The 20th Century World Drinking Water Committee, established with the support of the United Nations and the World Bank, pointed out through research that more than half of the world's major rivers are facing the threat of drying up and pollution, and the number of "environmental refugees" caused by pollution in the world reached 25 million from 65,438 to 0999, surpassing the number of refugees caused by war for the first time.
At present, nearly 50 countries in the world are seriously short of water, and 2 billion people have difficulty drinking water. There are more than 50 kinds of diseases caused by the lack of safe and sufficient drinking water in developing countries, with an average of 650,000 water-related diseases occurring every day and 25,000 people dying every day. According to the data of the United Nations Center for Population and Living Environment, at present, residents in developing countries 175 cities do not have adequate water supply. "Pollution is the primary factor that eventually leads to the increasingly serious urban water supply crisis."
As a developing country, the water pollution situation in China is very serious. 90% of urban water sources in China are polluted to varying degrees. Every year, 590× 108t sewage pollutes rivers, lakes and reservoirs, and the shortage of water resources will exist for a long time. According to a report (1999) published by the State Environmental Protection Bureau, 30 of the 7 1 water sources in 32 key cities in China did not meet the second-class drinking water standard, accounting for 42% of the total. Every year, a large number of domestic sewage, industrial sewage and 1.5× 108t fecal sewage are discharged into various natural water bodies, of which more than 95% are untreated. The surface water of more than 90% cities in China is seriously polluted. About 700 million people are drinking water with excessive Escherichia coli content, 654.38+0.7 billion people are drinking water polluted by organic matter, and nearly 300 million urban residents are drinking unclean water.
Because of water pollution, aquatic life in the Yangtze River is in jeopardy. According to incomplete statistics, there are more than 40,000 pollution sources in the whole basin, and the daily discharge of industrial wastewater and urban domestic sewage reaches 1.069× 1.04t, accounting for 75% of the sewage received in the main stream, making the total pollution zone along the Yangtze River more than 500 kilometers. Since February 25, 2000, the water body of Hanjiang River, a tributary of the Yangtze River, began to change, and algae proliferated rapidly. By March 2, the algae content had soared from 3 million per liter to 44 million per liter, a record high, and an extremely rare "water bloom" phenomenon appeared in the inland river basin of China. Pollution has caused serious harm to plankton, benthos and other fish food organisms, destroyed the food chain of fish and directly affected the growth of fish.
Environmental pollution is becoming more and more serious, which leads to changes in the composition of human diseases. Infectious diseases in the past have been replaced by non-infectious diseases such as cardiovascular and cerebrovascular diseases, public hazards and occupational diseases. Environmental pollution has aroused great concern of governments and people all over the world.
1. Migration and transformation law of environmental pollution
Environmental pollution can be divided into three categories according to its attributes:
1) First, chemical pollution is the main pollution source in the environment, which poses the greatest threat to human health and has the widest impact. Common are all kinds of harmful gases, toxic heavy metals, all kinds of pesticides and petrochemical pollutants.
2) Biological pollution, including various pathogenic microorganisms and parasite eggs.
3) physical contamination, often referring to noise and electromagnetic radiation.
(1) Migration and transformation of pollutants in the environment
The migration and transformation of pollutants in the environment refers to the migration and transformation process of pollutants discharged into the natural environment through physical, chemical and biological actions. This migration, transformation, circulation and enrichment have certain regularity, depending on the nature of pollutants and their environmental conditions. In abiotic environment media, pollutants always migrate from high concentration to low concentration; In organisms, accumulated chemical pollutants are easy to be enriched in organisms, so that pollutants can be concentrated step by step. After the death of organisms, these pollutants eventually return to the environment through corruption and decomposition. The transformation of pollutants in the environment includes degradation and synthesis. There are both inorganic and organic substances.
The migration and transformation mechanism of pollutants in the environment is very complicated, which can be summarized into three aspects: physical migration and transformation (dilution and precipitation), chemical migration and transformation (neutralization, redox, photochemical reaction) and biological migration and transformation (biodegradation, biotransformation, biological accumulation, concentration and amplification).
(2) Migration and transformation of pollutants in human body
Whether environmental pollutants (poisons) can harm human health after acting on human body depends on the concentration of pollutants and the metabolic rate of pollutants in human body. After pollutants enter the human body, on the one hand, they destroy the normal physiological functions of the human body, poisoning the human body or causing potential harm; On the other hand, the human body degrades pollutants and excretes them through various defense mechanisms and metabolic activities. Therefore, it is very important to understand the metabolic process of environmental pollutants in human body for studying the interaction between pollutants and human body. The metabolic process of pollutants in human body includes absorption, migration, distribution transformation and metabolism.
The process of environmental pollutants entering the blood through the human cell membrane is called absorption. The absorption routes are mainly respiratory tract, digestive tract and skin. Blood is the main medium for pollutants to migrate in human body. The combination of pollutants with which components in blood will affect their migration speed in blood.
