Field methods for amending marine sediment with activated carbon and assessing treatment effectiveness   总被引：1，自引：0，他引：1  

Cho YM  Smithenry DW  Ghosh U  Kennedy AJ  Millward RN  Bridges TS  Luthy RG 《Marine environmental research》2007,64(5):541-555

Previous laboratory studies have shown reductions in PCB bioavailability for sediments amended with activated carbon (AC). Here we report results on a preliminary pilot-scale study to assess challenges in scaling-up for field deployment and monitoring. The goals of the preliminary pilot-scale study at Hunters Point Shipyard (San Francisco, USA) were to (1) test the capabilities of a large-scale mixing device for incorporating AC into sediment, (2) develop and evaluate our field assessment techniques, and (3) compare reductions in PCB bioavailability found in the laboratory with well-mixed systems to those observed in the field with one-time-mixed systems. In this study we successfully used a large-scale device to mix 500kg of AC into a 34.4m(2) plot to a depth of 1ft, a depth that includes the majority of the biologically active zone. Our results indicate that after 7 months of AC-sediment contact in the field, the 28-day PCB bioaccumulation for the bent-nosed clam, Macoma nasuta, field-deployed to this AC-amended sediment was approximately half of the bioaccumulation resulting from exposure to untreated sediment. Similar PCB bioaccumulation reductions were found in laboratory bioassays conducted on both the bivalve, M. nasuta and the estuarine amphipod, Leptocheirus plumulosus, using sediment collected from the treated and untreated field plots one year after the AC amendment occurred. To further understand the long-term effectiveness of AC as an in situ treatment strategy for PCB-contaminated sediments under field conditions, a 3-year comprehensive study is currently underway at Hunters Point that will compare the effectiveness of two large-scale mixing devices and include both unmixed and mixed-only control plots.  相似文献   

Radio source calibration for the Very Small Array and other cosmic microwave background instruments at around 30 GHz     

Yaser A. Hafez  Rod D. Davies  Richard J. Davis  Clive Dickinson  Elia S. Battistelli  Francisco Blanco  Kieran Cleary  Thomas Franzen  Ricardo Genova-Santos  Keith Grainge  Michael P. Hobson  Michael E. Jones  Katy Lancaster  Anthony N. Lasenby  Carmen P. Padilla-Torres  José Alberto Rubiño-Martin  Rafael Rebolo  Richard D. E. Saunders  Paul F. Scott  Angela C. Taylor  David Titterington  Marco Tucci  Robert A. Watson 《Monthly notices of the Royal Astronomical Society》2008,388(4):1775-1786

Accurate calibration of data is essential for the current generation of cosmic microwave background (CMB) experiments. Using data from the Very Small Array (VSA), we describe procedures which will lead to an accuracy of 1 per cent or better for experiments such as the VSA and CBI. Particular attention is paid to the stability of the receiver systems, the quality of the site and frequent observations of reference sources. At 30 GHz the careful correction for atmospheric emission and absorption is shown to be essential for achieving 1 per cent precision.
The sources for which a 1 per cent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC 7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ∼30 GHz is given for each.
Cas A, Tau A, NGC 7027 and Venus were examined for variability. Cas A was found to be decreasing at 0.394 ± 0.019 per cent yr⁻¹ over the period 2001 March to 2004 August. In the same period Tau A was decreasing at 0.22 ± 0.07 per cent yr⁻¹. A survey of the published data showed that the planetary nebula NGC 7027 decreased at 0.16 ± 0.04 per cent yr⁻¹ over the period 1967–2003. Venus showed an insignificant (1.5 ± 1.3 per cent) variation with Venusian illumination. The integrated polarization of Tau A at 33 GHz was found to be 7.8 ± 0.6 per cent at position angle =148°± 3°.  相似文献   

Changes in European temperature extremes can be predicted from changes in PDF central statistics   总被引：1，自引：1，他引：0  

Joan Ballester  Filippo Giorgi  Xavier Rodó 《Climatic change》2010,98(1-2):277-284

