Pollutants arePollution sourceWhen discharged into the environment, new pollutants are generated under physical, chemical or biological action（Secondary pollutants）And produce
Secondary pollution
Re contamination of.Generally, the hazard ratio of secondary pollutionPrimary pollutionSerious, and because of its complex formation mechanism, it is difficult to prevent and control.Secondary pollution（Photochemical smog）It is discharged into the atmosphere by vehicles, factories and other pollution sourceshydrocarbon(HC) andnitrogen oxide (NOx), etcPrimary pollutant, occurs under the action of sunlightchemical reaction, generatingozone(O3)、aldehyde、ketone, acidPeroxyacetyl nitrate(PAN) and other secondary pollutantsPhotochemical reactionFormed by the mixture of primary and secondary pollutants of the processsmokeThe pollution phenomenon is called photochemical smog.E.g. USALos AngelesThe photochemical smog is caused by the photochemical reaction of hydrocarbons and other compounds discharged into the atmosphere by human production activities and vehicles under the action of sunlight, which further generates a variety of ozone based compoundsStrong oxidantThus causing more serious air pollution, namely secondary pollution.[1]
toxicity
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Secondary pollution
Photochemical smogAlthough the composition of formaldehyde is very complex, the secondary pollutants harmful to animals, plants and materials are ozone, PAN, acrolein, formaldehyde and so on.The main injuries to people and animals are irritation of eyes and mucous membranes, headache, respiratory disorders, deterioration of chronic respiratory diseases, abnormal lung function of children, etc.The plant is damaged by ozone. At the beginning, the epidermis fades and appears waxy. After a period of time, the pigment changes and reddish brown spots appear on the leaves.PAN makes the back of the leaves silver gray or bronze, affecting the growth of plants and reducing the resistance of plants to diseases and pests.Ozone, PAN, etc. can also cause aging and embrittlement of rubber products, fade dyes, and damage paint, textile fibers and plastic products.[1]
Production process
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In the 1940s, in the United StatesCaliforniaPhotochemical smog was first discovered in Los Angeles.1951 AJ. Hagen was the first to point out that ozone (O3) is generated by the photochemical reaction of the mixture of nitrogen oxides, hydrocarbons and air.Later FW. Winter found that ozone andUnsaturated hydrocarbonThe chemical reaction products (such as hydrocarbons in automobile exhaust) have the same harmful effect as Los Angeles smog.The main source of the active organic matter and nitrogen oxides that form ozone is the exhaust gas from automobiles.Through the simulation experiment on the formation of photochemical smog, it has been preliminarily clear that there are mainly the following processes in the interaction between hydrocarbons and nitrogen oxides: 1. The photolysis of NO2 in the polluted air is the initial reaction of the formation of photochemical smog.2. Hydrocarbons are oxidized by HO, O and other free radicals and ozone, resulting in the formation of aldehydes, ketones, alcohols, acids and other products as well as important intermediate products such as RO2, HO2, RCO and other free radicals.3. Peroxy radicals cause the conversion of NO to NO2, and lead to the formation of O3, PAN, etc.Ozone, aldehyde, ketone, alcohol, PAN, etc. generated in photochemical reaction are collectively referred to asPhotochemical oxidant, represented by ozone, so the indicator of photochemical smog pollution is the increase of ozone concentration.[1]
principle
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The formation and concentration of photochemical smog are directly determined by the automobileexhaustIn addition to the quantity and concentration of pollutantsSolar radiation intensity, weather, geography and other conditions.The intensity of solar radiation is a main condition. The intensity of solar radiation mainly depends on the height of the sun, that is, the projection angle between the solar radiation line and the ground, andAtmospheric transparencyEtc.Therefore, the concentration of photochemical smog, except thatdaily variationBesides, it is also affected by the latitude, altitude, season, weather, air pollution and other conditions of the place.Photochemical smog is a kind ofCyclic process, generated during the day and disappeared in the evening.The actual measurement of the atmosphere in the polluted area shows that the primary pollutant CH andnitric oxideThe maximum value of is in the morning rush hour. With the decrease of NO concentration, NO2 concentration increases. Secondary pollutants such as O3 and aldehydes accumulate with the increase of sunlight and the decrease of NO2 and HC concentration.Their peaks are generally 4-5 hours later than the NO peak.The change of PAN concentration with time is similar to that of ozone and aldehydes.Urban and suburbanPhotochemical oxidantThe concentration is usually higher than that in rural areas, but the concentration of photochemical oxidants in many rural areas is higher, sometimes even higher than that in cities.This is because the formation of photochemical oxidants not only includes the photochemical oxidation process, but also includes the diffusion and transportation process of primary pollutants, which is the result of two processes.Therefore, the pollution of photochemical oxidants is not only a problem of cities, but also a regional pollution problem.Short distance transportationThe maximum concentration of O3 can occur downwind of the pollution source. Mesoscale transport can diffuse ozone to downwind of hundreds of kilometers. If combined with the atmospheric high-pressure system, it can transmit hundreds of kilometers[1]。
