Academic literature on the topic 'Anoxic zones'
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Journal articles on the topic "Anoxic zones"
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de Beer, Dirk, Andreas Schramm, Cecilia M. Santegoeds, and Helle K. Nielsen. "Anaerobic processes in activated sludge." Water Science and Technology 37, no. 4-5 (February 1, 1998): 605–8. http://dx.doi.org/10.2166/wst.1998.0726.
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We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO2− and NO3−. Denitrification and sulfate reduction rates were mmeasured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. this indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.
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Deutsch, Curtis, William Berelson, Robert Thunell, Thomas Weber, Caitlin Tems, James McManus, John Crusius, et al. "Centennial changes in North Pacific anoxia linked to tropical trade winds." Science 345, no. 6197 (August 7, 2014): 665–68. http://dx.doi.org/10.1126/science.1252332.
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Climate warming is expected to reduce oxygen (O2) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ15N) from multiple sediment cores. Increasing δ15N since ~1990 records an expansion of anoxia, consistent with observed O2 trends. However, this was preceded by a longer declining δ15N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O2 demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean’s largest anoxic zone will contract despite a global O2 decline.
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Albertson, O. E., and H. D. Stensel. "Aerated Anoxic Biological NdeN Process." Water Science and Technology 29, no. 7 (April 1, 1994): 167–76. http://dx.doi.org/10.2166/wst.1994.0334.
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The conventional practice for an anoxic denitrification basin has been to minimize oxygen input on the basis that it is detrimental to the process. For existing secondary treatment systems, allotting 25-35% of the aeration volume for an unaerated anoxic zone will significantly reduce plant capacity. Further, one group has held that bulking control is best achieved by eliminating all forms of oxygen from the initial contact or biological selector zones. The Phoenix 91st Avenue WWTP was designed with nitrate recycle to aerated selector zones and the anoxic zones were provided with a dense array of fine bubble diffusers. The prototype NdeN process was able to maintain the 1.31 m3/s secondary capacity with aerated anoxic zone receiving 20-25% of the total airflow. Net sludge yields were 30-50% higher than anticipated due to primary clarifier solids losses at higher flows which reduced SRTT to ≤ 5 days. At 5.0-5.5 day SRTT, effluent averaged 8.3 mg/L TN, 1.75 mg/L NH4N and 5.7 mg/L NO3N. Nitrobacter N oxidation rates were unexplainably lower than the Nitrosomonas N oxidation rates causing effluent NO2N.
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Stevens, Gerald M., James L. Barnard, and Barry Rabinowitz. "Optimizing Biological Nutrient Removal in anoxic zones." Water Science and Technology 39, no. 6 (March 1, 1999): 113–18. http://dx.doi.org/10.2166/wst.1999.0275.
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During the initial years of the development of Biological Nutrient Removal (BNR) technology, it was assumed that the bacterial species responsible of the removal of phosphorus (BioP organisms) could not use nitrates as a final electron acceptor and could thus not denitrify. The carbon taken up in the form of Volatile Fatty Acids (VFA) in the anaerobic zone was thus deemed to be unavailable for denitrification in the anoxic zone. This was reinforced through experiments in which BioP organisms cultured in the high-rate Phoredox system in which no nitrification took place, did not denitrify when nitrates were added. Many researchers (e.g. Dold and Barker) have since shown that in BNR systems such as the 3-Stage Bardempho system, where nitrates are recycled to the anoxic zone which follows the anaerobic zone, a high degree of phosphorus uptake through denitrification does occur. In addition, the partial diversion of primary effluent directly to the anoxic zone has significantly improved phosphorus uptake under anoxic conditions. Full-scale operations at the Westbank, British Columbia, plant showed a substantial uptake of phosphorus in the anoxic zone in the absence of oxygen. The Westbank configuration includes side stream primary sludge fermentation, VFA rich fermenter supernatant addition directly to the anaerobic zone and diversion of a portion of primary effluent to the anoxic zone. This configuration stimulates P-uptake under anoxic conditions, demonstrates the efficient use of carbon and is instrumental in achieving an annual average effluent Total-P concentration of less than 0.17 mg/l. The phenomenon of denitrification by BioP organisms was included in the Biowin Model developed by Dold (Biowin Manual). This paper describes experiments and full-scale plant observations to establish the role of BioP organisms in the removal of nitrates in the anoxic zone of a plant which also receives a portion of the primary effluent and verification of the Biowin model.
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Jacobs, Judith. "Anoxic “dead zones” in oceans." Eos, Transactions American Geophysical Union 85, no. 14 (2004): 134. http://dx.doi.org/10.1029/2004eo140006.
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Schramm, Andreas, Cecilia M. Santegoeds, Helle K. Nielsen, Helle Ploug, Michael Wagner, Milan Pribyl, Jiri Wanner, Rudolf Amann, and Dirk de Beer. "On the Occurrence of Anoxic Microniches, Denitrification, and Sulfate Reduction in Aerated Activated Sludge." Applied and Environmental Microbiology 65, no. 9 (September 1, 1999): 4189–96. http://dx.doi.org/10.1128/aem.65.9.4189-4196.1999.
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ABSTRACT A combination of different methods was applied to investigate the occurrence of anaerobic processes in aerated activated sludge. Microsensor measurements (O2, NO2 −, NO3 −, and H2S) were performed on single sludge flocs to detect anoxic niches, nitrate reduction, or sulfate reduction on a microscale. Incubations of activated sludge with15NO3 − and35SO4 2− were used to determine denitrification and sulfate reduction rates on a batch scale. In four of six investigated sludges, no anoxic zones developed during aeration, and consequently denitrification rates were very low. However, in two sludges anoxia in flocs coincided with significant denitrification rates. Sulfate reduction could not be detected in any sludge in either the microsensor or the batch investigation, not even under short-term anoxic conditions. In contrast, the presence of sulfate-reducing bacteria was shown by fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes and by PCR-based detection of genes coding for the dissimilatory sulfite reductase. A possible explanation for the absence of anoxia even in most of the larger flocs might be that oxygen transport is not only diffusional but enhanced by advection, i.e., facilitated by flow through pores and channels. This possibility is suggested by the irregularity of some oxygen profiles and by confocal laser scanning microscopy of the three-dimensional floc structures, which showed that flocs from the two sludges in which anoxic zones were found were apparently denser than flocs from the other sludges.
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Garcia-Robledo, Emilio, Cory C. Padilla, Montserrat Aldunate, Frank J. Stewart, Osvaldo Ulloa, Aurélien Paulmier, Gerald Gregori, and Niels Peter Revsbech. "Cryptic oxygen cycling in anoxic marine zones." Proceedings of the National Academy of Sciences 114, no. 31 (July 17, 2017): 8319–24. http://dx.doi.org/10.1073/pnas.1619844114.
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Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O2to the otherwise anoxic environment. The SCM, commonly found within AMZs, was dominated by the picocyanobacteriaProchlorococcusspp. Free O2levels in this layer were, however, undetectable by conventional techniques, reflecting a tight coupling between O2production and consumption by aerobic processes under apparent anoxic conditions. Transcriptomic analysis of the microbial community in the seemingly anoxic SCM revealed the enhanced expression of genes for aerobic processes, such as nitrite oxidation. The rates of gross O2production and carbon fixation in the SCM were found to be similar to those reported for nitrite oxidation, as well as for anaerobic dissimilatory nitrate reduction and sulfate reduction, suggesting a significant effect of local oxygenic photosynthesis on Pacific AMZ biogeochemical cycling.
