Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.

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Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

Rising atmospheric carbon dioxide (CO 2 ) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state ofthe oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell– forming species. CaCO 3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO 3 dissolution rate for the global oceans is approximately 0.5 0.2 petagrams ofCaCO 3-C per year, which is approximately 45 to 65% ofthe export production ofCaCO 3 . Atmospheric CO 2 concentrations oscillated be

https://science.sciencemag.org/content/sci/305/5682/362.full.pdf

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans

Observed atmospheric concentrations of CO2 and data on the partial pressures of CO2 in surface ocean waters are combined to identify globally significant sources and sinks of CO2. The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO2 are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO2 in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO2. Therefore, a large amount of the CO2 is apparently absorbed on the continents by terrestrial ecosystems.

https://science.sciencemag.org/content/sci/247/4949/1431.full.pdf

Observational contrains on the global atmospheric co2 budget.

The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel Assessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potential feedbacks from climate, changing CO2, and other factors; this paper presents the key results from that assessment, together with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y−1. During the same period, the atmosphere gained 3.2 Gt C y−1 and the oceans are believed to have absorbed 2.0 Gt C y−1. The regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y−1 during this period. Meanwhile, tropical deforestation is thought to have released an average 1.6 Gt C y−1 over the 1980s. While the fluxes among the four pools should balance, the average 198Ds values lead to a ‘missing sink’ of 1.4 Gt C y−1 Several processes, including forest regrowth, CO2 fertilization of plant growth (c. 1.0 Gt C y−1), N deposition (c. 0.6 Gt C y−1), and their interactions, may account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interactive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper presents detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties.

Lack of knowledge about positive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO2 concentrations. Analyses of the atmospheric gradients of CO2 and 13 CO2 concentrations provide increasingly strong evidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive detection in direct biomass and soil measurements remains elusive.

Current regional-to-global terrestrial ecosystem models with coupled carbon and nitrogen cycles represent the effects of CO2 fertilization differently, but all suggest longterm responses to CO2 that are substantially smaller than potential leaf- or laboratory whole plant-level responses. Analyses of emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO2 concentrations are sensitive to the way in which biospheric feedbacks are modeled by c. 15%. Decisions about land use can have effects of 100s of Gt C over the next few centuries, with similarly significant effects on the atmosphere.

Critical areas for future research are continued measurements and analyses of atmospheric data (CO2 and 13CO2) to serve as large-scale constraints, process studies of the scaling from the photosynthetic response to CO2 to whole-ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.

Terrestrial ecosystems and the carbon cycle

Earths resources are consumed by one of its 5-30 million species homo sapiens or man at a rate disproportionately greater than any other species. Mans impact on the biosphere is measured in terms of net primary production (NPP). NPP is the amount of energy remaining after the respiration of primary producers (mostly plants) is subtracted from the total amount of biologically fixed energy (mostly solar). Human output is determined by 1) the direct NPP used for food fuel fiber or timber which yields a low estimate 2) all NPP of cropland devoted to human activity and 3) both 1) and 2) and land conversion for cities or pastures as well as conversion which results in desertification and overuse of lands. This last output determination yields a high estimate. Calculations are made for global NPP and each of the 3 estimates of low intermediate and high human output. Data are based on estimates by Ajtay et al. Armentano and Loucks and Houghton et al. and on the Food and Agriculture Organizations (FAO) summaries. Petagram (Pg) is used to calculate organic matter; this is equivalent to 10 to the 15th power grams or 10 to the 9th power metric tons. Carbon has been converted to organic matter by multiplying by 2.2. Matter in kilocalories has been converted to organic matter by dividing by 5. Intermediate or conservative estimates have been included. The standard of biomass is 1244 Pg and an annual NPP to 132.1. The NPP of marine and freshwater ecosystems is considered to be 92.4 Pg which is a low estimate. The low calculation of human (5 billion persons) consumption of plants at a caloric intake of 2500 kilocalories/person/day is .91 Pg of organic matter which equals .76 Pg of vegetable matter. The global production of human food is 1/7 Pg for grains and for human and livestock fed or .85 Pg of dry grain material and .3 Pg in nongrain dry material with dry grain material and .3 Pg in nongrain dry material with a subtraction of 20% for water content. 34% or .39 Pg is lost to waste and spoilage. Consumption by livestock forest usage and aquatic ecosystems is computed. The overall estimate for human use if 7.2 Pg of organic matter/year or 3% of total NPP/year. The intermediate figures take into account cropland pastureland forest use and conversion; the overall estimate of human use is 42.6 Pg of NPP/year of 19.0% (42.6/224.5) of NPP (30.7% on land and 2.2% on seas). The high estimate yields human use of 58.1 Pg/year on land or 40% (58.1/149.6) of potential land productivity or 25% (60.1/149.8 + 92.4) of land and water NPP. The remaining 60% of land is also affected by humans. The figures reflect the current patterns of exploitation distribution and consumption of a much larger population. These patterns amount to using >50% of NPP of land; there must be limits to growth.

/pdf/human-appropriation-of-the-products-of-photosynthesis-5arm1xw7mn.pdf

Human appropriation of the products of photosynthesis

The fate of fossil fuel carbon dioxide released into the atmosphere depends on the exchange rates of carbon between the atmosphere and three major carbon reservoirs, namely, the oceans, shallow-water sediments, and the terrestrial biosphere. Various assumptions and models used to estimate the global carbon budget for the last 20 years are reviewed and evaluated. Several versions of recent atmosphere-ocean models appear to give reliable and mutually consistent estimates for carbon dioxide uptake by the oceans. On the other hand, there is no compelling evidence which establishes that the terrestrial biomass has decreased at a rate comparable to that of fossil fuel combustion over the last two decades, as has been recently claimed.

https://science.sciencemag.org/content/sci/206/4417/409.full.pdf

Fate of Fossil Fuel Carbon Dioxide and the Global Carbon Budget

Redox control of arsenic mobilization in Bangladesh groundwater

Redox control of arsenic mobilization in Bangladesh groundwater. Appl Geochem 19:201-214

The crystal structure of L-alanine, C3H702N, has been determined and refined by analysis of complete three-dimensional diffraction data from copper X-radiation. The crystals are orthorhombic with space group P212~21 ; the unit-cell dimensions are a = 6.032, b = 12.343, c = 5.784 A. Least-squares refinement of the positional parameters of all 13 atoms and of the individual anisotropic temperature factors of the six heavy atoms, using 581 observed reflections of non-zero weight, yielded a final R index of 0.049. The structure bears a striking resemblance to that Of DL-alanine, and involves the use of all available protons in N-H • • • O hydrogen bonds, with lengths of 2.83, 2.85, and 2.81 A,.

The crystal structure of l-alanine

https://www.ldeo.columbia.edu/~avangeen/publications/documents/Zheng_GCA_05_000.pdf

Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources

H. J. Simpson

Papers

Fate of Fossil Fuel Carbon Dioxide and the Global Carbon Budget

Redox control of arsenic mobilization in Bangladesh groundwater

Redox control of arsenic mobilization in Bangladesh groundwater. Appl Geochem 19:201-214

The crystal structure of l-alanine

Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources