Water pollution

Water pollution is the contamination of water bodies by substances or energy forms.

This process alters the nature of the water in ways that negatively affect its legitimate uses. These uses include drinking, irrigation, and supporting biological communities. Contamination can occur in surface waters like rivers, lakes, and oceans. It can also affect groundwater, which is water found in aquifers beneath the Earth's surface.

Because water is essential for life, pollution poses a significant threat to both human health and global ecosystems.

Pollutants enter water systems through two primary methods: point sources and non-point sources. A point source is a single, identifiable location of contamination. Examples include a specific storm drain, an oil spill, or a wastewater treatment plant. In contrast, non-point sources are more diffuse and harder to trace to one spot. Agricultural runoff is a major non-point source, as rain carries chemicals across wide areas of farmland.

Pollution is often the result of the cumulative effect of these many small inputs over a long period of time.

Contaminants can be classified by their chemical or physical nature. Organic pollutants include petroleum hydrocarbons from fuels and lubricants, as well as pesticides and detergents. Some organic substances, like per- and polyfluoroalkyl substances (PFAS), are known as persistent organic pollutants because they remain in the environment for a long time. Inorganic pollutants include heavy metals from motor vehicles and acid mine drainage from mining operations.

Additionally, thermal pollution occurs when energy is added to water. Power plants often use water as a coolant, discharging heated water back into the environment. This increase in temperature lowers the level of dissolved oxygen, which can lead to fish kills.

Biological pollution involves the introduction of pathogens or invasive organisms. Pathogens are microorganisms like bacteria, viruses, protozoans, and parasitic worms that cause disease. In water testing, scientists often look for indicator organisms like Escherichia coli (E. coli) to detect fecal contamination. High levels of pathogens can result from inadequate sanitation, such as open defecation or poorly managed sewage systems.

As of 2017, an estimated 4.5 billion people globally did not have access to safely managed sanitation, which contributes to the spread of waterborne diseases.

Solid waste and plastic pollution represent a growing global challenge. Large pieces of garbage, known as macroscopic pollution, can be seen floating in canals and oceans.

Even more pervasive is microplastic pollution, which consists of tiny particles that are not easily visible. These microplastics often come from the erosion of synthetic textiles like polyester or nylon during washing. They also originate from car tires and urban dust. Together, these three sources account for over 80% of all microplastic contamination. Even if all plastic entering the ocean stopped today, microplastic levels would continue to rise due to existing particles.

Nutrient pollution is another critical form of contamination caused by excessive nitrogen and phosphorus. These nutrients often come from sewage and agricultural fertilizers. When these substances enter water, they can cause excessive algae growth. This process can deplete oxygen levels in the water, a condition known as hypoxia or anoxia.

Such conditions can destroy aquatic ecosystems and change the entire food chain. In humans, high nitrate levels in drinking water can lead to serious health issues like blue baby syndrome.

Managing water pollution requires a combination of infrastructure, technology, and legislation. Technical solutions include improving sewage treatment and implementing erosion and sediment control.

Scientists use specialized equipment to monitor water quality and track the presence of contaminants.

By understanding how pollutants move from land to sea, societies can develop better management plans to protect these vital resources. Protecting water quality is essential for maintaining biodiversity and ensuring safe water for the global population.