In view of the increasing popularity of "green environment", the pollution hazards caused by library buildings have seriously affected the indoor environmental quality. It is pointed out that avoiding or reducing the generation of pollutants from the source is the fundamental point to control indoor air pollution during the reconstruction and expansion of libraries and new buildings. We can control or even eliminate pollution sources by adopting reasonable methods, such as using green building materials, decorative materials, green chemical products, etc. At the same time, we can use natural forces to send fresh air or purified air indoors to eliminate indoor air pollutants, reduce the concentration of harmful substances in indoor air and prevent indoor environmental pollution.
In the mid-1990s, due to the in-depth development of China's higher education reform, the number of college students has doubled, the utilization rate of information resources by students has soared, and the contradiction of insufficient university libraries has become increasingly prominent. Therefore, the scale and quantity of library construction show a trend of rapid development. Take the universities in Hubei Province as an example. In the past three years, 65,438+00 libraries have been built or under construction. Among them, 60%~70% of the building area is over 20,000 m2, and the largest building area is 50,000m2 [1]. The upsurge of building new libraries has adapted to the demand for information resources in China's higher education, which is not only the inevitable growth of the overall demand for knowledge in the development of knowledge economy, society and science and technology, but also the concrete embodiment of the library's implementation of the "people-oriented" service concept. Creating a safe, comfortable and environmentally friendly library environment is an important aspect that cannot be ignored in library construction. The library environment in paper format includes outdoor environment and indoor environment, and the indoor environment of the library is mainly discussed here.
1. The influence of library indoor environment on readers The indoor environment of library mainly refers to the environment of reading room (book reading room, electronic reading room, audio-visual reading room), and also includes a series of factors such as atmosphere, furnishings, layout and air quality. As a place for readers to study, the indoor environment quality of the library should meet higher requirements. People's understanding of indoor environmental quality has gone through a long time. From the initial understanding of the environmental quality of preventing occupational diseases to the increasingly serious indoor environmental pollution exposed by closed buildings, people began to pay more and more attention to indoor environmental quality [2]. The functional division, spatial scale, temperature, ventilation and air quality of library buildings affect the indoor environmental quality. Among many factors, air quality is an important factor that affects the indoor environment, and it is considered to be the environmental factor that has the greatest impact on human health. Indoor environment is related to every reader's physical and mental health, and high-quality, fresh and pleasant air is to meet the needs of human comfort and health. The fresh air in the library can make readers feel quiet, produce a sense of tranquility and elegance, and stimulate readers' imagination and creativity. However, indoor air pollution will do harm to readers' physical and mental health, causing headaches, eye, nose and throat discomfort, and it is difficult to concentrate, which will reduce readers' learning efficiency for a long time. At present, there are two main factors that affect the indoor environmental quality of reconstruction and new libraries: one is indoor pollution caused by library building materials, mainly radioactive pollution such as radon pollution; The second is the pollution caused by decoration materials, which is also the most prominent and problematic indoor pollution at present. The main pollutants are formaldehyde, benzene and benzene series.
2. Harm of indoor air pollution to health Indoor environment is the environment with the closest relationship and the longest contact time in people's lives. Indoor air pollution is closely related to decoration materials. For indoor decoration materials, the state has formulated corresponding standards (GB 18580-200 1 to GB 18588-200 1), and the pollution sources that affect the indoor environment mainly come from decoration materials that do not meet the standards. Among these decorative materials, formaldehyde, benzene and benzene series have the most obvious influence.
