Visualization of spatial patterns and temporal trends for aerial surveillance of illegal oil discharges in western Canadian marine waters   总被引：1，自引：0，他引：1  

Serra-Sogas N  O'Hara PD  Canessa R  Keller P  Pelot R 《Marine pollution bulletin》2008,56(5):825-833

This paper examines the use of exploratory spatial analysis for identifying hotspots of shipping-based oil pollution in the Pacific Region of Canada’s Exclusive Economic Zone. It makes use of data collected from fiscal years 1997/1998 to 2005/2006 by the National Aerial Surveillance Program, the primary tool for monitoring and enforcing the provisions imposed by MARPOL 73/78. First, we present oil spill data as points in a “dot map” relative to coastlines, harbors and the aerial surveillance distribution. Then, we explore the intensity of oil spill events using the Quadrat Count method, and the Kernel Density Estimation methods with both fixed and adaptive bandwidths. We found that oil spill hotspots where more clearly defined using Kernel Density Estimation with an adaptive bandwidth, probably because of the “clustered” distribution of oil spill occurrences. Finally, we discuss the importance of standardizing oil spill data by controlling for surveillance effort to provide a better understanding of the distribution of illegal oil spills, and how these results can ultimately benefit a monitoring program.  相似文献   

Benthic macrofaunal community condition in the Southern California Bight, 1994-2003     

J. Ananda Ranasinghe  Kenneth C. Schiff  Tim K. Mikel  Ronald G. Velarde 《Marine pollution bulletin》2010,60(6):827-833

To assess benthic macrofaunal community condition in Southern California, 838 sites were sampled using spatially random designs in 1994, 1998, or 2003. Benthic community condition was assessed on a four-category scale and the area in each category estimated. Overall, benthic macrofauna in Southern California were in good condition during 2003, with 98% of the area in reference condition or deviating only marginally. There was no evidence of disturbance near Channel Islands or small wastewater discharges, and virtually none on the mainland shelf. In contrast, bay and estuary macrofaunal communities were more frequently disturbed with nearly 13% of the area supporting disturbed benthos. The condition of the mainland shelf did not change substantially over the 9-year period, with 1.6-2.8% of the area in poor benthic condition. Southern California benthic condition evaluations may be improved by extending the depth and salinity ranges of assessment tools, and improving trend detection methods.  相似文献   

Assessing coastal benthic macrofauna community condition using best professional judgement - Developing consensus across North America and Europe     

Heliana Teixeira  Ángel Borja  J. Ananda Ranasinghe  Daniel M. Dauer  Steven Degraer  Antoine Grémare  Roberto J. Llansó  João C. Marques  Anna Occhipinti-Ambrogi  Rafael Sardá  Ronald G. Velarde 《Marine pollution bulletin》2010,60(4):589-600

Benthic indices are typically developed independently by habitat, making their incorporation into large geographic scale assessments potentially problematic because of scaling inequities. A potential solution is to establish common scaling using expert best professional judgment (BPJ). To test if experts from different geographies agree on condition assessment, sixteen experts from four regions in USA and Europe were provided species-abundance data for twelve sites per region. They ranked samples from best to worst condition and classified samples into four condition (quality) categories. Site rankings were highly correlated among experts, regardless of whether they were assessing samples from their home region. There was also good agreement on condition category, though agreement was better for samples at extremes of the disturbance gradient. The absence of regional bias suggests that expert judgment is a viable means for establishing a uniform scale to calibrate indices consistently across geographic regions.  相似文献   

Quality of the Log-Geometric Distribution Extrapolation for Smaller Undiscovered Oil and Gas Pool Size     

Liu Chenglin  Ronald R. Charpentier 《Natural Resources Research》2010,19(1):11-21

The U.S. Geological Survey procedure for the estimation of the general form of the parent distribution requires that the parameters of the log-geometric distribution be calculated and analyzed for the sensitivity of these parameters to different conditions. In this study, we derive the shape factor of a log-geometric distribution from the ratio of frequencies between adjacent bins. The shape factor has a log straight-line relationship with the ratio of frequencies. Additionally, the calculation equations of a ratio of the mean size to the lower size-class boundary are deduced. For a specific log-geometric distribution, we find that the ratio of the mean size to the lower size-class boundary is the same. We apply our analysis to simulations based on oil and gas pool distributions from four petroleum systems of Alberta, Canada and four generated distributions. Each petroleum system in Alberta has a different shape factor. Generally, the shape factors in the four petroleum systems stabilize with the increase of discovered pool numbers. For a log-geometric distribution, the shape factor becomes stable when discovered pool numbers exceed 50 and the shape factor is influenced by the exploration efficiency when the exploration efficiency is less than 1. The simulation results show that calculated shape factors increase with those of the parent distributions, and undiscovered oil and gas resources estimated through the log-geometric distribution extrapolation are smaller than the actual values.  相似文献   

Hidden Components in Tropical Seascapes: Deep-Estuary Habitats Support Unique Fish Assemblages     

Michael Bradley  Ronald Baker  Marcus Sheaves 《Estuaries and Coasts》2017,40(4):1195-1206

