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Talking about water pollution

Today, with the rapid development of the whole world, the demand for water is increasing gradually. At the same time, the waste of water resources, soil erosion and water pollution also threaten the survival and development of mankind. Among them, water pollution is the most serious

Besides water itself, water also includes aquatic organisms and sediments. Natural water itself has the ability to purify pollutants, which is called self-purification of water. According to the purification mechanism, the self-purification of water can be divided into physical purification, chemical purification and biological purification. The self-purification process of water is very slow and its self-purification ability is limited. When pollutants enter the water body, its content exceeds the self-purification ability of the water body, which causes the water quality to deteriorate and destroys the original use of the water body, which is called water pollution.

The reason is largely due to the rapid development of industrialization and urbanization after the British industrial revolution in the19th century. On the one hand, the pollutant discharge of industrial wastewater and domestic sewage greatly exceeds the self-purification ability of water bodies, which makes the rivers, lakes and seas on the earth increasingly polluted; On the other hand, with the development of science, technology and productivity, there are more and more synthetic new chemical substances, many of which have mutagenic, teratogenic and carcinogenic effects. Once the water body is polluted, it will stay in the water for a long time, and the self-purification ability of the water body cannot decompose these synthetic new chemical substances.

The main pollutants in water can be divided into suspended solids, colloidal substances and dissolved substances according to their existing States.

Suspended solids are mainly silt and clay, mostly from soil and urban street runoff, and a small amount from washing wastewater.

Colloidal substances are mainly various organic substances, the biological part of organic substances in water, and the total coliform group is one of the indicators to test the existence of pathogenic microorganisms and the pollution degree of water. Dissolved oxygen concentration in water is one of the important indexes to measure the pollution degree of organic non-biological parts in water. The lower the dissolved oxygen concentration DO, the more serious the organic pollution. When DO is less than or equal to 4, the survival of fish will be affected and even die. Two more commonly used indicators of organic pollution are chemical oxygen demand (consumption) COD and biochemical oxygen demand (consumption) BOD. COD represents the amount of oxygen required (consumed) to oxidize organic matter in water samples with chemical oxidant, and the unit is mg/L. BOD represents the amount of dissolved oxygen consumed in the process of oxidizing all organic matter in water samples by microorganisms, and the unit is mg/L. The higher these two indicators are, the more serious the water pollution is.

Dissolved substances are mainly salts (chloride, sulfate, fluoride, etc. ) and dissolved gases (carbon dioxide, hydrogen sulfide, etc. ) completely soluble in water.

The main pollution of water pollution in China is oxygen-consuming organic matter, and the most harmful are heavy metals and biodegradable organic matter.

Not long ago, an experiment was conducted in Xixi River, Hangzhou. The COD (Mn) in the water sample was 28.07, which was nearly double the normal standard (see the attached experimental report for details). Environmental pollution is a major problem facing the world today, and water pollution has become the most important problem. The present situation of Xixi River is definitely not caused by people in a short time, but by the continuous pollution of coastal residents for decades. The oxygen consumption index is as high as 28.07, which is heartbreaking. Now, even fish can't survive in the crystal clear river water decades ago. How terrible and pathetic this is! A few years ago, factories along the river discharged hundreds of millions of industrial wastewater into the river every year, and garbage disposal sites dumped more than 10 thousand tons of domestic garbage into the river every year. Coupled with the uncontrolled discharge of domestic wastewater from surrounding residents, clean water has finally become sewage, smelly water and stagnant water. Nowadays, although the Hangzhou municipal government has invested huge manpower, material resources and financial resources to improve the water quality of Xixi River and shut down all factories and garbage disposal sites along the river, with the increase of residential areas, the discharge of domestic wastewater has greatly increased, making it impossible to fundamentally improve the water quality. All this has made all the "initiators" suffer. Especially in summer, the river gives off a stench, attracting mosquitoes and flies all over the sky along the river. Whenever the sluice of this river is closed, garbage piles up on the river. How well this scene matches the reputation of "Top Ten Health Cities in China"!

However, as the cleverest animal on earth, human beings must see this tragedy happen and even make up their minds to deal with it. Why is this? This has not only caused great pollution and destruction to water, environment and nature, but also wasted financial, material and human resources, and slowed down the economic development and the improvement of people's living standards in a region and even a country to some extent.

During the period of 1992, Yang Zhenhuai, then Minister of Water Resources, published the Report on Various Types of Soil Erosion in China, which was uploaded: As of June 1992, the area of various types of soil erosion in China was 4.92 million square kilometers, equivalent to 5 1. 15% of the total land area. Such amazing figures have told people that China is one of the countries with the most serious soil erosion in the world today, which shows the preciousness of water resources in China.

