What is Biosphere 2?

American Biosphere 2 and Its Research

Guo/Sun Jinbiao

Figure 2 1〓 appearance of Biosphere 2

Table 1 〓 〓 [WB] List of all components and structural parameters? (m2) Volume? (m3) Soil? (m3) Humidity? (m3) Atmosphere? (cubic meters)

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.

Biosphere 2, built in the desert in the north of Tucson, Arizona, USA, is a miniature artificial ecological circulation system, named after calling the earth biosphere 1. It was initiated by John Allen, a former American football player. It was jointly funded by several consortia and entrusted to the Space Biosphere Venture Capital Company. It lasted 8 years and cost 1? 500 million dollars.

199/kloc-0 * * 8 researchers, four men and four women, entered Biosphere 2 for the first time on September 26th,1June 26th, 993, 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, and may be applied to the future settlement of extraterrestrial spheres and manned exploration of the universe.

I. Overview

Floor space 1? The above-ground part of Biosphere 2 is 28 hectares. It is a three-dimensional steel frame structure, coated with powder and equipped with double glass windows. The grounding part is welded stainless steel plate and sealed with steel gasket. The total volume is about 180000m? 3。 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. See table 1 and figure 1 for its appearance and related structural parameters.

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, the change of temperature will inevitably lead to the change of pressure, and the pressure change in this expansion is enough to destroy the glass window plate (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. Through computer system, telephone, video camera and TV, we can exchange data and information with the outside world. Through TV, we can have face-to-face conversations with outside staff and relatives, and we can also 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 in any form.

Table 2 Atmospheric temperature, pressure and weight range in the circle

What are the maximum and minimum atmospheric component pressures at the temperature of biological community (C)? (kPa) percentage? (%) Total weight? (kg)

Tropical rain forest 35 13 O? 2 18? 10 20? 5 1 3 1800

Tropical grassland /38 13 N? 2 67? 5 1 76? 5 1 103775

Ocean/swamp company? 2 0? 03 0? 03 67

Desert 43 2 H? 2O 1？ 78 2? 02 176 1

Intensive agricultural area 30 13 Ar 0? 8 1 0? 92 1782

Residential area 35 15 Total amount 88? 24 100? 00 139 185

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 located in residential areas. 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 community command room can effectively control all the main operating parameters, such as temperature, humidity, light intensity, water flow, pH value and CO? 2 concentration, soil moisture, instrument operation, etc. , 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 ambient atmospheric pressure is not the standard pressure of 10 1? 3 kPa, and only about 88? 2kPa, so its internal pressure can only be slightly higher, that is, 88? 24 kPa. See Table 2 for details. Using mechanical system to simulate the natural environment of the earth, such as making waves, tides, streams and waterfalls, controlling wind, rain and humidity according to seasonal requirements, controlling salt gradient and nutrient circulation speed, desalination of seawater, etc.

Second, the ecological community

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 plankton, mollusks, arthropods, insects, fish, amphibians, reptiles, birds, mammals, etc. ), plants (including plankton, mosses, ferns, gymnosperms and angiosperms, etc. ) and about 65400 kinds of microorganisms (including bacteria, slime molds, fungi, microalgae, etc.). ).

The system has not only tall trees (such as mangroves), but also short shrubs and grasses, 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, thus protecting the internal tree species from strong side light, 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.

Three. Research scope and main achievements

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, carbon dioxide in the atmosphere? The average residence time of 2 is only 1 ~ 4 days, while it is about 3 years in the earth's biosphere.

Atmospheric CO with the concentration of 1500ppm in Biosphere 2? 2 (about the earth's atmosphere CO? 2) 4 times the concentration, equivalent to 100kg of carbon. Compared with the biomass in the circle and the organic carbon in the soil, this amount is greatly reduced, which is 100: 1 and 5000: 1 respectively, while the corresponding proportions in the earth are 1: 1 and respectively.

Carbon monoxide in Biosphere 2? The fluctuation range of 2 is 700 ~ 800 ppm/d, generally 500 ~ 600 ppm/d, and sometimes lower, which is directly related to the dynamic fluctuation of photosynthesis and respiration caused by seasons, daily cycles and weather changes. When the light intensity (light combined luminous flux, PPF) reaches the lowest value in a year (16? 8mol m？ -2? d？ - 1? )，CO？ The average concentration of 2 is 2466ppm. On the contrary, when PPF reaches the highest value (53? 7mol m？ -2? d？ - 1? )，CO？ The concentration of 2 reached the lowest value in a year 1060ppm.

