Biosphere 2, built in the desert north of Tucson, Arizona, is a miniature, man-made ecosystem, so named because the Earth itself is called Biosphere 1. It was initiated by former American football player John Allen and financed by a consortium of several companies, and commissioned by Space Biosphere Ventures at a cost of $150 million over eight years.
Four men and four women*** were first stationed on Biosphere 2 on September 26, 1991, and walked out on June 26, 1993, after a 21-month stay***, accumulating a wealth of scientific data and practical experience in their respective fields of study. After evaluating the first results and improving their techniques, four men and three women*** from five countries, namely the United Kingdom, Mexico, Nepal, Yugoslavia and the United States of America, moved in for a second stay on March 6, 1994, and left in January 1995 after 10 months of work. During this time they carried out extensive and systematic scientific research on the atmosphere, water and waste recycling, and food production. Biosphere 2 is the world's largest closed artificial ecosystem. It allows mankind for the first time to study ecology at a holistic level, thus opening new avenues for understanding the processes of ecological change that are currently taking place on a global scale in the Earth's biosphere. More importantly, it will serve as the first terrestrial simulator of a permanent bioregenerative biosafety system, and may be used for future extraterrestrial settlement and manned exploration of the universe.
Overview
The 1.28-hectare Biosphere 2 is a powder-coated, three-dimensional steel frame with double-glazed windows, and a welded stainless-steel floor sealed with steel gaskets. The interior consists of seven ecological communities and two atmospheric expansion chambers (also called "lungs"). In addition, there are energy centers and cooling towers. Its appearance and related structural parameters are shown in Table 1 and Figure 1.
In order to reduce the load on the three-dimensional structure, the internal pressure of Biosphere 2 is slightly higher than the surrounding atmospheric pressure. It is well known that a change in temperature inevitably leads to a change in pressure, and this pressure change in expansion and contraction is enough to damage the glass panes (the calculated value can easily exceed kPa). In order to solve this contradiction, instead of the usual pressure-resistant measures, the ring was fitted with two volume-variable chambers, called "lungs", which allow the atmosphere to expand and contract at a constant pressure. The two "lungs" are like giant pistons connected to a cylinder by a sealing membrane, moving vertically up and down over a distance of about 15 m. The weight of the pistons generates a positive internal pressure relative to the surrounding atmospheric pressure. Positive pressure has two main advantages: no matter where there is a leak, the internal atmosphere will diffuse outward, thus ensuring the removal of external pollution; the piston's continuous downward movement indicates that there is a leak somewhere. The volume of the two "lungs" accounts for 30% of the closed volume of the ring.
In addition to these facilities, the interior includes analytical, medical, veterinary, monitoring, maintenance, exercise and video rooms in various locations.
Like the Earth's biosphere, Biosphere 2 is materially closed-loop, engineered to prohibit material transformations with the outside atmosphere and subterranean soil. It is energetically open-loop, allowing sunlight to pass through the glass structure for plant photosynthesis and introducing electrical energy for the operation of technological systems. The information loop is similarly open, allowing the exchange of data and information with the outside world through computer systems, telephones, video cameras, television, face-to-face conversations with outside workers and relatives, as well as the screening of movies and commercial television programs. Electricity and heat control energy is delivered from the outside through an airtight device, which does not allow any form of exchange or mixing of internal and external fluids when energy transfer takes place.
Table 2 Atmospheric Temperature, Pressure and Weight Ranges in the Circle
Biome Temperature (°C) Maximum Minimum Atmospheric Composition Pressure? (kPa) Percentage? (%) Total weight? (kg)
Tropical rainforest 35 13 O2 18?10 20?51 31800
Tropical savannah/ 38 13 N2 67?51 76?51 103775
Marine/marsh CO?2 0?03 0.03 67
Desert 43 2 H.2O 1.78 2.02 1761
Biosphere 2's "nervous system" is a complete computerized data acquisition and control system, a network of microprocessors radiating from the command room in the residential area. This internal "nervous system" is linked by information pathways to the computing center in the nearby "flight control" building. This building serves as the analysis center and is the main window for analytical data and communications between Biospheres 1 and 2. The command room in the habitat is able to effectively control all major operational parameters such as temperature, humidity, light intensity, water flow, pH, CO2 concentration, soil moisture, instrumentation status, etc. through more than 5000 sensors (recorded every 15 minutes and read into an indefinitely growing database) located throughout the circle, as well as providing status displays of the data sensors and all alarm devices. Each unit has a manual control switch to prevent failure of any part of the "nervous system".