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Bartlett, Rick, Maya Elrick, James R. Wheeley, Victor Polyak, André Desrochers, and Yemane Asmerom. "Abrupt global-ocean anoxia during the Late Ordovician–early Silurian detected using uranium isotopes of marine carbonates." Proceedings of the National Academy of Sciences 115, no. 23 (May 21, 2018): 5896–901. http://dx.doi.org/10.1073/pnas.1802438115.
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Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ238U values of marine limestones as a global seawater redox proxy. The δ238U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ238U values and other local redox proxies suggests that the δ238U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ13C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones.
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Raven, M. R., R. G. Keil, and S. M. Webb. "Microbial sulfate reduction and organic sulfur formation in sinking marine particles." Science 371, no. 6525 (December 17, 2020): 178–81. http://dx.doi.org/10.1126/science.abc6035.
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Climate change is driving an expansion of marine oxygen-deficient zones, which may alter the global cycles of carbon, sulfur, nitrogen, and trace metals. Currently, however, we lack a full mechanistic understanding of how oxygen deficiency affects organic carbon cycling and burial. Here, we show that cryptic microbial sulfate reduction occurs in sinking particles from the eastern tropical North Pacific oxygen-deficient zone and that some microbially produced sulfide reacts rapidly to form organic sulfur that is resistant to acid hydrolysis. Particle-hosted sulfurization could enhance carbon preservation in sediments underlying oxygen-deficient water columns and serve as a stabilizing feedback between expanding anoxic zones and atmospheric carbon dioxide. A similar mechanism may help explain more-extreme instances of organic carbon preservation associated with marine anoxia in Earth history.
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Ruano, M. V., J. Ribes, A. Seco, and J. Ferrer. "Low cost-sensors as a real alternative to on-line nitrogen analysers in continuous systems." Water Science and Technology 60, no. 12 (December 1, 2009): 3261–68. http://dx.doi.org/10.2166/wst.2009.607.
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This paper is focused on the evaluation of the applicability of low-cost sensors (pH and ORP) versus nutrient analysers for controlling biological nitrogen removal in WWTPs. A nutrient removal pilot plant located in Carraixet WWTP (Valencia, Spain) that is equipped with a significant number of nutrient analysers and low-cost sensors was used. The relations between reliable, cheap on-line sensors such as pH and ORP (located in anaerobic, anoxic and aerobic zones) and the nitrification/denitrification processes are provided. The nitrification process can be evaluated by measuring the pH difference between the first and last aerobic zones. The denitrification process can be evaluated by measuring the pH difference between the first and last anoxic zones and the ORP in the last anoxic zone. Furthermore, when WWTPs include an anaerobic reactor, the ORP in the anaerobic zone can also be used. With all these factors in mind, these sensors give valuable information for applying advanced control systems such as fuzzy logic-based controllers. Also, low-cost sensors involve lower investment, maintenance and operational costs and lower energy consumption derived from aeration and pumping than nutrient analysers. Thus, low-cost sensors can be successfully used as an attractive alternative to nutrient analysers to control biological nitrogen removal in WWTPs.
Dissertations / Theses on the topic "Anoxic zones"
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Trouwborst, Robert Elisa. "Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.64 Mb., 177 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200548.
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Conway, Carol Leza, and n/a. "Oxic and anoxic transformations of leaf derived organic matter in freshwater systems." University of Canberra. Resource, Environmental & Heritage Sciences, 2005. http://erl.canberra.edu.au./public/adt-AUC20060519.105559.
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In Australia, significant effort goes into reducing the amount of nitrogen and phosphorus
entering inland waters from point sources. However, little is known of the extent to
which riparian organic matter may act as a source of these nutrients. Also, whilst the relationships
between the nitrogen, phosphorus and carbon cycles are broadly known, there
is little quantitative data regarding the release of these elements from Australian riparian
organic matter and their subsequent microbial mineralisation within aquatic environments.
In particular, comparatively little is known of their comparative role in nutrient and organic
matter cycling within anoxic zones, and the influence that different riparian organic matter
may have on stream water quality. This lack of such data presently hampers the ability of
water managers to make educated decisions regarding the management of riparian zones
in Australia. In order to improve understanding in this area, a combination of laboratory
and in situ experiments were carried out in order to compare the abiotic release and aerobic/
anaerobic mineralisation of leaf derived dissolved organic carbon (DOC), dissolved
nitrate/nitrite (NOx) and soluble reactive phosphorus (SRP) under different environmental
conditions. Four plants common to Australian riparian zones were investigated: two native
species, Eucalyptus camaldulensis (gum) and Phragmites australis (common reed), and
two exotic species, Salix babylonica (willow) and Lolium multiflorum (rye grass). After 30
days, formaldehyde inhibited 1g willow and rye grass extracts contained the most SRP (0.7
mg/L), whilst gum extracts contained 0.3 mg/L and common reed 0.1 mg/L of SRP.Willow
and rye grass abiotically released twice as much NOx than gum and common reed, although
concentrations were only between 0.05-0.1 mg/L. Gum and common reed released the most
DOC per gram of leaf matter (14 and 12 mmol/g of leaf matter respectively), but based on
the initial carbon content of each leaf type, the largest percentage contributor of DOC under
abiotic conditions was common reed and rye grass (both 38% mass/mass), with gum (33%
mass/mass) and willow (30% mass/mass) being smaller contributors. The most bioavailable
DOC was released by rye grass and common reed, with between 83 and 94% of this
DOC microbially mineralised after 30 days in oxic conditions. When conditions were not
inhibited, microbial growth was evident almost immediately in willow, rye grass and common
reed leaf extracts. However, microbial growth was suppressed for the first 48 hours
in gum leaf extracts. After this suppression period, the rate of DOC mineralisation was
equal in willow and gum leaf extracts (0.1 day-1). Under anoxic conditions, the rate and
extent of DOC mineralisation of willow and gum leaves depended on the type of electron
acceptor provided. Added nitrate and iron III enhanced the mineralisation of both willow
and gum leaves relative to no terminal electron acceptors (from zero to 0.01-0.04 and 0.002-
0.004 moles/day respectively), but added sulphate only enhanced the mineralisation of gum
leaves (0.04 moles/day). When no additional electron acceptors were provided, particulate
leaf mineralisation was more extensive under oxic than anoxic conditions. However, the
mineralisation of leaf derived DOC were the same regardless of oxygen availability, and
after 35 days in either condition the percentage of leaf DOC mineralised for each leaf type
was of the order common reed > rye grass > willow > gum. All the leaf types tested were
able to sustain the caddis fly larvae Triplectides australis under controlled laboratory conditions,
and survival rates were high using all four leaf types as a food source. Triplectides
australis did not significantly increase the amount of DOC released from each type of leaf
matter, but they did consistently increase the proportion of simple carbohydrates present
within the DOC fraction. The results of these experiments suggest that changes to riparian
vegetation, particularly from the native to exotic species used in this study, will inherently
alter in-stream concentrations of dissolved carbon and nutrients (particularly SRP). This
potentially will affect in-stream, hyporheic and subsurface processes, particularly in areas
where surface water flow is low and riparian leaf inputs are high.
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Nair, Arthur William. "Investigation of the Effects of Sequential Anaerobic, Anoxic and Aerobic Zones on Dissolved Oxygen Transfer Parameters in a biological Nutrient Removal Pilot Plant." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46264.