Nevertheless, many rivers are polluted to varying degrees. Xixi River in Hangzhou has long been "notorious". In addition, the canals and Guxin River in Hangzhou are as famous as Xixi River.

In Bangkok, the capital of Thailand, the Chao Phraya River, known as the mother river of Thailand, is now as black as ink and stinks as Xixi River. When you stir a stick with it, methane will keep pouring out. The reason why Menan River has fallen into such a situation is that hotels along the coast have discharged a lot of domestic sewage and waste oil from cargo ships. 1On the eve of the Asian Games in 1998, to make matters worse, the construction waste of cars was poured into the river. All this finally makes Thailand's "mother river" unrecognizable.

A large number of facts once again prove to mankind that water pollution is caused by human beings themselves, and all the consequences must be borne by human beings themselves.

Serious water pollution has attracted great attention from governments all over the world. How to protect the environment and limited water resources is an urgent problem.

In China, all pollutant discharge units in Taihu Lake Basin have achieved the discharge standards before 1998 12 3 1. This is enough to show that our government attaches importance to water resources protection.

Now, all actions are only temporary solutions, not permanent solutions. If we want to completely solve this worldwide problem, it will definitely not be completed in three to five years. We must protect unpolluted water bodies while treating polluted water bodies, fundamentally improve human quality, enhance human awareness of environmental protection, and make contributions to the benefit of future generations.

Nature needs human beings, and human beings need nature more. The environment is polluted, the ecological balance is destroyed, and the victims are human beings. For ourselves, for all living things and for the earth, human beings must solve environmental problems. Start with small things and make the air fresh! Turn the sky back to blue! Let the river clear again! Return the mountain to green! Let the earth return to health!

Attachment 1: water quality testing experiment report

Experimental Name: Determination of Chemical Oxygen Consumption in Water

Experimental purpose: 1 to consolidate the titration results.

2, understand the preliminary knowledge of water and water pollution.

3. By measuring the chemical oxygen consumption in water, we can know the pollution degree of different water bodies, thus stimulating and enhancing the awareness of environmental protection.

Experimental principle: The chemical oxygen consumption (COD) in water is calculated by using the principle of redox reaction. When DO≤4, fish can't survive.

Experimental instruments: iron frame, alcohol lamp, asbestos net, pipette, ear washing ball, 100ml measuring cylinder, 100ml measuring cylinder, beaker, conical flask, rubber-tipped dropper, acid burette, alkaline burette, 100ml acid volumetric flask,/kloc-

Experimental drugs: potassium permanganate solution, dilute sulfuric acid, sodium oxalate solution, distilled water and river water samples.

Source of water sample: Xixi River in Hangzhou

Experimental operation: KMnO4 solution and Na2C2O4 solution with the concentration of 0. 1N were respectively prepared into 1 and 0.0 1N solutions, and placed in 100ml volumetric flask;

2. Pour the prepared solution into the burette and set it to zero (KMnO4 solution in acid burette and Na2C2O4 solution in alkaline burette);

3. Take 100ml fully shaken wastewater sample and put it in a 250ml conical flask, and add 5 ml H2SO4 solution prepared with 1: 3 to mix it evenly;

4. Add KMnO4 solution with the volume of V0 into the burette, shake it well, and immediately put it into a boiling water bath for heating (the level of the boiling water bath is higher than that of the solution in the bottle). In this process, the solution must be light red, otherwise KMnO4 solution should be added to the bottle;

After 5.30 minutes, take out the conical flask and drop 10ml 0.0 1N na 2 c2o 4 standard solution into it while it is hot. Immediately after shaking, titrate with 0.0 1N potassium permanganate solution until the solution is pink and does not fade for half a minute, and record the volume of 0.0 1N potassium permanganate solution consumed by titration.

6. Drop 10ml 0.0 1N Na2C2O4 standard solution into the solution, titrate with 0.0 1N KMnO4 solution until the solution turns pink, record the volume of KMnO4 solution consumed by titration, and record it as V2, so as to determine the correction coefficient k = k =10. ;

7. Calculate DO index: DO = [(v0+V1) k-10.00] * 0.01* 8 *1000/100; (k value should be slightly less than1);

8. Perform three or four parallel operations.

Data from three parallel experiments

V0 V 1 V2 K DO

First time 37.9617.1912.68 0.789 26.438+0

Second time 38.7715.7912.26 0+06 27.62

Third time 33.2816.5110.55 0.948 29.76

The average is 28.07.

Appendix 2: References

1, 1999 65438+ 10, China Environment News.

2. Soil and Water Conservation Department of the Ministry of Water Resources "Various Soil Erosion Areas in China"

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