. An increased metabolic rate may result in fewer resources, giving an advantage to the more adapted organisms moving in. As a result, the food chains of the old and new environments may be compromised.

Primary producers such as plants and cyanobacteria are affected by warm water because higher water temperature increases plant growth rates, resulting in a shorter lifespan and species overpopulation. The increased temperature can also change the balance of microbial growth, including the rate of algae blooms, which reduce dissolved oxygen concentrations.

The release of unnaturally cold water from reservoirs can also dramatically change the fish and macroinvertebrate fauna of rivers and reduce river productivity. In Australia, where many rivers have warmer temperature regimes, native fish species have been eliminated, and macroinvertebrate fauna have been drastically altered. Survival rates of fish have dropped by up to 75% due to cold water releases.

Thermal pollution could be controlled by employing a few efficient scientific techniques, such as the construction of artificial lakes, cooling ponds, and cooling towers.

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