Laboratory studies of the diagenesis and mobility of ^239,240pu and ¹³⁷Cs in nearshore sediments     

Edward R. Sholkovitz  J.Kirk Cochran  Anne E. Carey 《Geochimica et cosmochimica acta》1983,47(8):1369-1379

Controlled laboratory experiments have been used to study the diagenetic chemistry of ^239,240Pu ¹³⁷Cs, and ⁵⁵Fe. Experiments using Buzzards Bay sediments in small tanks show that sulfate reduction is accompanied by the production of large pore water concentration gradients of alkalinity, phosphate, ammonia and dissolved organic carbon and the formation of subsurface maxima in Fe and Mn. These pore water profiles demonstrate that bacterially-mediated processes of organic matter degradation and redox reactions can be simulated in the laboratory.A vertical profile of ⁵⁵Fe in pore waters is reported for the first time: it follows the profile of stable Fe and as such has a large (200 dpm/100 kg) subsurface maximum between 2–4 cm depth. Comparison of ⁵⁵Fe/Fe ratios in sediments and pore waters shows that there is preferential solubilization of ⁵⁵Fe over stable Fe.The pore water activities of ^239,240Pu show no gradients within the large uncertainties of the counting statistics, but are two to four times higher than Buzzards Bay seawater (0.05 dpm/100 kg).The activity of ¹³⁷Cs in the pore water profile is constant (40 dpm/100 kg) within the large counting uncertainties and is twice that of Buzzards Bay seawater. Cs-137 does not appear to be involved in diagenetic chemistry but may increase in pore waters as a result of ion exchange reactions.Flux estimates based on the pore water data show that remobilization and transport of ^239,240 Pu in coastal sediments are not significant processes while the transport of ^l37Cs may be.  相似文献   

On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles   总被引：3，自引：15，他引：3  

M. J. Webb  C. A. Senior  D. M. H. Sexton  W. J. Ingram  K. D. Williams  M. A. Ringer  B. J. McAvaney  R. Colman  B. J. Soden  R. Gudgel  T. Knutson  S. Emori  T. Ogura  Y. Tsushima  N. Andronova  B. Li  I. Musat  S. Bony  K. E. Taylor 《Climate Dynamics》2006,27(1):17-38

Global and local feedback analysis techniques have been applied to two ensembles of mixed layer equilibrium CO₂ doubling climate change experiments, from the CFMIP (Cloud Feedback Model Intercomparison Project) and QUMP (Quantifying Uncertainty in Model Predictions) projects. Neither of these new ensembles shows evidence of a statistically significant change in the ensemble mean or variance in global mean climate sensitivity when compared with the results from the mixed layer models quoted in the Third Assessment Report of the IPCC. Global mean feedback analysis of these two ensembles confirms the large contribution made by inter-model differences in cloud feedbacks to those in climate sensitivity in earlier studies; net cloud feedbacks are responsible for 66% of the inter-model variance in the total feedback in the CFMIP ensemble and 85% in the QUMP ensemble. The ensemble mean global feedback components are all statistically indistinguishable between the two ensembles, except for the clear-sky shortwave feedback which is stronger in the CFMIP ensemble. While ensemble variances of the shortwave cloud feedback and both clear-sky feedback terms are larger in CFMIP, there is considerable overlap in the cloud feedback ranges; QUMP spans 80% or more of the CFMIP ranges in longwave and shortwave cloud feedback. We introduce a local cloud feedback classification system which distinguishes different types of cloud feedbacks on the basis of the relative strengths of their longwave and shortwave components, and interpret these in terms of responses of different cloud types diagnosed by the International Satellite Cloud Climatology Project simulator. In the CFMIP ensemble, areas where low-top cloud changes constitute the largest cloud response are responsible for 59% of the contribution from cloud feedback to the variance in the total feedback. A similar figure is found for the QUMP ensemble. Areas of positive low cloud feedback (associated with reductions in low level cloud amount) contribute most to this figure in the CFMIP ensemble, while areas of negative cloud feedback (associated with increases in low level cloud amount and optical thickness) contribute most in QUMP. Classes associated with high-top cloud feedbacks are responsible for 33 and 20% of the cloud feedback contribution in CFMIP and QUMP, respectively, while classes where no particular cloud type stands out are responsible for 8 and 21%.  相似文献   

Bimodal volcanism at the Katla subglacial caldera,Iceland: insight into the geochemistry and petrogenesis of rhyolitic magmas   总被引：1，自引：0，他引：1  

C. Lacasse  H. Sigurdsson  S. N. Carey  H. Jóhannesson  L. E. Thomas  N. W. Rogers 《Bulletin of Volcanology》2007,69(4):373-399

