Aspartic acid racemization in Late Wisconsin Lake Ontario sediments     

Roy Allen Schroeder  Jeffrey L. Bada 《Quaternary Research》1978,9(2):193-204

We have determined aspartic acid racemization and [¹⁴C] ages in sediment from a 17-m piston core recovered from Lake Ontario. This core represents a depositional record extending back into the Late Wisconsin. Total organic radiocarbon ages of the glaciolacustrine lower section of the core are older than the true depositional age. Hence we suggest that these ages do not represent time elapsed since deposition but rather may be up to several thousand years too old due to mixing with ¹⁴C-depleted organic matter and possibly also d-amino acids contained by the glacier and deposited as the glacier receded. Further studies are suggested that might test this hypothesis as well as establish the general applicability of racemization dating to clay sediments.  相似文献   

Absence of β-alanine and γ-aminobutyric acid in cleaned foraminiferal shells: Implications for use as a chemical criterion to indicate removal of non-indigenous amino acid contaminants     

Roy A. Schroeder 《Earth and Planetary Science Letters》1975,25(3):274-278

The amino acids β-alanine and γ-aminobutyric acid are known to compose only a very minor proportion of the total amino acid content in living matter. In deep-sea sediments, however, their abundance in high proportions is ubiquitous. The organic material within foraminiferal calcite tests that are recovered from marine sediments has been found to contain no β-alanine and γ-aminobutyric acid. This observation provides a chemical check that can be used to ensure that the tests have been thoroughly cleaned. Such checks are important because the amino acid composition of organic material contained within the test is currently being used to establish schemes for chronology and taxonomy of foraminifera.  相似文献   

Emulator-assisted data assimilation in complex models   总被引：1，自引：1，他引：0  

Nugzar Yu Margvelashvili  Mike Herzfeld  Farhan Rizwi  Mathieu Mongin  Mark E. Baird  Emlyn Jones  Britta Schaffelke  Edward King  Thomas Schroeder 《Ocean Dynamics》2016,66(9):1109-1124

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Shallow groundwater and soil chemistry response to 3 years of subsurface drip irrigation using coalbed-methane-produced water     

C. R. Bern  A. R. Boehlke  M. A. Engle  N. J. Geboy  K. T. Schroeder  J. W. Zupancic 《Hydrogeology Journal》2013,21(8):1803-1820

Disposal of produced waters, pumped to the surface as part of coalbed methane (CBM) development, is a significant environmental issue in the Wyoming portion of the Powder River Basin, USA. High sodium adsorption ratios (SAR) of the waters could degrade agricultural land, especially if directly applied to the soil surface. One method of disposing of CBM water, while deriving beneficial use, is subsurface drip irrigation (SDI), where acidified CBM waters are applied to alfalfa fields year-round via tubing buried 0.92 m deep. Effects of the method were studied on an alluvial terrace with a relatively shallow depth to water table (～3 m). Excess irrigation water caused the water table to rise, even temporarily reaching the depth of drip tubing. The rise corresponded to increased salinity in some monitoring wells. Three factors appeared to drive increased groundwater salinity: (1) CBM solutes, concentrated by evapotranspiration; (2) gypsum dissolution, apparently enhanced by cation exchange; and (3) dissolution of native Na–Mg–SO₄ salts more soluble than gypsum. Irrigation with high SAR (～24) water has increased soil saturated paste SAR up to 15 near the drip tubing. Importantly though, little change in SAR has occurred at the surface.  相似文献   

Gas migration through Opouawe Bank at the Hikurangi margin offshore New Zealand     

Stephanie Koch  Henning Schroeder  Matthias Haeckel  Christian Berndt  Joerg Bialas  Cord Papenberg  Dirk Klaeschen  Andreia Plaza-Faverola 《Geo-Marine Letters》2016,36(3):187-196

This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO₂ reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.  相似文献   

Mixing efficiency from microstructure measurements in the Sicily Channel     

Vladoiu  Anda  Bouruet-Aubertot  Pascale  Cuypers  Yannis  Ferron  Bruno  Schroeder  Katrin  Borghini  Mireno  Leizour  Stephane  Ismail  Sana Ben 《Ocean Dynamics》2019,69(7):787-807

Ocean Dynamics - The dissipation flux coefficient, a measure of the mixing efficiency of a turbulent flow, was computed from microstructure measurements collected with a vertical microstructure...  相似文献   

Erste Ergebnisse des Projektes CANVAS (Contaminants and Nutrients in Variable Sea Areas) (Kurzfassung)     

Nies  H.  Br&#;gge  B.  Sterzenbach  D.  Theobald  N.  Dick  S.  Knauth  H. -D.  Schroeder  F. 《Ocean Dynamics》1999,51(10):187-187

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FerryBox and MERIS – Assessment of coastal and shelf sea ecosystems by combining in situ and remotely sensed data     

W. Petersen  H. WehdeH. Krasemann  F. ColijnF. Schroeder 《Estuarine, Coastal and Shelf Science》2008

An automatic measuring system called “FerryBox” was installed in the North Sea on a ferry travelling between Germany (Cuxhaven) and Great Britain (Harwich), enabling online oceanographic and biological measurements such as salinity, temperature, fluorescence, turbidity, oxygen, pH, and nutrient concentrations. Observations made along the ferry transect reveal characteristic phenomena such as high salinity inflow through the Channel into the Southern Bight, algal bloom dynamics and related oxygen and pH changes. Combination of these online observations with remote sensing enhances the spatial resolution of the transect related measurements. Several examples of the synergy between these two measuring strategies are shown, both for large-scale algal blooms in the North Sea as well as for local intense but short-term blooms in the German Bight. Coherence of the data sets can be gained and improved by using water transport models in order to obtain synoptic overviews of the remotely sensed and FerryBox related parameters. Limitations of the currently used algorithms for deriving chlorophyll-a from remote sensing images for coastal and shelf seas (Case-2 water) are discussed, as well as depth related processes which cannot be properly resolved on the basis of water intake at a fixed point. However, in unstratified coastal waters under normal conditions FerryBox data represent average conditions. The importance of future applications of this combination of methods for monitoring of coastal waters is emphasized.  相似文献