In order to buffer the high CO of this system in the weak light in the first winter? 2 concentration level, with a set of co? 2 circulation system first forms CaCO through chemical reaction? 3. If necessary, heat the latter to 950°C to release carbon monoxide? Enter the atmosphere. 4 months [DK 10]? About 53880mol (equivalent to 9450ppm)? CO？ 2 CaCO by frequently using this materialized system? In the form of 3. This precipitation can indirectly explain about 1% of atmospheric O? 2 (by organic carbon oxidation and subsequent CaCO? 3 separation). On the COntrary, increasing 199 1 year1February 10% external atmosphere has little effect on compensating atmospheric leakage, and co? The concentration of 2 temporarily decreased by 200ppm, which is a daily normal change of 1/3.

CO？ The increase of 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 value at 7? More than seven.

Table 3. 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 grain rice 196? Sorghum 13 1? Wheat 1 13? Starch vegetable sweet potato 198? Sweet potato 1335? Malanga 84? Dioscorea 20? High-fat tofu pudding raw 24? Soybean 14? Low-fat beans and broad beans 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 year to June of 1992, the oxygen concentration of Biosphere 2 ranged from 20? 5 1% decreased to 16? 95%, by the middle of 1993 65438+ 10, that is 14? 5%。 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%. o？ The concentration decreased mainly in the first 4 months after sealing, when it was 18%, and after April of 1992, O? 2 concentration is 0? The linear level of 25% drops. o？ The real reason for the decrease of concentration is still unclear, and several methods are still continuing to study oxygen kinetics, including the distribution of oxygen isotopes in the 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 kinds of * * 150 varieties in intensive agricultural areas, and about 30 kinds are planted in each round, mainly including grain, vegetables and fruits, as well as animals and fish (planted in rice fields). Animal feed includes alfalfa, elephant grass, water hyacinth and various crops (using their inedible biomass), as shown in Table 3 and Figure 2.

Fig. 2〓 growth of some crops in Biosphere 2 intensive agricultural area

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 should 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 must be supplemented. 12? And vitamin D. There is little meat, one egg per person per week. The average calorie value of food in the first 10 month is limited to 2000Cal/d( 1Cal = 4? 18J), which was later increased to 2200 calories/day, and the food was weighed and recorded before eating.

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 water 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 large 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.

The number of wild species began to decrease, 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 the direct intervention of human beings, the biodiversity will inevitably decline during the initial operation of Biosphere 2? Put it down. 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.

The oxygen concentration after the above reduction is equivalent to O? 2 partial pressure, by constantly monitoring the number and morphology of red blood cells, their physiological and biochemical indicators and respiratory frequency, we can know the low O? 2 adverse effects of concentration on health. An o? When the concentration of 2 continues to decrease, it is expected to adapt to O? 2 partial pressure. In addition, there is no infectious disease between people and animals in the circle

Four. Concluding remarks

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 up to now, there are few soil-based technical tests of 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 main reasons for public criticism are subjective and objective reasons: (1) Commercial investment has caused a constant stream of tourists visiting the post office, 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.

Compared with its design life of 100 years, Biosphere 2 is only in the cradle era, so it is reasonable to have such problems and objections. As long as we constantly sum up experience, learn lessons, be diligent in practice and be brave in exploration, we will certainly achieve fruitful results. Going to the universe can be regarded as an inevitable problem for human survival. In order to establish a residential area there, it is necessary to develop an ecological life support system and create a comfortable small environment similar to the earth, so as to provide all kinds of nutritious food, oxygen and water, as well as carbon dioxide for future astronauts. 2, waste water and waste recycling for effective resource utilization and reuse. Biosphere 2 can just teach people this skill. In addition, by understanding: (1) the result of the gradual maturity of the ecosystem; (2) the stability of components in various stress environments; (3) the continuity of recombinant inbred lines; (4) Biogeochemical cycle is expected to find a way out for the deteriorating earth ecosystem.

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