Underground Storage of Treated Water: A Field Test     

Charles G. Smith  Jr.  Jeffrey S. Hanor 《Ground water》1977,15(5):410-417

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The tunica hills,Louisiana-Mississippi: Late glacial locality for spruce and deciduous forest species     

Paul A. Delcourt  Hazel R. Delcourt 《Quaternary Research》1977,7(2):218-237

Reinvestigation of Quaternary sediments in West Feliciana Parish, southeastern Louisiana, and adjacent Wilkinson County, southwestern Mississippi, has resulted in revision of previous terrace stratigraphy of this portion of the Gulf Coastal Plain. Plant-macrofossil and pollen assemblages incorporated in fluviatile terrace deposits in the study area are reexamined in light of the current stratigraphic understanding. Macrofossils identified as white spruce (Picea glauca), tamarack (Larix laricina), and northern white cedar (Thuja occidentalis), recovered from these terrace deposits along with fossil remains of distinctly southern plant species, were initially interpreted as the result of dynamic intermixing of aggressive boreal species within a southern forest during the early Wisconsin (Brown, 1938). Failure to distinguish chronologically separate fossiliferous deposits resulted in the conceptual “mixing” of northern and southern plant species which came from two distinct fluviatile terrace sequences. Terrace 2 is now believed to be a fluviatile and coastwise depositional terrace of Sangamon Interglacial age; deposits of terrace 2 contain a distinctly warm-temperate plant assemblage. Fluviatile terrace 1 dates from 12,740 ± 300 to 3457 ± 366 BP and is now considered to be related to late glacial and Holocene aggradation and lateral migration of the Mississippi River (the local base level for streams in the study area); basal portions of terrace 1 contain fossils of white spruce, tamarack, and many plant species today characteristic of the cool-temperate Mixed Mesophytic Forest Association. Terrace 1 fossil deposits occur in fluviatile terraces along tributary streams of the Mississippi River at elevations 15 to 30 m above the maximum recorded historic flood stage of the Mississippi River. The plant macrofossils represent remains of species that grew at or very near the site of deposition; they were not “rafted in” by floodwaters of the Mississippi River. We present quantitative data for plant macrofossils and pollen that support our hypothesis that at least local cooling along the Blufflands of Mississippi and Louisiana promoted southward migrations of mixed mesophytic forest species and certain boreal species along this major pathway during late Wisconsin continental glaciation.  相似文献   

Spatial pattern of Abies and Picea surface pollen distribution along the elevation gradient in the Qinghai–Tibetan Plateau and Xinjiang, China     

HOUYUAN LU  NAIQIN WU  XIANGDONG YANG  CAIMING SHEN  LIPING ZHU  LUO WANG  QUAN LI  DEKE XU  GUOBANG TONG  XIANGJUN SUN 《Boreas: An International Journal of Quaternary Research》2008,37(2):254-262

In this study we examine the relationships between Abies and Picea abundance in surface pollen and sub-alpine coniferous forest (SCF) distribution, elevation and climate in the Qinghai–Tibetan Plateau using a large modern pollen data set consisting of 857 samples. Results indicate that Abies and Picea pollen are abundant in the southern and eastern Qinghai–Tibetan Plateau, where SCF dominates the landscape. Pollen percentages of both Abies and Picea show a unimodal pattern with changes in elevation and climate, and their optima occur at elevations from 2500 to 4000 m a.s.l., mean annual temperature from −1 to 10 °C and mean annual precipitation from 450 to 850 mm. The optimal elevation of Abies and Picea pollen distribution decreases with latitude from c . 4000 m in the south (21–32°N) to c . 2500 m in the north (43–49°N). The spatial pattern of Abies and Picea pollen abundance is highly correlated with the modern distribution of these taxa, which is largely controlled by elevation and climate. These relationships could provide a practical reference for interpretation of fossil pollen data in terms of climate and elevation in the Qinghai–Tibetan Plateau.  相似文献   

Anthropogenic pollution and oxygen depletion in the lower Yangtze River as revealed by sedimentary biomarkers     

《Organic Geochemistry》2012

The Yangtze River receives 37.5% of the municipal sewage of China, whose fate constitutes a major environmental and health concern. This study applied phytosterols, 5β(H)-stanols, tetrahymanol and 17α,21β(H)-C₃₀-hopane to examine sewage and petroleum-derived organic pollutants, and assess their impact on the biogeochemistry of the lower river benthic environment. The results showed that significant contributions from sewage and petroleum pollutants were preserved in the riverbed. These potentially contributed to O₂ depletion and apparently an anoxic environment in the riverbed, either directly or via an impact on primary productivity.  相似文献   

Deep-sea hydrocarbon seep gastropod Bathynerita naticoidea responds to cues from the habitat-providing mussel Bathymodiolus childressi     

Sharmishtha Dattagupta  Jonathan Martin  Shu-min Liao  Robert S. Carney  & Charles R. Fisher 《Marine Ecology》2007,28(1):193-198