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Bench and pilot scale determinations of the volumetric oxygen transfer coefficient, KLa, were performed on an improved A²/O biological nutrient removal (BNR) pilot plant. Effluent from a full scale primary clarifier, used as pilot plant influent, was found to have an alpha (ratio of process to clean water KLa) of 0.71 as determined in a 21 liter bench scale reactor and an alpha of 0.332 as determined in a 0.45 m³ aeration basin of the 2.4 m³ pilot plant. Alpha of a 1:1 mixture of primary clarifier effluent with pilot plant return activated sludge was determined to be 0.94 at bench scale and 0.71 at pilot scale. An assay of alphas through the initial non aerated treatment zones of the pilot plant using the bench scale reactor indicated that alphas peaked in the effluent of the first anaerobic zone (alpha equal to 1.01) and were lower in the second anaerobic zone and first anoxic zone. An assay of alphas in the three pilot plant series sideline aeration basins indicated that alpha was maximum in the first aeration basin (alpha equal to 0.905) and were lower in the second and third aeration basins (0.716 and 0.661 respectively). A consistent increase in average surface tension was noted from the first to second to third aeration basins, however the differences were not statistically significant. A comparison of pilot plant alphas determined in the first aeration basin following anaerobic nominal hydraulic retention times of 0.0, 0.21, 0.43, and 0.64 hours yielded alpha values of 0.71, 0.94, 0.64, and 0.74 respectively. Like the assay using the bench scale reactor, the alpha values at pilot scale peaked following treatment in only one anaerobic zone (nominal HRT of 0.21 hours). The study concludes that short exposures in an initial anaerobic reactor as required for biological phosphorus removal may benefit oxygen transfer efficiency through increased alphas, however the benefits of long periods of anaerobic reaction time (over 0.43 hours) are uncertain.Master of Science
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Montes-Herrera, Enrique. "Seasonal Changes in the Sinking Particulate Flux and in the Nitrogen Cycle within the Euphotic and Twilight Zones of the Cariaco Basin, Venezuela." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3253.
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This study explored the effects of seasonal variability on the geochemistry of sinking pthesiss and on the nitrogen cycle of the Cariaco Basin. Pthesis fluxes were measured at the base of the euphotic zone (the depth of 1% of photosynthetically active radiation - PAR) with drifting sediment traps during months of upwelling and non-upwelling regimes from March 2007 to November 2009. Flux estimates were analyzed in the context of seasonal variations in sea surface temperature, primary productivity, and chlorophyll a concentrations using data generated by the CARIACO Time-series Program as well as satellite data. Additionally, nine years (1996-2000 and 2004-2007) of nutrients, phytoplankton taxonomy and δ15N of sinking pthesis data within the twilight zone (225 m) from the CARIACO Time-series Program were examined. Results showed that the flux of organic matter responded to changes in surface chlorophyll a but not to primary production. Sinking organic matter decreased by an order of magnitude from the base of the euphotic zone to the oxic-anoxic interface; most of the organic matter produced in surface waters was remineralized before leaving the upper 50-100 m. Lithogenic material often represented a large fraction of the flux. Isotopic analyses showed that 13C/12C ratios of sinking organic carbon were enriched (~-19‰) during the upwelling period and depleted during relaxation (~-23‰). This reflects seasonal changes in inorganic carbon utilization by phytoplankton and suggests that the δ13C of organic carbon in Cariaco sediments can be used as a proxy for carbon fixation by primary producers. The δ15N of the settling flux was influenced by the strength of the upwelling and the presence of the nitrogen fixer Trichodesmium thiebautii in the basin in different seasons; the 15N/14N ratio of sinking nitrogen reflects both imported and local nitrogen fixation signals. This result argues against previous interpretations of the δ15N from the basin's sedimentary record, which suggested that the nitrogen isotopic composition of flux is influenced by denitrification at the oxic-anoxic interface.
Dissolved gas samples from the Cariaco eastern and western sub-basins from September 2008 (non-upwelling) and March 2009 (upwelling) were studied to assess the production of biogenic nitrogen gas through mass spectrometric N2/Ar ratiometry. Excess nitrogen gas indicated that upwelling affects the intensity of denitrification at the oxic-anoxic interface. In four of the six stations the concentration of biogenic nitrogen gas at the oxic-anoxic interface was 2.7-6.1 µM N higher during the upwelling period than during the relaxation season (p< 0.001), implying that denitrification in the basin was stimulated by the vertical flux of organic matter and/or the ventilation of the oxic-anoxic interface by oxygenated and nutrient-rich intermediate Caribbean waters.
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Buchwald, Carolyn. "Nitrogen cycling in oxygen deficient zones : insights from [delta]¹⁵N and [delta]¹⁸O of nitrite and nitrate." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79346.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.In title on title page, "[delta]" appears as lower case Greek letters. Cataloged from PDF version of thesis.
Includes bibliographical references.
The stable isotopes, [delta]¹⁵N and [delta]¹⁸O, of nitrite and nitrate can be powerful tools used to interpret nitrogen cycling in the ocean. They are particularly useful in regions of the ocean where there are multiple sources and sinks of nitrogenous nutrients, which concentration profiles alone cannot distinguish. Examples of such regions are "oxygen deficient zones" (ODZ). They are of particular interest because they are also important hot spots of fixed N loss and production of N₂O, a potent greenhouse gas. In order to interpret these isotope profiles, the isotope systematics of each process involved must be known so that we can distinguish the isotopic signature of each process. One of the important processes to consider here is nitrification, the process by which ammonium is oxidized nitrite and then to nitrate. This thesis describes numerous experiments using both cultures of nitrifying organisms as well as natural seawater samples to determine the oxygen isotope systematics of nitrification. These experimental incubations show that the accumulation of nitrite has a large effect on the resulting [delta]¹⁸ONO3. In experiments where nitrite does not accumulate, [delta]¹⁸ONO3 produced from nitrification is between -1 to l%o. These values will be applicable for the majority of the ocean, but the nitrite isotopic exchange will be important in the regions of the ocean where nitrite accumulates, such as the base of the euphotic zone and oxygen deficient zones. [delta]¹⁸ONO2 was developed as a unique tracer in this thesis because it undergoes abiotic equilibration with water [delta]¹⁸O at a predictable rate based on pH, temperature and salinity. This rate, its dependencies, and how the [delta]¹⁸ONO2 values can be used as not only biological source indicators but also indicators of age are described. This method was applied to samples from the primary nitrite maximum in the Arabian Sea, revealing that the dominant source and sinks of nitrite are ammonia oxidation and nitrite oxidation with an average age of 37 days. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets multiisotope nitrate and nitrite profiles in the Costa Rica Upwelling Dome using a simple ID model. The nitrite isotopes showed that there were multiple sources of nitrite in the primary nitrite maximum including (1) decoupling of ammonia oxidation and nitrite oxidation, (2) nitrate reduction during assimilation and leakage of nitrite by phytoplankton. In the oxygen deficient zone and secondary nitrite maximum, there were equal contributions of nitrite removal from nitrite oxidation and nitrite reduction. This recycling of nitrite to nitrate through oxidation indicates that the percentage of reduced nitrate fully consumed to N2 gas is actually smaller than previous estimates. Overall, this thesis describes new nitrogen and oxygen isotopic tracers and uses them to elucidate the complicated nitrogen biogeochemistry in oxygen deficient zones.
by Carolyn Buchwald.
Ph.D.
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Turner, Andrew David. "Recognition of photic zone anoxia from LC-MS studies of porphyrin distributions in ancient sediments." Thesis, University of Bristol, 1998. http://hdl.handle.net/1983/23c52c13-eaf1-4c6d-9282-60c42e81f228.
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Gibbison, Robert. "Porphyrins and 1H-pyrrole-2,5-diones (maleimides) as indicators of anoxygenic photosynthesis in palaeowater columns." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296647.
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Crawford, Neil Adrian. "Maleimides (1H-pyrrole-2, 5-diones) from ancient sediments as indicators of photic zone anoxia." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299604.
