4 research outputs found
De produktie van acrylzuur uitgaande van propeen: Fabrieksvoorontwerp
No full textDocument uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science
The Angola Gyre is a hotspot of dinitrogen fixation in the South Atlantic Ocean
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marshall, T., Granger, J., Casciotti, K. L., Dahnke, K., Emeis, K.-C., Marconi, D., McIlvin, M. R., Noble, A. E., Saito, M. A., Sigman, D. M., & Fawcett, S. E. The Angola Gyre is a hotspot of dinitrogen fixation in the South Atlantic Ocean. Communications Earth & Environment, 3(1), (2022): 151, https://doi.org/10.1038/s43247-022-00474-x.Biological dinitrogen fixation is the major source of new nitrogen to marine systems and thus essential to the ocean’s biological pump. Constraining the distribution and global rate of dinitrogen fixation has proven challenging owing largely to uncertainty surrounding the controls thereon. Existing South Atlantic dinitrogen fixation rate estimates vary five-fold, with models attributing most dinitrogen fixation to the western basin. From hydrographic properties and nitrate isotope ratios, we show that the Angola Gyre in the eastern tropical South Atlantic supports the fixation of 1.4–5.4 Tg N.a−1, 28-108% of the existing (highly uncertain) estimates for the basin. Our observations contradict model diagnoses, revealing a substantial input of newly-fixed nitrogen to the tropical eastern basin and no dinitrogen fixation west of 7.5˚W. We propose that dinitrogen fixation in the South Atlantic occurs in hotspots controlled by the overlapping biogeography of excess phosphorus relative to nitrogen and bioavailable iron from margin sediments. Similar conditions may promote dinitrogen fixation in analogous ocean regions. Our analysis suggests that local iron availability causes the phosphorus-driven coupling of oceanic dinitrogen fixation to nitrogen loss to vary on a regional basis.This work was supported by the South African National Research Foundation (114673 and 130826 to T.M., 115335, 116142 and 129320 to S.E.F.); the US National Science Foundation (CAREER award, OCE-1554474 to J.G., OCE-1736652 to D.M.S. and K.L.C., OCE-05-26277 to K.L.C.); the German Federal Agency for Education and Research (DAAD-SPACES 57371082 to T.M.); the Royal Society (FLAIR fellowship to S.E.F.); and the University of Cape Town (T.M., J.G., S.E.F.). The authors also recognize the support of the South African Department of Science and Innovation’s Biogeochemistry Research Infrastructure Platform (BIOGRIP)
Oxygen isotopic composition of nitrate and nitrite produced by nitrifying cocultures and natural marine assemblages
No full textAuthor Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 57 (2012): 1361-1375, doi:10.4319/lo.2012.57.5.1361.The δ18O value of nitrate produced during nitrification (δ18ONO3,nit) was measured in experiments designed to mimic oceanic conditions, involving cocultures of ammonia-oxidizing bacteria or ammonia-oxidizing archaea and nitrite-oxidizing bacteria, as well as natural marine assemblages. The estimates of ranged from −1.5‰ ± 0.1‰ to +1.3‰ ± 1.4‰ at δ18O values of water (H2O) and dissolved oxygen (O2) of 0‰ and 24.2‰ vs. Vienna Standard Mean Ocean Water, respectively. Additions of 18O-enriched H2O allowed us to evaluate the effects of oxygen (O) isotope fractionation and exchange on . Kinetic isotope effects for the incorporation of O atoms were the most important factors for setting overall values relative to the substrates (O2 and H2O). These isotope effects ranged from +10‰ to +22‰ for ammonia oxidation (O2 plus H2O incorporation) and from +1‰ to +27‰ for incorporation of H2O during nitrite oxidation. values were also affected by the amount and duration of nitrite accumulation, which permitted abiotic O atom exchange between nitrite and H2O. Coculture incubations where ammonia oxidation and nitrite oxidation were tightly coupled showed low levels of nitrite accumulation and exchange (3% ± 4%). These experiments had values of −1.5‰ to +0.7‰. Field experiments had greater accumulation of nitrite and a higher amount of exchange (22% to 100%), yielding an average value of +1.9‰ ± 3.0‰. Low levels of biologically catalyzed exchange in coculture experiments may be representative of nitrification in much of the ocean where nitrite accumulation is low. Abiotic oxygen isotope exchange may be important where nitrite does accumulate, such as oceanic primary and secondary nitrite maxima.This research was funded by the National Science
Foundation Chemical Oceanography grants 05-26277 and 09-
610998 to K.L.C
Characteristics of meat, pet, and research rabbit farms in Brazil: An overview based on twelve farms
No full text[EN] Rabbit production has great growth potential in a country where animal production is very important. However, there is little data about this industry in Southern and Southeast Brazil. The aim of this study was to describe Brazilian rabbit farms that provide meat, pets and animals for learning or research. Three pet farms, four meat farms and five research rabbit farms were visited, and the production and farm characteristics data were collected between June 2018 and March 2019. A total of 1170 rabbits and 617 cages were evaluated. Most farms had 21 to 60 (58.3%) does. Considering all farms, the farmers reported an average rate of conception of 71.8%, prolificacy rate of 6.7 kits per parturition, average interval between parturitions of 65 d and 6.3 parturitions/doe yr. The mean mortality rate for breeding rabbits was 10.4%, compared to 1.7% for growing rabbits (rabbits post-weaning until slaughter or sale). The average area of a cage was 0.43±0.1 m², with an average stocking density for growing rabbits of 3 rabbits/m². The most common cage system used by farmers was a flat-deck (66.7% of farms) system with a wire cage (91.7%). Metal (41.7%) and clay (33.3%) feeders were the most common types of feeders, and automatic nipple drinkers were present in 75% of the farms. Dirt accumulation was observed in 11.2% of the cages and 5.7% of the drinkers, but not in feeders. A total of 4.1% of the cages were considered unsafe, and 0.8% had problems with the drinkers. The farms studied ranged from small to medium in size, used an extensive reproductive rhythm and followed basic production techniques. Animal health and management aspects need to be reviewed by the farmer if the rabbit production conditions are to improve.: This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) – Finance Code 001. 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