Complexing capacity of the nutrient medium and its relation to inhibition of algal photosynthesis by copper     

Dr. René Gächter  Ken Lum-Shue-Chan  Y. K. Chau 《Aquatic Sciences - Research Across Boundaries》1973,35(2):252-261

The toxic effect of copper on phytoplankton production is investigated in waters having different complexing capacities. It is demonstrated that a water’s complexing capacity does not guarantee that an equivalent amount of copper could be tolerated without adversely affecting algal production. Possible explanations for these findings are offered and discussed. It is deduced that ionic copper probably is already toxic to planktonic algae at concentrations of about 10^?10 mole/l.  相似文献   

Organic facies and geochemical aspects in Neogene neritic sediments of the Takafu syncline area of central Japan: Paleoenvironmental and sedimentological reconstructions     

Ken  Sawada 《Island Arc》2006,15(4):517-536

Abstract Organic petrological observations of kerogen macerals and organic geochemical analyses of carbon isotopes of kerogen macerals and biomarkers were conducted on Neogene neritic sediments of the Takafu syncline area of central Japan. The Senmi, Sakainomiya and Lower Shigarami Formations in that area were deposited at the neritic provinces on the southern edge of the paleo‐Japan Sea during the Late Miocene to Early Pliocene. Sedimentary organic matter in these formations was almost terrigenous in origin. Changes in kerogen maceral compositions reflect sedimentological and tectonic histories evaluated in previous studies from sedimentary facies and paleontology. It was found that carbon isotope ratios (δ¹³C) of kerogen macerals increased from ?28‰ to ?25‰ from the Sakainomiya to the lower part of the Lower Shigarami Formations. The cause of that increase was presumably the expansion of C₄ plants into southwest Japan. The timing was concordant with that of the expansion of C₄ plant grasslands in East Asia. The oxicity (oxic to anoxic) conditions of sea bottoms evaluated from pristane/phytane ratios varied. Particularly, in the lower part of the Senmi Formation, layers in which no steroid biomarkers could be detected were found, and had presumably formed under oxic conditions when strong biodegradation had occurred. Concentrations of regular (C₂₇–C₂₉) steranes and dinosteranes were higher in the Sakainomiya and Lower Shigarami Formations. This indicates that dinoflagellates‐dominant primary productions were higher at those stages. In addition, concentrations of diatomaceous biomarkers such as C₂₆ norsterane increased from the Lower Shigarami Formation, thus adding diatoms to the major producers. Furthermore, similar associations between the increases of δ¹³C values of kerogen macerals and concentrations of diatomaceous biomarkers were observed in the Takafu syncline area. Thus, the expansion of C₄ plants was possibly associated with the high production of diatom in the shallow‐marine areas of the paleo‐Japan Sea during the Neogene Period.  相似文献   

Towards medium-term (order of months) morphodynamic modelling of the Teign estuary, UK     

Marcos E. C. Bernardes  Mark A. Davidson  Keith R. Dyer  Ken J. George 《Ocean Dynamics》2006,56(3-4):186-197

The main objective of this paper is to address the principal mechanisms involved in the medium-term (order of months to years) morphodynamic evolution of estuaries through the application of a process-based numerical modelling. The Teign estuary (Teignmouth, UK) is the selected site. The system is forced by the macrotidal semi-diurnal tide in the English Channel and is perturbed to a minor extent by high river discharge events (freshets). Although waves have a definite influence on the adjacent coastal area, Wells (Teignmouth Quay Development Environmental Statement: Changes to Physical Processes. Report R.984c:140. ABP Marine Environmental Research Ltd., Southampton, 2002b) suggested that swell waves do not enter the estuary. Hence, wave effects are neglected in this study, as only tides and the river discharge are taken into account. The sediment grain size is highly variable, but mainly sandy. Within the frame of the COAST3D project (), four bathymetric surveys of the adjacent coastal area were carried out at a nearly weekly intervals. The outer estuary and the adjacent coastal area were also surveyed every 6 months as part of the COASTVIEW project (). Based on these data and on continuously measured parameters, such as water level, waves, wind and river discharge, numerical modelling of the morphodynamic processes can be tested. To replicate the morphological changes in the medium-term within a feasible simulation time, forcing conditions are reduced through the use of an input reduction method (called ensemble technique). In this study, simulations are based on the coupling between Telemac-2D and its non-cohesive sediment transport module, Sisyphe (version 5.3 for both modules). Three different sediment transport formulae were tested: (1) Engelund and Hansen (A monograph on sediment transport in alluvial streams, 3rd edn. Technological University of Denmark, Copenhagen, 1967) including the modifications proposed by Chollet and Cunge (J Hydraul Eng 17(1):1–13, 1979); (2) Bijker (Mechanics of sediment transport by the combination of waves and current. In: Design and reliability of coastal structures. 23rd international conference on Coastal Engineering, pp 147–173, 1968) and (3) Soulsby (Dynamics of Marine Sands. A manual for practical applications. HR Wallingford, Wallingford, p 142, 1997) modified version of van Rijn [J Hydraul Eng 110(10):1431–1456, 1984a, J Hydraul Eng 110(11):1613–1641, 1984b] formulation. Both a qualitative (i.e. visual comparison) and a quantitative tool [Brier Skill Score (BSS); described in Sutherland et al. in Coast Eng 51:917–939, 2004b] are applied to assess the similarity of simulations when compared to model predictions and observations. Tests confirmed the reliability and time efficiency of the ensemble technique, since it reproduced very well the results of a reference run, a computation based on the observed boundary conditions. For the spring-neap cycle modelled, the BSS was of 0.91 (a perfect modelling would have a BSS of 1), with a reduction in the simulation time on the order of 80%. For the 6-month-period simulation, results were also excellent: BSS=0.92 and a computer time reduction of 85%. In principle, this method has the advantage of being applied to any process-based numerical model.  相似文献   

