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1.
Slack Tim Parks Vanessa Ayer Lynsay Parker Andrew M. Finucane Melissa L. Ramchand Rajeev 《Natural Hazards》2020,102(3):1207-1224
Natural Hazards - Researchers have traditionally conceptualized hazards that give rise to disasters as “natural” or “technological.” An extensive literature has documented... 相似文献
2.
Kristine L. Delong Suyapa Gonzalez Jeffrey B. Obelcz Jonathan T. Truong Samuel J. Bentley Sr Kehui Xu Carl A. Reese Grant L. Harley Alicia Caporaso Zhixiong Shen Beth A. Middleton 《Boreas: An International Journal of Quaternary Research》2021,50(3):871-892
Approximately 13 km south of Gulf Shores, Alabama (United States), divers found in situ baldcypress (Taxodium distichum) stumps 18 m below the ocean surface. These trees could have only lived when sea level fell during the Pleistocene subaerially exposing the tectonically stable continental shelf. Here we investigate the geophysical properties along with microfossil and stratigraphical analyses of sediment cores to understand the factors that lead to this wood’s preservation. The stumps are exposed in an elongated depression (~100 m long, ~1 m deep) nested in a trough of the northwest–southeast trending Holocene sand ridges and troughs with 2–5 m vertical relief and ~0.5 km wavelength. Radiocarbon ages of the wood were infinite thus optically stimulated luminescence (OSL) dating was used to constrain the site’s age. Below the Holocene sands (~0.1–4 m thick), separated by a regional erosional unconformity, are Late Pleistocene mud-peat (72±8 ka OSL), mud-sand (63±5, 73±6 ka OSL), and palaeosol (56±5 ka OSL) facies that grade laterally from west to east, respectively. Foraminiferal analysis reveals the location of the terrestrial-marine transitional layer above the Pleistocene facies in an interbedded sand and mud facies (3940±30 (1σ) 14C a BP), which is part of a lower shoreface or marine-dominated estuarine environment. The occurrence of palaeosol and swamp facies of broadly similar ages and elevation suggests the glacial landscape possessed topographic relief that allowed wood, mud and peats to be preserved for ~50 ka of subaerial exposure before transitioning to the modern marine environment. We hypothesize that rapid sea-level rise occurring ~60 or ~40 ka ago provided opportunities for local flood-plain aggradation to bury the swamp thus preserving the stumps and that other sites may exist in the northern Gulf of Mexico shelf. 相似文献
3.
The temporal‐spatial resolution of input data‐induced uncertainty in a watershed‐based water quality model, Hydrologic Simulation Program‐FORTRAN (HSPF), is investigated in this study. The temporal resolution‐induced uncertainty is described using the coefficient of variation (CV). The CV is found to decrease with decreasing temporal resolution and follow a log‐normal relation with time interval for temperature data while it exhibits a power‐law relation for rainfall data. The temporal‐scale uncertainties in the temperature and rainfall data follow a general extreme value distribution and a Weibull distribution, respectively. The Nash‐Sutcliffe coefficient (NSC) is employed to represent the spatial resolution induced uncertainty. The spatial resolution uncertainty in the dissolved oxygen and nitrate‐nitrogen concentrations simulated using HSPF is observed to follow a general extreme value distribution and a log‐normal distribution, respectively. The probability density functions (PDF) provide new insights into the effect of temporal‐scale and spatial resolution of input data on uncertainties involved in watershed modelling and total maximum daily load calculations. This study exhibits non‐symmetric distributions of uncertainty in water quality modelling, which simplify weather and water quality monitoring and reducing the cost involved in flow and water quality monitoring. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
5.
Aqueous oxidation of sulfide minerals to sulfate is an integral part of the global sulfur and oxygen cycles. The current model for pyrite oxidation emphasizes the role of Fe2+-Fe3+ electron shuttling and repeated nucleophilic attack by water molecules on sulfur. Previous δ18O-labeled experiments show that a variable fraction (0-60%) of the oxygen in product sulfate is derived from dissolved O2, the other potential oxidant. This indicates that nucleophilic attack cannot continue all the way to sulfate and that a sulfoxyanion of intermediate oxidation state is released into solution. The observed variability in O2% may be due to the presence of competing oxidation pathways, variable experimental conditions (e.g. abiotic, biotic, or changing pH value), or uncertainties related to the multiple experiments needed to effectively use the δ18O label to differentiate sulfate-oxygen sources. To examine the role of O2 and Fe3+ in determining the final incorporation of O2 oxygen in sulfate produced during pyrite oxidation, we designed a set of aerated, abiotic, pH-buffered (pH = 2, 7, 9, 10, and 11), and triple-oxygen-isotope labeled solutions with and without Fe3+ addition. While abiotic and pH-buffered conditions help to eliminate variables, triple oxygen isotope labeling and Fe3+ addition help to determine the oxygen sources in sulfate and examine the role of Fe2+-Fe3+ electron shuttling during sulfide oxidation, respectively.Our results show that sulfate concentration increased linearly with time and the maximum concentration was achieved at pH 11. At pH 2, 7, and 9, sulfate production was slow but increased by 4× with the addition of Fe3+. Significant amounts of sulfite and thiosulfate were detected in pH ? 9 reactors, while concentrations were low or undetectable at pH 2 and 7. The triple oxygen isotope data show that at pH ? 9, product sulfate contained 21-24% air O2 signal, similar to pH 2 with Fe3+ addition. Sulfate from the pH 2 reactor without Fe3+ addition and the pH 7 reactors all showed 28-29% O2 signal. While the O2% in final sulfate apparently clusters around 25%, the measurable deviations (>experimental error) from the 25% in many reaction conditions suggest that (1) O2 does get incorporated into intermediate sulfoxyanions (thiosulfate and sulfite) and a fraction survives sulfite-water exchange (e.g. the pH 2 with no Fe3+ addition and both pH 7 reactors); and (2) direct O2 oxidation dominates while Fe3+ shuttling is still competitive in the sulfite-sulfate step (e.g. the pH 9, 10, and 11 and the pH 2 reactor with Fe3+ addition). Overall, the final sulfate-oxygen source ratio is determined by (1) rate competitions between direct O2 incorporation and Fe3+ shuttling during both the formation of sulfite from pyrite and from sulfite to final sulfate, and (2) rate competitions between sulfite and water oxygen exchange and the oxidation of sulfite to sulfate. Our results indicate that thiosulfate or sulfite is the intermediate species released into solution at all investigated pH and point to a set of dynamic and competing fractionation factors and rates, which control the oxygen isotope composition of sulfate derived from pyrite oxidation. 相似文献
6.