Although uncertainties are still large, many potentially dangerous effects have already been identified concerning the impacts of global warming on human societies. For example, the record-breaking 2003 summer heat wave in Europe has given a glimpse of possible future European climate conditions. Here we use an ensemble of regional climate simulations for the end of the twentieth and twenty-first centuries over Europe to show that frequency, length and intensity changes in warm and cold temperature extremes can be derived to a close approximation from the knowledge of changes in three central statistics, the mean, standard deviation and skewness of the Probability Distribution Function, for which current climate models are better suited. In particular, the effect of the skewness parameter appears to be crucial, especially in the case of cold extremes, since it mostly explains the relative warming of these events compared to the whole distribution. An application of this finding is that the future impacts of extreme heat waves and cold spells on non-climatological variables (e.g., mortality) can be estimated to a first-order approximation from observed time series of daily temperature transformed in order to account for simulated changes in these three statistics.  相似文献   

Hydrogen peroxide concentrations in the Peru upwelling area     

Rod G Zika  Eric S Saltzman  William J Cooper 《Marine Chemistry》1985,17(3):265-275

The concentration of hydrogen peroxide was measured in waters off the coast of Peru during June and July 1983. The study period coincided with the end of the 1982/83 El Niño and the onset of coastal upwelling. Depth profiles of hydrogen peroxide concentration exhibit surface maxima and decrease with depth to the base of the mixed layer. Surface peroxide concentrations ranged from 0.8 to 5 × 10^?8 M. Below the mixed layer hydrogen peroxide was below the detection limit (5 × 10^?9 M). Diel variations were observed, with surface peroxide levels increasing during the day and decreasing at night. The nearshore station exhibited lower hydrogen peroxide concentrations than offshore stations, a reversal of the trend found in other coastal regions. This is attributed to the lack of coastal vegetation and runoff, and to active coastal upwelling of deeper water with low hydrogen peroxide concentrations.  相似文献   

Population Health, Environment and Economic Development     

Shilu Tong  Rod Gerber  Rodney Wolff  Kenneth Verrall 《Global Change & Human Health》2002,3(1):36-41

There are fundamental links between population health, environment and economic development. The ultimate goal of economic development is to improve the quality of human life and increase people's longevity. This goal cannot be achieved without a clean and prosperous Earth. There has been increasing evidence showing that the expansion of economic activities can have significant impacts on the environment and can cause large-scale and sometimes irreversible environmental changes. It is beyond reasonable doubt that these changes will have serious public health consequences. How to tackle these issues is a unprecedented challenge to scientists and policy-makers. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Reversal of three global atmospheric fields linking changes in SST anomalies in the Pacific, Atlantic and Indian oceans at tropical latitudes and midlatitudes     

X. Rodó 《Climate Dynamics》2002,18(7):625-625

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<Emphasis Type="Italic">sub</Emphasis>ATTO indoor GPS – pitfalls,solutions and performance using a conventional correlator     

Rod Bryant 《GPS Solutions》2002,6(3):138-148

A key requirement for emergency call location (e.g. E911), for robust operation of location-based m-commerce systems and for telematics systems is that the location technology be able to operate in urban canyons and inside buildings. We start from a definition of the target environments, which includes multi-level parking garages, office buildings and homes, but not underground parking garages or tunnels. Based on experience in these target environments and understanding of typical applications we derive specific requirements for sensitivity and acquisition speed. The primary problems associated with weak signal operation are as follows. (1) In conventional GPS receivers sampling at the correlator output typically occurs at a sampling interval of the order of 1 ms. With weak signals, however, the signal-to-noise ratio of these samples is too low to support lock-in of a phase-locked or frequency-locked loop. (2) With weak signals, the signal-to-noise ratio is too low to support the extraction of the 50BPS navigation message from the signal. Therefore, aiding data is required from an external source. (3) Because the data cannot be extracted, it is not possible for the receiver to synchronize to the incoming bits, words or subframes. Therefore, it is not possible to construct pseudoranges without prior information. (4) The paper describes Sigtec Navigation's subATTO technology. This technology provides sensitivity down to –185 dBW (19 dBHz assuming NF of 1.5 dB and no other implementation loss). This is 5 dB below an attoWatt (10^–18 W) and has been shown to provide reliable positioning inside buildings, multi-level parking garages and in urban canyons without any aiding at all. The paper describes the patented signal processing scheme, how ambiguity resolution and time synchronization are achieved, the wireless assistance technique, the acquisition strategy and the use of scanning channels. Results are presented from trials in a multi-level parking garage. The results obtained in most parking garages are similar to these in terms of availability of fixes, signal strengths received and location accuracy achieved. The performance achieved in multi-level parking garages is rarely worse than this. One of the major impediments to practical application of weak signal-processing schemes is the limited dynamic range imposed by the GPS C/A code signal structure. This problem is discussed along with the problems of multipath distortion in the context of telematics operation in urban canyons. A realistic urban accuracy goal of 20 m for 95% of fixes is proposed based on experience with GPS and dead reckoning. Enhancements under development will provide sensitivity of –188 dBW, which will provide continuous availability within a broader range of indoor environments. For practical applications, this will require the use of modern 'search engine' hardware for acceptable acquisition speed. As the paper shows, this sensitivity is near the practical limit of sensitivity with acceptable acquisition times and dynamic capability. Electronic Publication  相似文献   