Reducing standard errors by incorporating spatial autocorrelation into a measurement scheme for soil carbon credits     

Siân Mooney  Ken Gerow  John Antle  Susan Capalbo  Keith Paustian 《Climatic change》2007,80(1-2):55-72

Several studies have suggested that geostatistical techniques could be employed to reduce overall transactions costs associated with contracting for soil C credits by increasing the efficacy of sampling protocols used to measure C-credits. In this paper, we show how information about the range of spatial autocorrelation can be used in a measurement scheme to reduce the size of the confidence intervals that bound estimates of the mean number of C-credits generated per hectare. A tighter confidence interval around the mean number of C-credits sequestered could increase producer payments for each hectare enrolled in a contract to supply C-credits. An empirical application to dry land cropping systems in three regions of Montana shows that information about the spatial autocorrelation exhibited by soil C could be extremely valuable for reducing transactions costs associated with contracts for C-credits but the benefits are not uniform across all regions or cropping systems. Accounting for spatial autocorrelation greatly reduced the standard errors and narrowed the confidence intervals associated with sample estimates of the mean number of C-credits produced per hectare. For the payment mechanism considered in this paper, tighter confidence intervals around the mean number of C-credits created per hectare enrolled could increase producer payments by more than 100 percent under a C-contract.  相似文献   

Excitation of secondary Love and Rayleigh waves in a three-dimensional sedimentary basin evaluated by the direct boundary element method with normal modes     

Ken Hatayama  & Hiroyuki Fujiwara 《Geophysical Journal International》1998,133(2):260-278

  相似文献   

Petrology and geochronology of basalt breccia from the 1996 earthquake swarm of Loihi seamount, Hawaii: magmatic history of its 1996 eruption     

Michael O. Garcia  Ken H. Rubin  Marc D. Norman  J. Michael Rhodes  David W. Graham  David W. Muenow  Khalil Spencer 《Bulletin of Volcanology》1998,59(8):577-592

 Samples of basalt were collected during the Rapid Response cruise to Loihi seamount from a breccia that was probably created by the July to August 1996 Loihi earthquake swarm, the largest swarm ever recorded from a Hawaiian volcano. ²¹⁰Po–²¹⁰Pb dating of two fresh lava blocks from this breccia indicates that they were erupted during the first half of 1996, making this the first documented historical eruption of Loihi. Sonobuoys deployed during the August 1996 cruise recorded popping noises north of the breccia site, indicating that the eruption may have been continuing during the swarm. All of the breccia lava fragments are tholeiitic, like the vast majority of Loihi's most recent lavas. Reverse zoning at the rim of clinopyroxene phenocrysts, and the presence of two chemically distinct olivine phenocryst populations, indicate that the magma for the lavas was mixed just prior to eruption. The trace element geochemistry of these lavas indicates there has been a reversal in Loihi's temporal geochemical trend. Although the new Loihi lavas are similar isotopically and geochemically to recent Kilauea lavas and the mantle conduits for these two volcanoes appear to converge at depth, distinct trace element ratios for their recent lavas preclude common parental magmas for these two active volcanoes. The mineralogy of Loihi's recent tholeiitic lavas signify that they crystallized at moderate depths (∼8–9 km) within the volcano, which is approximately 1 km below the hypocenters for earthquakes from the 1996 swarm. Taken together, the petrological and seismic evidence indicates that Loihi's current magma chamber is considerably deeper than the shallow magma chamber (∼3–4 km) in the adjoining active shield volcanoes. Received: 21 August 1997 / Accepted: 15 February 1998  相似文献   