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Lehours, Anne-Catherine. "La communauté procaryotique dans les zones anoxiques de deux écosystèmes lacustres : structure et diversité. Etude plus particulière de son rôle fonctionnel dans le monimolimnion." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2006. http://tel.archives-ouvertes.fr/tel-00703327.
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Les études présentées dans ce manuscrit traitent de la diversité et de l'écologie des communautés procaryotiques des zones anoxiques pélagiques de deux écosystèmes lacustres : le lac d'Aydat, typiquement eutrophe, qui présente en période de stratification thermique un hypolimnion anoxique ; et le lac Pavin, unique lac méromictique de France, exhibant une zone anoxique permanente. Les analyses de la structure, de la diversité, et de la dynamique spatiale et- /ou temporelle du bacterioplancton des strates anoxiques de ces deux lacs par des approches moléculaires ont révélé une forte diversité microbienne accentuée par une stratification spatiale du bacterioplancton. Les investigations complémentaires sur les relations phylogénétiques et sur l'étude de métabolismes microbiens ont été focalisées sur les communautés de la zone anoxique du Lac Pavin en raison de son caractère original. Les banques de clones construites à partir d'échantillons d'eau anoxique prélevés à différentes strates dans le monimolimnion ont révélé que les communautés bactériennes sont dominées par des espèces affiliées aux δ-Proteobacteria, aux Verrucomicrobia, aux Bacteroidetes et à la division candidate OP11. Les séquences ARNr16S des Archaea sont principalement affiliées au groupe des Méthanosarcinales, observation confirmée par hybridation in situ. Les études in vitro de la réduction dissimilatrice du Fe (III), dans des cultures d'enrichissements, ont confirmé que les concentrations élevées en fer ferreux observées dans la sub-chémocline du Lac Pavin résultaient pour partie de l'activité de microorganismes. Dans ces enrichissements, les microorganismes couplent la réduction du Fe (III) avec l'oxydation préférentielle du fumarate, de l'H2, du CH4 et du lactate. Aucune accumulation de Fe (II) n'a été notée dans les enrichissements supplémentés en acétate comme donneur d'électrons. Cette observation suggère que ce métabolite pourrait être principalement utilisé dans le processus de méthanogénèse, et pourrait être produit pour partie par l'activité de bactéries Gram-positives homoacétogènes. L'hétérogénéité des profils TTGE réalisés à partir des différentes conditions d'enrichissements de BFR suggère que ces dernières peuvent occuper des niches écologiques très diverses dans le monimolimnion du Lac Pavin. Aucune séquence n'a été affiliée à des BFR* obligatoires identifiées dans d'autres écosystèmes. L'affiliation de séquences à des espèces appartenant au genre Desulfovibrio suggère que certaines BSR† utilisent cet accepteur d'électron. Des activités significatives de réduction du Fe (III) ont également été mises en évidence chez des souches fermentatives isolées de la zone anoxique de ce lac. L'étude plus particulière de la souche BS2 a révélé que cette voie métabolique pouvait lui conférer un avantage énergétique et donc écologique. L'ensemble du travail qui se situe dans les domaine de l'écologie microbienne et de l'environnement ouvre un large champ d'investigations tant au niveau cognitif qu'appliqué. Les perspectives prévoient d'affiner la compréhension du rôle des microorganismes anaérobies des systèmes lacustres dans les cycles biogéochimiques et plus généralement dans la compréhension du rôle de la biodiversité microbienne afin de répondre de façon raisonnée à une demande sociétale forte dans ces domaines.
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Terrisse, Fanny. "Influence des oscillations anoxie/oxie sur des communautés microbiennes hydrocarbonoclastes de sédiments intertidaux." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3056/document.
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Les écosystèmes côtiers sont des milieux complexes au sein desquels les communautés microbiennes, jouant un rôle majeur dans leur fonctionnement et leur maintien, s’adaptent et sont tolérantes à des conditions environnementales fluctuantes. En effet, au rythme des marées et de l'activité de la macrofaune, des oscillations oxie/anoxie influencent la composition et la dynamique des communautés microbiennes et par conséquent leur implication métabolique. Afin d’appréhender le devenir du pétrole dans ces écosystèmes, il est donc indispensable d’apporter des connaissances sur l’écologie des microorganismes intervenant dans son élimination, notamment dans des conditions oscillantes anoxie/oxie. Ainsi, ce travail de thèse a eu pour objectif de décrypter l’assemblage de communautés microbiennes hydrocarbonoclastesde sédiments intertidaux soumises à des oscillations anoxie/oxie en présence de pétrole lors d’une expérience en bioréacteurs. Les réponses écologiques des communautés bactériennes globales et de micro-organismes sulfato-réducteurs en conditions oscillantes ont pu être décrites en comparaison avec celles obtenues en conditions d’oxie ou d’anoxie permanentes, par l’analyse des données obtenues par séquençage haut-débit des gènes de l’ARN 16S et dsrB au niveau transcriptionnel. Ces études comparatives ont mis en évidence des profils écologiques en réponseaux conditions oscillantes, pouvant être répandus dans différents environnements marins côtiers. En réponse à ces conditions particulières, de nombreux microorganismes semblent avoir le potentiel à tolérer et/ou s’adapter aux différentes conditions d'oxygénation. Cette capacité d’acclimatation rapide des communautés bactériennes aux conditions oscillantes se sont accompagnées de capacités de dégradation équivalentes ou supérieures dans ces conditions par rapport à la condition d’oxie permanente montrant l’influence des oscillations anoxie/oxie sur le devenir du polluant dans les environnements pollués soumis à ces conditionsCoastal ecosystems are complex environments in which microbial communities, playing a major role in their functioning and maintain, are tolerant and adapt to changing environmental conditions. Indeed, the tides and the macrofauna’s activity generate oxic/anoxic oscillations which influence the composition and dynamics of microbial communities and consequently their metabolic in volvement. To understand the fate of oil in these ecosystems, it is essential to provide knowledge on the ecology of microorganisms involved in these systems, taking into account anoxic/oxicoscillating conditions. Thus, this thesis aimed to decipher the organization of hydrocarbonoclastic microbial communities inhabiting intertidal sediments, when they are subjected to anoxic/oxic oscillations in an experiment in bioreactors with oil addition. Ecological responses of bacterial communities and sulfate-reducing microorganisms in oscillating conditions have been described comparing with those obtained with permanent oxic or anoxic conditions, using high-throughputsequencing analyses of the 16S rRNA and dsrB genes at the transcriptional level. These comparatives studies have highlighted ecological profiles in response to the oscillating conditions, which can be prevalent in different coastal marine environments. In response to these particular conditions, many organisms seem to have the potential to tolerate and / or adapt to the different conditions of oxygenation. This rapid acclimation capacity of bacterial communities tothese changing conditions have been accompanied by equivalent or greater degradation capacity under these conditions compared to the permanent oxic condition, showing the influence of the anoxic/oxic oscillations on the fate of pollutant in environments subjected tothese conditions
Books on the topic "Anoxic zones"
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Saniye, Atayman, ed. The Permian extinction and theTethys: An exercise in global geology. Boulder, Colo: Geological Society of America, 2009.
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Şengör, A. M. Celâl. The Permian extinction and the Tethys: An exercise in global geology. Boulder, Colo: Geological Society of America, 2009.
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Renaud, Maurice L. Annotated bibliography on hypoxia and its effects on marine life, with emphasis on the Gulf of Mexico. Seattle, Wash.]: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, 1985.
