Experimental research on the biosphere?

Biosphere 2 is a miniature artificial ecological circulation system built in the desert north of Tucson, Arizona, USA. It is named because it calls the earth itself the biosphere 1. It was written by former American football player John? The project was initiated by Allen, funded by several consortia, and entrusted to the Space Biosphere Venture Capital Company, which lasted for 8 years and cost 654.38+0.5 billion US dollars. Biosphere 2 aims to carry out ecological and environmental research in a closed state, help people understand how the earth works, and study whether human beings are suitable for survival under the condition of simulating the ecological environment of the earth. In order to be as close to the natural environment as possible, the soil, turf, seawater and fresh water in the circle are taken from different geographical areas outside and reused after some manual treatment. For example, the seawater used in the experiment is a mixture of seawater and fresh water in a proper proportion.

Overview of Biosphere 2

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Biosphere 2 covers an area of 1.28 hectares, and the ground part is a powder-coated three-dimensional steel frame structure with double glass windows; The grounding part is welded stainless steel plate and sealed with steel gasket. The total volume is about 180000m3. Its interior is mainly composed of seven ecological communities and two atmospheric expansion chambers (also known as "lungs"). In addition, there are facilities such as energy center and cooling tower. Relevant structural parameters are shown in the following table:

Table 1: List of components and structural parameters in Biosphere 2

Area (m2) Volume (m3) Soil (m3) Humidity (m3) Atmosphere (m3)

Intensive agricultural area 2000 38000 2720 60 35220

Residential area100011000 2110997.

Rainforest 2000 35000 6000 100 28900

Savanna/ocean/swamp 2500? 49000 4000? 3400 4 1600

Desert1400 22000 4000 40017600

"West Lung"1800150000015000

Nanfei180015750 0 75015000

Note: The volume of the above two "lungs" is only 50% when they are fully expanded.

In order to reduce the load of the three-dimensional structure, the internal pressure of Biosphere 2 is slightly higher than the surrounding atmospheric pressure. As we all know, temperature change will inevitably lead to pressure change, which is enough to damage the glass window panel (the calculated value easily exceeds kPa). In order to solve this contradiction, we did not take the usual anti-pressure measures, but assembled two variable-volume cabins called "lungs" for the ring, which made the atmosphere expand and contract under constant pressure. The two "lungs" are like a huge piston, which is connected with the cylinder through a sealing membrane, and the vertical movement distance is about 15m. The weight of that piston generate an internal positive pressure relative to the ambient atmospheric pressure. Positive pressure has two advantages: no matter where there is leakage, the internal atmosphere will spread outward to ensure the elimination of external pollution; The continuous sliding of the piston indicates a leak somewhere. The volume of the two "lungs" accounts for 30% of the closed volume of the circle.

In addition to the above facilities, it also includes analysis, medical treatment, veterinary medicine, monitoring, maintenance, exercise and film and television rooms, which are distributed in different parts.

Similar to the Earth's biosphere, Biosphere 2 is closed-loop, and it is forbidden to carry out material transformation with the external atmosphere and underground soil by engineering means. Open-loop in energy, allowing sunlight to pass through the glass structure for plant photosynthesis, and at the same time introducing electric energy for technical system operation. Information is also open-loop. You can exchange data and information with the outside world through computer systems, telephones, cameras and televisions. You can have face-to-face conversations with outside staff and relatives through televisions. You can show movies and watch commercial TV programs. Electric energy and thermal control energy are transported from the outside through a closed device. During energy transfer, internal and external fluids are not allowed to exchange or mix.

Ecological Community in Biosphere 2

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& ltIMG style = " FLOAT:left " class = editorImg title =-src = "/70 cffyinkgqfm 2 e 88 ium _ a/baike/ab pic/item/ 7e7f 790996 e 43 ad 93 AC 76354. jpg "> Biosphere 2 has five wildlife communities (tropical rain forest, savanna, ocean, swamp and desert) and two artificial biological communities (intensive agricultural area and residential area). They were designed by biologists and ecologists in the United States and Britain respectively, taking the ecosystem between the Tropic of Cancer and the Tropic of Capricorn as the model.

There are about 4,000 species in the circle, including about 3,000 species of animals (including mollusks, arthropods, insects, fish, amphibians, reptiles, birds, mammals, etc. ), plants (including plankton, mosses, ferns, gymnosperms and angiosperms, etc. ) and about 654,300 kinds of microorganisms (including bacteria, slime molds, fungi, microalgae, etc. ).