Geophysical Expression of Low Sulphidation Epithermal Au-Ag Deposits and Exploration Implications –Examples from the Hokusatsu Region of SW Kyushu, Japan–     

Craig A. FEEBREY  Hajime HISHIDA  Ken YOSHIOKA  Ken NAKAYAMA 《Resource Geology》1998,48(2):75-86

Abstract: Low sulphidation epithermal Au-Ag deposits constitute a major exploration target for many mining companies worldwide. These deposits are commonly characterized by quartz vein systems which formed at temperatures often in the range 150–250°C giving rise to major alteration halos. Accompanying mineralization and associated alteration is the destruction and redistribution of magnetite in the host rocks and the formation of various K-bearing minerals such as adularia, illite and alunite. These alteration halos can often cover an area of at least several square kilometres and as such have the potential to be detected during reconnaissance geological surveys utilizing high resolution airborne aeromagnetic and radiometric sensors.
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan.  相似文献   

From subduction to transform motion: a seabeam survey of the Hellenic trench system     

Xavier Le Pichon  Jacques Angelier  Jean Aubouin  Nicolas Lyberis  Serge Monti  Vincent Renard  Henri Got  Ken Hsu¨  Yossi Mart  Jean Mascle  Drummond Matthews  Dimitri Mitropoulos  Pandelis Tsoflias  Georges Chronis 《Earth and Planetary Science Letters》1979,44(3):441-450

Preliminary results of a multi-narrow beam survey of the Hellenic trench system, in the Eastern Mediterranean, are presented. The southwestern Ionian branch is divided in small basins, partly filled with Pleistocene sediments. The morphology suggests that the basins are deformed by a compressional stress acting roughly perpendicularly to the trench along N50°E. This direction is the direction of the regional slip vector of the shallow thrust-type earthquakes. The structure of the southeastern Pliny-Strabo branch is quite different. Narrow en-e´chelon slots, oriented N40°E, have been mapped within the main troughs oriented N60°E. The regional earthquake slip vector is also oriented along N40°E. We conclude that the Hellenic trench system is an active subduction system, dominated by thrust along the Ionian branch and by transform motion along the Pliny-Strabo branch.  相似文献   

Lichens and the determination of river channel capacity     

Ken J. Gregory 《地球表面变化过程与地形》1976,1(3):273-285

The identification of channel capacity associated with a particular frequency of peak discharges is necessary for discharge estimation for planning purposes at ungauged sites. Although lichen limits have been suggested to be useful for this purpose, previous studies have not elaborated their hydrological significance. Lichen limits are clearly defined on the sides of rock channels in New England. Australia and they are analyzed in relation to discharge at 6 gauging stations with up to 52 years of continuous record. It is demonstrated that the lowest lichen limit is maintained by peak discharges which occur on average at least once or twice each year. Recurrence intervals based on Annual Series and on Annual Exceedance Series are calculated and for the annual series are fairly consistent for the lowest lichen limit and range from 1·14 to 1·37 years. Lichenometry can be applied to the analysis of river channels in relation to the frequency of peak discharges. By reference to growth curves based upon lichens on Armidale tombstones it is shown that lichenometry may be employed to indicate dates for channel modification due to the removal of blocks and to dam construction and also to date the rock surface between lichen limits. Detailed analysis of the record from gauging stations indicates that where several lichen limits occur in a channel cross section each limit is related to periods when peak discharges exceeded the limits on at least 5 occasions. The lichen-free surfaces were then recolonized by Parmelia spp. and the size of the lichen thalli indicates the time elapsing since these frequent high discharges.  相似文献   

Non-Stoichiometric magnesian spinels in shale xenoliths from a native iron-bearing andesite at Asuk,Disko, central West Greenland     

Asger Ken Pedersen 《Contributions to Mineralogy and Petrology》1978,67(3):331-340

A strongly reduced native iron-bearing andesite breccia from Disko contains graphite-rich modified shale xenoliths with magnesian spinels. These spinels are free from or very poor in ferric iron and vary considerably within the MgO-FeO-Cr₂O₃-Al₂O₃ compositional space. Through a simple substitution of the type 3 (Mg, Fe)²⁺ ⇆ 2(Al, Cr)³⁺+□_vacancy, the spinels vary from stoichiometric (Mg, Fe)²⁺ (Al, Cr)³⁺ ₂O₄ towards (Al, Cr)₂O₃. The simple substitution of Cr for Al suggests that Cr was accepted into the spinel structure as Cr³⁺, despite the reduced nature of the enclosing andesite. The most magnesian spinels are cation deficient spinel_ss in the synthetic systems MgO-Al₂O₃ and MgO-Al₂O₃-Cr₂O₃. The absence of exolved (Al, Cr)₂O₃-component is probable due to rapid quenching.  相似文献