Sewage discharge is the primary source of freshwater pollution in urban areas, as it contains a variety of contaminants such as bacteria, viruses, nutrients, and heavy metals.

Phosphorus is a major contributor to eutrophication in freshwater ecosystems, as it stimulates the growth of algae and other aquatic plants, leading to a decrease in water quality and oxygen levels.

Bioaccumulation is the process by which toxic substances accumulate in the tissues of organisms, often through the food chain.

Heavy metal pollution can have a variety of negative effects on aquatic organisms, including reduced reproduction, impaired growth, and increased susceptibility to disease.

Industrial wastewater discharge is the primary cause of thermal pollution in freshwater ecosystems, as it often contains heated water that can raise the temperature of the receiving water body.

All of the above methods can be used to reduce nutrient pollution from agricultural runoff, as they help to trap nutrients and prevent them from entering waterways.

Biodegradation is the process by which bacteria break down organic matter in water, converting it into simpler compounds.

The presence of Escherichia coli (E. coli) is a common indicator of fecal contamination in freshwater ecosystems, as it is a bacteria that is found in the intestines of warm-blooded animals.

Industrial emissions, particularly those containing sulfur dioxide and nitrogen oxides, are the primary cause of acidification in freshwater ecosystems.

All of the above methods can be used to restore degraded freshwater ecosystems, as they help to improve water quality, habitat, and biodiversity.

Phytoremediation is the process by which plants absorb and remove pollutants from water, soil, and air.

Oil spills can have a variety of negative effects on marine ecosystems, including reduced oxygen levels, habitat destruction, and contamination of marine life.

All of the above sources contribute to plastic pollution in oceans, as plastic waste can be transported from land to sea by wind, rain, and rivers.

All of the above methods can be used to reduce plastic pollution in oceans, as they help to reduce the amount of plastic waste entering the environment and to remove existing plastic pollution.

Bioaccumulation is the process by which microplastics accumulate in the tissues of organisms, often through the food chain.