Despite the tropical climate of the entire enclosure, the different biomes have relatively independent temperatures due to their different cooling and heating requirements. Since Biosphere 2 is located in a desert at an altitude of 1200m, its outer atmospheric pressure is not the standard pressure of 101.3 kPa but only about 88.2 kPa, so its inner pressure can only be slightly higher, i.e. 88.24 kPa. For details, see Table 2. humidity, etc., as well as controlling salt gradients and nutrient cycling rates and desalination.
Two, ecological communities
Biosphere 2 has five wild biomes (rainforests, savannahs, oceans, marshes, deserts) and two artificial biomes (intensive agricultural areas and residential areas). They are modeled after the ecosystems between the Tropic of Cancer and the Tropic of Capricorn, designed by American and British biologists and ecologists.
There are about 4,000 species in the circle***, including about 3,000 species of animals (including planktonic, mollusc, arthropods, insects, fish, amphibians, reptiles, birds, mammals, etc.), 3,000 species of plants (including planktonic, mosses, ferns, nudibranchs and peridiniums, etc.), and 1,000 species of microorganisms (including bacteria, slime molds, fungi, and microalgae, etc.), which come from Australia, Africa, South America, North America, and other places. They are from Australia, Africa, South America, North America, etc.
The system is a mixture of tall trees (such as mangroves) and small shrubs and grasses, and is very beautifully organized. The habitats in each wildlife community are not uniform, they are 4,6,4,4,4,6 kinds of habitats, such as the ocean has a beach, shallow saltwater lakes, coral reefs and seawater and so on 4 kinds of types. Biomes are separated from each other by relatively independent ecological zones, e.g., tropical grasslands and deserts are separated by clusters of shrubs. In order to protect the communities from environmental stresses, tolerant plants are planted around them, e.g., the rainforest is surrounded by dense zingiber officinale, which protects the inner tree species from strong lateral sunlight, and bamboo is planted at the interface with the sea to resist salt infiltration.
In order to be as close to the natural environment as possible, the soil, turf, seawater, and freshwater in the circle are all taken from different geographic zones in the outside world and reused through certain artificial treatments. For example, the seawater used in the experiment was prepared by mixing seawater and freshwater brought in at an appropriate ratio.
The criteria for selecting plants for Biosphere 2 are based on animal consumer life support, taxonomic diversity, physical parameters, plant availability and aesthetic value. In keeping with the Darwinian process of natural selection, plant species are initially more numerous than the system can support, which compensates for the loss or extinction of species and ultimately contributes to the continued stability of the system.
The scope of the research and the main results
The first eight scientists conducted extensive, detailed and in-depth observations, documentation, and analysis during 21 months of confinement in an artificial ecosystem according to their respective scopes of research, which included biogeochemistry, soils, water, oceans, "global" biomass, agriculture, genetics, physiology, nutrition, medicine, psychology, as well as technology and engineering. Engineering, etc. Just a few of the more important findings are summarized as follows:
1. Atmospheric Dynamics and Atmospheric Leakage
Biogeochemical cycling rates increase dramatically in small closed ecosystems, which lack the large storage capacity of the Earth's biosphere and have a greatly increased ratio of organisms to inorganic matter. Even in an installation as large as Biosphere 2, the average retention time of atmospheric CO2 is only 1 to 4 days, compared with about 3 years in the Earth's biosphere.
Atmospheric CO2 concentration of 1500 ppm in Biosphere 2 (about 4 times the Earth's atmospheric CO2 concentration) is equivalent to about 100 kg of carbon, an amount that is significantly lower than the biomass in the enclosure and the organic carbon in the soil, which are 100:1 and 5000:1, respectively, compared with the corresponding ratios in the Earth, which are 1:1 and 2:1, respectively.
