Today, a significant part of the surface water of the land is polluted, and it is becoming more and more difficult to find potable, clean water. The greatest damage to the state of the aquatic environment is caused by human economic activity.
Substances that pollute water bodies enter the aquatic environment from both anthropogenic and natural sources. The latter include the destruction of rocks, volcanic activity, and waste products of aquatic organisms. Anthropogenic sources are population growth, development of agricultural and industrial production. Domestic, industrial and agricultural waste water is discharged into the surrounding water bodies.
Anthropogenic pollution is subdivided into primary and secondary. In the primary case, the quality of the aquatic environment deteriorates directly due to the entry of polluting emissions into water bodies. Secondary is caused by an excessive concentration of decomposition products of dead aquatic animals, which occurred as a result of a violation of the ecological balance.
The main sources of pollution include drainage water, domestic and industrial wastewater, storm sewers, wastewater from livestock farms, fields and settlements, forest transportation along rivers, and water transport.
For human health, a special danger is posed by water pollution by organic substances with high toxicity - pesticides. A person uses them in the course of his life. When large forest and agricultural areas are treated with pesticides by aircraft, up to 70% of these toxic substances are carried by the wind for hundreds of kilometers, polluting drains and water bodies. After precipitation, pesticides penetrate into the soil, into groundwater, and then into lakes and rivers.
The most dangerous among the pesticides used are persistent organochlorine compounds that accumulate in the tissues of various organisms. Being involved, for example, in the food chain of aquatic organisms, these compounds will be transferred from one trophic level to another. For example, if a fisherman caught and ate a fish that feeds on planktonic crustaceans living in a reservoir polluted with pesticides, poison will settle in his body. It is almost impossible to remove it from the body, and high concentrations of the poison can lead to cancer. Also, synthetic detergents - detergents - have high biochemical stability. Once in water bodies with toxic effluents, they also accumulate in the organisms of aquatic inhabitants and then enter the human body.
A great danger is posed by radionuclides entering water bodies along with waste from power plants, some industries and nuclear ships. The most toxic mineral compounds are lead, arsenic, zinc, mercury, and copper. They enter the water through precipitation from the atmosphere, where they accumulate again due to human activity (emissions from industrial enterprises). Mine runoff is also rich in heavy metals. It is difficult to dispose of oil and its derivatives. And only a few aquatic organisms are capable of processing and destroying oil suspension.