There are both tall trees (such as mangroves) and short shrubs and grasses in the system, which are scattered and beautiful. There are 4, 6, 4, 4 and 6 habitats in each wildlife community. For example, there are four types of oceans, such as beaches, shallow saltwater lakes, coral reefs and seawater. There are relatively independent ecological zones between biological communities, such as a cluster of shrubs between savanna and desert. In order to protect each community from environmental stress, plants with strong tolerance are planted around it, for example, the tropical rain forest is surrounded by dense zingiberaceae plants, so as to protect the internal tree species from side strong sunlight, and bamboo is planted at the interface with the ocean to resist salt penetration.

In order to be as close to the natural environment as possible, the soil, turf, seawater and fresh water in the circle are taken from different geographical areas outside and reused after some manual treatment. For example, the seawater used in the experiment is a mixture of seawater and fresh water in a proper proportion.

Biosphere 2' s criteria for selecting plants mainly consider animal consumers' life support, classification diversity, physical parameters, plant availability and aesthetic value. In order to adapt to Darwin's natural selection process, the number of plant species exceeds the number that the system can initially support, which can make up for the loss or extinction of species and ultimately promote the sustainable stability of the system.

Biosphere 2 experimental course

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199/kloc-0 * * 8 researchers, four men and four women, entered Biosphere 2 for the first time, left on1June 26, 1993, and stayed in * * * for 2 1 month, accumulating rich scientific data and practical experience in their respective research fields. Seven experimenters from Britain, Mexico, Nepal, Yugoslavia and the United States * * * entered the laboratory for the second time on March 6, 1994 after evaluating the first batch of results and improving the technology, and went out after working for 10 months. During this period, they conducted extensive and systematic scientific research on the recycling of air, water and waste and food production. Biosphere 2 is the largest closed artificial ecosystem in the world. It enables human beings to study ecology on the whole level for the first time, thus opening up a new way to understand the global ecological change process of the earth's biosphere. More importantly, it will be used as the ground simulation device of the first permanent biological regenerative life support system, which may be applied to the settlement of extraterrestrial planets and manned exploration of the universe in the future.

The "nervous system" of Biosphere 2 is a complete computer data acquisition and control system, and it is a microprocessor network system radiated from the command room of residential area. This internal "nervous system" communicates with the computing center in the "flight control" building near the outside world through information channels. As an analysis center, this building has become the main window for obtaining analysis data and communication between Biosphere 1 and Biosphere 2. The command room in the residential area can effectively control all the main operating parameters, such as temperature, humidity, light intensity, water flow, pH value, CO2 concentration, soil humidity, instrument operation status and so on. , through more than 5000 sensors all over the circumference (recorded every 15 minutes and read into the infinite growth database), and can display the status of data sensors and all alarm devices. Each device has a manual control switch to prevent any part of the "nervous system" from failing.

Although the whole circle has a tropical climate, different biological communities have different cold and warm requirements, so they have relatively independent temperatures. Because Biosphere 2 is located in the desert at an altitude of 1200m, its external atmospheric pressure is only about 88.2kPa, instead of the standard pressure 10 1.3 kPa, so its internal pressure can only be slightly higher, that is, 88.24kpa. The mechanical system is used to simulate the earth's natural environment, such as making waves, tides, streams and waterfalls.

At first, the purpose of Biosphere 2 experiment was to study whether human beings and various living things (plants and animals) can survive healthily and happily in a sealed and isolated artificial system through the circulation and reuse of air, water and nutrients in the system. In the experiments from 199 1 to 1993, the researchers found that the atmospheric composition ratio of oxygen and carbon dioxide in Biosphere 2 could not be balanced by itself. The cement building in Biosphere 2 affects the normal carbon cycle; Most animals and plants can't grow or reproduce normally, and the extinction rate is faster than expected. After extensive discussion, it was confirmed that the experiment of "Biosphere 2" failed and failed to reach the original designer's predetermined goal, which proved that under the known scientific and technological conditions, it would be difficult for human beings to survive forever without the earth. At the same time, it also proves that the earth is still the only life support system that human beings can rely on and trust.

From 65438 to 0996, Bath handed over Biosphere 2 to Columbia University to manage and plan its future direction as a research and teaching base for ecology and environmental change. Columbia University began to integrate the existing ecosystem simulation experiments and new research plans of Biosphere 2, and opened it as a research and learning center to explore the interactive influence of our human life and environmental ecology.