Biosphere 2
The fluctuation of CO2 in Biosphere 2 ranges from 700 to 800 ppm/d, generally 500 to 600 ppm/d, and sometimes lower, which is directly related to the dynamics of photosynthesis and respiration due to seasonal, diurnal, and weather changes. The average CO2 concentration was 2466 ppm when the light intensity (photosynthesis flux (PPF)) was at its lowest value of the year (16.8 mol-m-2d-1); on the contrary, when the PPF was at its highest value (53.7 mol-m-2d-1), the CO2 concentration was at its lowest value of the year (1060 ppm).
In order to buffer the high CO2 levels during the low-light winter in the first year of the system, a new system was established in the first year. In order to buffer the system from the high CO2 concentration levels during the low-light winter season, a CO2 recycling system was used to first chemically form CaCO3, which was heated to 950°C to release CO2 into the atmosphere if required. Over a period of 4 months [DK10], approximately 53,880 mol (9450 ppm) of CO2 was deposited by regular use of the system in the form of CaCO3. . This deposition can indirectly account for the decrease of about 1% of the atmospheric O2 (through the oxidation of organic carbon and the subsequent separation of CaCO3). In contrast, the addition of 10% of the external atmosphere in December 1991 to compensate for the atmospheric leakage had less of an effect, and the CO2 concentration temporarily dropped by 200 ppm, or 1/3 of the normal daily variation.
Elevated CO2 concentrations can lead to an increase in the acidity of seawater. In order to avoid this, sodium carbonate and sodium bicarbonate were added to the seawater in stages so that the pH could be maintained above 7.7. Swiss Chard58, Sweet Potato Leaf64, Tomato288, Winter Squash261; Grain: Rice196, Sorghum131, Wheat113; Starchy Vegetables: White Potato198, Sweet Potato1335, Malanga84, Dioscorea20; High-Fat Pulses: Peanuts24, Soybeans14; Low-Fat Pulses: Fava Beans63, Peas15; Fruits: Apples1, Bananas1024, Figs1024, Fruits: Apples1, Bananas1024, Fruits:1,1,1,1,1,1,1,1,1,1,1,1,1 1024, figs 39, guava 41, kumquats 4, lemons 10, limes 4, mandarins 6, papayas 639; animal products: goat's milk 407, goat's meat 8, pork 35, fish 10, eggs 6, chicken 8, total 6630 .
Oxygen dynamics are puzzling. Between September 1991 and June 1992, the oxygen concentration in Biosphere 2 dropped from 20.51 percent to 16.95 percent, and by mid-January 1993 it was 14.5 percent. On the basis of medical advice, pure oxygen was continuously fed into the enclosure in the weeks following June 1992 to bring the concentration back to 19%. The decline in O2 concentration occurred mainly in the first 4 months of confinement, when it was 18%, and after April 1992, it declined linearly at a rate of 0.25% per month. The true cause of the decline in O2 concentration is not well understood, and O2 kinetic studies, utilizing several methods, are still in progress, including studies of the oxygen concentration in Biosphere 2, which is the largest in the world, and the most important in the world. The real cause of the decline in O2 concentration is not well understood, and oxygen dynamics studies using several methods are still underway, including studies of the distribution of oxygen isotopes in the ring.
Biosphere 2 is very tight. An annual leakage rate of 6% has been deduced from the relationship between leakage rate and pressure, while measurements of the gradual dilution of the labeled trace gas (SF6) have demonstrated that the annual leakage rate does not exceed 10%. During the first four months (September-December 1991), the atmospheric leakage was about 10%, and the corresponding external gas was injected in a single injection at the end of 1991. Other closed artificial ecosystems (e.g., the biomass production capsule built at the Kennedy Space Center) have leakage rates of between 1 and 10 percent per day.
2, Food Production and Waste Disposal
The agricultural system in Biosphere 2 must meet three main requirements: non-polluting, intensive and sustainable. Space Biosphere Ventures and the University of Arizona's Environmental Research Laboratory, the main consultant for the agricultural area, initially experimented with hydroponics and aeroponics, but eventually had to switch to soil-based agronomic techniques for a variety of reasons. One reason is that hydroponics must rely on chemical nutrient inputs, which are difficult to address in space. Another reason is that without the ability to compost or utilize plant/microbial systems for wastewater reclamation, the problems associated with recycling animal and human wastes and the inedible biomass portion of the crop are even more difficult to solve. In addition, composting or swamp wastewater treatment systems are more energy efficient than physical systems such as wet oxidation or incineration.
