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991.
Brian Mills Dan Unrau Carla Parkinson Brenda Jones Jennifer Yessis Kelsey Spring Laurel Pentelow 《Natural Hazards》2008,47(2):157-183
This article summarizes research completed to assess the risk of lightning-related injuries and fatalities in Canada. Although
lightning mortality has declined significantly over the past century, it remains a common meteorological hazard that regularly
kills and injures. Based on an analysis of media reports, vital statistics, hospital admission and emergency room visit records,
and fire loss data, the authors estimate that on average about 9–10 lightning-related deaths and 92–164 injuries occur each
year in Canada. The distribution of casualties reflects current provincial population and cloud-to-ground lightning densities.
Consistent with similar studies in other developed nations, most lightning-related fatalities and injuries in Canada occur
during the June-August summer season, coincident with peak lightning, and during the Thursday-Saturday period, most likely
related to higher rates of participation in outdoor activities. The majority of victims are male, less than 46 years old,
and engaged in outdoor recreational activities when injured or killed in a lightning incident. Media reports used in the study
were found to underestimate both lightning mortality (36%) and morbidity (20–600%).
相似文献
Brian MillsEmail: |
992.
Comparison of dissolution under oxic acid drainage conditions for eight sedimentary and hydrothermal pyrite samples 总被引:1,自引:0,他引:1
Ran Liu Amy L. Wolfe David A. Dzombak Brian W. Stewart Rosemary C. Capo 《Environmental Geology》2008,56(1):171-182
The abiotic oxidative dissolution behaviors of eight natural pyrite samples, five sedimentary and three hydrothermal, from
various geological environments were compared under oxic conditions at pH 3 and 6 in a highly controlled batch reactor dissolution
system. The three sedimentary pyrite samples associated with coal had greater specific surface areas and also exhibited greater
apparent dissolution rates and extent than the other two sedimentary and three hydrothermal samples under both pH conditions.
However, after normalizing for surface area, the dissolution rate constants for the different pyrite samples were similar;
the greatest difference was between the two non-coal sedimentary pyrite samples. Pyrite morphology and the presence of trace
metals could contribute to the differences in dissolution behavior as reflected in the normalized dissolution rates. The sulfur:iron
ratio observed in the aqueous solution at pH 3 increased with time, but was always less than 2.0 (predicted from the stoichiometry
of dissolution) for all the pyrite samples during the 24-h experimental duration. This can be explained by the disproportionation
dissociation of thiosulfate, an initial product of pyrite dissolution, to elemental sulfur and sulfate which does not occur
in a 1:1 ratio. The results of this work indicate the importance of extracting and using the specific pyrite(s) relevant to
particular mining areas in order to understand pyrite dissolution rates and the influence of environmental conditions on those
rates. 相似文献
993.
In this paper the development of a large-scale gravitational deformation involving the eastern lateral moraine of the Athabasca
Glacier in Jasper National Park, Alberta, Canada, is described. Interpretation and analysis of sequential aerial photographs
indicates that a 540-m-wide segment of the eastern lateral moraine began to deform in the early 1950s; however, significant
movement only began in the late 1960s. Since then, the moraine has undergone progressive gravitational deformation leading
to a network of fractures, bulging, and the development of a large gap in the moraine crest. Geographic information system
analysis of topographic changes between 1967 and 2006 indicates that the displaced volume of the moraine is approximately
9.0 × 105 m3. In the last 39 years, the moraine crest has displaced 55 m (1.4 m yr−1) down towards the glacier. The development of slope instability is linked to a combination of debuttressing from recent glacier
recession, deformation of the moraine, as well as the movement of a large, mobile, debris-mantled slope impinging the upslope
margin of the lateral moraine. This case study illustrates the importance of glacial conditioning and local geomorphological
factors in creating conditions for large-scale moraine instability in recently deglacierized alpine basins. 相似文献
994.