Specific research scope and main achievements (detailed)

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The first batch of eight scientists conducted extensive, detailed and in-depth observation, recording and analysis in a closed artificial ecological environment for 2 1 month. Research projects include biogeochemistry, soil, water, ocean, "global" biomass, agriculture, genetics, physiology, nutrition, medicine, psychology, technology and engineering. This paper only summarizes several important research results as follows:

1, atmospheric dynamics and atmospheric leakage

In the tiny closed ecosystem, the biogeochemical cycle rate is significantly increased, which is due to the lack of the huge storage function of the earth's biosphere, and the ratio of organisms to inorganic substances is greatly increased. Even in a device as big as Biosphere 2, the average residence time of atmospheric CO2 (carbon dioxide) is only 1 ~ 4 days, while it is about 3 years in the earth's biosphere.

The atmospheric CO2 concentration in Biosphere 2 is 1500 ppm (about four times that of the earth's atmospheric CO2), which is equivalent to 100kg of carbon. Compared with the biomass in the biosphere and the organic carbon in the soil, this amount is greatly reduced, being 100: 1 and 5000: 1 respectively. On the earth, the fluctuation range of CO2 in Biosphere 2 is 700-800 ppm/d, generally 500-600 ppm/d, and sometimes it is lower. When the light intensity (light combined luminous flux, PPF) reaches the lowest value in a year (16.8mol? M-2D- 1), the average concentration of CO2 is 2466ppm；; On the contrary, when PPF reaches the highest value (53.7 mol? M-2D- 1), the CO2 concentration reached the lowest value in a year 1060ppm.

In order to buffer the high CO2 concentration level of the system in the low light of the first winter, CaCO3 is formed by chemical reaction using a CO2 circulation system, and the latter can be heated to 950.d egree. C. to release CO2 into the atmosphere if necessary. In four months, about 53880mol (equivalent to 9450ppm) of CO2 was deposited in the form of CaCO3 (calcium carbonate) by using this physical and chemical system regularly. This precipitation can indirectly explain the reduction of about 1% atmospheric O2 (through organic carbon oxidation and subsequent CaCO3 separation). On the contrary, in February, the addition of 199 10% external atmosphere to compensate for atmospheric leakage had little effect, and the CO2 concentration temporarily decreased by 200ppm, which was a daily normal change of 1/3. The increase of CO2 concentration will lead to the increase of seawater acidity. In order to avoid this phenomenon, sodium carbonate and sodium bicarbonate are added to seawater in stages to keep the pH above 7.7.

Table 2: Total agricultural output of Biosphere 2 in one year (kg);

Vegetables:

Bean 8? Beet leaf 273? Beetroot root 308? Pepper 13? Carrot 88? Pepper 63? Chinese cabbage 83 cucumber 17? Eggplant 155? Kale 1 1? Lettuce 90? Onion 107? Bok choy 12？ Snow beans 1? Pumpkin seed 8? Zucchini 287? Swiss franc 58? Sweet potato leaf 64? Tomato 288? Wax gourd 26 1

Food:

Rice 196? Sorghum 13 1? Wheat 1 13

Starch vegetables:

Sweet potato 198? Sweet potato 1335? Malanga 84? Dioscorea 20

High-fat beans:

Peanut 24? Soybean 14

Low-fat beans:

Broad bean 63? Pea 15

Fruit:

Apple 1? Banana 1024? Figure 39? Guava 4 1? Kumquat 4 lemon 10? Lime 4 citrus 6? Papaya 639

Animal products:? Goat milk 407? Goat mutton 8? Pork 35? Fish 10? Egg 6? Chicken 8?

Total 6630

Oxygen dynamics is puzzling. From September of 199 1 to June of 1992, the oxygen concentration of Biosphere 2 decreased from 20.5 1% to 16.95%, and was at 1938/kloc-0. According to the doctor's advice, pure oxygen was injected into the circle for several weeks after June 1992 to restore its concentration to 19%. The oxygen concentration decreased mainly in the first four months after sealing, which was 65438 08%. 19 After April 1992, the oxygen concentration decreased linearly by 0.25% every month. The real reason for the decrease of O2 concentration is still unclear, and the research on oxygen kinetics by several methods continues, including the distribution of oxygen isotopes in the research circle.

Biosphere 2 is very airtight. According to the relationship between the leakage rate and the pressure, the annual leakage rate is 6%, and the measurement results of the gradual dilution of the marked trace gas (SF6) prove that the annual leakage rate does not exceed 10%. The atmospheric leakage in the first four months (19 9 1 September ~1February) is about 10%, and the corresponding external gas is injected once at the end of199/kloc-0. The daily leakage rate of other closed artificial ecosystems (such as the biomass production cabin manufactured by Kennedy Space Center) is between 1%- 10%.