The Katla subglacial caldera is one of the most active and hazardous volcanic centres in Iceland as revealed by its historical volcanic activity and recent seismic unrest and magma accumulation. A petrologic and geochemical study was carried out on a suite of mid-Pleistocene to Recent lavas and pyroclastic rocks originated from the caldera. The whole series is characterised by a bimodal composition, including Fe-Ti transitional alkali basalts and mildly alkalic rhyolites. Variations in trace-element composition amongst the basalts and rhyolites show that their chemical differentiation was mainly controlled by fractional crystallisation and possible assimilation. The petrology and chemistry of the few intermediate extrusive rocks show that they were derived from magma mingling or hybridisation. The absence of extrusive rocks of true intermediate magmatic composition and the occurrence of amphibole-bearing felsic xenoliths support the hypothesis of partial melting of the hydrated basalt crust as the main process leading to the generation of rhyolites. The ¹⁴³Nd/¹⁴⁴Nd and ⁸⁷Sr/⁸⁶Sr values of Katla volcanic rocks fit the general isotopic array defined by late Quaternary to Recent lavas from Iceland. A few rock specimens are distinguished by low ¹⁴³Nd/¹⁴⁴Nd values suggesting assimilation and mixing of much older crustal material. Despite their similar whole-rock chemical compositions, the postglacial rhyolitic extrusives differ from the felsic xenoliths by their glass composition and the absence of amphibole. This, together with the general chemical trend of volcanic glasses, indicates that the postglacial rhyolitic extrusives were probably derived by a process involving late reheating and partial melting of crustal material by intrusion of basaltic magmas.  相似文献   

The January 2013 Wanganui River debris flood resulting from a large rock avalanche from Mt Evans,Westland, New Zealand     

J. M. Carey  G. T. Hancox  M. J. McSaveney 《Landslides》2015,12(5):961-972

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IPN turbines: A source of underwater power     

D.J. Carey 《Ocean Engineering》1976,3(2):71-81

The effect of hydrostatic pressure on the basic performance of a simple isopropyl nitrate (IPN) power turbine is discussed, with particular reference to the choice of suitable design parameters for systems operating at depths down to 3100 ft. It is shown that the decomposition heat energy available from a perfect turbine system decreaseswith increasing depth, from 19·9 kWh/ft³ at sea level to 2·34 kWh/ft³ for a critical pressure ratio design. Approximately two-thirds of this energy may be recoverable in a practical system as usable power on the sea bed.  相似文献   

A thermodynamic formulation of hydrous cordierite     

J. William Carey 《Contributions to Mineralogy and Petrology》1995,119(2-3):155-165

A thermodynamic formulation of hydrous Mg-cordierite (Mg₂Al₄Si₅O₁₈·nH₂O) has been obtained by application of calorimetric and X-ray diffraction data for hydrous cordierite to the results of hydrothermal syntheses. The data include measurements of the molar heat capacity and enthalpy of hydration and the molar volume. The synthesis data are consistent with a thermodynamic formulation in which H₂O mixes ideally on a single crystallographic site in hydrous cordierite. The standard molar Gibbs free energy of hydration is-9.5±1.0 kJ/mol (an average of 61 syntheses). The standard molar entropy of hydration derived from this value is-108±3 J/mol-K. An equation providing the H₂O content of cordierite as a function of temperature and fugacity of H₂O is as follows (n moles of H₂O per formula unit, n<1): $$\begin{gathered}n = {{f_{{\text{ H}}_{\text{2}} O}^{\text{V}} } \mathord{\left/{\vphantom {{f_{{\text{ H}}_{\text{2}} O}^{\text{V}} } {\left( {f_{{\text{ H}}_{\text{2}} O}^{\text{V}} + {\text{exp}}\left[ { - {\text{3}}{\text{.8389}} - 5025.2\left( {\frac{1}{T} - \frac{1}{{298.15}}} \right)} \right.} \right.}}} \right.\kern-\nulldelimiterspace} {\left( {f_{{\text{ H}}_{\text{2}} O}^{\text{V}} + {\text{exp}}\left[ { - {\text{3}}{\text{.8389}} - 5025.2\left( {\frac{1}{T} - \frac{1}{{298.15}}} \right)} \right.} \right.}} \hfill \\{\text{ }}\left. {\left. { - {\text{ln}}\left( {\frac{T}{{{\text{298}}{\text{.15}}}}} \right) - \left( {\frac{{298.15}}{T} - 1} \right)} \right]} \right) \hfill \\\end{gathered}$$ Application of this formulation to the breakdown reaction of Mg-cordierite to an assemblage of pyrope-sillimanite-quartz±H₂O shows that cordierite is stabilized by 3 to 3.5 kbar under H₂O-saturated conditions. The thermodynamic properties of H₂O in cordierite are similar to those of liquid water, with a standard molar enthalpy and Gibbs free energy of hydration that are the same (within experimental uncertainty) as the enthalpy and Gibbs free energy of vaporization. By contrast, most zeolites have Gibbs free energies of hydration two to four times more negative than the corresponding value for the vaporization of water.  相似文献   

