Experimental determination of quartz solubility and melting in the system SiO2–H2O–NaCl at 15–20 kbar and 900–1100 °C: implications for silica polymerization and the formation of supercritical fluids     

Miguel F. Cruz  Craig E. Manning 《Contributions to Mineralogy and Petrology》2015,170(4):1-17

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Residues of toxaphene in finfish and shellfish from Terry and Dupree Creeks, Georgia, U.S.A.     

Keith A. Maruya  Tina L. Walters  Randall O. Manning 《Estuaries and Coasts》2001,24(4):585-596

To better characterize human health risks associated with potentially contaminated seafood, 56 composite samples of edible tissue of several finfish and shellfish species were analyzed for residues of toxaphene using gas chromatography with electron capture and negative ion mass spectrometric detection (GC-ECD and GC-ECNI-MS). Toxaphene in these samples, collected in 1997 near a former toxaphene plant in Brunswick, Georgia, were previously reported as non-detectable using non-selective techniques. Estimated total toxaphene concentrations (ΣTOX) ranged from less than 0.01 to 26 μ g⁻¹ on a wet tissue basis. Smaller, bottom dwelling finfish such as croaker, mullet, and spot exhibited the highest ΣTOX (0.76–26 μg g⁻¹), larger predatory fish including seatrout contained intermediate levels (0.08–4.4 μg g⁻¹), and shellfish (blue crab and shrimp) contained the lowest levels (<0.01 to 0.27 μg g⁻¹). For a given species, samples from the site furthest from the toxaphene plant had lower ΣTOX than samples from the other 3 sites. On a congener specific basis, levels ranged from <0.0025 to 3.5 μg g⁻¹. Congener distributions were, in general, dominated by 2-exo, 3-endo, 6-exo,8,9,10-hexachlorobornane (Hx-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane (Hp-Sed), breakdown products of Cl₈−Cl₁₀ toxaphene homologs. Other prominent congeners confirmed by GC-ECNI-MS included Parlar numbers 26, 40/41, 42, 44, 50, 62, and 63, as well as several unidentified Cl₆−Cl₉ homologs. Minor differences in congener distribution among species and sampling locations suggested that exposure regimes and/or intrinsic biotransformation capabilities were not uniform. These results indicate that toxaphene residues were detectable in all species surveyed and at concentrations higher than estimated previously.  相似文献   

Modelling the effect of a slope-water intrusion on advection of fish larvae in May 1995 on Georges Bank   总被引：1，自引：0，他引：1  

Manning  J. P.; Lough  R. G.; Naimie  C. E.; Churchill  J. H. 《ICES Journal of Marine Science》2001,58(5):985-993

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Evaluation of non-specific immune functions in dab,Limanda limanda L., following short-term exposure to sediments contaminated with polyaromatic hydrocarbons and/or polychlorinated biphenyls     

Hutchinson TH  Field MD  Manning MJ 《Marine environmental research》2003,55(3):193-202

Experimental exposure tanks were set up containing 'clean' marine sediment spiked with set doses of polyaromatic hydrocarbons (PAH), or polychlorinated biphenyls (PCB), or both. Reference tanks contained only 'clean' sediment. Female dab Limanda limanda L., exposed to these sediments for 7 days showed no differences in serum total protein concentration, serum lysozyme activity or body growth. Their kidney leucocytes were assayed for extracellular production of reactive oxygen species of the phagocytic respiratory burst. No significant differences in superoxide anion (O2-) production were found between fish exposed to the 'spiked' sediments and those on the 'clean' reference sediment. The production of hydrogen peroxide (H2O2) was, however, reduced in the fish held on the PAH and PAH/PCB spiked sediments. H2O2 levels for fish exposed to PCBs alone, did not differ significantly from those of control fish. Our results suggest that the decrease in H2O2 production was due to exposure to PAHs, rather than to PCBs.  相似文献   

Geochemical Characteristics and Expansion Properties of a Highly Potassic Perlitic Rhyolite from Lopburi, Thailand     