Managing spatial uncertainty using attribute,geometric, and neighborhood measures in an empirical rule-based model approach     

Rod Allan  Kim Lowell 《Journal of Geographical Systems》2002,4(2):141-156

 A rule-based model for managing uncertainty in spatial databases is presented. The overall goal of the model is to allow a user to assign to a single map class each polygon whose class is not entirely certain using more information than only the map class attributes of such polygons (that are herein termed abjects). This situation might arise when multiple map realizations of an area are available and interpreters/cartographers are not in agreement as to what class is present at a given location or when a digital image is classified by algorithmic/probabilistic means. The scale-based model developed relies on attribute, geometric, and neighborhood measures of abjects arranged in a hierarchical rule-based structure. Structural knowledge of these measures leads to the procedural knowledge that determines what action – e.g., merge, reclassify, retain – is to be taken for a given abject. The wider applicability of the model and associated methodology is also discussed. Received: 5 July 2001 / Accepted: 11 April 2002  相似文献   

Model for Quantitatively Estimating Marine Biogeographic Provinciality——A Case Study of the Permian Marine Biogeography Provincialism     

Shi Guangrong School of Aquatic Science  Natural Resources Management  Deakin University  Rusden Campus  Blackburn Ro  Victori  Australia 《《地质学报》英文版》1997,71(3):317-327

The relationship between the number, position and orientation of lithosphericplates and marine biogeographic provinciality may be quantified since the spatial distribution oforganisms is primarily controlled by latitude-related temperature gradients and geographicalbarriers-two dynamic biogeographic determinants whose variation is closely related to thespatial disposition of continents and oceans. This paper modifies Schopf s (1976) model forquantitatively estimating shallow marine provinciality in recognition of latitude-related tem-perature gradients as the primary biogeographical factor. A test of the modified model againstmodern marine zoogeography reveals high consistency between them. Using this modified mod-el and the Permian palaeogeographical reconstruction maps of Scotese and McKerrow (1990),fifteen shallow benthic marine provinces are estimated to be Early and Late Permian in agerespectively. A comparison of the estimated Permian marine provinciality with previouslyrecognised empirical provincial patterns reveals a high degree of congruity, which may implythat there existed moderate to high latitudinal thermal gradients during the Permian, a levelprobably similar to that of the present world.  相似文献   

Preservice Primary Teachers’ Depth and Accuracy of Knowledge of Tropical Cyclones     

Rod Lane  Simon Catling 《The Journal of geography》2016,115(5):198-211

Climatic hazards are a key feature of life. It is vital that teachers are knowledgeable about these phenomena in order to develop their students’ understanding of them. This study used a mixed methods approach to examine the accuracy and depth of preservice primary teachers’ (n = 430) knowledge of tropical cyclones. The findings suggest that prospective primary teachers hold alternative conceptions about the causes, spatial distribution, and impacts of these phenomena and that their explanations of processes lack structural complexity and integration. Issues raised by these findings and implications for teachers’ geographical knowledge and their professional standards and preservice teacher education are discussed.  相似文献