2. 1. Formaldehyde and its harm Formaldehyde (HCHO) is the simplest aldehyde with volatile characteristics, with a melting point of -92℃ and a boiling point of-19.5℃. Formaldehyde is a colorless gas with pungent smell, slightly higher density than air, and easily soluble in water at room temperature. Commonly used is 40% (mass fraction) aqueous solution or paraformaldehyde. Under normal pressure, when the temperature is higher than 150℃, formaldehyde is deCOmposed into methanol and co, and it is easily catalyzed into CO2 when there is light. Formaldehyde easily reacts with tracers and pollutants in the air. When there is no NO2 in the daytime, the half-life of formaldehyde is 50 minutes, and when there is NO2, its half-life drops to 35 minutes. Formaldehyde has a strong stimulating effect on skin and mucosa, and can cause selective damage to vision and retina. When its mass concentration is 1mg/m3, it can be smelled by people. Long-term exposure to formaldehyde can cause memory loss, drowsiness and other neurasthenia symptoms, which can cause genetic material mutation and damage chromosomes. Table 1 gives the dose-response relationship between formaldehyde exposure and health effects [3]. Table 1 Dose-response relationship table between formaldehyde exposure and health effect 1 Relative amount of formaldehyde exposure and health effect reflection /(mg? M-3) has no irritating and uncomfortable reaction to human body 0~0.05~ 1.0 odor threshold 0.05~ 1.5 neurophysiological effect 0.0 1~2.0 eye irritation reaction formaldehyde mass concentration /(mg? M-3) human reaction 0. 1~25 upper respiratory tract stimulation reaction 5.0~30 respiratory system and lung stimulation reaction 50~ 100 pulmonary edema and pneumonia >: 100 death.
2.2. Benzene, benzene series and their hazards Benzene, toluene and xylene are colorless, aromatic, volatile and flammable liquids, which exist in the air in vapor state. Poisoning reactions are generally caused by inhalation of steam or skin absorption. Benzene is a moderately toxic substance. Chronic poisoning is mainly harmful to hematopoietic tissue and nervous system, while acute poisoning is mainly toxic to central nervous system. If you are exposed to toluene and xylene for a long time, it will cause chronic poisoning and neurasthenia symptoms such as headache, insomnia, listlessness and memory loss [3]. Table 2 lists the dose-response relationship between exposure to benzene and benzene homologues and health effects [3]. Table 2 Dose-response relationship between benzene and benzene series exposure and health effects Table 2 Cumulative amount of benzene and benzene series as health storage and mass concentration of benzene and benzene series /(mg? M-3) Classification of exposure range of irritation and discomfort 0.2 Non-irritation and discomfort 0.2~3.0 When combined with other exposure factors, irritation and discomfort may occur; When combined with other exposure factors, irritation and discomfort occur; When combined with other exposure factors, headache and discomfort occur >; In addition to headache, other neurotoxic effects may occur in a moderate range.
2.3. Radon pollution and its harm Radon is a naturally occurring radioactive gas, which comes from the radioactive decay of uranium in nature. Radon with high content can be found in soil, granite and shale containing uranium. Radon is an inert gas with no chemical activity, which is the decay product of radioactive nuclide uranium decay series. It is a colorless and odorless radioactive gas, and its density is 7.5 times heavier than air. Its decay parent uranium -238 is widely found in the earth's crust, with a half-life of 4.47 billion years ... Uranium -238 decays into radium -226 through a series of processes, with a half-life of 1602a. According to the annual report of national environmental statistics in 20001year, the radon content in the national ambient air is 14.3~4 1.6Bq/m3. Radon is very penetrating and can move freely in the soil and rocks under the foundation of a house. It can enter the room through cracks in mud floor, concrete floor, joint surface and cracks or holes in hollow brick wall. Radon can continue to decay into a series of solid radiation, which can be adsorbed on aerosol particles and inhaled into the lungs. Radon and its progeny, once inhaled into human body, will deposit in trachea, bronchus and other parts, and continuously release alpha particles in the lungs to form internal irradiation, which will kill or kill lung cells or local tissues. If people live in an environment with high radon content for a long time, radon may also cause harm to people's blood circulation system, such as leukopenia and thrombocytopenia, and even lead to leukemia in severe cases. Radon and its daughters will also emit penetrating gamma rays when they decay, which will cause external irradiation to human body.
