Geochemical conditions in groundwater systems: Implications for the attenuation of agricultural nitrate   总被引：1，自引：0，他引：1  

Thabo Thayalakumaran  Keith L. Bristow  Philip B. Charlesworth  Thorsten Fass 《Agricultural Water Management》2008,95(2):103-115

Nitrate resulting from nitrogen fertilisers used in Agriculture is a widespread contaminant of shallow groundwater and causes adverse effects on human, animal and ecosystem health. In order to evaluate the full extent of groundwater nitrate contamination, and how it might evolve in time, it is essential to understand controls on aquifer assimilative capacity. This level of understanding will also help to better target policies and incentives aimed at controlling the amount of nitrate entering downstream water systems.The potential for nitrate attenuation in groundwater was assessed by examining the concentration and distribution pattern of electron donors such as dissolved organic carbon (DOC), ferrous iron, and redox indicators such as dissolved oxygen (DO) and Eh in 57 monitoring bores on the lower Burdekin coastal floodplain, one of Queensland's and Australia's premier irrigation districts. Nitrate concentrations ranged from 0.1 to 14.4 mg/L NO₃-N but were mostly undetectable in bores close to the coast. Groundwater age dates suggest that while there are nitrate ‘hot spots’ in certain areas, some or most of the nitrate is being consumed on its way to the ocean. Low nitrate concentrations were coupled with high ferrous concentrations. The low DO concentrations (<2 mg/L) and high ferrous concentrations found in 55% of the bores indicate that redox conditions are suitable for nitrate attenuation by either denitrification or dissimilatory nitrate reduction to ammonium. The reducing environment may be associated with the high DOC concentrations (up to 82 mg C/L) found in these groundwaters. Furthermore, high levels of ferrous iron found in the Ayr area combined with the wide spread geographical distribution of DOC indicate that these areas have a high potential for sustaining geochemical processes that reduces nitrate levels. The distribution of geochemical indicators also suggests that the shallower depths (<15 m) of the groundwater systems have more potential for nitrate reduction than the deeper depths. The map identifying areas within the lower Burdekin with most potential for denitrification is a valuable first step in helping to understand and manage the fate of nitrate entering the groundwater.  相似文献   

Synthetic resampling strategies and machine learning for digital soil mapping in Iran     

Ruhollah Taghizadeh‐Mehrjardi  Karsten Schmidt  Kamran Eftekhari  Thorsten Behrens  Mohammad Jamshidi  Naser Davatgar  Norair Toomanian  Thomas Scholten 《European Journal of Soil Science》2020,71(3):352-368

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Substances interfering with the gas-liquid chromatographic determination of T-2 mycotoxin.     

C J Mirocha  S V Pathre  J Behrens 《Journal of the Association of Official Analytical Chemists》1976,59(1):221-223

Two substances interfering with the gas-liquid chromatographic (GLC) detection of T-2 mycotoxin were identified as 1-glyceryl-monooleate and 1-glycerylmonolinoleate. These monoglycerides are natural products formed by species of Fusarium growing on cereal grains and are also additives contained in liquid vegetable and animal fats added to the feed mixture. The monoglycerides can be removed from the analytical sample by resolution by thin layer chromatography prior to separation by GLC. Trimethylsilyl ether derivatives of the monoglycerides and T-2 toxin have almost identical retention times on 3% OV-1 columns, whereas the trifluoroacetyl and pentafluoropropionyl derivatives give baseline separation on the same column. The monoglycerides can be misidentified as the T-2 toxin in analyses involbing GLC.  相似文献   

Einfluß eines alimentären Zinkmangels auf die Lipidzusammensetzung der Erythrocytenmembran wachsender Ratten     

G. Behrens  J. Pallauf 《Journal of animal physiology and animal nutrition》1992,68(3):156-164

In der vorliegenden Untersuchung wurde der Einfluß eines alimentären Zn-Mangels auf die Zn-Verteilung im Vollblut sowie das Phospholipid- und das Fettsäurenmuster der Erythrocytenmembran wachsender Ratten geprüft. Dazu erhielten 100 g schwere männliche Wistar Ratten über einen Zeitraum von 28 Tagen eine Eiklarprotein-Diät mit einem nativen Zn-Gehalt < 1 mg/kg ad libitum verabreicht (-ZnAl). Den Kontrolltieren wurde dieselbe, jedoch auf 50 mg Zn/kg supplementierte Diät entweder ad libitum (+ ZnAl) oder restriktiv (+ ZnPF) zugeteilt. Die Zn-Depletion hatte das parallele Absinken von Plasma- und Erythrocytenmembran-Zn bei konstantem Cytosolzinkgehalt zur Folge. Im Phospholipidmuster der depletierten Erythrocytenmembranen konnten keine Veränderungen nachgewiesen werden, der Membrancholesteringehalt ging zurück. Das Fettsäurenmuster der Mangelgruppe unterschied sich nur punktuell von dem der Kontrollgruppen. Eine Zunahme des Docosahexaensäureanteils (C 22:6) im Phosphatidylcholin und -ethanolamin sowie der Lignocerinsäure (C 24:0) im Sphingomyelin bei gleichzeitiger Abnahme des Palmitinsäuregehaltes (C 16:0) im Phosphatidylcholin war bei den Mangeltieren zu verzeichnen. Die aus Phospholipid- und Cholesterinverteilung sowie Fettsäurenmuster berechneten Parameter der Erythrocytenmembranfluidität ließen keinen gerichteten Einfluß des alimentären Zn-Mangels erkennen. Der membranprotektive Mechanismus des Zn scheint deshalb von einer direkten Einwirkung des Kations auf die Membranoberfläche herzurühren.  相似文献   

