Группа 1714. Урок 21

1. Выучите слова Water pollution. Загрязнение воды

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WATER POLLUTION

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, groundwater). Water pollution affects plants and organisms living in water. Water pollution occurs when pollutants are released directly or indirectly into water without adequate treatment to remove harmful compounds.

Water pollution is one of the major problems in the global context. Some 90% of China's cities suffer from some degree of water pollution, and nearly 500 million people lack access to safe drinking water. Source of water pollution are divided into point and non-point.

Point source pollution refers to contaminants that enter a waterway through a discrete conveyance, such as a pipe or ditch. Examples of sources in this category include discharges from plants or a city storm drain.

Non-point source pollution refers to diffuse contamination that does not originate from a single discrete source. Non-point source pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. The leaching out of nitrogen compounds from agricultural land which has been fertilized is a typical example.

Causes of water pollution

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, natrium, iron, manganese, etc.), the concentration is often the key in determining what a natural component of water is, and what a contaminant is.

Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication.