A modified profile method for determining the vertical fluxes of NO,NO2, ozone,and HNO3 in the atmospheric surface layer     

Gerhard Kramm  Hans Müller  David Fowler  Klaus D. Höfken  Franz X. Meixner  Eberhard Schaller 《Journal of Atmospheric Chemistry》1991,13(3):265-288

A modified profile method for determining the vertical deposition (or/and exhalation) fluxes of NO, NO₂, ozone, and HNO₃ in the atmospheric surface layer is presented. This method is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with group concentrations c ₁=[NO]+[NO₂]+[HNO₃], c ₂=[NO₂]+[O₃]+3/2·[HNO₃], and c ₃=[NO]–[O₃]–1/2·[HNO₃]. The fluxes of the individual species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HNO₃ (decoding method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO₂, ozone, and HNO₃.The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989).  相似文献   

An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of Th as a POC flux proxy     

K.O. Buesseler  C.R. Benitez-Nelson  S.B. Moran  A. Burd  M. Charette  J.K. Cochran  L. Coppola  N.S. Fisher  S.W. Fowler  W.D. Gardner  L.D. Guo   . Gustafsson  C. Lamborg  P. Masque  J.C. Miquel  U. Passow  P.H. Santschi  N. Savoye  G. Stewart  T. Trull 《Marine Chemistry》2006,100(3-4):213

Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the ²³⁴Th activity distribution (in order to calculate ²³⁴Th fluxes) and an estimate of the C / ²³⁴Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C / ²³⁴Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C / ²³⁴Th either increases or is relatively invariant with increasing particle size (size classes > 1 to 100s μm). Observations also suggest that C / ²³⁴Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from ²³⁴Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2–3). We recommend sampling for C / ²³⁴Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple ²³⁴Th profiles and C / ²³⁴Th samples during the course of longer observation periods to better sample temporal variations in both ²³⁴Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.  相似文献   

Temperature effects on uptake and retention of contaminant radionuclides and trace metals by the brittle star Ophiothrix fragilis     

D.A. Hutchins  J.-L. Teyssié  F. Boisson  S.W. Fowler  N.S. Fisher 《Marine environmental research》1996,41(4):363-378

Recent revelations of extensive dumping of radioactive wastes in Arctic seas emphasize the need to understand the processes affecting accumulation of contaminants in polar marine food webs. Little is known, however, about the effects of low temperatures on bioaccumulation of radionuclides and toxic metals. To address this question, we examined the effects of temperature on uptake and retention of 11 dissolved radioisotopes (including both nuclear waste components and required, and toxic metals) by the brittle star Ophiothrix fragilis, typical of species which dominate Arctic benthic communities. Lower temperatures significantly reduced uptake rates of all elements examined, but had little effect on loss rates. These results raise questions about the validity of extrapolating previous work on biological dynamics of dissolved contaminants, largely carried out at temperate zone temperatures, to polar ecosystems. This work suggests that the effects of low Arctic temperatures may need to be taken into consideration in order to understand the potential for food chain accumulation of nuclear wastes and toxic metals in high-latitude seas.  相似文献   

Bioavailability of technetium from artificially labelled north-east atlantic deep-sea sediments     

S.W Fowler  S.R Aston  G Benayoun  P Parsi 《Marine environmental research》1983,8(2):87-100

Laboratory experiments were designed to measure the uptake of Tc by clams from North-East Atlantic sediments which were contaminated with different oxidation states of ^95mTc. Distribution coefficients between solid sediment and pore water were similar for Tc IV and VII and never exceeded 3·5 during the 36-day experiment. Furthermore, ^95mTc was rapidly leached from the sediments with a half-time of about 4·5 days. Biological uptake was low, with transfer factors between clam tissues and sediment ranging between 0·04 and 0·6. Greater relative uptake was noted in the soft tissues than in shell, although the latter contained the largest fraction (70%) of the clam's whole body ^95mTc content. Contaminated clams, transferred to uncontaminated sediments, displayed a very long biological half-life (～120 days) for ^95mTc. This observation suggests that following acute contamination, clams living in an environment of this type would still retain Tc in their tissues long after the radionuclide had been leached from the sediments.  相似文献   

Biokinetics of selected heavy metals and radionuclides in two marine macrophytes: the seagrass Posidonia oceanica and the alga Caulerpa taxifolia     

Michel Warnau  Scott W. Fowler  Jean-Louis Teyssié 《Marine environmental research》1996,41(4):343-362

