Carbon dioxide (CO2) is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at Clinton Creek, Yukon Territory, and Cassiar, British Columbia, Canada. Accelerated weathering is attributed to a dramatic increase in surface area, which occurs during the milling of ore. We provide a detailed account of the natural process of carbon trapping and storage as it occurs at Clinton Creek and Cassiar, including mineralogy, modes of occurrence, methods of formation for carbonate alteration, light stable isotope geochemistry, and radiocarbon analysis. Powder X-ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite, and less commonly lansfordite [MgCO3⋅5H2O]. Textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings. Samples of efflorescent nesquehonite are characterized by δ 13 C values between 6.52 and 14.36 per mil, δ 18 O values between 20.93 and 26.62 per mil, and F 14 C values (fraction of modern carbon) between 1.072 and 1.114, values which are consistent with temperature-dependent fractionation of modern atmospheric CO2 during mineralization. Samples of dypingite ± hydromagnesite collected from within 0.2 m of the tailings surface give δ 13 C values between -1.51 and +10.02 per mil, δ 18 O values between +17.53 and +28.40 per mil, and F 14 C values between 1.026 and 1.146, which suggests precipitation from modern atmospheric CO2 in a soil-like environment. Field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments. Nesquehonite formed in an evaporative environment on the surface of tailings piles, and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate. In both cases, these minerals †
Background: This study provides experimental evidence for biologically induced precipitation of magnesium carbonates, specifically dypingite (Mg 5 (CO 3 ) 4 (OH) 2 ·5H 2 O), by cyanobacteria from an alkaline wetland near Atlin, British Columbia. This wetland is part of a larger hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O) playa. Abiotic and biotic processes for magnesium carbonate precipitation in this environment are compared.
The kinetics of thermochemical sulfate reduction (TSR) were studied in experiments at 205-250°C, with determination of both sulfate and sulfide at intervals during the runs of up to 430 h. Analysis of the data indicates the reaction to have first-order kinetics, and extrapolating these data, plus data from the literature, to 150°C gives a range of possible rate constants from 10 0 to 10 )4 year )1 . Although the rate law has not been well established, a reasonable estimate allows calculation of the amount of sulfide ore formed as a function of flow conditions and time. It is here concluded that TSR could happen during the formation of Mississippi Valley-type ore deposits, subject to several caveats.
Lungs from fetal guinea pigs (54-67 days of gestation) were supported in vitro, and lung liquid secretion rates were measured by a dye-dilution technique. The average secretion rate in the first hour was 2.14 +/- 0.08 (SE) mL x kg-1 body weight.h-1 (0.21 +/- 0.01 mL/h) (n = 450); this was comparable to intact preparations. In an independent study of 30 lungs, secretion continued unchanged for 3 h, with no significant change in fluid composition. Between 54 days and term, production appeared to fall in terms of millilitres per kilogram per hour. The following agents were placed in the supporting saline during the middle hour of incubation. (i) Sodium iodoacetate: at 10(-4) M this produced a fall in secretion (fall, succeeding hours; 55.4 +/- 23.0 and 64.9 +/- 17.5%; n = 6); at 10(-3) M it stopped secretion (fall, succeeding hours; 87.2 +/- 10.3 and 100%, n = 6). (ii) Ouabain: at 10(-5) M there was no change in production (n = 6); at 10(-4) M, four preparations were unaffected, two reduced production. (iii) Epinephrine (10(-7) M) produced a significant fall in production in all cases (n = 6); in four preparations secretion reduced (average fall, 64.4 +/- 10.8%); in two preparations there was reabsorption (average rate, -1.03 mL.kg-1.h-1). This extends the effect of epinephrine to the guinea pig, and suggests that the in vitro preparation is a useful model for studies of the fetal lung.
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