Response of saproxylic beetles to small-scale habitat connectivity depends on trophic levels     

Jörn Buse  Martin H. Entling  Thomas Ranius  Thorsten Assmann 《Landscape Ecology》2016,31(5):939-949

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Adverse effects of a 10‐day course of ibuprofen in Holstein calves          下载免费PDF全文

P. Walsh  F. R. Carvallo Chaigneau  M. Anderson  N. Behrens  H. McEligot  B. Gunnarson  L. J. Gershwin 《Journal of veterinary pharmacology and therapeutics》2016,39(5):518-521

Nonsteroidal anti‐inflammatory drugs (NSAIDs) are recommended for various conditions in cattle. Ibuprofen is an inexpensive short‐acting NSAID and is readily available in liquid formulation for administration to bottle‐fed calves. We compared the adverse effects of a 10‐day course of ibuprofen and placebo in 16 five‐ to six‐week‐old Holstein bull calves that were being treated for experimentally induced bovine respiratory syncytial virus infection. Ibuprofen was administered as a liquid in milk replacer at 30 mg/kg divided three times daily. We found an increased prevalence of abomasal ulceration 5 of 8 in the ibuprofen compared to placebo group 2 of 6 (P = NS). There was one (1 of 8) case of mild interstitial nephritis in the ibuprofen and none (0 of 8) in the placebo group (P = NS). Renal function as measured by serum BUN and creatinine levels was not different between groups; no animal demonstrated an increase in creatinine.  相似文献   

THE DETERMINATION OF THE TOTAL D-AMINO ACID CONTENT OF HUMAN TUMORS AND NORMAL TISSUES BY MEANS OF D-AMINO ACID OXIDASE     

Lipmann F  Behrens OK  Kabit EA  Burk D 《Science (New York, N.Y.)》1940,91(2349):21-23

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Biomarker evidence for a major preservation pathway of sedimentary organic carbon     

Hebting Y  Schaeffer P  Behrens A  Adam P  Schmitt G  Schneckenburger P  Bernasconi SM  Albrecht P 《Science (New York, N.Y.)》2006,312(5780):1627-1631

Hydrogenation processes leading from biomolecules to fossil biomarkers in anoxic sediments are crucial for the preservation of organic matter. However, these processes are still poorly understood. The present identification of several reduced carotenoids in recent sediments attests that these processes operate at the earliest stages of diagenesis without structural or stereochemical specificity, implying a nonbiological reduction pathway. Sulfur species (e.g., H2S) are the hydrogen donors involved in such reduction, as demonstrated with laboratory experiments. These reactions allow the preservation of abundant organic carbon in the rock record.  相似文献   

Color and albedo heterogeneity of Vesta from Dawn     

Reddy V  Nathues A  Le Corre L  Sierks H  Li JY  Gaskell R  McCoy T  Beck AW  Schröder SE  Pieters CM  Becker KJ  Buratti BJ  Denevi B  Blewett DT  Christensen U  Gaffey MJ  Gutierrez-Marques P  Hicks M  Keller HU  Maue T  Mottola S  McFadden LA  McSween HY  Mittlefehldt D  O'Brien DP  Raymond C  Russell C 《Science (New York, N.Y.)》2012,336(6082):700-704

Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet.  相似文献   

iRhom2 regulation of TACE controls TNF-mediated protection against Listeria and responses to LPS     

McIlwain DR  Lang PA  Maretzky T  Hamada K  Ohishi K  Maney SK  Berger T  Murthy A  Duncan G  Xu HC  Lang KS  Häussinger D  Wakeham A  Itie-Youten A  Khokha R  Ohashi PS  Blobel CP  Mak TW 《Science (New York, N.Y.)》2012,335(6065):229-232

Innate immune responses are vital for pathogen defense but can result in septic shock when excessive. A key mediator of septic shock is tumor necrosis factor-α (TNFα), which is shed from the plasma membrane after cleavage by the TNFα convertase (TACE). We report that the rhomboid family member iRhom2 interacted with TACE and regulated TNFα shedding. iRhom2 was critical for TACE maturation and trafficking to the cell surface in hematopoietic cells. Gene-targeted iRhom2-deficient mice showed reduced serum TNFα in response to lipopolysaccharide (LPS) and could survive a lethal LPS dose. Furthermore, iRhom2-deficient mice failed to control the replication of Listeria monocytogenes. Our study has identified iRhom2 as a regulator of innate immunity that may be an important target for modulating sepsis and pathogen defense.  相似文献