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United States. Congress. Senate. Committee on Environment and Public Works. Water quality in Lake Erie: Field hearing before the Committee on Environment and Public Works, United States Senate, One Hundred Seventh Congress, second session, on anoxia in the central basin of Lake Erie, and the impact of "dead zones" on the ecology of the Great Lakes region, August 5, 2002, Cleveland, OH. Washington: U.S. G.P.O., 2004.
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Hand, Carol. Dead Zones. Lerner Publishing Group, 2016.
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Hand, Carol. Dead Zones: Why Earth's Waters Are Losing Oxygen. Lerner Publishing Group, 2016.
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Anoxia Evidence For Eukaryote Survival And Paleontological Strategies. Springer, 2011.
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Anoxic Zone. Black Water Books, 2009.
Find full textBook chapters on the topic "Anoxic zones"
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Reolid, Matías, José Miguel Molina, Luis Miguel Nieto, and Francisco Javier Rodríguez-Tovar. "The Betic External Zones." In The Toarcian Oceanic Anoxic Event in the South Iberian Palaeomargin, 5–22. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-67211-3_2.
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Bazylinski, Dennis A., Christopher T. Lefèvre, and Richard B. Frankel. "Magnetotactic Protists at the Oxic–Anoxic Transition Zones of Coastal Aquatic Environments." In Cellular Origin, Life in Extreme Habitats and Astrobiology, 131–43. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1896-8_7.
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Diaz, Robert J. "Anoxia, Hypoxia, And Dead Zones." In Encyclopedia of Estuaries, 19–29. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-8801-4_82.
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Suvorov, A. M., V. N. Eremeev, A. Kh Khaliulin, and E. A. Godin. "Oceanographic Data Development for Anoxic Zone Boundary in the Black Sea." In Integrated Approach to Environmental Data Management Systems, 487–94. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5616-5_42.
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"anodic zone." In Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik, 53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41714-6_12076.
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Mijaylova Nacheva, Petia, Danilo Gamboa-Santana, and Edson B. Estrada-Arriaga. "Secondary Sludge Biodegradation and Electricity Generation in Biocathode Microbial Fuel Cells." In Sewage - Recent Advances, New Perspectives and Applications. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.100305.
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The looking for sustainable sewage sludge management technology in the wastewater treatment plants, has brought to light the biocathode microbial fuel cells (bMFCs) which allow simultaneous biological stabilization and direct energy generation, avoiding the production of biogas. In the present study, the performance of bMFCs for the treatment of secondary sludge as anodic substrate was evaluated by analyzing the removal of organic matter, destruction of volatile solids and the generation of electrical energy under different operating conditions and applying two types of cathode chambers. The results indicated that VSS and tCOD removals up to 92% and 87% respectively can be achieved in the anodic chamber generating simultaneously energy. Current and power densities of 1.80 ± 0.09 A∙m−3 and 0.43 ± 0.02 W∙m−3 respectively were reached, showing that bMFCs are a reliable alternative to generate electricity during the sewage sludge stabilization process. It was revealed that the pH value and the type of cathodic zone are statistically significant factors that influenced the performance of the bMFCs. The obtained results demonstrated that the electrochemical performance of the bMFCs was better at pH value of 6 in the anodic chamber and when aerobic cathode zone was used.
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Schoepfer, Shane D., and Charles M. Henderson. "Paleogeographic Implications of Open-Marine Anoxia in the Permian–Triassic Slide Mountain Ocean." In Late Paleozoic and Early Mesozoic Tectonostratigraphy and Biostratigraphy of Western Pangea, 205–25. SEPM (Society for Sedimentary Geology), 2022. http://dx.doi.org/10.2110/sepmsp.113.10.
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The end-Permian mass extinction was associated with the onset of anoxia in widespread marine environments; however, the extent of this anoxia remains controversial. Proposed models range from near-universal “superanoxia” in the Panthalassic Basin to a more limited expansion of anoxia in the upper water column in response to enhanced primary productivity. The Peck Creek and Ursula Creek sections of northern British Columbia were deposited at ~200 m water depth in the Ishbel Trough, on the margin of cratonic North America. This trough was generally contiguous with the Slide Mountain Ocean, and thus with the broader Panthalassic Ocean, though it may have been partially separated by structural highs at various times during the Permian. Both sections include continuous Wordian to Changhsingian sedimentary successions, which span the end-Permian mass extinction boundary and continue into the earliest Triassic. The extinction is recognizable as the disappearance of biogenic silica from the environment, which defines the contact between the Fantasque Formation and overlying Grayling Formation. This surface also corresponds with the onset of anoxia, and the accumulation of redox-sensitive trace metals. The covariation trends in these metals, and in other isotopic proxies, can be used as tools to trace the degree of communication between the Ishbel Trough–Slide Mountain Ocean and the broader Panthalassic Basin. Molybdenum-uranium covariation trends indicate that the northern Slide Mountain Ocean and Ishbel Trough remained in communication with the larger global ocean throughout this interval, suggesting inversion of the Wordian structural high to form a depositional subbasin by the Changhsingian. This is in contrast to the Opal Creek section of southern Alberta, which shows evidence for some degree of restriction, suggesting that the Slide Mountain Ocean may have maintained a north–south gradient in water chemistry. Several lines of evidence suggest that this onset of anoxia was not related to expansion of an upwelling-driven oxygen minimum zone. No clear changes in primary productivity, as recorded by organic carbon or authigenic phosphorus and barium, are observed across the extinction horizon. Changhsingian nitrogen isotope values are generally in the 2 to 3‰ range, suggesting minimal denitrification at thermocline water depths, and these values decreased in the earliest Triassic, likely in response to enhanced nitrogen fixation. This suggests that anoxia was driven by shoaling of a chemocline that developed due to stratification of the Slide Mountain Ocean, rather than western-boundary upwelling effects.
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Hallam, Tony. "Oxygen deficiency in the oceans." In Catastrophes and Lesser Calamities. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198524977.003.0009.
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We are all very much aware that oxygen deprivation leads quickly to death, and this is true not just of our own species but of virtually the whole organic world. There are indeed very few exceptions, such as the anaerobic bacteria that derive their energy from reducing sulphates to sulphides, which flourish in the absence of free oxygen. (As these organisms do not leave a fossil record they provide no clues for the geological detective.) Today the atmosphere never lacks oxygen, except in artificially enclosed conditions, but oxygen deficiency can be lethal in certain marine environments and thus must be explored as a possible factor in causing mass extinctions. Mixing with atmospheric winds ensures that the surface waters of the ocean, down to the greatest depth attained by storm waves, always contain plenty of oxygen. Most of the oceans and marginal seas today contain oxygen throughout their depth, but in certain circumstances an oxygen deficiency can occur in the lower parts of the ocean. In parts of some tropical oceans, for instance, the oxygen content decreases with depth until near the ocean bottom, where under the influence of currents driven by cold water from around Antarctica, the oxygen content increases again. This gives rise to a zone in the ocean known as the oxygen minimum zone. The rapid deep ocean circulation is today driven ultimately by the presence of polar ice on Antarctica, which is the main cause of the strong sea-water temperature gradient from the tropics to the poles. For long periods in the Earth’s history substantial polar ice caps were lacking, and many geologists believe that during those periods latitudinal ocean currents were more sluggish. The deep ocean must then have been largely deficient in oxygen, if not completely lacking in oxygen (anoxic). (Sea water with a content of one or more millilitres of oxygen per litre of water is called oxic; 0.1 ml or less is anoxic; and for any intermediate value the water is dysoxic.) Certain parts of the sea bed where the overlying water is deficient in oxygen are enriched in organic matter derived principally from the plankton.