3. Control and prevention of indoor air pollution
3. 1. Advocating green building is the achievement of comprehensive application of modern science and technology such as contemporary architecture and ecology, which will build the building into a small ecosystem and provide a vibrant, natural, convenient, comfortable, energy-saving and pollution-free environment for human beings. Its "green" essence is a virtuous circle material system, which is connected end to end, without waste and pollution, efficient and harmonious, open and closed. By establishing the circulation system of natural air, moisture, energy and other substances inside and outside the building, the "green" building is designed and endowed with ecological cultural and artistic connotation. The concept of green building can be summarized as: 1) The building environment should have clean air, water and soil; 2) Buildings can effectively use water, energy, materials and other resources; 3) Recovery and reuse of resources; 4) Orientation, shape and indoor layout of the building; 5) Try to maintain and open up green space, plant trees around buildings, improve the landscape and maintain ecological balance. In a word, green building is the effective utilization of resources and energy, and it is a building that protects the environment, is friendly to nature, is comfortable, healthy and safe [4].
3.2. The use of green building materials refers to clean production technology. A large number of non-toxic and pollution-free building materials produced by industrial or urban solid wastes are beneficial to human health. In the paper format of 1992, the international academic circles clearly put forward the definition of green materials: green materials refer to materials that have the least load on the earth and are beneficial to human health in the processes of raw material adoption, product manufacturing, use or recycling, and waste disposal, and are also called "environmentally harmonious materials". Green building materials are a big category of green materials [5]. The basic characteristics of green building materials are as follows
. 1) The raw materials used in its production use as little natural resources as possible, and a large number of wastes such as tailings, waste residue, garbage and waste liquid are used.
2) Adopt low energy consumption manufacturing technology and production technology that does not pollute the environment.
3) formaldehyde, halide solvents or aromatic hydrocarbons are not used in the production process; Products shall not contain mercury and its compounds, and pigments and additives containing lead, cadmium, chromium and its compounds shall not be used. 4) The design of the product aims at improving the living environment and quality of life, that is, the product is not only harmless to human health, but also beneficial to human health, and the product is multifunctional. 5) The product can be recycled or reused without environmental pollution. The construction of Sydney Olympic venues provides us with a good example. The selection principle of building materials in Sydney Olympic Stadium is a very good interpretation of the concept of green building materials. In the process of building materials selection and construction, the concept of "3R" environmental protection runs through all the time, that is, reducing the scale and materials, reusing and recycling, emphasizing harmony with the environment, requiring the building materials used to be pollution-free and recyclable, and not using toxic and harmful substances. The use of building materials in Sydney Olympic venues has the following characteristics. 1) building materials are mainly traditional building materials, and "green building materials are not the same as new building materials". The building materials of Sydney Olympic Stadium are mainly cement, glass, steel structure, wood and other traditional materials, and the main structure is basically a combination of concrete and steel structure. 2) The materials are durable and do not pursue high-grade. Most venues are simple in design and rarely use high-grade stone and other decorative materials. The internal and external walls are basically concrete surfaces. Most permanent buildings and components are considered to have high durability, while temporary buildings are guaranteed to be recycled as much as possible on the basis of meeting the use requirements. 3) The selection of materials should fully consider the requirements of environmental protection, pay great attention to making better use of existing materials and minimize the amount of materials. "Cutting materials is environmental protection". In the design of venues, a large number of recyclable materials such as steel, glass, gypsum board, particleboard, plastic and wood products made of artificial fast-growing forests are used to avoid indoor air pollution caused by improper selection of decorative materials [6].
In a word, a main goal of green building and green building materials is to seek the coordination between indoor environment and building efficiency, so as to achieve the purpose of controlling and preventing indoor air pollution. Building materials are the main source of indoor air pollution, so controlling building materials from the source and using green building materials are the key to prevent indoor air pollution. In order to avoid air pollution after indoor decoration, first of all, in the choice of building materials, we should choose internationally developed green environmental protection materials, such as non-toxic coatings, antibacterial coatings, ecological building coatings, adhesive coatings and other decorative materials. , and try to use logs and cork plywood instead of particleboard, hardwood plywood and strength fiberboard to reduce indoor formaldehyde emission and volatile organic compounds entering the room. Controlling the pollution release of decoration materials and reducing the concentration of pollutants in indoor air is an important link in the prevention and control of indoor decoration pollution in libraries [7].
