The environmental tritium concentration of underground water and its hydrological interpretation     

G.B. Allison  J.W. Holmes 《Journal of Hydrology》1973,19(2):131-143

Two models which attempt to correlate the tritium concentration of water taken from aquifers to aquifer parameters are discussed. The first takes into account flow along individual streamlines and relates aquifer parameters to the observed tritium concentration at outflow. For the Gambier Plain unconfined aquifer in southern Australia, the calculated tritium concentration at outflow derived from known aquifer parameters and an environmental tritium input function for the area, is 0.7 T.U. The mean tritium concentration of several springs at outflow is also 0.7 T.U.Using the complete mixing model and the approximation that samples withdrawn from an aquifer on Eyre Peninsula, South Australia, are fully mixed, mean annual recharge for the area is estimated at 3 cm/year.  相似文献   

Sensitivity to climate change of land use and management patterns optimized for efficient mitigation of nutrient pollution     

Hui Xu  Daniel G. Brown  Allison L. Steiner 《Climatic change》2018,147(3-4):647-662

Beginning in the mid-1990s, re-eutrophication has reemerged as severe problems in Lake Erie. Controlling non-point source (NPS) nutrient pollution from cropland, especially dissolved reactive phosphorus (DRP), is the key to restore water quality in Lake Erie. To address NPS pollution, previous studies have analyzed the effectiveness of alternative spatially optimal land use and management strategies (represented as agricultural conservation practices (CPs)). However, few studies considered both strategies and have analyzed and compared their sensitivity to expected changes in temperature and precipitation due to climate change and increased greenhouse gas concentrations. In this study, we evaluated impacts of climatic change on the economic efficiency of these strategies for DRP abatement, using an integrated modeling approach that includes a watershed model, an economic valuation component, and a spatial optimization model. A series of climate projections representing relatively high greenhouse gas emission scenarios was developed for the western Lake Erie basin to drive the watershed model. We found that performance of solutions optimized for current climate was degraded significantly under projected future climate conditions. In terms of robustness of individual strategies, CPs alone were more robust to climate change than land use change alone or together with CPs, but relying on CPs alone fails to achieve a high (>?71%) DRP reduction target. A combination of CPs and land use changes was required to achieve policy goals for DRP reductions (targeted at ~?78%). Our results point to the need for future spatial optimization studies and planning to consider adaptive capacity of conservation actions under a changing climate.  相似文献   

Evaluation of a Movie Theater Advertisement Campaign to Promote Behaviors that Prevent Spread of Aquatic Invasive Species     

Bret R. Shaw  Allison Howell  Ken Genskow 《社会与自然资源》2014,27(7):768-776

One of the primary causes of the spread of aquatic invasive species (AIS) is boaters and anglers who move between bodies of water. Engaging with recreational boaters and anglers to encourage preventative behaviors is crucial for managing the spread of AIS. The use of cinema advertising for disseminating pro-environmental messages is a relatively novel and understudied outreach strategy. To explore this approach, an AIS-related public service announcement was placed in the preshow advertising at a movie theater in north central Wisconsin. Movie patrons were surveyed as they left the theater to determine demographic, AIS awareness, advertising exposure, and recall information. The results of this study suggest movie theater advertising is a potentially efficacious medium for pro-environmental outreach efforts.  相似文献   

Decentralized and coordinate-free computation of critical points and surface networks in a discretized scalar field     

Myeong-Hun Jeong  Matt Duckham  Allison Kealy  Harvey J. Miller  Andrej Peisker 《International journal of geographical information science》2014,28(1):1-21

This article provides a decentralized and coordinate-free algorithm, called decentralized gradient field (DGraF), to identify critical points (peaks, pits, and passes) and the topological structure of the surface network connecting those critical points. Algorithms that can operate in the network without centralized control and without coordinates are important in emerging resource-constrained spatial computing environments, in particular geosensor networks. Our approach accounts for the discrepancies between finite granularity sensor data and the underlying continuous field, ignored by previous work. Empirical evaluation shows that our DGraF algorithm can improve the accuracy of critical points identification when compared with the current state-of-the-art decentralized algorithm and matches the accuracy of a centralized algorithm for peaks and pits. The DGraF algorithm is efficient, requiring O(n) overall communication complexity, where n is the number of nodes in the geosensor network. Further, empirical investigations of our algorithm across a range of simulations demonstrate improved load balance of DGraF when compared with an existing decentralized algorithm. Our investigation highlights a number of important issues for future research on the detection of holes and the monitoring of dynamic events in a field.  相似文献   

Erratum to: Quantifying and monetizing potential climate change policy impacts on terrestrial ecosystem carbon storage and wildfires in the United States     