There are 50 species and 150 varieties in the intensive agriculture area***, with about 30 species planted in each rotation, mainly grains, vegetables, and fruits, in addition to feeder animals and fish (cultivated in rice paddies), and animal fodder, including alfalfa, elephants' grass, water hyacinths, and a variety of crops (utilizing their inedible biomass), as shown in Table 3 and Fig. 2.
Figure 2: Some of the crops in the Biosphere 2 intensive agriculture area. Growth
The agricultural system established after the confinement provides, on average, 80% of the nutritional needs of eight people, including grains, legumes and vegetables, but the first few months of the confinement require the consumption of food grown before the confinement (the remaining 20% of the nutritional needs). Due to the lack of ultraviolet radiation in the enclosure, vitamin B12 and vitamin D supplements are necessary. Meat is rare and eggs average one per person per week. The average caloric value of the food was limited to 2000 Cal/d (1 Cal = 4.18 J) for the first 10 months, then increased to 2200 Cal/d. The food was weighed and recorded before consumption.
Instead of using pesticides, beneficial insects and sprays (e.g., soapy water and sulfur, bacillus subtilis) are used to control pests and diseases in the agricultural area. Waste recycling is the composting of animal waste and inedible plant biomass, and the use of aquatic plant lagoon systems for "resident" wastewater treatment. Utilization of "soil bed reactors" to reduce the accumulation of trace gases. Provision of drinking water using an atmospheric moisture condensation system.
3.Dynamics of species populations
The plants in the wilderness area are growing vigorously, with biomass increasing by 60-75% in the first nine months. In tropical rainforests, the canopy is so dense and connected that it inhibits the growth of small plants, especially succulents. The rapid growth of perennial herbs in deserts is also evidence that arid soils favor perennials.
The number of wild species initially declined, with less than 10% of plants, less than 30% of terrestrial animals and insects, and about 10-20% of marine species. As the food web becomes more integrated and the canopy matures, the number of species lost slows down and many plants and animals reproduce to varying degrees during this period. Since the establishment of ecosystems, humans have been the main predator in controlling weeds and pests and maintaining biodiversity. Without direct human intervention, biodiversity would have declined during the initial operation of Biosphere 2.
4. Physiological, nutritional and medical tests
Biosphere 2 produces food that essentially meets the Recommended Daily Dietary Allowance (RDA), but there is little surplus. The occupants have lost about 10-20% of their body weight since confinement, the result of initial discomfort with the new environment. After April 1992, there has been no further weight loss, and some have even gained some weight. The low-fat, low-calorie, nutrient-rich diet significantly lowered cholesterol (from an average of about 195 to 125), blood pressure, white blood cell counts and blood sugar levels. Similar results have been shown in previous tests on mice and have been shown to slow aging and increase longevity.
This decreased oxygen concentration corresponds to the partial pressure of O2 at an altitude of 2900 meters, and the adverse health effects of low O2 concentrations can be detected by continuously monitoring the number and morphology of red blood cells, their physiological and biochemical indices, and respiratory rate. Once the O2 concentration continues to decrease, it is expected that the O2 partial pressure equivalent to that at 4600 meters above sea level can be adapted. In addition, no infectious diseases have been reported among humans and animals in the enclosure.
IV. Concluding Remarks
There is a great deal of evidence that Martian soil and lunar topsoil can be used as potential substrates for plant cultivation after certain biological and chemical treatments, which would make the application of bioregenerative life-support systems in space habitats much more economical than devices that require Earth resources. To date, however, there have been few experiments with soil-based technologies for biorenewable life support systems. Biosphere 2 is the first soil-based bioregenerative life-support system to be built and operated. Therefore, data on its operational performance would be very useful for similar systems used in space.
Biosphere 2, in terms of its size, technical difficulty and complexity, as well as the results achieved, is a masterpiece in the history of human science and has received widespread international attention and appreciation. However, it has recently been severely criticized by some members of the public.
The public criticism is mainly due to both objective and subjective reasons: (1) commercial investment, resulting in an endless stream of tourists, giving people an impression of a lack of scientific seriousness; (2) encountered severe rainy weather and pests, resulting in poor harvests, the beginning of the atmospheric leakage; (3) the people do not know much about their scientific experimental activities; (4) theoretical and practical experience is insufficient; (5) poor management, resulting in the possibility of a scientific experiment, and the public has been criticized by some members of the public. mismanagement, resulting in what could have been done not being done.