Uptake and loss kinetics of Zn, Ag, Cd, ¹³⁴Cs, and ²⁴¹Am by shoots of the seagrass Posidonia oceanica and fronds of the green alga Caulerpa taxifolia were determined in controlled laboratory radiotracer experiments using low contaminant concentrations. The two species accumulated most of the elements efficiently. The only exceptions were ¹³⁴Cs in both P. oceanica and C. taxifolia and Cd in C. Taxifolia (concentration factors 6.4). Steady state in uptake was reached in C. taxifolia for each element except Ag. In P. oceanica, steady state was noted for the uptake of Ag and ¹³⁴Cs whereas Zn, Cd, and ²⁴¹Am were linearly accumulated during the course of the experiment (15 d). With respect to relative metal bioavailability, the different compartments of P. oceanica shoots were generally ranked in the order: leaf epiphytes > adult LEAVES = intermediate leaves > leaf sheaths. The long-lived component of the loss kinetics for each element in P. oceanica was characterized by a relatively short biological half-life (T_b1/2 28 d). However, observations for the individual compartments indicated that adult leaves had a high retention capacity for Ag and ¹³⁴Cs, with virtually 100% retained after 21 d in uncontaminated sea water. In C. taxifolia, the long-lived component of the loss kinetics for each element was characterized by a T_b1/2 value that was not significantly different from infinity, an observation which suggests that a substantial fraction of the metal or radionuclide incorporated during a contamination event would be irreversibly bound by this algal species.  相似文献   

Uptake from water and tissue distribution of neptunium-237 in crabs, shrimp and mussels     

Jean-Claude Guary  Scott W. Fowler 《Marine pollution bulletin》1978,9(12):331-334

The uptake of ²³⁷Np has been followed in the tissues of mussels, shrimp and crabs exposed to the actinide in sea-water under controlled conditions. Bioaccumulation was observed in all tissues examined with the highest concentration factors noted in the external shells of the three species. Despite some incorporation of ²³⁷Np into internal tissues, it is noteworthy that after prolonged exposure 92–98% of the organisms' total ²³⁷Np content was associated with the non-edible shells. The general behaviour of this toxic transuranic element in invertebrate tissues appears to be very similar to that of plutonium.  相似文献   

Trace metals in mussels from the N.W. Mediterranean     

S.W. Fowler  B. Oregioni 《Marine pollution bulletin》1976,7(2):26-29

A coastal survey in the northwestern Mediterranean region was initiated to measure existing levels of selected trace metals in mussels. For most metals the highest values were found in samples from port cities and areas in the vicinity of river discharge. Marked seasonal variation for many metals was evident; an overall increase in metal concentration in mussels from most stations during March 1974 was attributed to high precipitation and attendant run-off rather than to local pollution. Data comparison indicates that average metal levels in northwestern Mediterranean mussels do not differ markedly from those measured in similar species from different localities throughout the world.  相似文献   

The formation of vesicular cylinders in pahoehoe lava flows     

A.C. Fowler  Alison C. Rust  M. Vynnycky 《地球物理与天体物理流体动力学》2015,109(1):39-61

  相似文献   

Convection of a fluid with strongly temperature and pressure dependent viscosity     

A. C. Fowler  P. D. Howell  Tania S. Khaleque 《地球物理与天体物理流体动力学》2016,110(2):130-165

Plate tectonics on the Earth is a surface manifestation of convection within the Earth’s mantle, a subject which is as yet improperly understood, and it has motivated the study of various forms of buoyancy-driven thermal convection. The early success of the high Rayleigh number constant viscosity theory was later tempered by the absence of plate motion when the viscosity is more realistically strongly temperature dependent, and the process of subduction represents a continuing principal conundrum in the application of convection theory to the Earth. A similar problem appears to arise if the equally strong pressure dependence of viscosity is considered, since the classical isothermal core convection theory would then imply a strongly variable viscosity in the convective core, which is inconsistent with results from post-glacial rebound studies. In this paper we address the problem of determining the asymptotic structure of high Rayleigh number convection when the viscosity is strongly temperature and pressure dependent, i.e. thermobaroviscous. By a method akin to lid-stripping, we are able to extend numerical computations to extremely high viscosity contrasts, and we show that the convective cells take the form of narrow, vertically-oriented fingers. We are then able to determine the asymptotic structure of the solution, and it agrees well with the numerical results. Beneath a stagnant lid, there is a vigorous convection in the upper part of the cell, and a more sluggish, higher viscosity flow in the lower part of the cell. We then offer some comments on the possible meaning and interpretation of these results for planetary mantle convection.  相似文献   

Comparison of derivative-free optimization methods for groundwater supply and hydraulic capture community problems     

K.R. Fowler  J.P. Reese  C.E. Kees  J.E. Dennis Jr.  C.T. Kelley  C.T. Miller  C. Audet  A.J. Booker  G. Couture  R.W. Darwin  M.W. Farthing  D.E. Finkel  J.M. Gablonsky  G. Gray  T.G. Kolda 《Advances in water resources》2008

Management decisions involving groundwater supply and remediation often rely on optimization techniques to determine an effective strategy. We introduce several derivative-free sampling methods for solving constrained optimization problems that have not yet been considered in this field, and we include a genetic algorithm for completeness. Two well-documented community problems are used for illustration purposes: a groundwater supply problem and a hydraulic capture problem. The community problems were found to be challenging applications due to the objective functions being nonsmooth, nonlinear, and having many local minima. Because the results were found to be sensitive to initial iterates for some methods, guidance is provided in selecting initial iterates for these problems that improve the likelihood of achieving significant reductions in the objective function to be minimized. In addition, we suggest some potentially fruitful areas for future research.  相似文献