Oxygen loss in biosphere 2

Abstract

Oxygen concentrations have dropped sharply in the air of “Biosphere 2,” an enclosed experimental ecosystem located in southern Arizona. Biosphere 2 is a 3.15‐acre airtight structure roofed in glass and underlain by an impermeable liner. It houses an artificial ecosystem containing soil, air, water, flora, and fauna and was built primarily as an apparatus for the experimental investigation of biogeochemical cycles, whole ecosystems, and life‐support systems for space habitation [see Nelson et al., 1993]. O2 in Biosphere 2 decreased during the first 16 months of closure from the ambient 21% to 14%, enough to cause health problems in the human occupants. We present evidence that the O2 loss is caused by microbial respiration of the excessive amount of organic matter incorporated into the experiment's soils and furthermore, that the respired CO2 is reacting with the structure's concrete to form calcium carbonate.

Simulation of the water cycle in Biosphere 2

“…Changes in water management mostly affected the level of the primary storage (PS), and flows in (J5) and out (J6) of it. But, it did not have much effect on other storages and flows, implying that variation in sunlight energy can account for the seasonal water cycle in Biosphere 2. of the storages are close to the measured values in Severinghaus et al (1994)and Severinghaus (1995). The result clearly shows the natural trend of isotopic concentration, heavy isotope concentrations decreasing in the order: ocean\ freshwater\ atmospheric vapor.…”

“…1 and 2 assume mass conservation of water molecules during simulation. To be consistent with the measured values of l 18 O (− 0.77 ‰ for ocean, −9.56 ‰ for condensate, and − 14.70 ‰ and − 17.85 ‰ for vapor) in Severinghaus et al (1994), Severinghaus (1995), a weighted average Fig. 4.…”

“…Typical value of M (7.5) in the North Pacific was used for the model in this paper. The resultant values for each category in Severinghaus et al (1994), Severinghaus (1995) are −5.78 ‰ for ocean, −66.48 ‰ for condensate, and − 90.24 ‰ for vapor, and the weighted average is − 28.91 ‰. Fig.…”

Simulation of community metabolism and atmospheric carbon dioxide and oxygen concentrations in Biosphere 2

“…This absorption rate, however, is subject to error associated with the baseline data set. Severinghaus (1994) …”

“…Their work also explored the effect of different quantities of organic matter at the start in generating excess carbon dioxide or oxygen. In another study, Severinghaus (1994) presented estimates of carbon dioxide flows including uptake by the concrete using carbon isotopes. A static model with a budget for average flows and storages of carbon was prepared by Dempster (1993) using observational data.…”