Biosphere 2 is only in its cradle age compared with its 100-year design life, and it is reasonable that problems and objections have arisen. As long as we continue to summarize the experience, learn from the lessons, practice diligently and explore, we will certainly be able to achieve fruitful results. The movement towards the universe can be seen as an unavoidable problem for the survival of mankind. In order to establish a habitat there, it is necessary to develop an ecological life-support system and create a comfortable, small-Earth-like environment that will provide future astronauts with a variety of nutritious foods as well as oxygen and water, and that will reuse CO2, wastewater, and wastes by recycling them into useful resources. Biosphere 2 will be able to teach people exactly this skill. In addition, by understanding (1) the results of ecosystem maturation; (2) the stability of components under various stresses; (3) the continuity of genetic populations; and (4) the cyclical effects of biogeochemistry, it is hoped that a way out can be found for the deteriorating ecosystems of the Earth.
What is the status of Biosphere 2, which has been regarded as a negative example? Is it still "extravagant pseudoscience"?
Biosphere 2, are you OK
Several years ago, after the failure of the experiment to recreate a "mini-Earth" in the desert of the U.S. state of Arizona, the $200-million Biosphere 2 became a laughing stock. The Biosphere 2 project became a laughing stock and was even criticized as "extravagant pseudo-science". To this day, Biosphere 2 is viewed by many as the antithesis of contempt for nature. However, few have noticed that Biosphere 2 has been quietly changing over the years: it has attracted a large number of tourists and students, making it an excellent tourist attraction and educational base; and, most importantly, it has gradually gained the respect of the scientific community, becoming a rare center for research on the effects of global climate change.
"Extravagant pseudoscience"
Once upon a time, there was a seemingly fanciful idea of creating a "mini-Earth" on the planet we live on, exploring the possibilities of human self-sufficiency in this modern-day "Nanniwan," and of building a future living space on the moon or Mars. Edward Bass, the Texas oil baron, has longed for this.
From 1984 to 1991, Bass personally contributed 200 million dollars to build "Biosphere 2" in the desert north of Tucson, Arizona. Biosphere 2 is a 13,000-square-meter facility that resembles a giant greenhouse, with rainforest, desert, grassland, and ocean." Biosphere 1 is the Earth we live on, and Biosphere 2 is, as the name suggests, a "miniature Earth".
On September 26, 1991, Biosphere 2 welcomed its first volunteers, four men and four women who began a two-year period of living in isolation. Despite the fact that these residents had spent several years receiving good training in engineering, agriculture, etc. (one of them even received dental training), with technical support costing millions of dollars a year, a variety of disasters still came one after another: a variety of plants and animals died in large numbers, cockroaches and ants but the children and grandchildren; even worse, by January 1993, the oxygen level in the Biosphere 2 from 21% to 14%, and had to be replaced by a new one, the oxygen level in the Biosphere 2 from 21% to 14%. In January 1993, the oxygen level in Biosphere 2 dropped from 21% to 14%, and the illusion of self-sufficiency was shattered as oxygen had to be replenished from the outside world.
The experiment failed. After a short break, Biosphere 2 welcomed a second group of inhabitants. Five men and two women stayed for a month and a half, but were forced to leave on September 17, 1994, due to excessive accumulation of nitrous oxide (N2O), and the experiment ended in failure once again. Since then, no one has lived in Biosphere 2.
A "utopian" scientific research program was in ruins. Biosphere 2 was mercilessly ridiculed by some, even dismissed as "extravagant pseudoscience".
Biosphere 2, of course, also reinforced the seemingly simple truth that "for now, the Earth is still the only home for mankind." Not only that, but it's also inadvertently left some great stories.
Biosphere 2 is a small United Nations, with residents from the United States, the United Kingdom, Mexico, Nepal and seven other countries. In this "small United Nations", cultivated the flower of love. A few months after the end of the experiment, a couple from each of the two groups of residents got married. It may be true to the old adage that love in times of trouble is the best thing that ever happened to you.