difference
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Primary pollutant
Also called“Primary pollutants”Is a pollutant discharged directly into the environment by the pollution source, and its physical and chemical properties have not changed.Environmental pollution is mainly caused by primary pollutants, whose sources are clear and can be controlled by taking measures.[1]
Secondary pollutants
Also called“Secondary pollutants”It refers to a new pollutant whose physicochemical characteristics are different from those of primary pollutants when primary pollutants change under physical, chemical or biological effects, or react with other substances in the environment, which is generally more harmful to the environment and human body than primary pollutants.For example, inorganic mercury compounds in water can be transformed into more toxic methyl mercury compounds through microbial action, which are easy to be absorbed into the human body, not easy to degrade, excreted slowly, and easy to accumulate in the brain.Atmosphericsulfur dioxideAnd water vapor can be oxidized to sulfuric acid, and then generateSulfuric acid fogIts stimulating effect is 10 times stronger than that of sulfur dioxide.[1]
Household appliance pollution
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summary
Secondary pollution of household appliances
Electrical appliances prone to "secondary pollution" are often contacted or used by us, such as washing machines, water dispensers, air conditioners, humidifiers, water heaters, microwave ovensair cleanerEtc.According to the survey, 60.2%% of the washing machines that have been used for more than half a year can detect mold inside, so the washing machines have become a source of "secondary pollution".The mold growing in the inner cylinder will not only pollute clothes, but also cause various diseases by contacting different parts of the human body.Health hazards caused by pollution[1]
harm
Air pollution and water pollution caused by household appliances are very common in our lives, which has brought great hidden dangers to our health.“epidemiological investigation And research shows that,indoor air pollution With respiratory diseasesCardiovascular disease, weakened lung function, asthma and other diseases have a great relationship, but also increased the morbidity and mortality. "Zhao BinSo said the associate professor.The "secondary pollution" caused by air conditioners often causes dizziness, coma and even decreased immunity. The medical community calls this pathological reaction“Air conditioning syndrome”The biggest victims of indoor air pollution are children, pregnant women, the elderly and chronic patients, especially children are more vulnerable to indoor pollution than adults.Children's bodies are growing,Respiratory capacityBy weight, it is nearly 1/2 higher than that of adults, and they live indoors most of the time, so it is difficult to detect the pollution damage, and when they find the problem, it is irreparable.The clothes are easy to be polluted after the washing machine grows mold. Not only the clothes cannot be washed clean, but also they may cause disease.Especially when the close fitting clothes are contaminated by mold, it may also cause relatively bad harm to women's personal health.It is reported that although there is no clear data indicating the relationship between gynecological diseases and the "secondary pollution" of washing machines, many gynecologists often encounter some innocent patients in the daily outpatient service of hospitalscolpitis mycoticaWhen we investigate the reasons, we can't help thinking about the "secondary pollution" of washing machines.The harm of "secondary pollution" of drinking fountains is even more obvious. After drinking contaminated water that breeds bacteria, the harm to human body is very obvious, and it is easy for people to catch various diseases.[1]
Countermeasures
Secondary pollution of household appliances
How to deal with the "secondary pollution" of air conditioners reflected by consumers,Tsinghua UniversityBuilding Environment and Equipment Research InstituteZhu YingxinThe professor pointed out: "The accumulated dust from the filter nozzle of the return air outlet of the household air conditioner enters the air again or the air conditioner will breed mold, polluting the indoor environment; the air conditioner will breed mold, which has a sour smell. The solution to the accumulated dust is that the user regularlyClean the filter, try to clean it once a month, it is easy to disassemble and clean it yourself;For mold, the user cannot clean it himself, so he can only ask the after-sales service unit to clean it. ""For ordinary people, it is necessary to develop reasonable and correct use habits." Associate Professor Zhao Bin said that for washing machines, they should be placed in ventilated and bright places;Secondly, underwear and coat should be washed separately to reduce cross contamination of clothes;Finally, after washing clothes, you should open the cover of the washing machine to ventilate for a period of time to keep the inside dry, so as to promote the volatilization of residual water and inhibit the growth of microorganisms. In addition, clothes should be taken out to dry immediately, instead of being stuffy inside.If conditions permit, the washing machine can be cleaned regularly after 3 months or half a year of use;The water dispenser should be cleaned regularly to ensure the use of water of good quality and avoid long-term storage of water without drinking;Regular cleaning is also essential for humidifiers and purifiers.[1]