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Gaines, Susan M., Geoffrey Eglinton, and Jürgen Rullkötter. "Weird Molecules, Inconceivable Microbes, and Unlikely Environmental Proxies: Marine Ecology Revised." In Echoes of Life. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195176193.003.0014.
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Anaerobic methanotrophs are not the only ecologically important archaea to surprise microbiologists in the last decade. And their isoprenoid ethers are not the only useful lipids—and certainly not the strangest—to have joined the lexicon of microbial biomarkers. Though much of that lexicon is still too generic to be of much use in understanding geologic history, some of these structures have allowed geochemists to transcend biological complexity and garner clues to past climates and environments. In the 1990s, when Stefan Schouten first started finding ring-containing biphytanyl ethers in his sediment samples, he was still working on his doctorate at NIOZ. Like everyone else at the time, he assumed that they derived from the lipids of methanogenic archaea and that it was only a matter of time before ring-containing biphytanyl tetraethers would be identified among the lipids of some newly isolated culture of methanogens, as Guy Ourisson had predicted. Schouten was studying oxygen- and sulfur-bound biomarkers, which meant he treated his sediment extracts chemically to cleave the ether and sulfur bonds, and the treatments often turned up biphytanes. But then, he says, he and another student started finding the ring-containing compounds in some really unlikely places, such as the oxic surface layer of marine sediments where neither methanogens nor extreme thermophilic and halophilic archaea were likely to make a home. The only thing they could think of at the time was that the tetraethers had come from methanogens that lived in the oxygen minimum zone, the layer of water beneath the photic zone where heterotrophic bacteria are active, sometimes to the point of using up all of the oxygen. When Schouten presented these ideas at the 1995 organic geochemistry meeting, Stuart Wakeham immediately piped up with the suggestion that they look for the lipids in the water column—and offered the perfect samples for the enterprise. He had collected particulate matter at different depths in the Black Sea and Cariaco Basin, just the sort of anoxic environments where one might expect to find methanogens in the water column. . . .
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Gulin, Maksim Borisovich, Ekaterina Alexandrovna Ivanova, Pavel Antonovich Stunzhas, and Oleg Igorevich Podimov. "Study of oxygen regime in the near-bottom water layer and reaction of zoobenthos to hypoxia/anoxia at the contact zone of the Black Sea chemocline with continental slope." In Some results of multidisciplinary coastal expedition «Black Sea-2017» at R/V «Ashamba», 149–54. Nauchnyj Mir, 2018. http://dx.doi.org/10.29006/978-5-91522-472-7-2018.7.
Full textConference papers on the topic "Anoxic zones"
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Bieleń, W., and I. Matyasik. "Aryl Isoprenoids as Indicators of Photic Zone Anoxia." In 29th International Meeting on Organic Geochemistry. European Association of Geoscientists & Engineers, 2019. http://dx.doi.org/10.3997/2214-4609.201902983.
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Naitoh, Masanori, Shunsuke Uchida, Yasushi Uehara, Hidetoshi Okada, and Seiichi Koshizuka. "Evaluation of Wall Thinning Rate Due to Flow Accelerated Corrosion With the Coupled Models of Electrochemical Analysis and Double Oxide Layer Analysis." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77583.
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Systematic approaches for evaluating flow accelerated corrosion (FAC) are desired before discussing application of countermeasures for FAC. Future FAC occurrence should be evaluated to identify locations where a higher possibility of FAC occurrence exists, and then, wall thinning rate at the identified FAC occurrence zone should be evaluated to obtain the preparation time for applying countermeasures. Wall thinning rates were calculated with the coupled models of static electrochemical analysis and dynamic double oxide layer analysis. Anodic current density and electrochemical corrosion potential (ECP) were calculated with the electrochemistry model based on an Evans diagram and ferrous ion release rate determined by the anodic current density was applied as input for the double oxide layer model. The thickness of oxide layer was calculated with the double oxide layer model. The dependences of mass transfer coefficients, oxygen concentrations ([O2]), pH and temperature on wall thinning rates were calculated with the coupled model. It was confirmed that the calculated results of the coupled models resulted good agreement with the measured ones. The effects of candidates for countermeasures, e.g., optimization of N2H4 injection point into the feed water system, on FAC mitigation was demonstrated as a result of applying the model.
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Sergeyeva, Tatyana K., Igor A. Tychkin, and Gennady G. Vasiliev. "Hydrogen-Induced Stress Corrosion Cracking of Pipe Lines of Russia." In 1996 1st International Pipeline Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/ipc1996-1857.
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The results of expert studies of large diameter pipes damaged due to external stress corrosion cracking are presented in the report. These data obtained in the 1993–1995 are typical for various regions of Russia. The results of laboratory studies of the stress-corrosion mechanism for pipe steels in suspensions of soils from the places where the operating failure had occurred are given in the report also. The mechanism of hydrogen-induced stress-corrosion cracking (HISCC) realizing through local hydrogenation of steel during plastic deformation has been determined by means of the technique of slow strain rate test (SSRT) of samples in the soil under cathodic, anodic and free corrosion potentials in combination with hydrogenation and hydrogen distribution analyses along length of a sample. No hydrogenation of volumes of pipes non-subjected to cracking was observed but hydrogenation took place in the zones subjected to stress corrosion.
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Lee, Ching-Jiun, and Horn-Jiunn Sheen. "Multifunctional Microfluidic Device Utilizing Unsteady Flow." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62052.
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This study describes experimental results for a multifunctional microfluidic device with fluid pumping, mixing and particle removal. The obstacle-type valveless micropump, micromixer and particle separator are further integrated into the proposed multifunctional device. The process for fabricating this device is simple as only 1 photo mask, 1 inductively coupled plasma (ICP) etching step and anodic glass bonding are required. This novel device was developed utilizing an unsteady flow in a microchannel induced by the piezoelectric zirconium titanate (PZT) membrane oscillation of an obstacle-type valveless micropump. Flow direction is controlled by the amplitude and frequency of power driving the vibrating membrane. The optimal operational frequency for this device is 1.0 kHz. Very high mixing (>95%) and particle removal efficiency (close to 100%) exist at the inlet region and trifurcate zone, respectively. Image processing is utilized to count the number of particles and assess removal efficiency.
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Fang, B., R. L. Eadie, and M. Elboujdaini. "Blunt Crack Initiation and its Transition to Sharp Cracks in Pipeline Steel in Near-Neutral pH Solution." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90088.
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This paper reviews our research into pipeline stress corrosion cracking (SCC) in near-neutral pH (NNpH) environment to help understand the mechanisms on pit-to-crack transition and early growth to contribute to pipeline integrity management so that the risk of failure can be avoid or reduced. Pitted specimens by using two different techniques (passivation/immersion and electrochemical methods) were cyclically loaded in NNpH environment sparged with 5% CO2 / balance N2 gas mixture at high stress ratios (minimum stress/maximum stress), low strain rates and low frequencies which are close to the operational pipelines in the field. Blunt cracks initiation was seen first and associated with the pit geometry, and most of the blunt cracks were observed to have initiated from the corrosion pits that had the pit depth to surface width aspect ratios greater than 0.5. The blunt crack growth was engendered by anodic dissolution, which was facilitated by stress. So it was called as stress facilitated dissolution crack growth. These blunt cracks had considerably large crack tip width to crack mouth width aspect ratios, and the majority were below 0.5 to 0.6 mm deep, and considered dormant. Once cracks surpassed the critical value, around 0.5 to 0.6 mm, the cracks would be reactivated and the crack tip width to crack mouth width ratios became significantly smaller. Meanwhile, more hydrogen would be trapped in the plastic zones. Thus, hydrogen would play an important role in the crack propagation. So in this stage, cracks tended to become sharp and the mechanism was referred to hydrogen facilitated cracking. The observations from the field can be interpreted very well by using the proposed models. It was proposed that two different mechanisms are responsible for the early-stage crack growth and sharp cracks be removed to reduce the risk of failure in pipelines.