Darunee Saisuttichai  David A. C. Manning 《Resource Geology》2007,57(3):301-312

Miocene volcanic rocks from northeast of Lopburi, Thailand, include a suite of highly potassic (<6.3% K₂O) perlitic rhyolites that are similar chemically to rhyolites from Sardinia (which are also perlitic) and Vulcano. Electron microprobe analysis using a defocussed beam has shown that glass compositions contain up to 12.9% K₂O (0.9% Na₂O), and within the same samples spherulites are enriched in Na₂O (<6.2%) and depleted in K₂O (2.1%). The perlitic rhyolites contain up to 4% water of meteoric origin; from Fourier transform infra‐red spectroscopy data, expansion on heating involves a reduction in both hydroxyl and molecular water contents. When expanded using a laboratory test furnace, specific gravities as low as 26 kg/m³ have been achieved for a 0.15–0.3‐mm feed size fraction (reference perlite ores from Milos and Sardinia gave 47 and 33 kg/m³, respectively), and 10 kg/m³ for a 0.5–1‐mm fraction separated after expansion. Expansion involves the loss of fluorine from the perlite, presumably as HF; unexpanded perlite contains 90–550 mg/kg F, which is reduced on expansion by 4–65%. Water‐soluble fluorine after expansion is increased by a factor of 10 up to 3.3 mg/kg. Expansion also increases the availability of K to plants by a factor of up to 6, with a maximum available K content of 1245 mg K/kg perlite. This contrasts markedly with the chemically inert character of other, commercial, perlites, suggesting that the distinctive K‐enrichment of the perlitic rhyolite has given a raw material capable of generating products with nutritional functionality for plant growers.  相似文献   

A record of Holocene climate change from lake geochemical analyses in southeastern Arabia   总被引：6，自引：0，他引：6  

Adrian G. Parker  Andrew S. Goudie  Stephen Stokes  Kevin White  Martin J. Hodson  Michelle Manning  Derek Kennet 《Quaternary Research》2006,66(3):465-476

Lacustrine sediments from southeastern Arabia reveal variations in lake level corresponding to changes in the strength and duration of Indian Ocean Monsoon (IOM) summer rainfall and winter cyclonic rainfall. The late glacial/Holocene transition of the region was characterised by the development of mega-linear dunes. These dunes became stabilised and vegetated during the early Holocene and interdunal lakes formed in response to the incursion of the IOM at approximately 8500 cal yr BP with the development of C3 dominated savanna grasslands. The IOM weakened ca. 6000 cal yr BP with the onset of regional aridity, aeolian sedimentation and dune reactivation and accretion. Despite this reduction in precipitation, the lake was maintained by winter dominated rainfall. There was a shift to drier adapted C4 grasslands across the dune field. Lake sediment geochemical analyses record precipitation minima at 8200, 5000 and 4200 cal yr BP that coincide with Bond events in the North Atlantic. A number of these events correspond with changes in cultural periods, suggesting that climate was a key mechanism affecting human occupation and exploitation of this region.  相似文献   

An assessment of a new settling velocity parameterisation for cohesive sediment transport modeling     

