Rapid movement of wastewater from on-site disposal systems into surface waters in the Lower Florida Keys     

John H. Paul  Molly R. McLaughlin  Dale W. Griffin  Erin K. Lipp  Rodger Stokes  Joan B. Rose 《Estuaries and Coasts》2000,23(5):662-668

Viral tracer studies have been used previously to study the potential for wastewater contamination of surface marine waters in the Upper and Middle Florida Keys. Two bacteriophages, the marine bacteriophage ϕHSIC and theSalmonella phage PRD1, were used as tracers in injection well and septic tank studies in Saddlebunch Keys of the Lower Florida Keys and in septic tank studies in Boot Key Harbor, Marathon, of the Middle Keys. In Boot Key Harbor, both phages were detected in a canal adjacent to the seeded septic tank within 3 h 15 min of the end of the seed period. The tracer was then detected at all sampling sites in Boot Key Harbor, including one on the opposite side of U.S. Highway 1 in Florida Bay, and at an Atlantic Ocean beach outside Boot Key Harbor. Rates of migration based on first appearance of the phage ranged from 1.7 to 57.5 m h⁻¹. In Saddlebunch Keys, ϕHSIC and PRD1 were used to seed a residential septic tank and a commercial injection well. The septic tank tracer was not found in any surface water samples. The injection well tracer was first detected at a site most distant from the seed site, a channel that connected Sugarloaf Sound with the Atlantic Ocean. The, rate of tracer migration from the injection well to this channel ranged from 66.8 to 141 m h⁻¹. Both tracer studies showed a rapid movement of wastewater from on-site sewage treatment and disposal systems in a southeasterly direction toward the reef tract and Atlantic Ocean, with preferential movement through tidal channels. These studies indicate that wastewater disposal systems currently in widespread use in the Florida Keys can rapidly contaminate the marine environment.  相似文献   

Recognition of down-valley translation in tidally influenced meandering fluvial deposits,Athabasca Oil Sands (Cretaceous), Alberta,Canada     

Milovan Fustic  Stephen M. Hubbard  Ron Spencer  Derald G. Smith  Dale A. Leckie  Barry Bennett  Steve Larter 《Marine and Petroleum Geology》2012,29(1):219-232

The vast Athabasca Oil Sands of Alberta, Canada has an estimated resource of more than 1.7 trillion barrels of bitumen in-place, the majority of which is hosted in the Lower Cretaceous McMurray Formation. Despite its economical significance the depositional environment of the formation, and particularly the middle part that is the primary reservoir in most areas, is still a matter of considerable debate. These strata of interest are widely known to comprise fluvial and estuarine point bar deposits that were subject to varying degrees of marine influence. The orientation of point bar strata from the formation is tabulated and the majority is observed to dip paleo-basinward, to the north. This observation has proven difficult to explain by geologists attempting to build predictive models for the formation over the last two decades. However, the basinward-dipping point bar strata can be attributed to widespread down-valley translation of point bars in confined north-south oriented valleys, which have previously been delineated in the region. Differentiating the deposits of lateral point bar migration and down-valley translation in the rock record is not possible at the facies scale, and thus translated point bars have not been previously recognized or interpreted in the rock record, despite their prevalence in numerous modern fluvial valley systems. Their identification in the McMurray Formation has important implications for the delineation and development of Canada’s economically significant oil sands resources.  相似文献   

Evidence for ice flow prior to trough formation in the martian north polar layered deposits     

Dale P. Winebrenner  Michelle R. Koutnik  Asmin V. Pathare  Bruce C. Murray  Jonathan L. Bamber 《Icarus》2008,195(1):90-105

The relative importance of surface mass fluxes and ice flow in shaping the north polar layered deposits (NPLD), now or in the past, remains a fundamental and open question. Motivated by observation of an apparent ice divide on Gemina Lingula (also known as Titania Lobe), we propose a two-stage evolution leading to the present-day topography on that lobe of the NPLD. Ice flow approximately balances surface mass fluxes in the first stage, but in the second stage ice flow has minimal influence and topography is modified predominantly by the formation of troughs. We focus here on evidence for the first stage, by testing the fit of topography between troughs to an ice-flow model. We find that independent model fits on distinct flow paths closely match inter-trough topography, uniformly over a broad region on Gemina Lingula, with mutually consistent and physically reasonable fitting parameters. However, our model requires ice to occupy and flow in spaces where troughs currently incise the ice. We therefore infer that the troughs (and the distribution of mass balance that caused them) post-date deposition of the inter-trough material and its modification by flow. Because trough formation has apparently altered inter-trough topography very little, we infer that trough formation must have been rapid in comparison to the (still unknown) time-scale of flow since troughs began to form. We view the evidence for past flow as strong, but we do not think that topographic evidence alone can be conclusive. Observations of englacial stratigraphy using orbital sounding radars will yield conclusive tests of our inferred mechanism for the formation of inter-trough topography.  相似文献   