Sound sources and levels in the ocean   总被引：1，自引：0，他引：1  

Carey  W.M. 《Oceanic Engineering, IEEE Journal of》2006,31(1):61-75

The standard definitions found in the American National Standards on Acoustics are applied to common sound sources used in both underwater acoustics research and naval sonar system operation. Recommended metrics are quantified for both continuous and transient sources of sound. Standard definitions are reviewed with theoretical sound source models. Requisite metrics are derived and applied to examples of energy sources of sound, such as transients from a small omnidirectional explosive, an air gun, a light bulb, and a dolphin click. A generic quantitative model of surface ship sonar system emissions is developed. Active sonar transmissions are analyzed with the requisite quantitative metrics required to characterize these emissions. These results should be useful in environmental assessments, biological experiments, and the sonar system design.  相似文献   

Foreword to this Special Issue of “Ore Geology Reviews”     

Hilton Ingram 《Ore Geology Reviews》2008,34(1-2)

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Synoptic sampling reveals spatial stability in flow and chemistry patterns despite large seasonal variability in a subarctic mountain catchment     

Arsh Grewal  Sean K. Carey 《水文研究》2024,38(2):e15080

Seasonality plays a critical role in cold mountain regions as variation in air temperature, ground thermal status, and precipitation phase alter the rate, timing and magnitude of hydrological and chemical transport. Additionally, cold mountain catchments can have highly variable topography, geology, permafrost, and landcover, which intrinsically add to this irregularity. Understanding how external and internal variability act to control mass fluxes requires sampling at a high spatial resolution over time, which rarely occurs in cold remote regions. In this work, we conduct five snapshot sampling surveys across 34 subcatchments during the ice-free period in Wolf Creek Research Basin (a mesoscale montane subarctic catchment) and two additional winter surveys across a subset of sites to assess the drivers of variability in stream chemistry and discharge. We sampled for specific conductance (SpC), major ions, and dissolved organic carbon (DOC) and used statistical metrics and Bayesian mixing analysis to quantify patterns of flow and chemistry across space and time. Our results indicate patterns in both flow and chemistry remain largely consistent across seasons for all solutes. However, there was weaker correlation of chemistry between sites, suggesting asynchronous behaviour within the catchment. There was evidence of increasing production of ions and DOC along the stream network during high spring flows but not during low flows. Although concentrations and flows exhibit high seasonality in subarctic mountains, this seasonal variability does not alter spatial patterns that arise from highly variable catchment characteristics.  相似文献   

Using stable isotopes to estimate travel times in a data‐sparse Arctic catchment: Challenges and possible solutions          下载免费PDF全文

Doerthe Tetzlaff  Thea Piovano  Pertti Ala‐Aho  Aaron Smith  Sean K. Carey  Philip Marsh  Philip A. Wookey  Lorna E. Street  Chris Soulsby 《水文研究》2018,32(12):1936-1952

Use of isotopes to quantify the temporal dynamics of the transformation of precipitation into run‐off has revealed fundamental new insights into catchment flow paths and mixing processes that influence biogeochemical transport. However, catchments underlain by permafrost have received little attention in isotope‐based studies, despite their global importance in terms of rapid environmental change. These high‐latitude regions offer limited access for data collection during critical periods (e.g., early phases of snowmelt). Additionally, spatio‐temporal variable freeze–thaw cycles, together with the development of an active layer, have a time variant influence on catchment hydrology. All of these characteristics make the application of traditional transit time estimation approaches challenging. We describe an isotope‐based study undertaken to provide a preliminary assessment of travel times at Siksik Creek in the western Canadian Arctic. We adopted a model–data fusion approach to estimate the volumes and isotopic characteristics of snowpack and meltwater. Using samples collected in the spring/summer, we characterize the isotopic composition of summer rainfall, melt from snow, soil water, and stream water. In addition, soil moisture dynamics and the temporal evolution of the active layer profile were monitored. First approximations of transit times were estimated for soil and streamwater compositions using lumped convolution integral models and temporally variable inputs including snowmelt, ice thaw, and summer rainfall. Comparing transit time estimates using a variety of inputs revealed that transit time was best estimated using all available inflows (i.e., snowmelt, soil ice thaw, and rainfall). Early spring transit times were short, dominated by snowmelt and soil ice thaw and limited catchment storage when soils are predominantly frozen. However, significant and increasing mixing with water in the active layer during the summer resulted in more damped steam water variation and longer mean travel times (~1.5 years). The study has also highlighted key data needs to better constrain travel time estimates in permafrost catchments.  相似文献