The distribution of pollutants in human body is closely related to the toxicity, solubility, existing state, metabolic characteristics and special conditions of organs. For example, the invasion rate of mercury vapor inhaled through the lungs is relatively high with the blood flowing to the brain tissue, which is one of the important reasons why mercury vapor mainly causes brain tissue damage; Soluble beryllium salts are mainly deposited in bones after inhalation, and insoluble beryllium salts are mainly left in the lungs.
The process of transforming environmental pollutants into other derivatives in the body is called biotransformation. The result of biotransformation is often to enhance the polarity of pollutants and become more water-soluble compounds. Metabolites or pollutants are easily excreted, and their toxicity is relatively weakened or disappeared, but a few pollutants are more toxic after biotransformation.
Excretion is the process that pollutants are excreted by their metabolites, and it is the last link in the whole process of human metabolism. The main way of excretion is through the kidney into urine or through the liver bile into feces. In addition, people's breathing, sweat, lotion, saliva, tears and alopecia are also excretion routes. The kidney is the most important way to excrete pollutants, which exceeds the sum of all other ways.
2. Environmental pollution and human health
The pollutants that have been harmful to human health for a long time and have a wide range of influence are mainly chemical pollutants, and biological pollutants such as parasites, bacteria and viruses will also have a light or heavy impact on human health. Chemical pollutants can be divided into gas pollutants, liquid pollutants and solid pollutants according to their forms. It can be divided into inorganic pollutants and organic pollutants according to chemical composition. The harm of chemical pollutants to human body is mainly manifested in the long-term effect of low concentration, the comprehensive effect of many factors and the long-term potential effect.
Any environmental pollution will directly or indirectly affect human health. The degree of influence depends on the degree of environmental pollution, the duration of pollution and the human body's tolerance. Some environmental pollution can cause serious acute damage in a short time, while others take a long time to show chronic damage to human body, and even affect the health of future generations through heredity. According to the degree of human poisoning and the time of symptoms, the impact of environmental pollution on human health can be divided into three types: acute impact, chronic impact and long-term impact.
The acute effects are mainly acute or subacute poisoning events. For example, in April of 1983, pesticide plant, jiangling county City, Hubei Province, China, discharged arsenic-containing wastewater, which seriously polluted nearby drinking water sources, causing acute arsenic poisoning in 1046 workers and farmers. Poisoned people have symptoms such as nausea, vomiting, limb weakness, eyelid edema, and many people have symptoms such as coughing up blood, vomiting blood, and bloody stool. This kind of influence is often serious and easy to attract people's attention. The 1952 London fog and haze incident and the 1984+02 Bhopal gas leakage accident in India, which shocked the world, both caused thousands of deaths.
When the pollutant concentration is low and it acts on human body for a long time, it can cause chronic poisoning. Because of the long incubation period of chronic poisoning, the progress of the disease is not obvious, and it is easy to be ignored. Once symptoms appear, it will often cause irreparable consequences.
The long-term impact of environmental pollution on human health is only a special case of chronic impact, and its harmful results may be revealed in a longer time. Long-term effects are mostly carcinogenic and teratogenic, so it is very harmful.
3. Countermeasures for prevention and control of environmental pollution
From the perspective of environmental geochemistry, environmental pollution is nothing more than the superposition of some man-made metallic and nonmetallic elements and various inorganic and organic compounds on the natural geochemical background value. Therefore, most basic theories, research methods and working methods of geochemistry can be used to study environmental pollution. Using the theory and method of environmental geochemistry, it is another historical task for geoscientists to systematically study the migration, transformation, distribution and enrichment of chemical elements in the lithosphere, PEDOSPHERE, hydrosphere, atmosphere, biosphere and all layers, to theoretically clarify the mechanism and influence of environmental pollution, to study countermeasures and to guide comprehensive environmental management.
In order to effectively prevent and control environmental pollution, the following work must be carried out:
1) By means of regional environmental geochemical mapping, the environmental quality is evaluated from the geochemical point of view through the investigation of regional environmental background, the nature of pollutants, pollution sources and pollution scope.
2) From the perspective of environmental geochemistry, the interaction between man-made pollutants and the natural environment, its impact on the global environment and its development trend are studied.
3) By studying the geochemical effects of pollutants and using the geochemical characteristics of pollutants, the comprehensive control scheme of environmental pollution is determined.
4) Geochemical study of nuclear waste pollution and disposal.
5) The investigation of environmental geochemical background values and the determination of environmental quality parameters in the proposed economic development zone provide a basis for selecting a reasonable comprehensive treatment scheme.
To control environmental pollution, we must treat both the symptoms and the root causes. Strict implementation of pollutant discharge standards, all kinds of toxic and harmful substances must be treated harmlessly first; Vigorously build urban sewage treatment plants to treat domestic sewage and industrial wastewater. In the development of geology and mineral resources, the types and properties of pollution that may be caused by development should be predicted according to the combination law of mineral elements, and prevention measures should be put forward; For mines that have caused pollution, it is necessary to strengthen monitoring, find out the pollution type, pollution degree and influence scope as soon as possible, formulate remediation plans as soon as possible, and carry out pollution control work.