John V. Baugh  Andrew J. Manning 《Continental Shelf Research》2007

An important element within the Defra funded Estuary Process Research project “EstProc” was the implementation of the new or refined algorithms, produced under EstProc, into cohesive sediment numerical models. The implementation stage was important as any extension in the understanding of estuarine processes from EstProc was required to be suitable for dissemination into the wider research community with a level of robustness for general applications demonstrated. This report describes work undertaken to implement the new Manning Floc Settling Velocity Model, developed during EstProc. All Manning component algorithms could be combined to provide estimates of mass settling flux. The algorithms are initially assessed in a number of 1-D scenarios, where the Manning model output is compared against both real observations and the output from alternative settling parameterisations. The Manning model is then implemented into a fully 3-D computational model (TELEMAC3D) of estuarine hydraulics and sediment transport of the Lower Thames estuary. The 3-D model results with the Manning algorithm included were compared to runs with a constant settling velocity of 0.5 mm s⁻¹ and settling velocity based on a simple linear multiplier of concentration and with the above mentioned observations of suspended concentration. The findings of the 1-D case studies found the Manning empirical settling model could reproduce 93% of the total mass settling flux observed over a spring tidal cycle. The floc model fit was even better within the turbidity maximum (TM) zone. A constant 0.5 mm s⁻¹ only estimated 15% of the TM mass flux, whereas the fixed 5 mm s⁻¹ settling rate over-predicted the TM mass flux by 47%. Both settling velocity as a simple linear function of concentration, and van Leussen's method, did not fare much better estimating less than half the observed flux during the various tidal and sub-tidal cycle periods. When the Manning-settling model was applied to a layer with suspended concentrations approaching 6 g l⁻¹, it calculated 96% of the observed mass flux. The main conclusions of the implementation exercise were that it was feasible to implement a complex relationship between settling velocity and concentration in a 3-D computational model of estuarine hydraulics, without producing any significant increase in model run times or reducing model stability. The use of the Manning algorithm greatly improved the reproduction of the observed distribution of suspended concentration both in the vertical and horizontal directions compared to the other simulations. During the 1-D assessments, the Manning-settling model demonstrated flexibility in adapting to a wide range of estuarine environmental conditions (i.e. shear stress and concentration), specifically for applied modelling purposes.  相似文献   

Modelling the tides and their impacts on the vertical stratification over the Sofala Bank,Mozambique     

CM Chevane  P Penven  FPJ Nehama  CJC Reason 《African Journal of Marine Science》2016,38(4):465-479

The Sofala Bank, a wide shelf located along the central coast of Mozambique, hosts tides with high amplitudes. The Regional Ocean Modelling System (ROMS) was used to analyse the tidal currents on the bank and to investigate their effects on the stratification and generation of tidal fronts. During spring tides, barotropic tidal currents with maximum values ranging from 40 cm s^–1 to 70 cm s^–1 are found on the central bank. The major axis of the tidal ellipses for M₂ and S₂ follow a cross-shelf direction with mainly anticlockwise rotation. Similar to observations, three distinct regimes occur: (i) a warm well-mixed region on the inner shelf where the depths are <30 m; (ii) a wellmixed colder region above the shelf edge; and (iii) a stratified region offshore. The model shows that the tides lead to cooling where two criteria are satisfied: the Simpson and Hunter parameter log₁₀(h/U³) <3.2 and the depth h >30 m. The shelf edge of the bank is important for internal tide generation. Two frontal structures result, one offshore between cooler mixed waters and warmer stratified waters and the other in shallow inshore waters, between cooler mixed waters and solar heated mixed waters.  相似文献   

Morphometric variation in the cutlassfish Trichiurus lepturus on the Kenyan coast: implications for stock identification and management     

SM Mwakiti  B Kaunda-Arara  CM Mlewa  R Ruwa 《African Journal of Marine Science》2016,38(1):49-56

Morphometric variation was used to study population structure of the cutlassfish Trichiurus lepturus on the Kenyan coast. In all, 16 morphometric measurements taken from 193 individuals from six sites were subjected to multivariate statistical analysis in order to determine possible stock differentiation. Multivariate analysis of variance indicated significant differences in the means of a combination of the morphometric characters among the sites, and discriminant function analysis by groups showed the presence of phenotypically distinct populations on the south and north coasts of Kenya. A classification tree analysis of morphometric characters validated the distinct groups and indicated certain characters to be useful for classifying specimens to source sites. The likely presence of distinct north and south stocks of T. lepturus on the Kenyan coast observed in our study will require validation by other methods, but indicates the potential need for spatially explicit models for managing fish populations on a large spatial scale.  相似文献   

Improving 9-intersection model by replacing the complement with voronoi region     

CHEN Jun LI Chengming LI Zhilin Gold C M 《地球空间信息科学学报》2000,3(1):1-10

1 Overview of the original 9-inter-section modelThe spatial re1ations betWeen spatial entities areknown as important as the entities themselves. It istherefore very essential to know what poSSibIe spa-tial relationships are and how they can be deter-mined. The 9-intersection model is the most POpu-lar mathematical framework fOr formalizing spatialrelations and have been widely used in spatial querylanguages(EngenhOfer, l991; Clementinietal., l994;Mark et al., l995). Using this medel the t…  相似文献