Siyuan Ye Edward A. Laws Xigui Ding Hongming Yuan Guangming Zhao Jin Wang 《Environmental Earth Sciences》2011,64(6):1641-1646
Samples of porewater and the edible tissue of mottled clams, Ruditapes variegatus, were collected simultaneously at each of 12 stations from Jiaozhou Bay near Qingdao, China, in June of 2003. Chemical analysis
focused on trace metals and major elements. Porewater concentrations of Cd, Cr, Pb, and Zn were distributed in a bimodal fashion
among the 12 stations, with mean concentrations at six of the stations being 8–32 times mean values at the other six stations.
The concentrations of the same metals in clams were remarkably similar among stations, the coefficients of variation being
only 12–37%. Calculations performed with the computer program PHREEQC indicated that Pb and Cr in porewater were present only
in the +2 and +3 states, respectively, and because dissolved Cd and Zn exist only in the +2 state, the bimodal distribution
of these four metals likely reflects secondary effects associated with their scavenging by Fe and/or Mn under oxidizing conditions
and subsequent dissolution in the reducing environment of the porewaters. Consistent with this hypothesis is the fact that
the distribution of high and low metal concentrations was closely correlated with the granularity of the sediment, with lower
metal concentrations associated with relatively coarse sediment. Comparison of published biological concentration factors
with the ratios of metal concentrations in the clams to porewater metal concentrations indicated that the porewaters were
not the primary sources of the metals in the clams. Mixing processes in the bay likely account for the rather uniform concentrations
of metals in clam tissue. 相似文献
7.
Michio J. Kishi Shin-ichi Ito Bernard A. Megrey Kenneth A. Rose Francisco E. Werner 《Journal of Oceanography》2011,67(1):3-16
The evolution of the North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO) family of models to study
marine ecosystems is reviewed. Applications throughout the North Pacific have shown the models to be robust and to be able
to reproduce 1D, 2D and 3D components of nutrient, carbon cycle and biogeochemical cycles as well as aspects of the lower
trophic levels ecosystem (phyto- and zooplankton). NEMURO For Including Saury and Herring, an extension that includes higher
trophic levels, can be run uncoupled or coupled to NEMURO. In the uncoupled mode, the growth and weight of an individual fish
is computed using plankton densities simulated by NEMURO but with no feedback between fish consumption and plankton mortality.
In the coupled mode, the feeding, growth and weight of a representative fish are computed, and prey removals due to feeding
by fish appear as mortality terms on the prey. The NEMURO family of models continues to evolve, including effects of the microbial
loop and iron limitation at lower trophic levels, and full life cycle, multi-species and multi-generational simulations at
higher trophic levels. We outline perspectives for future end-to-end modeling efforts that can be used to study marine ecosystems
in response to global environmental change. 相似文献
8.
9.
Louisiana’s Haynesville Shale is one of several unconventional gas plays that have been discovered in the U.S. in recent years
and promise to dramatically change the course of future domestic energy development. The Haynesville Shale is the deepest,
hottest, and highest pressured shale among the big four plays in the U.S. with drilling and completion cost ranging between
7 and7 and 10 million per well. The average Haynesville well has an initial production rate of 10 MMcfd and declines rapidly,
producing 80% of its expected recovery during the first 2 years of production. The purpose of this article is to describe
the productivity characteristics of Haynesville wells, project future production from the inventory of active wells, and assess
production potential based on drilling scenarios. We offer statistical analysis of the wells drilled to date and construct
type profiles to characterize the play. We estimate that the current inventory of Haynesville wells will produce 3 Tcf over
their lifecycles, and within the next 3 years, cumulative build-out in the region will range between 3 and 9 Tcf. To maintain
current gas production levels in the state, we estimate that about 550 shale gas wells per year will need to be brought online
over the next 3 years. 相似文献
10.
This article studies how burglars select a house to burglarize. We draw on the rational choice perspective to investigate how burglars select a target by relying on house-related attributes to optimize a combination of perceived rewards, efforts and risk. It extends current applications of the discrete spatial choice framework to burglary target selection by adopting the house as the spatial unit of analysis and studies burglars' target selection process in a larger and more diverse study area than that of earlier studies. Using data on 650 residential burglaries and on approximately 500,000 residential properties in the Belgian province East Flanders, we consider a discrete spatial choice model of burglary target selection to establish which house-related attributes influence burglars' target selection process. Our findings demonstrate that terraced houses, houses without a garage, houses that have not been outfitted with a central heating and/or air-conditioning system and houses nearby burglars' residences are more likely to be selected. Overall, our analysis suggests that burglars rely on effort-related attributes to distinguish between targets while higher perceived rewards actually decrease the odds of a house being burglarized. Risk-related attributes are unimportant for burglars' target choice. 相似文献