Water pollution and its harm
Release time：2015-12-23 08:47:54 Visits：1332
Water pollution, according to different pollutants, affects all aspects of people''s life.
One, the eutrophication of water bodies
Eutrophication is a kind of organic pollution type, such as too much nitrogen and phosphorus nutrients into the natural water body and deteriorating water quality. Into farmland chemical fertilizer, usually about half of the nitrogen fertilizer was not used, into the underground water lakes or ponds, also often make a lot of sewage water body fat. Too many nutrients to promote the phytoplankton in the waters, such as cyanobacteria, diatoms and aquatic plants thrive, sometimes the entire surface is covered by algae and form "splash", after the death of algae and deposited on the bottom, microbes consume a large amount of dissolved oxygen, killing fish and a large number of lack of oxygen. Eutrophication will accelerate the decay of lakes, this to swamp the development.
Marine coastal sea area, eutrophication phenomenon, make the waist dinoflagellates (such as bare ditch algae and noctiluca) such as a large number of breeding, closely together, make the water pink or reddish brown, known as red tides, great harm to the fishery. In recent years, the bohai sea in the north and the south China sea has happened many times.
Second, the pollution of toxic substances
Toxic substances include two categories: one kind is referred to as mercury, cadmium, aluminum, copper, lead, zinc and other heavy metals; Another kind is organochlorines, organophosphorus, polychlorinated biphenyls (PCBS), aromatic amine compounds and other chemical products. Many enzymes depend on proteins and metal ions complexation can play its role, and therefore requires certain trace elements (such as manganese, boron, zinc, copper, molybdenum, cobalt, etc.), however, is not desirable metal, such as mercury and lead, even the quantity of essential trace elements is overmuch, such as zinc and copper, etc., can destroy the balance of the proteins and metal ions, and thus weaken or terminate the activity of some proteins. Such as mercury and lead and some enzymes of the central nervous system in combination with a very strong trend, and therefore easy to cause neurological disorder, such as disease, mental lethargy, coma and even death. In addition, mercury and a kind of interact with genetic material DNA protein into the combination of the specificity, this is mercury poisoning often causes severe birth defects.
These heavy metals combined with protein not only can lead to poisoning, and can cause biological accumulation. Heavy metal atoms to the protein, can''t be drained out, and gradually from the low dose accumulation to high levels, causing harm. A typical example is mentioned of minamata disease in Japan. Through the survey found that the metal in the form of mercury is not very poisonous, most of the mercury can not be absorbed by the digestive tract. However the bacteria in the water body sediment absorbed mercury, the mercury produces chemical reaction, the reaction of mercury and methyl groups produced methyl mercury (Hg - CH3) of organic compounds, it''s different from mercury itself, absorption rate nearly equal to 100% of methyl mercury, toxicity is almost 100 times larger than mercury, and not easy to drain off.
Organochlorine (or chlorinated hydrocarbons) is a kind of organic compounds, one or more hydrogen atoms are replaced by chlorine atoms, the compound is widely used in plastics, electric insulation, pesticides, fire extinguishing agent, wood preservative, etc. Organochlorine has the characteristics of two particularly prone to bioaccumulation, the chemical properties of the extreme stability and high lipid solubility and low solubility in water. Chemical properties of stability is not easy to decompose in the environment, also cannot by organism metabolism. High fat soluble easily absorbed by organism, once in can''t drain out, because the discharge requirements of water-soluble, produce biological accumulation as a result, form a poison. Typical organochlorine pesticides such as DDT, such as the 666, because they cause serious harm of biological and human body has been disabled by many countries.
Third, thermal pollution
Many industrial production process of waste heat to the environment, the environment temperature increase to the point of not ideal or biological does not adapt, known as thermal pollution. Such as two-thirds of the thermal power plant fuel release again in steam condensation process releasing into the surrounding environment and dissipate heat is the most commonly used method by pump pumped the water from the river''s lake, pour on the cooling pipe, and then the heated water is returned to natural water bodies. Heat from the cooling system, through the water itself is enough to kill most organisms. The experiments show that the water temperature has a far-reaching influence on the ecological system of tiny changes.
Fourth, Marine pollution
Along with the development of the population explosion and the production, the Chinese have been varying degrees of pollution and damage to the Marine environment.
Survey in 1980 showed that the annual industrial and living sewage directly discharged into offshore as 6.65 billion m3, each year with the sewage water of poisonous and harmful material for oil, mercury, cadmium, lead, arsenic, aluminum, cyanide, etc. The pesticide quantity coastal counties across the country each year, about a quarter into the offshore, about more than 50000 tons. These pollutants harm is very wide, to the serious pollution of the Yangtze estuary, hangzhou bay and began to endanger China''s largest fishery zhoushan islands.
Marine pollution makes part of the Marine fish death, reduce of biological species, residual poison in the body of aquatic products increased, fishery offshoring, many beaches farm waste. The jiaozhou bay, for example, 1963-1964 gulf intertidal zone has 171 kinds of Marine organisms; Reduced to 30, 1974-1974; Only 17 species in the early 80 s. Laizhou bay whitewater river, whitebait highest annual output of 300000 kg, 1963, about 100000 kg, and now has been largely produce certainly.
Source: the Chinese society of desalination and water reuse