3.3. Reasonable use of indoor air conditioning and control of air velocity and cleanliness can make the air quality reach a better state. Reasonable use of indoor air conditioning is an indispensable and effective way to improve the indoor environment of libraries. At present, people are more concerned about creating a healthy and comfortable air environment for the working environment. As we all know, clean and fresh air is the most basic element to maintain life and is very important to anyone. Fresh air can ensure oxygen supply to readers' brains, enhance memory and improve learning effect. The library is a place for readers to learn, especially the literature reading room, which uses paper documents as the media and has a large flow of readers. In addition, the reader's breathing emissions and dust on documents, especially in winter, doors and windows are closed, so the indoor air quality can be imagined. So how to reduce indoor air pollution? Indoor air quality can be improved by low-pollution outdoor air dilution. Dilution can be accomplished partially or completely by osmosis, natural wind and mechanical ventilation [8]. How to improve the indoor air quality of air-conditioned rooms is also an important issue. The methods and measures to improve indoor air quality are as follows: 1) Raise awareness-proper fresh air volume is the premise of diluting indoor air pollutants and improving indoor air quality. While ensuring fresh air volume, we should pay enough attention to fresh air quality issues; 2) Improve the equipment-avoid setting the new air outlet in the downwind direction of the pollution source, set the fresh air filter in the fresh air duct, and regularly clean or replace the easily polluted parts of the air conditioning system; 3) Strengthen maintenance-indoor air pollution is easy to occur due to long-term sealing, high humidity and inconvenient cleaning. Therefore, the filters, silencers, surface coolers and inner walls of air ducts in air conditioning systems should be maintained and cleaned regularly, and the equipment that produces condensed water should be drained in time and kept dry to ensure the best air quality in the working area. Creating a comfortable and healthy environment is not only determined by air quality, but also influenced by many factors. People's feelings about comfortable and healthy indoor environmental factors are very complicated. In addition to indoor air quality, indoor temperature, humidity, wind speed and other indicators, conventional air-conditioned rooms also have different requirements for other environmental factors. In order to protect the physical and mental health of library readers, the state has also formulated the Library Hygiene Standard [9] (GB 9669- 1996), and the relevant contents are shown in Table 3. Table 3 Hygienic standard of library Table 3 Hygienic standard Library temperature /℃S- 1)φ(CO2)/%ρ (formaldehyde) /(mg? M-3)18 ~ 28 ≥1645 ~ 65 ≤ 0.5 ≤ 0.10 ≤ 0.12 To sum up, the prevention and control methods of indoor air pollution can be realized by blocking sources, ventilation and indoor air purification. Blocking the source is to control the pollution source, which is the basis of controlling indoor air pollution. Controlling or even eliminating pollution sources through reasonable methods is far better than treating pollutants after they enter the room, such as using green building materials and decorative materials, prohibiting people from smoking and using chemical products. Ventilation is the use of natural or mechanical force to exhaust the dirty air that does not meet the hygiene standards outdoors or to the air purification system, and at the same time introduce fresh air. Indoor air purification refers to the use of chemical and biological methods, with the help of specific purification equipment to collect indoor air pollutants, and then recycled indoors or discharged outdoors [9].
4. Conclusion
Library is a treasure house of human civilization and a specific place for cultural dissemination. In colleges and universities, libraries are information centers and academic exchange centers, which play an important role in teaching and scientific research. The level of university library also marks the level of running a school. Library building should not only become the symbol of a university, but also become a pollution-free green library, allowing readers to read and study in a healthy environment, creating a quiet and friendly learning atmosphere that is connected with nature and humanistic feelings, and the internal and external environment is naturally harmonious.
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