Water resources pollution and its control

5. Seawater intrusion and flooding in coastal areas

Seawater flooding is the phenomenon of seawater intrusion into freshwater aquifers. The main cause of saltwater invasion is the overexploitation of fresh water from groundwater. Due to the excessive exploitation of underground freshwater, the freshwater - seawater interface on coastal or island is in an unbalanced state. In the northern coastal areas of China, there has been a continuous drought for many years, the rainfall is low, and the groundwater supply is reduced, but the water demand for industry and agriculture is constantly increasing, and the underground fresh water is "beyond the income", resulting in seawater intrusion and backflow.

Three, the main hazards of water pollution

Increasingly aggravated water pollution has posed a major threat to human survival and security, and has become a major obstacle to human health, economic and social sustainable development. According to the survey of the world authority, in developing countries, 80% of all kinds of diseases are spread because of drinking unsanitary water, and at least 20 million people die every year because of drinking unsanitary water, so water pollution is called "the world's number one killer".

Water pollution affects industrial production, increases equipment corrosion, affects product quality, and even makes production impossible. Water pollution also affects people's lives, destroys ecology, directly endangers people's health, and does great damage.

A. Harm to human health

After water pollution, through drinking water or the food chain, pollutants enter the human body, causing acute or chronic poisoning. Arsenic, chromium, ammonium, benzo (a) pyrene, etc., can also cause cancer. Water contaminated with parasites, viruses or other pathogens can cause a variety of infectious and parasitic diseases.

Water polluted by heavy metals is harmful to people's health. Cadmium contaminated water, food, human diet, will cause kidney, bone lesions, ingestion of cadmium sulfate 20 mg, will cause death. Poisoning from lead, causing anemia, confusion. Hexavalent chromium is highly toxic, causing skin ulcers and carcinogenic effects. Acute or chronic poisoning can occur when drinking water containing arsenic. Arsenic inhibits or inactivates many enzymes, resulting in metabolic disorders, skin keratinization, and skin cancer.

Organophosphorus pesticides can cause nerve poisoning, and organochlorine pesticides can accumulate in fat, causing harm to the endocrine, immune and reproductive functions of humans and animals. Most of the polycyclic aromatic hydrocarbons have carcinogenic effects. Cyanide is also a highly toxic substance. After entering the blood, it binds to the pigment oxidase of cells, which interrupts breathing and causes respiratory failure and asphyxia.

We know that 80 percent of the world's diseases are related to water. Typhoid fever, cholera, gastroenteritis, dysentery, infectious hepatitis are the five major human diseases, all caused by unclean water.

⒉ Harm to industrial and agricultural production

After water pollution, industrial water must be invested in more treatment costs, resulting in the waste of resources and energy, food industry water requirements are more stringent, water quality is unqualified, will make production halt. This is also the factor of low efficiency and poor quality of industrial enterprises.

The use of sewage in agriculture has reduced crop production, reduced the quality of crops, and even harmed people and livestock. Large areas of farmland have been polluted, reducing the quality of soil.

The consequences of Marine pollution are also very serious, such as oil pollution, causing the death of seabirds and Marine life.

The harm of water eutrophication

Under normal conditions, oxygen has a certain solubility in water. Dissolved oxygen is not only a condition for the survival of aquatic organisms, but also participates in various REDOX reactions in water to promote the transformation and degradation of pollutants, which is an important reason for the self-purification ability of natural water bodies. The discharge of domestic sewage containing a large amount of nitrogen, phosphorus and potassium, the degradation of a large number of organic matter in the water and the release of nutrient elements, promote algae clumping in the water, the growth of plants, the poor ventilation of the water, the decline of dissolved oxygen, and even the appearance of anaerobic layer. It causes a large number of aquatic plants to die, the water surface is black, the water body is smelly and forms a "dead lake", "dead river", "Dead Sea", and then becomes a swamp, but also can lead to red tide phenomenon. This phenomenon is called water eutrophication. The eutrophication water is smelly, dark in color, and has many bacteria. The quality of this water is poor, and it cannot be directly used.

Methods to prevent water pollution

⒈ Strengthen the protection of intakes of drinking water sources

The relevant departments shall delimit the water source areas, set up billboards in the areas and strengthen the greening of water intake outlets. Regularly organize personnel to inspect, eliminate pollution from the root, to achieve the purpose of treating both symptoms and root causes.