Contents of Volume 29     

C. Emdad Haque  Dale Dominey-Howes  Nuray Karanci  Gerassimos Papadopoulos  Ahmet Yalciner 《Natural Hazards》2003,29(3):603-606

Volume Contents

Contents of Volume 29  相似文献   

Creating Carbon Offsets in Agriculture through No-Till Cultivation: A Meta-Analysis of Costs and Carbon Benefits   总被引：6，自引：0，他引：6  

James Manley  G. Cornelis van Kooten  Klaus Moeltner  Dale W. Johnson 《Climatic change》2005,68(1-2):41-65

Carbon terrestrial sinks are often seen as a low-cost alternative to fuel switching and reduced fossil fuel use for lowering atmospheric CO₂. To determine whether this is true for agriculture, one meta-regression analysis (52 studies, 536 observations) examines the costs of switching from conventional tillage to no-till, while another (51 studies, 374 observations) compares carbon accumulation under the two practices. Costs per ton of carbon uptake are determined by combining the two results. The viability of agricultural carbon sinks is found to vary by region and crop, with no-till representing a low-cost option in some regions (costs of less than $10 per tC), but a high-cost option in others (costs of 100–$400 per tC). A particularly important finding is that no-till cultivation may store no carbon at all if measurements are taken at sufficient depth. In some circumstances no-till cultivation may yield a triple dividend of carbon storage, increased returns and reduced soil erosion, but in many others creating carbon offset credits in agricultural soils is not cost effective because reduced tillage practices store little or no carbon.  相似文献   

The crater lake and hydrothermal system of Mount Pinatubo,Philippines: evolution in the decade after eruption     

James?A.?StimacEmail author  Fraser?Goff  Dale?Counce  Adrienne?C.?L.?Larocque  David?R.?Hilton  Uwe?Morgenstern 《Bulletin of Volcanology》2004,66(2):149-167

The June 1991 eruption of Mount Pinatubo, Philippines breached a significant, pre-eruptive magmatic-hydrothermal system consisting of a hot (>300 °C) core at two-phase conditions and surrounding, cooler (<260 °C) liquid outflows to the N and S. The eruption created a large, closed crater that accumulated hydrothermal upwellings, near-surface aquifer and meteoric inflows. A shallow lake formed by early September 1991, and showed a long-term increase in level of ~1 m/month until an artificial drainage was created in September 2001. Comparison of the temporal trends in lake chemistry to pre- and post-eruptive springs distinguishes processes important in lake evolution. The lake was initially near-neutral pH and dominated by meteoric influx and Cl–SO₄ and Cl–HCO₃ hydrothermal waters, with peaks in SO₄ and Ca concentrations resulting from leaching of anhydrite and aerosol-laden tephra. Magmatic discharge, acidity (pH~2) and rock dissolution peaked in late 1992, during and immediately after eruption of a lava dome on the crater floor. Since cessation of dome growth, trends in lake pH (increase from 3 to 5.5), temperature (decline from 40 to 26 °C), and chemical and isotopic composition indicate that magmatic degassing and rock dissolution have declined significantly relative to the input of meteoric water and immature hydrothermal brine. Higher concentrations of Cl, Na, K, Li and B, and lower concentrations of Mg, Ca, Fe, SO₄ and F up to 1999 highlight the importance of a dilute hydrothermal contribution, as do stable-isotope and tritium compositions of the various fluids. However, samples taken since that time indicate further dilution and steeper trends of increasing pH and declining temperature. Present gas and brine compositions from crater fumaroles and hot springs indicate boiling of an immature Cl–SO₄ geothermal fluid of near-neutral pH at approximately 200 °C, rather than direct discharge from magma. It appears that remnants of the pre-eruptive hydrothermal system invaded the magma conduit shortly after the end of dome emplacement, blocking the direct degassing path. This, along with the large catchment area (~5 km²) and the high precipitation rate of the area, led to a rapid transition from a small and hot acid lake to a large lake with near-ambient temperature and pH. This behavior contrasts with that of peak-activity lakes that have more sustained volcanic gas influx (e.g., Kawah Ijen, Indonesia; Poas and Rincón de la Vieja, Costa Rica).Editorial responsibility: H. Shinohara  相似文献   