Tropical coastal seascapes are biodiverse and highly productive systems composed of an interacting mix of habitats. They provide crucial ecosystem services that support people’s livelihoods, yet key components of these seascapes remain unstudied. We know little about the deep (>2 m) subtidal areas of tropical estuaries, because, due to gear restrictions, there have been no detailed studies of the habitats they contain and the fish that use them. Consequently, potentially important functions and linkages with surrounding habitats remain unknown. Using unbaited videos, an approach capable of sampling the full breadth of benthic habitats and whole fish assemblages, we investigated patterns of fish occupancy of the deep subtidal habitats (2–20 m) in one of Australia’s largest tropical estuaries. We identified 19 taxa not previously recorded from estuaries of tropical eastern Australia, along with 36 previously identified estuary taxa. Three recognisable fish assemblages were associated with distinct benthic habitat types: open bottom fine sediment, seagrass and structurally complex rocky areas. In deep water, habitats often overlooked in shallow water become important, and there are sharp differences in habitat function. Deep subtidal habitats are potentially an important zone for direct interaction between estuary and marine fauna, with a range of consequences for intertidal habitat use and nursery ground functioning. The interface between marine areas and the shallow-water estuary may be richer and more complex than previously recognised.  相似文献   

A new species of the genus <Emphasis Type="Italic">Ammonicera</Emphasis> (Prosobranchia,Omalogyridae) in a coralline algae community from Jeju Island,off the south coast of Korea     

Tsukasa Waki  Emilio Rolán  Ronald G. Noseworthy  Hyun-Sil Kang  Kwang-Sik Choi 《Ocean Science Journal》2017,52(4):587-591

A species of the genus Ammonicera Vayssière, 1893 collected from coralline algae communities in Jeju Island, South Korea, is described as a new species, A. aurea, for science. Its morphological characters are described and illustrated by SEM micrographs. This new species can be clearly distinguished from other Ammonicera species from the Pacific Ocean by the presence of a spiral cord and about 25 slightly-elevated axial ribs, resulting in about 25 nodules at intersecting points of the cord and ribs on the last whorl of the teleoconch.  相似文献   

An XMM–Newton observation of the young open cluster NGC 2547: coronal activity at 30 Myr     

R. D. Jeffries  P. A. Evans  J. P. Pye  K. R. Briggs 《Monthly notices of the Royal Astronomical Society》2006,367(2):781-800

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HISTORICAL SOURCES FOR GEOMORPHOLOGICAL RESEARCH IN THE UNITED STATES*     

Stanley W. Trimble  Ronald U. Cooke 《The Professional geographer》1991,43(2):212-228

The use of historical sources in geomorphological analysis has had a long tradition in geography and is now undergoing a resurgence. A substantial body of data is available, and the search for it should extend from the National Archives to state and company records and county and city offices.  相似文献   

Batse spectroscopy detector calibration     

D. Band  L. Ford  J. Matteson  J. P. Lestrade  B. Teegarden  B. Schaefer  T. Cline  M. Briggs  W. Paciesas  G. Pendleton  R. Austin  G. Fishman  C. Meegan  R. Wilson 《Experimental Astronomy》1992,2(5):307-330

We describe the channel-to-energy calibration of the Spectroscopy Detectors of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (GRO). These detectors consist of NaI(Tl) crystals viewed by photomultiplier tubes whose output in turn is measured by a pulse height analyzer. The calibration of these detectors has been complicated by frequent gain changes and by nonlinearities specific to the BATSE detectors. Nonlinearities in the light output from the NaI crystal and in the pulse height analyzer are shifted relative to each other by changes in the gain of the photomultiplier tube. We present the analytical model which is the basis of our calibration methodology, and outline how the empirical coefficients in this approach were determined. We also describe the complications peculiar to the Spectroscopy Detectors, and how our understanding of the detectors' operation led us to a solution to these problems.  相似文献   

An Analytical Approach to Shear Dispersion and Tracer Age     

Ronald?B.?SmithEmail author 《Boundary-Layer Meteorology》2005,117(3):383-415

Solutions to the sheared Fickian advection–diffusion equation in a half-space with arbitrary surface source are given using a ‘transfer function’ method. The method uses Fourier transforms in two horizontal coordinates and time, along with complex Airy functions in the vertical coordinate. Surface deposition and tracer decay are included in the formulation. ‘Puff’ and steady ‘plume’ solutions are compared with Saffman’s moment formulae. The inclusion of a decay rate factor (α) allows the average tracer age to be computed from steady state solutions for concentration C(x, y, z) according to Age = − dln C/dα. A comparison between the puff centroid formula of Saffman and plume Age computations confirms that shear causes tracer puffs to accelerate horizontally as they diffuse upward into a different wind regime. In forward shear, tracer ages are younger than in unsheared flow but the range of ages is greater due to the existence of a high fast pathway and a low slow pathway. In reverse shear, concentrations, ages and the range of ages all rise markedly near the source. Large tracer age suggests that some tracer has taken a very distant path involving a low-level outbound trip and a high-level return. The effect of surface deposition is to reduce the influence of the distant path. In the case of reverse shear, deposition makes the tracer younger. In a turning wind, the time needed to reach a given radius increases due to the curved path of the plume.  相似文献