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Sarnet, T., and M. Autric. "Corrosion Resistance Improvements of Metallic Alloys Using One-Step Excimer Laser Treatment." In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/cleo_europe.1996.cwf64.
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This study concerns the structural modifications of metallic alloys such as aluminum alloys, titanium alloys and steels in order to improve their mechanical and physic-chemical properties. These modifications induce changes in the lifetime of these metallic samples as far as the corrosion resistance is concerned. Effects have been studied as a function of incident energy density, overlapping, number of pulses using a KrF excimer laser (20 ns; 80 W; 248 nm). Structural modifications analysed by low-incidence X-ray diffraction have been observed for all materials with micro and nano-structures formation due to the high values of the cooling rate (>108 K.s−1). The most interesting structures were, for instance, the titanium Ti6Al4V (α+β) which after processing becomes a fine lath martensitic structure which has a thickness of approximately of 250 nm, and also steel 35NCD16 (ferrite+perlite) which is austenitic+martensitic after treatment. An investigation was carried out after scanning large surfaces into corrosion resistance of these metallic materials. Electrochemical tests -anodic polarisation- revealed a significant increase in the resistance to pitting of the aluminum alloys. This improvement is due to the dissolution of khatyrkite phase in the matrix leading to a redistribution of the copper atoms within the melted layer (few microns). On the other hand, 2017A aluminum can be slightly softened by the processing. In the opposite, for other materials a hardening can occur. This hardening can be weak and due to a simple grain refinement, as is the case for the 1050A aluminum. This hardening is significant when treating the Ti6A14V titanium and even more so for the 35NCD16 steel which goes from 250HV to almost 1000HV, which is impossible to obtain with classic thermal processes. In the case of 35NCD16 steel samples, the gain in the corrosion resistance is due to change in the structure and due to a galvanic coupling between the irradiated and the non irradiated zones.
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Gunaltun, Yves. "Possible Missing Link in CO2 Corrosion Prediction." In SPE International Oilfield Corrosion Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205056-ms.
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Abstract CO2 corrosion prediction models predict a general corrosion rate, but field failures are due to localised CO2 corrosion. That is why predicted corrosion rates are correlated to a corrosivity level. These models generally consider that the corrosion rate remains, after the initiation period, unchanged as long as operating and/or production parameters remain unchanged. However, 25 years of field experience and also some recent research results confirmed that after an initial phase of high corrosion rates, the CO2 corrosion rates may significantly decrease with time forming flat-bottom large corrosion features (mesa corrosion) and stabilise. Depending on the corrosivity level the time needed for the stabilisation would be up to about 12 months. To be noted that the stabilization has been known since 2003-2004. It was first used in 2005 for the development of two gas fields with success. In 2008, it was used for the prediction of the remaining life of gas pipelines transporting very corrosive wet gas. The use of costly CRA / cladded pipes was avoided. Gunaltun Y. and call. made the first publication about the importance of the stabilization on the remaining pipeline service life in 2009. Then, possible mechanisms of stabilization were published by Gunaltun Y. in 2012 and Gunaltun Y. and call. 2013. In the present paper the field experience, the research results and the mechanisms leading to stabilisation are discussed in detail and summarised. The main driving force is the galvanic action between anodic and cathodic zones. The clustering of corrosion features completes the process of stabilisation. Re-initiation of corrosion, after stabilisation, has not been observed neither in the laboratory nor in field. The reasons why stabilisation is a non-reversible process are also explained in detail. The conclusions are integrated in the general understanding of CO2 corrosion mechanism. Then a new method is proposed to complete the corrosion prediction approaches used by the industry. Even though some research is still needed to validate the impact of some parameters involved in the stabilisation process, the stabilisation concept is now mature enough for including it in the prediction models. It is very likely that stabilisation is one of the missing links in CO2 corrosion prediction chain.
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Shvalyuk, Elizaveta, Alexei Tchistiakov, and Mikhail Spasennykh. "Integration of Computed Tomography Scanning and Nuclear Magnetic Resonance Results with Conventional Laboratory Test Data for Effective Reservoir Characterization." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211638-ms.
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Abstract The paper suggests a new laboratory tests workflow, aimed at reservoir characterization and rock typing of a polimineral clastic formation, based on microstructural characteristics. The proposed approach is accompanied by a comparative study of various laboratory techniques, including CT, NMR, MICP, centrifuging, and thin section analysis. The methodology for combining quantitative porous medium characteristics, derived from these multi-scale tests is also provided. The developed laboratory test program includes porosity and permeability measurements, capillary pressure, electrical resistivity, NMR and CT-scanning tests. For initial differentiation of samples based on porosity, permeability and irreducible water saturation, we applied methods of flow zone indicator (FZI) and Winland R35. Afterwards, we performed joint interpretation of FZI with the results of centrifuging, resistivity, NMR and CT-scanning tests. Finally, for the most representative samples from the rock types, defined at previous steps, we performed X-ray fluorescence spectroscopy, XRD, MICP and thin section analyses. In our study, we applied FZI, calculated as a function of irreducible water and porosity. Compared to conventional FZI, derived from porosity and permeability, our approach enabled more reliable rock typing in both sandstones and low-permeable siltstones. CT tests showed that within the distinguished 4 rock types grain and pore sizes increase from the 1st to the 4th rock types. CT-scanning and X-ray fluorescence spectroscopy detected presence of pyrite in all samples. Siltstones contain more pyrite than sandstones that reflects deeper marine and consequently more anoxic depositional environment. The obtained NMR T2-spectra appeared to be effected by both porous medium and mineralogical composition. Pyrite inclusions caused shifting of the T2-spectra to lower values, while carbonate presence – to higher ones. Therefore, since NMR signal is effected by multiple factors, applying of a single T2cutoff value for reservoir characterization and rock typing can lead to ambiguous interpretation. The proposed algorithm for combining quantitative parameters of the porous medium allowed integration of pore size distributions, derived from CT and capillary tests. This enabled characterization of the whole range of pore sizes covered only partly by the different methods. The resulted pore size distribution enabled calibrating NMR Т2 spectra and defining individual surface relaxivity values for each rock type. The selected set of techniques allowed confident differentiation and characterization of the rock samples based on multiple parameters, which were interpreted in relationship with each other. Moreover, the developed methodology was verified by applying additional laboratory tests, which confirmed the results of the proposed rock typing and reservoir characterization.
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Zumpano, Petrônio, Juliana L. Cardoso, Zehbour Panossian, Ilson P. Baptista, Helio Miranda, and Marilia F. Franco. "Susceptibility to Preferential Corrosion of Pipeline Welded Joints in Condensed and Dragged Water Droplet - Part 1." In ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/omae2021-63044.