Spectrophotometry of J8, J9, and four Trojan asteroids from 0.32 to 1.05 μm     

Dale W. Smith  Paul E. Johnson  Richard W. Shorthill 《Icarus》1981,46(1):108-113

New 30-channel narrowband photometry from 0.32 to 1.05 μm of the retrograde Jovian satellites J9 (to 0.7 μm) and J8 and the trailing Trojan asteroids 617, 884, 1172, and 1173 is presented. The data confirm previous measurements of J8, 617, 884, and 1172 at λ < 0.8 μm, but the extension into the infrared shows that the normalized spectral reflectance of these objects rises steadily from ～0.8 at 0.4 μm to ～ 1.4 at 1.05 μm, suggesting they are too bright in the near infrared to be C-type asteroids. The C classification of 1173 is confirmed. J9 is markedly redder than J8 at visible wavelengths. The results indicate a greater taxonomic contrast between these distant objects and main-belt asteroids than previously thought.  相似文献   

Temperature of Comet IRAS-Araki-Alcock (1983d)     

Robert Hamilton Brown  Dale P. Cruikshank  David Griep 《Icarus》1985,62(2):273-281

Infrared (1.5–20 μm) observations of the nuclear condensation of Comet IRAS-Araki-Alcock (1983d) during the interval 5–8 May 1983 (UT) show that the distribution of 3.5- to 20-μm radiation was blackbody in character with no evidence of 10-μm emission from silicate grains in the coma of the comet. The observed color temperature of the nuclear condensation of the comet was 319 ± 5°K on 7 May and 307 ± 5°K on 8 May. Low-resolution spectrophotometry on 5 May in the 1.5- to 2.6-μm region shows no obvious emission or absorption features, but thermal radiation of approximately the same color temperature as the 3.5- to 20-μm radiation was present along with reflected sunlight. Scans of the nuclear region of the comet indicate that most of the thermal radiation observed at 11.6 and 20.0 μm came from an ≤120-km-diameter, unresolved area centered on the nuclear region. Absolute flux measurements suggest that projected areas (unit emissivity) of 70 and 40 km² were responsible for the thermal radiation from the nuclear condensation on 7 and 8 May, respectively. This large change in total surface area suggests that the amount of dust in the nuclear region of Comet 1983d was highly variable and is consistent with the observation by M.A. Feierberg, F.C. Witteborn, J.R. Johnson, and H. Campins (1984, Icarus, 60, 449–454) of an outburst on 11 May 1983.  相似文献   

Comet color changes with solar distance     

William K. Hartmann  Dale P. Cruikshank 《Icarus》1984,57(1):55-62

JHK colors of 14 comets are correlated with cometary distance from the Sun. The correlation could be explained by (1) changes in coma particle size as comets approach the Sun, (2) decrease in the ice/dirt ratio in coma grains as comets approach the Sun, and/or (3) phase reddening. Short-term color changes in individual comets at fixed phase angles suggest that phase reddening does not explain all color changes. Short-term changes are consistent with jets injecting fresh (high ice/dirt) nuclear material into parts of the coma. All colorimetric data are consistent with pristine coma material being relatively low-albedo dirty ice grains colored by carbonaceous dirt like that in RD-type asteroids. Ice sublimation near the Sun may leave residual pure RD dirt grains, explaining the observed color changes.  相似文献   

Tertiary fluvial gravels and evolution of the Western Canadian Prairie Landscape     

Dale A. Leckie   《Sedimentary Geology》2006,190(1-4):139-158

The early Tertiary of Western Canada and northern United States was marked by a change from compressional to extensional tectonics. The result was regional uplift and magmatic events. The uplift resulted in a major unconformity and deposition of extensive regional sheets of gravel and sand, of which only isolated remnants remain. These units are the Eocene to Miocene Cypress Hills Formation, the Miocene Wood Mountain Formation, Miocene Flaxville Formation and preglacial Souris River gravels, All four stratigraphic units consist of gravel and sand with lesser amounts of clay. The formations were largely deposited as laterally continuous sheets of braided river gravels, with some occurrences of meandering-river sedimentation. The sediment was deposited several hundred kilometres downstream of their source areas. Paleocurrent data for the Cypress Hills and Wood Mountain formations indicate that regional paleoslope dipped towards the north–northeast. The modern prairie landscape of western Canada began to evolve with the deposition of these gravels during the Eocene with creation of a basin-wide unconformity followed by deposition of an extensive braidplain system that was subsequently uplifted, incised, and molded into its present form.  相似文献