Sulphur uptake by salt grasses,mangroves, and seagrasses in anaerobic sediments     

Brian Fry  Richard S Scalan  J.Kenneth Winters  Patrick L Parker 《Geochimica et cosmochimica acta》1982,46(6):1121-1124

Stable sulfur isotope analyses show that rooted estuarine plants growing in anoxic sediments incorporate substantial amounts of ³⁴S-depleted sulfides, or oxidation products thereof. In roots, this incorporation predominates over sulfate uptake from interstitial porewater. Either the plants incorporate normally toxic sulfides, or they are creating and using a specialized nutrient pool of oxidized sulfides at the root-sediment interface.  相似文献   

4352590 Stabilization of erodible marine or fluviatile sediments     

William R Parker  Robert Kirby 《Marine pollution bulletin》1983,14(3):120

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Progress in isotope paleohydrology using lake sediment cellulose     

Brent B. Wolfe  Matthew D. Falcone  Ken P. Clogg-Wright  Cherie L. Mongeon  Yi Yi  Bronwyn E. Brock  Natalie A. St. Amour  William A. Mark  Thomas W. D. Edwards 《Journal of Paleolimnology》2007,37(2):221-231

Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced by studies conducted over the past 15 years that span Holocene and pre-historical timescales.  相似文献   

Confidence intervals for earthquake source parameters   总被引：2，自引：0，他引：2  

G. A. Prieto  D. J. Thomson  F. L. Vernon  P. M. Shearer  R. L. Parker 《Geophysical Journal International》2007,168(3):1227-1234

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The gas content and buoyancy of strombolian ash plumes     

Matthew Patrick 《Journal of Volcanology and Geothermal Research》2007

Plinian plumes erupt with a bulk density greater than that of air, and depend upon air entrainment during their gas-thrust phase to become buoyant; if entrainment is insufficient, the column collapses into a potentially deadly pyroclastic flow. This study shows that strombolian ash plumes can be erupted in an initially buoyant state due to their extremely high initial gas content, and in such cases are thus impervious to column collapse. The high gas content is a consequence of decoupled gas rise in the conduit, in which particles are ultimately incidental. The relations between conduit gas flow, eruption style and plume density are explored here for strombolian scenarios and contrasted with conventional wisdom derived from plinian eruptions. Considering the inherent relation between gas content and initial plume density together with detailed measurements of plume velocities can help unravel ambiguities surrounding conduit processes, eruption styles and hazards at poorly understood volcanoes. Analysis of plume dynamics at Santiaguito volcano, Guatemala adds further support for a model involving decoupled gas rise in the conduit.  相似文献   

The Effect of Increasing the Mean on the Percentage of Extreme Values in Gaussian and Skew Distributions. Response to X. Zhang et al.     

E. B. Horton  D. E. Parker  C. K. Folland  P. D. Jones  M. Hulme 《Climatic change》2001,50(4):509-510

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Use of deuterated water as a conservative artificial groundwater tracer     

Matthew W. Becker  Tyler B. Coplen 《Hydrogeology Journal》2001,9(5):512-516

Conservative tracers are necessary to obtain groundwater transport velocities at the field scale. Deuterated water is an effective tracer for this purpose due to its similarity to water, chemical stability, non-reactivity, ease of handling and sampling, relatively neutral buoyancy, and reasonable price. Reliable detection limits of 0.1 mg deuterium/L may be obtained in field tests. A field example is presented in which deuterated water, bromide, and pentafluorobenzoic acid are used as groundwater tracers. Deuterated water appeared to be transported conservatively, producing almost identical breakthrough curves as that of other soluble tracers. Electronic Publication  相似文献   

Modelling potential impacts of bottom trawl fisheries on soft sediment biogeochemistry in the North Sea†     

Daniel E Duplisea  Simon Jennings  Stephen J Malcolm  Ruth Parker  David B Sivyer 《Geochemical transactions》2001,2(1):1-6

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Thermal evolution of the Tertiary Shimanto Belt, Muroto Peninsula, Shikoku, Japan     

Michael B.  Underwood  Matthew M.  Laughland  Tim  Byrne  J. P. Hibbard  Lee  DiTullio 《Island Arc》1992,1(1):116-132

Abstract The Shimanto accretionary complex on the Muroto Peninsula of Shikoku comprises two major units of Tertiary strata: the Murotohanto Sub-belt (Eocene-Oligocene) and the Nabae Sub-belt (Oligocene-Miocene). Both sub-belts have been affected by thermal overprints following the peak of accretion-related deformation. Palaeotemperatures for the entire Tertiary section range from ～ 140 to 315°C, based upon mean vitrinite reflectance values of 0.9–5.0%R_m. Values of illite crystallinity index are consistent with conditions of advanced diagenesis and anchimetamorphism. Illite/mica b₀ lattice dimensions indicate that burial pressures were probably no greater than 2.5kbar. In general, levels of thermal maturity are higher for the Murotohanto Sub-belt than for the Nabae Sub-belt. The Eocene-Oligocene strata also display a spatial decrease in thermal maturity from south to north and this pattern probably was caused by regional-scale differential uplift following peak heating. Conversely, the palaeothermal structure within the Nabae Sub-belt is fairly uniform, except for the local effects of mafic intrusions at the tip of Cape Muroto. There is a paleotemperature difference of ～ 90°C across the boundary between the Murotohanto and Nabae Sub-belts (Shiina-Narashi fault), and this contrast is consistent with approximately 1200 m of post-metamorphic vertical offset. Subduction prior to Middle Miocene probably involved the Kula or fused Kula-Pacific plate and the background geothermal gradient during the Eocene-Oligocene phase of accretion was ～ 30–35°C/km. Rapid heating of the Shimanto Belt evidently occurred immediately after a Middle Miocene reorganization of the subduction boundary. Hot oceanic lithosphere from the Shikoku Basin first entered the subduction zone at ～ 15 Ma; this event also coincided with the opening of the Sea of Japan and the rapid clockwise rotation of southwest Japan. The background geothermal gradient at that time was ～ 70°C/km. Whether or not all portions of the inherited (Eocene-Oligocene) palaeothermal structure were overprinted during the Middle Miocene remains controversial.  相似文献   