Future initiatives
"The future measure is to develop truly healthy and green household appliances on the premise of saving costs (such as reducing consumables) and reducing operating costs," said Associate Professor Zhao Bin,"In the future, a multidisciplinary team should be established, including household appliance R&D personnel, indoor environmental engineering, health and hygiene researchers, and a comprehensive technical and sanitary specification should be established. Under such a framework, household appliance R&D, production, inspection and even the use rules should be formulated."[1]
Drinking water pollution
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survey
Secondary pollution of drinking water
At present, China's domestic drinking water has been seriously polluted, mainly from water source pollution and secondary pollution.With a large number of industrial waste, agricultural pollutantsDomestic pollutantsThe pollution of groundwater and surface water in China has become increasingly serious due to a large number of untreated discharges, resulting in water pollution of drinking water sources.According to the investigation of the Ministry of Water ResourcesWastewater dischargeThe total amount reached 71.7 billion tons, of which 2/3 were discharged directly into water bodies without treatment, resulting in 90% of urban surface waters being polluted to varying degrees.According to China'senvironmental qualityIt was announced that 59% of the seven major water systems in the country are not suitable for drinking water sources.[1]
Due to the relatively backward equipment and process, the conventional treatment processes of coagulation, sedimentation, coarse filtration and chlorination in China's waterworks can no longer meet the requirements.In May 2007, the most serious cyanobacteria incident broke out in Wuxi, Jiangsu Province. The tap water from the tap smelled foul, which fully proved this.At the same time, the secondary pollution of the water supply network is inevitable.As the pipe network is in disrepair for a long time, the sanitation management and maintenance of the pipe network, water storage tank and other water supply facilities are not in place, and red waterBlackwater, white and turbid water.There are more and more sediments in the water pipe network, breeding bacteria, viruses, etcBiological pollutionThe emergence of red worms, leeches, etc., makes the water quality of terminal tap water unsafe.[1]
source
Secondary pollution of drinking water[1]
1. The water tank of high-rise building is a breeding ground for bacteria and lichen
2. In addition, rusty water pipes are also one of the main reasons for pollution.
Secondary pollution of drinking water
The pollutants in water are mainly divided into the following categories:[1]
1. Suspended solids: sediment,rust, visible to the naked eye
6. Radiation particles: radiation particles produced in the nuclear industry and nuclear medicine
endanger one's health
world health organizationAccording to the statistics of WHO, 80% of the global diseases and more than 1/3 of the deaths directly come from unclean drinking water.It is true that about 50% of the 18 million children who die each year are related to drinking water pollution.It is estimated that in the future ten years, on average, about 6000 children and adults will die from dirty drinking water every day.Long term use of unclean water will lead to digestive diseases, infectious diseases, various skin diseases, diabetes, cancer, lithiasis, cardiovascular diseases and other diseases, and endanger human health.For example, in waterMycobacterium tuberculosisCause tuberculosis,RotavirusAnd gastroenteritis virus can cause gastroenteritis, cryptosporidium can causeCryptosporidiosis, Algae productionAlgal toxinsAfter drinking, it will cause poisoning. In light cases, it will cause gastroenteritis, and in severe cases, it can cause death.In addition, various chlorine or phosphorus containingOrganic pesticideMost of them have carcinogenic effects, and can cause esophageal cancer, gastric cancer, liver cancer, blood cancer, etc. Many chlorohaloalkanes have carcinogenic, teratogenic and mutagenic effects, posing a very serious threat to human health.[1]
People's governments at or above the provincial level may demarcate the table of drinking water according to lawWater source protection area。The surface water source protection of domestic and drinking water is divided into Grade I protection zone and other protection zones.A certain water area and land area can be demarcated near the surface water source intake of domestic and drinking water as a Class I protection area.Outside the first grade surface source protection zone for domestic and drinking water, certain water areas and land areas may be designated as protection zones of other grades.Protection zones at all levels should have clearGeographical boundary。It is forbidden to discharge sewage into the water bodies of the first grade surface source protection zones for domestic and drinking water.Tourism, swimming and other activities that may pollute the water body of domestic and drinking water are prohibited in the first grade surface source protection zone for domestic and drinking water.It is prohibited to build or expand construction projects unrelated to water supply facilities and protection of water sources in the first grade surface source protection zone for domestic and drinking water.The people's government at or above the county level shall, within the limits of its authority as prescribed by the State Council, order the removal or treatment of the sewage outlets that have been set up in the first grade surface sources protection zone for domestic and drinking water within a time limit.[1]
