Behaviour of crushed rock aggregates used in asphalt surface layer exposed to cold climate conditions     

Ana Patricia Pérez Fortes  Sara Anastasio  Elena Kuznetsova  Svein Willy Danielsen 《Environmental Earth Sciences》2016,75(21):1414

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An occurrence of cadmiferous phosphorite soil concretions in Jamaica     

Robert G. Garrett  Anthony R.D. Porter  Patricia A. Hunt 《Applied Geochemistry》2010

Bauxite exploration drilling revealed the presence of phosphate minerals through the chemical and XRD analysis of recovered drill hole samples at Spitzbergen, in Manchester Parish, Jamaica. A subsequent pit led to the discovery of phosphorite concretions composed of hard competent masses of finely crystalline fluorapatite, with some minor crandallite. The phosphorite contains anomalously high levels of Zn (>5000 mg kg⁻¹), Cd (>1.1%), Ag (>20 mg kg⁻¹), Be (>80 mg kg⁻¹) and, to a lesser extent, U. Textural and geochemical evidence indicates that the phosphorite concretions were most likely formed by the replacement of limestone by secondary deposition proximal to fossil guano deposits, postulated to be Late Miocene or Pliocene sea-bird colonies. Mechanical dispersion of the phosphorite concretions through karst weathering processes has led to their wider spatial distribution than the original guano deposits. Subsequent weathering of the concretions and the admixture of their decomposition products into the bauxitic and Terra Rossa soils is postulated to be the cause of the widespread anomalous levels of Zn, Cd and Be in these soils in central Jamaica, and the elevated levels of P in the bauxite.  相似文献   

Effects of long-term irrigation with treated wastewater. Part I: Evolution of soil physico-chemical properties     

Lobna Gharbi Tarchouna  Patricia Merdy  Michel Raynaud  Hans-Rudolf Pfeifer  Yves Lucas 《Applied Geochemistry》2010

The long-term impact of irrigation on a Mediterranean sandy soil irrigated with Treated wastewater (TWW) since 1980 was evaluated. The main soil properties (CEC, pH, size distribution, exchangeable cations and chloride, hydraulic conductivity) as well as the organic matter and Cu, Cr and Pb speciation in an irrigated soil and a non-irrigated control soil at various soil depths were monitored and compared during a 2 years experiment. In this first part, the evolution of the physico-chemical soil properties was described. The irrigation with TWW was beneficial with regard to water and nutrient supplying. All the exchangeable cations other than K⁺ were higher in the irrigated soil than in the reference one. A part of the exchangeable cations was not fixed on the exchange complex but stored as labile salts or in concentrated soil solution. Despite the very sandy soil texture, both saturated and unsaturated hydraulic conductivity exhibited a significant diminution in the irrigated soil, but remained high enough to allow water percolation during rainy periods and subsequent leaching of accumulated salts, preventing soil salinization. In the irrigated soil, exchangeable sodium percentage (ESP) exhibited high values (20% on average) and the soil organic C was lower than in the reference. No significant effect was noticed on soil mineralogical composition due to irrigation.  相似文献   

A multispecies virtual population analysis of the eastern Bering Sea   总被引：4，自引：1，他引：3  

Livingston  Patricia A.; Jurado-Molina  Jesus 《ICES Journal of Marine Science》2000,57(2):294-299

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Dependence of upper atmosphere photochemistry on the shape of the diurnal cycle of the photolysis rates     

Sonia MONTECINOS  Patricia BARRIENTOS 《大气科学进展》2006,23(2):207-214

A photochemical model of the atmosphere constitutes a non–linear, non–autonomous dynamical system, enforced by the Earth’s rotation. Some studies have shown that the region of the mesopause tends towards non–linear responses such as period-doubling cascades and chaos. In these studies, simple approximations for the diurnal variations of the photolysis rates are assumed. The goal of this article is to investigate what happens if the more realistic, calculated photolysis rates are introduced. It is found that, if the usual approximations—sinusoidal and step fiunctions—are assumed, the responses of the system are similar: it converges to a 2–day periodic solution. If the more realistic, calculated diurnal cycle is introduced, a new 4–day subharmonic appear.  相似文献   

The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion     

Joanna Miko&#;ajewska  Estela Brandi †  Warren Hack  Patricia A. Whitelock  Rodolfo Barba ‡  Lia Garcia  Freddy Marang 《Monthly notices of the Royal Astronomical Society》1999,305(1):190-210

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The effect of sewage plant effluent on brown trout (Salmo trutta fario): a cage experiment     

Matthias Escher  Thomas Wahli  Sabina Büttner  Willy Meier  Patricia Burkhardt-Holm 《Aquatic Sciences - Research Across Boundaries》1999,61(2):93-110

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The source of raw materials for Roman pottery from Leptiminus,Tunisia     

Barbara L. Sherriff  Patricia Court  Shannon Johnston  Lea Stirling 《Geoarchaeology》2002,17(8):835-861

Leptiminus, a Roman port city on the west coast of Tunisia, North Africa, exported olive oil and a garum fish paste to Rome. Excavations have uncovered many facilities including kilns and a potter's workshop, indicating an extensive ceramic industry. The vessels, manufactured at Leptiminus, included African red‐slip fineware, coarseware, and amphorae. A petrographic study of pottery sherds showed them to contain very similar temper, rounded aeolian sand grains and limestone, but varying in proportions to produce different textures. An investigation of the source of raw materials for the pottery found three distinct types of clay within a 50 km radius of Leptiminus: grey Miocene, brown Pliocene, and green Late Pliocene clay. Statistical analysis of trace element compositions, using induced neutron activation, of clays and sherds showed that the Pliocene brown clay was used to create all types of pottery. The specific clay horizon, used in Roman times, has apparently been removed by quarrying. However, a lateral continuation of this bed was found 7 m beneath the Leptiminus site 290. © 2002 Wiley Periodicals, Inc.  相似文献   

Nitrogen abundances in damped Lyman α systems: the combined effects of SNII and SNIa in a hierarchical clustering scenario     

Patricia B. Tissera  Diego G. Lambas  †  Sofia A. Cora ‡  Mirta B. Mosconi 《Monthly notices of the Royal Astronomical Society》2002,337(3):L27-L30

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Saltwater sport fishing for food or income in the Northeastern US: Statistical estimates and policy implications     

Scott Steinback  Kristy Wallmo  Patricia Clay 《Marine Policy》2009

In the Northeast US fishery managers have attempted to control marine recreational fishing mortality through annual adjustments to the number and/or size of fish that can be kept. These measures, with a few exceptions, have generally failed to prevent recreational fishing mortality rates from exceeding annual target levels. In this study, we show that one of the reasons why keep limits may have failed is that a substantial number of anglers obtain little value from being able to keep self-caught fish. Our findings are based on a telephone survey administered to marine anglers in all of the coastal counties in the Northeast US in 2004/2005. To evaluate the importance of keeping self-caught fish, we provide estimates of the size of the marine angling population in the Northeast US that keeps fish for food or income and also for those that fish primarily for recreation and place little or no value on keeping fish. Demographic characteristics of the two groups of anglers are compared statistically and differences related to consumption of self-caught marine resources and to health warning advisories are discussed. We also estimate the size of the Northeast US angling population that relies on their self-caught marine resources as a cost-saving food source or as a supplement to household income. This information could improve the effectiveness of fisheries regulations and the ability of policy analysts to predict how anglers might be affected by proposed fishery management actions.  相似文献