Also, the residents of Biosphere 2 were forced to control their diets because of food failures. As a result, four men in the first group of residents lost an average of 18% of their body weight, four women lost an average of 10% of their body weight, and the average cholesterol dropped from 195 to a normal value of 125, which made these people, who usually suffered from weight loss, a pleasant surprise, which can be said to be a blessing in disguise. One resident at the time, Prof. Roy Walford of the University of California, Los Angeles, even continued to eat at the same level "because it's good for your health".
Out of Utopia
Painfully aware of the situation, Bass decided to reposition Biosphere 2. So he turned to scientists at Columbia University to see what the $200 million Biosphere 2 could do.
In January 1996, Bass simply turned Biosphere 2 over to Columbia University and invested $40 million in renovation and operating costs for the next five years. After much deliberation, Columbia planned to turn Biosphere 2 into a research center dedicated to Earth system science, and brought in William Harris as its new director. Harris, who worked for many years at the National Science Foundation, is a master at managing large-scale research projects.
In fact, the $200 million spent on Biosphere 2 isn't "all for naught," as some in the media have claimed. The 3.78-million-liter artificial ocean is an excellent platform for marine science. That's probably one of the reasons why Columbia and Harris were willing to take over.
Biosphere 2's transition has been marked by pain and confusion. Scientists were divided over what use could be made of Biosphere 2, with some wanting to turn it into a biodiversity research center and others wanting to focus on the effects of global change. Combined with technical difficulties, the transition program was thwarted, morale was affected, and a number of scientists left Biosphere 2.
As the saying goes, it all comes back to bite you in the ass. Two years later, the artificial ocean finally "made some splash". A paper published in the February 13, 1998 issue of the American journal Science claims that the survival of corals in the man-made ocean is threatened by increasing levels of the greenhouse gas carbon dioxide in Biosphere 2.
Such a paper may not seem like a big deal to the layman, but it probably marks a turning point for Biosphere 2. At a time when global warming is receiving increasing attention from the international community, the paper makes it clear that Biosphere 2 is an ideal platform for studying how global warming affects ecosystems.
In April 2001, world-renowned botanist Berry Osmond succeeded Harris as head of Biosphere 2. Dr. Lam Kwong Fai of the Biosphere 2 Research Center told this reporter that a number of research projects related to global climate change are now being carried out at Biosphere 2, attracting many of the world's leading scientists.
New dreams
The shadow of Biosphere 2's past failures is fading, and a new image is emerging.
According to Dr. Lin, in December 2001, an academic conference was held at Biosphere 2, attended by scientists from around the world and officials from the U.S. Department of Energy. The experts at the conference highly evaluated the results of the past five years of scientific research at Biosphere 2 and proposed future research programs.
Today, Biosphere 2 is Columbia's trump card." Our goal is to develop Biosphere 2 as the premier destination for education, research, and communication on Earth system science, policy, and management matters." said Michael Crowe, vice chancellor of the university. It's a more pragmatic goal than the one that was derided, but it's just as ambitious.
Because Biosphere 2's performance over the past five years was recognized by all parties, Columbia renewed its contract with Bass for another 10 years after it expired. Columbia's board of trustees decided to spend $20 million from 2001 to 2005, and Bass has offered an additional $30 million.
Bass, who was once ridiculed for his lack of understanding of science, has been "very kind" to scientific research. In the January 2002 issue of Scientific American, Columbia's Gerrit Holloway wrote that by 2010, Bass was likely to finally sell Biosphere 2 and 100 hectares of surrounding land to Columbia for a symbolic $1 million.
What will Biosphere 2 bring to human life after all this time? Will new dreams come true? Will new efforts fail again? Perhaps the words of Joel Cohen of Rockefeller University and David Tillman of the University of Minnesota will give us confidence.
The two scientists see some similarities between Biosphere 2 and the Hubble telescope. The costly Hubble telescope was criticized when it first took to the skies for taking blurry pictures, but it has become an indispensable tool for astronomical research. Likewise. Biosphere 2 is expected to become an important base for furthering humanity's understanding of the Earth in the future.
In scientific research, no one can guarantee a return on investment, and hundreds of millions of dollars have been invested without return. The question is whether we understand the real reasons for the failure of scientific research programs, and whether we truly understand that "failure is the mother of success". The past and present of Biosphere 2 provide us with an excellent model.