Brian Fry 《Estuaries and Coasts》2008,31(4):776-789
Previous studies of Louisiana estuaries have indicated a central role of Spartina alterniflora marshes in supporting production of the commercially important brown shrimp, Farfantepenaeus aztecus. Brown shrimp are an estuarine-dependent species and spend one to three springtime months in estuaries as small juveniles, with highest shrimp densities found at marsh edges. Later estuarine and offshore production of brown shrimp is correlated both with marsh area and with abundance of smaller juveniles found in unvegetated open bays near marshes. This paper investigates the idea that open bays are an additional important nursery habitat for Louisiana brown shrimp, with bays possibly supporting the bulk of shrimp populations even while shrimp densities expressed on a square meter basis are lower in the bays. To assay possible differences in shrimp abundances and residency in marsh ponds vs. adjacent open bays, springtime field work was conducted in 2004–2006 near the Louisiana University Marine Consortium Laboratory at Cocodrie, Louisiana. Seine surveys showed similar-sized shrimp were present in marsh ponds (<20 m in diameter) and an adjacent open bay (<1 m deep, 2 km in diameter) and that shrimp were twice as dense in the marsh ponds. Natural C, N, and S isotope tags provided distinctive labeling of shrimp from marsh ponds versus bays; shrimp residency appeared high in both areas with <10% of shrimp present as immigrants from other areas. Widely spaced collections from several Louisiana bay systems and also Galveston Bay, Texas showed that the S isotope tags provided the most general tags for marsh origins, with low S isotope values of 1–9‰ in shrimp muscle tissue consistently indicating marsh origins. Importance of marshes for brown shrimp production across Terrebonne and Barataria Bays, Louisiana was evaluated with S isotopes using spring 2005 collections. Results showed that marshes supported about 1/3 of total shrimp production; 2/3 of Louisiana brown estuarine shrimp production may depend on the three to four times more extensive open bays. Given these results, coastal restoration efforts in Louisiana might focus on measures such as barrier island conservation and restoration that protect both bays and marshes, rather than focusing on measures that specifically target marshes and neglect open bays. 相似文献
995.
The late Quaternary stratigraphy and geochronology of San Mateo and Las Flores Creeks indicates that both streams, which drain into the Pacific Ocean along the southern California coast, had a synchronous landscape history. Both San Mateo and Las Flores Creeks cut deep valleys during the late Pleistocene in response to the worldwide drop in sea level. A long period of aggradation followed as sea level rose to its present position during the late Pleistocene and Holocene. Around 500 years ago, the channels of both streams downcut into their respective floodplains creating a prominent terrace (T-2). This was followed by renewed deposition and later channel incision which created a second terrace (T-1). These channel changes are probably the result of a complex response of the fluvial system to major flooding during the late Holocene. The geologic history of these drainages provides a framework that can be used to assess the buried archaeological record along the coast and evaluate regional prehistoric settlement patterns. Based on this study, the post-4000 B.P. valley floor archaeological record along the southern California coast will be more complete and accessible, resulting in a better understanding of the spatial distribution of sites. On the other hand, the pre-4000 B.P. valley floor record lies deeply buried and inaccessible to researchers, which results in a distortion of settlement patterns before 4000 B.P. Finally, examination of post-4000 B.P. sites in the alluvium of San Mateo and Las Flores creeks yielded a pattern of large sites that were occupied extensively for multiple seasons and had considerable evidence of marine exploitation. These findings are contrary to models of cultural development along this portion of the southern California coast. © 1999 John Wiley & Sons, Inc. 相似文献
996.