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Abstract Preferential weld corrosion (PWC) is due to the formation of galvanic cells between the weld metal (WM), the parent metal (PM) and the heat affected zone (HAZ). This work has studied PWC susceptibility in longitudinal and circumferential welded joints of submarine systems and the applicability of corrosion inhibitors to mitigate the corrosive process. DNVGL SAW 450, DNVGL SMLS 450 and low alloy forged, with different nickel, copper and silicon content were tested. Several factors influence PWC susceptibility in welded structures and those selected to be studied were weld joint geometry, PM fabrication process, welding process and welding consumable chemical content. For each welding processes, welded coupons were made with similar heat input. Pipe SAW seam welds of two different plate suppliers and different nickel and copper content were tested. Tests in circumferential weld joints were predicted for 79 different combination of chemical composition: PM chemical composition and manufacturing process; welding processes; chemical composition of welding consumables. Selected welding processes are the most used by offshore industry (SAW, mechanized GMAW and manual GTAW). The root configuration of respective welding procedure specifications produce a desired variation in width geometry. The corrosion tests started with the longitudinal joints and will be further reproduced for circumferential joints. A test procedure has been developed for corrosion evaluation through immersion test, galvanic current measurement (GCM) through zero resistance ammeter (ZRA) and localized electrochemical test through SVET. Two test solutions were considered, simulating condensed and dragged water droplets in order to verify the susceptibility or occurrence of the preferential welding corrosion in the welded joints. The results for longitudinal joints indicated a greater susceptibility to PWC in dragged water than in condensed water droplets and a greater susceptibility of joints with greater anodic potential due to a higher nickel and copper content in the parent metal. A correlation between the corrosion rates obtained in both medium and the moisture contents of gas pipelines will be performed to determine the need for the addition of corrosion inhibitors and to establish the minimum required dosage. A future work will involve circumferential joints and the evaluation of the optimal dosage of corrosion inhibitors.
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Abraham, Marine. "Jeunesse et plage : approche sociolinguistique des publicités contemporaines." In XXV Coloquio AFUE. Palabras e imaginarios del agua. Valencia: Universitat Politècnica València, 2016. http://dx.doi.org/10.4995/xxvcoloquioafue.2016.3171.
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Lors de la présente étude, mon objectif sera de révéler de quelle manière les professionnels de la publicité emploient les allégories se référant à l'eau de mer afin de convaincre leurs futurs clients de consommer le produit objet de la publicité. Nous centrerons nos recherches sur les campagnes situées en zone blanéaire mettant en scène les jeunes d'aujourd'hui, population représentant un autre mythe manifeste de nos sociétés occidentales. L'emploi des images de l'eau dans les spots ou affiches actuels n'est pas anodin. En effet, elle symbolise un temps de rupture et d'évasion, des moments jouissifs dont tout individu souhaite profiter. La plage transmet ainsi des émotions positives, ce qui permet d'une part de capter l'attention des consommateurs et, d'autre part, de formater leurs sentiments envers le produit ou la marque. La publicité réussit de cette manière à rendre matériel des notions abstraites telles que la liberté, idéal qui semble désormais pouvoir s'acheter à travers la consommation. Associer à la figure du jeune, la campagne publicitaire s'inscrivant en bord de mer n'est que plus attirante. De ce fait, la jeunesse représente en quelque sorte l'âge idéal pour tout type de public, tant chez les enfants qui désirent accéder à cette vie d'apparence autonome que chez les adultes qui rêvent de jeunesse éternelle. C'est d'ailleurs la raison pour laquelle non seulement il sont acteurs de la plupart des publicités mais aussi des films, des séries et des médias en général. Dans le corpus analysé, nous rendrons compte de la sémiotique des propagandes contemporaines en accord avec des aspects linguistiques ancrés dans le monde des jeunes. Les professionnels de la publicité disposent ainsi des réalités sociolinguistiques adolescentes et mettent en scène une sélection de leurs préoccupations environnantes dans un univers idyllique. En définitive, nous démontrerons que la combinaison de l'élément eau et du facteur jeune s'avère être judicieux dans les campagnes publicitaires modernes.DOI: http://dx.doi.org/10.4995/XXVColloqueAFUE.2016.3171
Reports on the topic "Anoxic zones"
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Prasad, N., and S. M. Roscoe. Profiles of Altered Zones At Ca 2.45 Ga Unconformities Beneath Huronian Strata, Elliot Lake, Ontario: Evidence For Early Aphebian Weathering Under Anoxic Conditions. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1991. http://dx.doi.org/10.4095/132559.
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Banin, Amos, Joseph Stucki, and Joel Kostka. Redox Processes in Soils Irrigated with Reclaimed Sewage Effluents: Field Cycles and Basic Mechanism. United States Department of Agriculture, July 2004. http://dx.doi.org/10.32747/2004.7695870.bard.
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The overall objectives of the project were: (a) To measure and study in situ the effect of irrigation with reclaimed sewage effluents on redox processes and related chemical dynamics in soil profiles of agricultural fields. (b) To study under controlled conditions the kinetics and equilibrium states of selected processes that affect redox conditions in field soils or that are effected by them. Specifically, these include the effects on heavy metals sorption and desorption, and the effect on pesticide degradation. On the basis of the initial results from the field study, increased effort was devoted to clarifying and quantifying the effects of plants and water regime on the soil's redox potential while the study of heavy metals sorption was limited. The use of reclaimed sewage effluents as agricultural irrigation water is increasing at a significant rate. The relatively high levels of suspended and, especially, dissolved organic matter and nitrogen in effluents may affect the redox regime in field soils irrigated with them. In turn, the changes in redox regime may affect, among other parameters, the organic matter and nitrogen dynamics of the root zone and trace organic decomposition processes. Detailed data of the redox potential regime in field plots is lacking, and the detailed mechanisms of its control are obscure and not quantified. The study established the feasibility of long-term, non-disturbing monitoring of redox potential regime in field soils. This may enable to manage soil redox under conditions of continued inputs of wastewater. The importance of controlling the degree of wastewater treatment, particularly of adding ultrafiltration steps and/or tertiary treatment, may be assessed based on these and similar results. Low redox potential was measured in a field site (Site A, KibutzGivat Brenner), that has been irrigated with effluents for 30 years and was used for 15 years for continuous commercial sod production. A permanently reduced horizon (Time weighted averaged pe= 0.33±3.0) was found in this site at the 15 cm depth throughout the measurement period of 10 months. A drastic cultivation intervention, involving prolonged drying and deep plowing operations may be required to reclaim such soils. Site B, characterized by a loamy texture, irrigated with tap water for about 20 years was oxidized (Time weighted average pe=8.1±1.0) throughout the measurement period. Iron in the solid phases of the Givat Brenner soils is chemically-reduced by irrigation. Reduced Fe in these soils causes a change in reactivity toward the pesticide oxamyl, which has been determined to be both cytotoxic and genotoxic to mammalian cells. Reaction of oxamyl with reduced-Fe clay minerals dramatically decreases its cytotoxicity and genotoxicity to mammalian cells. Some other pesticides are affected in the same manner, whereas others are affected in the opposite direction (become more cyto- and genotoxic). Iron-reducing bacteria (FeRB) are abundant in the Givat Brenner soils. FeRB are capable of coupling the oxidation of small molecular weight carbon compounds (fermentation products) to the respiration of iron under anoxic conditions, such as those that occur under flooded soil conditions. FeRB from these soils utilize a variety of Fe forms, including Fe-containing clay minerals, as the sole electron acceptor. Daily cycles of the soil redox potential were discovered and documented in controlled-conditions lysimeter experiments. In the oxic range (pe=12-8) soil redox potential cycling is attributed to the effect of the daily temperature cycle on the equilibrium constant of the oxygenation reaction of H⁺ to form H₂O, and is observed under both effluent and freshwater irrigation. The presence of plants affects considerably the redox potential regime of soils. Redox potential cycling coupled to the irrigation cycles is observed when the soil becomes anoxic and the redox potential is controlled by the Fe(III)/Fe(II) redox couple. This is particularly seen when plants are grown. Re-oxidation of the soil after soil drying at the end of an irrigation cycle is affected to some degree by the water quality. Surprisingly, the results suggest that under certain conditions recovery is less pronounced in the freshwater irrigated soils.