Comparison Of Three Uncertainty-Analysis Methods To Assess Impacts On Groundwater Of Constituents Leached From Land-Disposed Waste     

K. Ünlü  J. C. Parker  P. K. Chong 《Hydrogeology Journal》1995,3(2):4-18

Assessment of the environmental fate and behavior of constituents that have the potential to leach from waste-disposal pits that are associated with petroleum exploration and production activities is a problem of interest to industry and regulatory agencies. A stochastic modeling approach for the migration of constituents in soil and groundwater was developed to assess the impact on groundwater at receptors that are downgradient from a waste pit. The model evaluates uncertainties in constituent concentrations in groundwater due to uncertainties in waste-composition and hydrogeologic properties of waste sites, and it determines the probability distributions of constituent concentration at receptor points by using Monte Carlo (MC), First-Order (FO), and Point-Estimate (PE) methods. Application of the FO and PE methods to assess probability distributions requires an assumption of the form of the probability density function for concentration at a receptor point. A log-normal distribution is employed here. A comparison of the three uncertainty-analysis methods is performed to evaluate the efficiency and accuracy of the FO and PE methods relative to the MC method. Results suggest that for non-reactive and conservative constituents the level of accuracy provided by FO method is similar to that of the MC method. The computational effort for the FO method is about 1 percent of that for the MC method. For nonconservative constituents, the FO method compared less favorably with the MC results. Thus, the use of the MC method is warranted, for nonconservative constituents or for cases where a higher degree of precision in the probability distribution is needed. RÉSUMÉ: L'industrie et les organismes de contrôle s'intéressent particulièrement au problème de la prédiction du devenir et du comportement environnemental de composés susceptibles de lixivier des pollutants à partir de puits de stockage de déchets associés à des zones d'exploration et de production pétrolières. Une modélisation stochastique de la migration de composées dans le sol et les eaux souterraines est proposée en vue de prédire l'impact sur les eaux souterraines en des points de prélèvement situés en aval-gradient d'un puits de stockage. Le modèle fournit une estimation des incertitudes sur les teneurs des composés dans les eaux souterraines en fonction de la composition des déchets et des propriétés hydrogéologiques des sites de stockage; il détermine les distributions de probabilité de la concentration des composés à des points de prélèvement au moyen des méthodes de Monte-Carlo (MC), du Premier Ordre (PO) et de l'Estimation Ponctuelle (EP). Le recours aux méthodes PO et EP pour prédire les distributions de probabilité impose une hypothèse sur la forme de la fonction de densité de probabilité pour la concentration en un point de prélèvement. Une distrubution log-normale est utilisée ici. Une comparaison des trois méthodes d'analyse de l'incertude a été réalisée afin d'estimer l'efficacité et la précision des méthodes PO et EP par rapport à la méthode MC. Les résultats indiquent que, pour des composés conservatifs, le degré de précision atteint par la méthode PO est comparable à celle de la méthode MC. La puissance de calcul requise par la méthode PO est 1% environ de celle nécessaire pour la méthode MC. Pour des composés non conservatifs, la comparaison avec la méthode MC est moins favorable à la méthode PO. Par conséquent, la méthode MC est préférable pour les composés non conservatifs ou dans les cas où un meilleur degré de précision de la distribution de probabilité est nécessaire. RESUMEN: La evaluación del comportamiento de constituyentes lixiviables desde vertidos de residuos asociados a actividades de exploración y producción petrolífera, así como su posible impacto ambiental, es un problema de interés para la industria y las agencias reguladoras. Se ha desarrollado una modelación estocástica para estudiar la migración de los constituyentes en el suelo y el agua subterránea, con el objetivo de evaluar su impacto en receptores situados aguas abajo de un vertido. El modelo evalúa las incertidumbres en las concentraciones de los constituyentes debidas a las incertidumbre en la composición de los residuos y de las propiedades hidrogeológicas de la zona de vertido y determina las distribuciones de probabilidad de dichas concentraciones en puntos de recepción mediante los métodos de Monte Carlo (MC), Primer-Orden (FO) y Estimación Puntual (PE). La aplicación de los métodos FO y PE para evaluar las distribuciones de probabilidad reqiere suponer conocida la forma de la función de densidad de probabilidad para la concentración en el punto receptor. En este caso, se emplea una distribución log-normal. Se lleva a cabo una comparación entre los tres métodos de análisis de errores para evaluar la eficiencia y exactitud de los métodos FO y PE respecto al MC. Los resultados sugieren que para constituyentes conservativos no-reactivos, el nivel de exactitud suministrado por el método FO es comparable con el del MC. El esfuerzo computacional para el método FO, en cambio, es alrededor del 1% del método MC. Para constituyentes no conservativos, es método FO no compara tan favorablemente frente a los resultados del MC. Por tanto, el uso del método MC está obligado para constituyentes no conservativos y para casos en los que se requiere un alto nivel de precisión en la distribución de probabilidad.  相似文献