The study concerns sand deposition within a regular array of vertical cylinders placed in the path of a sand-laden wind. Twelve wind tunnel experiments using three preselected shear velocities (28·78, 32·86 and 45·1 cm s−1), with associated rates of sand feed (0·3, 2·0 and 3·8 g cm−1 s−1), and four roughness element concentrations (λ = 0·046, 0·092, 0·184 and 0·369) were carried out to evaluate the factors that affect sand deposition and sand flux in the presence of immobile rough elements. The measurements showed that as the concentration of non-erodible elements increased, the percentage reduction in the initial sand flux increased and a particularly sharp reduction occurred when λ ≥ 0·18. The pattern of reduction was found to be qred = qeq (d/H) [Δy/(Δy−d)](0·68 −3·5λ) when λ ≤ 0·18, and qred = qeq(d/H)[Δy/(Δy−d)](0·025) when λ > 0·18, where qeq is the equilibrium rate of sand transport arriving at the best bed, d is the diameter of the cylinder, H is the height of the cylinder, and Δy is the width of unit area associated with a cylinder. The experimenal results also showed that the sand flux downstream of the array started to increase immediately upon the commencement of burial of the array's cylinders. Thus the sand deposition and sand flux along an array consisting of regularly distributed, non-erodible elements were shown to be neither uniform nor steady. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
997.
998.
A hydrological investigation was conducted in a small headwater peatland located in the Experimental Lakes Area, north-western Ontario, Canada, to determine the subsurface and surface flow paths within the peatland, and between the peatland and an adjacent forested upland during baseflow and storm flow conditions. Distinct zones of groundwater recharge and discharge were observed within the peatland. These zones are similar to those found in much larger flow systems even though the peatland was only influenced by local groundwater flow. Groundwater emerging in seeps and flowing beneath the peatland sustained the surface wetness of the peatland and maintained a constant baseflow. The response of the peatland stream to summer rain events was controlled by peatland water table position when the basin was dry and antecedent moisture storage on the uplands when the basin was wet. The magnitude and timing of peak runoff during wet conditions were controlled by the degree of hydrological connectivity between the surrounding upland terrain and the peatland. © 1998 John Wiley & Sons, Ltd. 相似文献
999.
Brian Jones 《Sedimentology》2020,67(4):1844-1878
Phosphatic limestones on the west end of Little Cayman, at an elevation of 3 to 4 m above sea level and ca 320 to 550 m inland of the coast, lie on top of a phytokarst surface that defines the upper boundary of the Pedro Castle Formation (Pliocene). These phosphatic limestones are formed of phosphatic lithoclasts, detrital phosphate grains, coated grains (glaebules), composite coated grains, biofragments and phosphate rafts that are held in a matrix that is formed of micrite, calcite cement, and non-crystalline masses formed of P, Al, Si and Fe. The phosphate in these limestones is primarily hydroxylapatite, whereas the overlying soils, found in some areas, are formed of hydroxylapatite, crandallite and minor amounts of boehemite, kaolinite and quartz. Textures in the lithoclasts and detrital phosphate grains indicate that they were derived from older insular phosphates that that were largely removed by mining in 1890 to 1895. The coated grains (glaebules) typically have nuclei formed of a detrital phosphate grains that are encased by non-crystalline cortical laminae that are composed primarily of Al with their variable red colour reflecting the variable Fe content. The phosphatic limestones developed in a low-lying coastal area where the guano produced by a large seabird colony that was close to or mixed with terra rossa and marine carbonates that were washed onshore during storms/hurricanes. The Al, Fe, Si and rare earth elements found in the phosphatic limestones came from the terra rossa. Critically, this study documents the complex depositional regimes and diagenetic processes that can exist at the interface of marine carbonates, coastal phosphates and terrestrial soils as sea-level fluctuations control phases of sediment accumulation that were periodically interrupted by periods of non-deposition. 相似文献
1000.
Real-time hybrid simulation is an attractive method to evaluate the response of structures under earthquake loads.The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time,thus allowing investigation of structural systems with rate-dependent components.Real-time hybrid simulation is challenging because it requires performance of all calculations,application of displacements,and acquisition of measured forces,within a very small increment of time.Furthe... 相似文献