David Mills  Russell Jones  Karen Carney  Alexis St. Juliana  Richard Ready  Allison Crimmins  Jeremy Martinich  Kate Shouse  Benjamin DeAngelo  Erwan Monier 《Climatic change》2015,131(1):179-181

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Spatio-temporal Variability in Larval-Stage Feeding and Nutritional Sources as Factors Influencing Striped Bass (Morone saxatilis) Recruitment Success     

Allison C. Shideler  Edward D. Houde 《Estuaries and Coasts》2014,37(3):561-575

Prey availability and feeding success affect survival of larval striped bass (Morone saxatilis) in Chesapeake Bay and contribute to the >30-fold interannual recruitment variability. Gut contents and stable isotope analyses (δ¹⁵N and δ¹³C) were conducted on striped bass larvae to evaluate sources of nutrition in 2007 and 2008, years of high and poor recruitment, respectively. Ichthyoplankton and zooplankton were surveyed in the upper Chesapeake Bay, in proximity to the estuarine turbidity maximum and associated salt front. Feeding incidence and numbers of prey per gut were similar in both years and varied in relation to the salt front. The primary prey in each year was the estuarine copepod Eurytemora affinis. Substantial consumption of the freshwater cladoceran Bosmina spp. also occurred, especially up-estuary of the salt front in 2007, demonstrating that secondary prey are important to larval diets in some years. Stable isotope analysis of yolk sac and feeding-stage larvae of striped bass revealed an ontogenetic shift from maternal stable isotope signatures to those indicative of prey source. Feeding-stage larvae from up-estuary locations had the most negative δ¹³C values, indicating a relatively high terrestrial carbon source in prey. Spatio-temporal variability in δ¹⁵N signatures of larvae followed similar trends of δ¹⁵N variability in zooplankton prey with the highest δ¹⁵N values up-estuary of the salt front and estuarine turbidity maximum. A stable isotope analysis on archived striped bass larvae collected in 1998 and 2003, years of moderate and high recruitment, respectively, expanded the documented range of isotope signatures but did not clearly distinguish effects of nutritional sources on recruitment.  相似文献   

An application of geological survey and ceramic petrology to provenance studies of Guangala phase Ceramics of ancient Ecuador     

Maria Masucci  Allison Macfarlane 《Geoarchaeology》1997,12(7):765-793

The foundation of provenance studies of ceramics is the regional geology. Unfortunately, archaeologists often depend on regional geologic maps for comparative information. In many areas the scale of maps is too small to determine the lithological variation, which is necessary information for a robust provenance study of ceramic materials. Accurate determination requires geologic field mapping and analysis of the lithologies and clay-rich sediments present. In this provenance study of prehistoric ceramics from southwest Ecuador, we have established the lithological variation of both rocks and clay-rich sediments through geological survey. Petrographic analysis of geological samples and ancient ceramic materials determined the variation in both populations and established cases of significant correlation as well as noncorrelation between objects and local materials. Ceramic production at the Ecuadorian sites was complex and involved local production of domestic wares as well as importation of tempering materials and vessels and adoption of foreign decorative motifs. © 1997 John Wiley & Sons, Inc.  相似文献   

Book Review: Geomorphological Hazards of Europe by C. Embleton and C. E. Embleton-Hamman,Elsevier, Amsterdam, 1997. No. of pages: x + 524. Price: $240.75 (hb). ISBN 0-444-88824-1.     

Robert J. Allison 《地球表面变化过程与地形》1998,23(5):479-480

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The mechanics of deep-seated landslides     

David N. Petley  Robert J. Allison 《地球表面变化过程与地形》1997,22(8):747-758

Results are presented of a sequence of laboratory tests undertaken to elucidate the behaviour of deep-seated landslides. In deep-seated failures deformation has been reported at depths of up to 250 m. In the movement zone, owing to the weight of the overburden and the surrounding stress environment, conventional soil mechanics cannot be used to explain effectively associations between the landslip activity and the deformation mechanisms operating within the moving mass. A series of experiments has been undertaken on London Clay using a high pressure, servohydraulically controlled triaxial deformation system, to replicate the stresses acting at the base of a large, deep-seated landslide. A number of tests were undertaken, the most significant focusing on the transition between ductile and brittle behaviour. Although sediments usually behave in a brittle manner at low effective stresses (common to many geomorphological studies) and in a ductile manner at high effective stresses, the results presented here identify for the first time in mudrocks a transitional phase of behaviour in which creep-like movement will manifest itself at the base of a deep-seated landslide as the growth of microcracks. The microcracks may eventually coalesce to form a shear surface, a consequence of which is likely to be sudden failure. The results thus have important implications in the understanding of movement mechanisms in large, deep-seated failures, rates of displacement and how they may change through time. © 1997 by John Wiley & Sons, Ltd.  相似文献