2. Food production and waste disposal

The agricultural system of Biosphere 2 must meet three main requirements, namely, pollution-free, intensive and sustainable. Space Biosphere Venture Capital Company and its main consultant in the agricultural field, the Environmental Research Laboratory of Arizona University, initially experimented with hydroponics and fog culture, and finally had to turn to soil agronomy for various reasons. One of the reasons is that hydroponics must rely on the input of chemical nutrient solution, which is difficult to solve in space. Another reason is that it will be more difficult to solve the related problems of promoting the recycling of animal and human wastes and inedible biomass of crops if there is no ability to compost or use plant/microbial system to regenerate wastewater. In addition, composting or swamp wastewater treatment system is more energy-saving than physical systems such as wet oxidation or incineration.

There are 50 species of * * 150 in intensive agricultural areas, and about 30 species are planted in each round, mainly including grain, vegetables and fruits, as well as raising animals and fish (planted in rice fields). Animal feed includes alfalfa, elephant grass, water hyacinth and various crops (using their inedible biomass). The agricultural system established after sealing provides 80% of the nutritional needs of eight people on average, including grains, beans and vegetables, but the food planted before sealing is required to be eaten in the first few months after sealing (the remaining 20% of nutritional needs). Due to insufficient ultraviolet radiation in the circle, vitamin B 12 and vitamin D must be supplemented. There is little meat, one egg per person per week. The average calorie value of food in the first 10 month was limited to 2000 cal/d (1cal = 4.18 j), and then increased to 2200 cal/d. Before eating, the food was weighed and recorded. Agricultural areas do not use pesticides, but use beneficial insects and sprayers (such as soapy water, sulfur and Bacillus) to control the occurrence of pests and diseases. Waste recycling is to compost animal waste and plant inedible biomass, and use aquatic plant saltwater lake system to treat the wastewater of "resident personnel" Using "soil bed reactor" to reduce the accumulation of trace gases and using atmospheric moisture condensation system to provide drinking water.

3. Dynamic changes of species population

Plants grow vigorously in wild areas, and the biomass increased by 60% ~ 75% in the first 9 months. In the tropical rain forest, the crown is huge and dense, which forms a shadow, thus inhibiting the growth of small plants, especially succulent plants. The perennial herbs in the desert grow rapidly, which also proves that sandy soil is beneficial to the growth of perennial herbs under dry conditions.

At first, the number of wild species decreased, including plants less than 10%, land animals and insects less than 30%, and marine species about 10%~20%. When the food web is more complete and the crown is mature, the number of species loss will slow down, and many animals and plants will reproduce in different degrees during this period. Since the establishment of the ecosystem, human beings have been the main predators to control the occurrence of weeds and pests and maintain biodiversity. Without direct human intervention, biodiversity will inevitably decline during the initial operation of Biosphere 2.

4. Physiology, Nutrition and Medical Experiments

The food produced by Biosphere 2 can basically meet the requirements of RDA, but there is not much left. Since being sealed, residents have lost about 10%~20% of their weight, which is the result of not adapting to the new environment at first. After April of 1992, weight loss stopped, and some people even gained some weight. This low-fat, low-calorie and nutritious food can significantly reduce cholesterol (from about 195 to 125 on average), blood pressure, white blood cell count and blood sugar content. Previous experiments on mice have similar results, which confirmed that it can delay aging and prolong life.

Evaluation of Biosphere 2

A large amount of evidence shows that Martian soil and lunar topsoil can be used as potential plant cultivation substrates after certain biological and chemical treatments, which makes the application of biological regenerative life support system in space living much more economical than that of devices that need earth resources. But so far, there are few technical experiments based on soil in the biological regeneration life support system. Biosphere 2 is the first life support system based on soil biological regeneration. Therefore, the data about its running performance is very useful for similar systems used in space.

No matter from the scale, technical difficulty and complexity, as well as the achievements, Biosphere 2 is a masterpiece in the history of human science, which has attracted worldwide attention and appreciation. But it has also been severely criticized by some public recently.

The public's criticism is mainly caused by subjective and objective reasons: (1) commercial investment leads tourists to wander around, giving people an impression of lack of scientific seriousness; (2) In case of severe rainy weather and diseases and insect pests, the initial harvest is not smooth and the atmosphere leaks; (3) People don't know much about their own scientific experiments; (4) Lack of theoretical and practical experience; (5) Poor management leads to failure to do what can be done.

Although the experimental goal of the Biosphere II project has not been achieved, it has also taught mankind a good lesson: nature is not as simple as we thought, and every breeze may be indispensable to life in the complex and huge system connection; Man is not omnipotent, and man lives on the earth; Humans should know how to conform to nature and cherish everything in nature; Can we continue to develop with everything on earth?