Bathynerita naticoidea (Gastropoda: Neritidae) is a numerically dominant heterotrophic gastropod found at hydrocarbon seep sites on the upper Louisiana slope of the Gulf of Mexico. Snails of this species are commonly associated with beds of the methanotrophic mussel Bathymodiolus childressi (Bivalvia: Mytilidae), and their population structure mirrors that of the mussels they are found among. Previous studies have shown that these snails feed on bacteria and decomposing periostracum on the B. childressi shell. We predicted that B. naticoidea might be attracted to cues specific to its preferred habitat, such as dissolved methane, mucus from conspecific snails, or metabolites produced by B. childressi mussels. To examine this, we used a flow‐through Y‐maze system to investigate the behavior of B. naticoidea exposed to these potential cues. We found that the nerite is not attracted to methane, but is strongly attracted to seawater conditioned with B. childressi. The attractant appears to be specific to this type of mussel, and is not a soluble cue produced by conspecific snails.  相似文献   

Late Pliocene glaciation and landscape evolution of Vestfirðir,Northwest Iceland     

《Quaternary Science Reviews》2007,26(1-2):243-263

Vestfirðir, Northwest Iceland, has been extensively modified by glacial activity, but the timing and landscape impact of pre-Last Glacial Maximum (LGM) glacial activity is not well known. We present new geochemical and chronological data from two tephras, Óþoli and Hjallanes, which constrain the age of high altitude ice-dammed lake sediments near the plateau surface of Skagafjall, located on the outer westernmost fjords of Vestfirðir. Our findings provide the first dated evidence of Late Pliocene glaciation on Vestfirðir. The 2.26±0.11 Ma fission-track age of the airfall rhyolitic Óþoli tephra is compatible with reversed palaeomagnetic polarity data and suggests an ice-dammed lake existed on Skagafjall at broadly the same time as a major and well-documented Late Pliocene downturn in global climate. We assess the likely impact of Late Pliocene and subsequent glacial activity on Vestfirðir landscapes and propose that: (1) geomorphological features and sedimentary deposits on or near the Skagafjall plateau surface could have survived beneath relatively low basal velocity areas and/or relatively non-erosive areas of glacial maxima ice sheets on Vestfirðir at glacial maxima, and (2) the heavily incised fjord network, the principal macroscale landscape feature of Vestfirðir, existed in the Late Pliocene.  相似文献   

Quantifying the seasonal variations in fluvial and eolian sources of terrigenous material to Cariaco Basin,Venezuela     

Aurora C. Elmore  Robert C. Thunell  Richard Styles  David Black  Richard W. Murray  Nahysa Martinez  Yrene Astor 《Journal of South American Earth Sciences》2009,27(2-3):197-210

The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region’s climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ～10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ～90% is fluvial. This represents an annual dust accumulation rate of ～0.59 mg/cm²/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone.  相似文献   

A real-time,event-triggered storm surge forecasting system for the state of North Carolina     

《Ocean Modelling》2009,26(3-4):95-119

A new real-time, event-triggered storm surge prediction system has been developed for the State of North Carolina to assist emergency managers, policy-makers and other government officials with evacuation planning, decision-making and resource deployment during tropical storm landfall and flood inundation events. The North Carolina Forecast System (NCFS) was designed and built to provide a rapid response assessment of hurricane threat, accomplished by driving a high-resolution, two-dimensional, depth-integrated version of the ADCIRC (Advanced Circulation) coastal ocean model with winds from a synthetic asymmetric gradient wind vortex. These parametric winds, calculated at exact finite-element mesh node locations and directly coupled to the ocean model at every time step, are generated from National Hurricane Center (NHC) forecast advisories the moment they are inserted into the real-time weather data stream, maximizing the number of hours of forecast utility. Tidal harmonic constituents are prescribed at the open water boundaries and applied as tidal potentials in the interior of the ocean model domain. A directional surface roughness parameterization that modulates the wind speed at a given location based on the types of land cover encountered upwind, a forest canopy sheltering effect, and a spatially varying distribution of Manning’s–n friction coefficient used for computing the bottom/channel bed friction are also included in the storm surge model. Comparisons of the simulated wind speeds and phases against their real meteorological counterparts, of model elevations against actual sea surface elevations measured by NOAA tide gauges along the NC coast, and of simulated depth-averaged current velocities against Acoustic Doppler Current Profiler (ADCP) data, indicate that this new system produces remarkably realistic predictions of winds and storm surge.  相似文献   

Formation of mud ridge and runnels in the intertidal zone of the Severn Estuary,UK     

P.A. Carling  J.J. Williams  I.W. Croudace  C.L. Amos 《Continental Shelf Research》2009,29(16):1913-1926

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Temperature variability in the Bay of Biscay during the past 40 years,from an in situ analysis and a 3D global simulation     

S. Michel  A.-M. Treguier  F. Vandermeirsch 《Continental Shelf Research》2009,29(8):1070-1087

A global in situ analysis and a global ocean simulation are used jointly to study interannual to decadal variability of temperature in the Bay of Biscay, from 1965 to 2003. A strong cooling is obtained at all depths until the mid-1970's, followed by a sustained warming over ～30 years. Strong interannual fluctuations are superimposed on this slow evolution. The fluctuations are intensified at the surface and are weakest at ～500 m. A good agreement is found between the observed and simulated temperatures, in terms of mean values, interannual variability and time correlations. Only the decadal trend is significantly underestimated in the simulation. A comparison to satellite sea surface temperature (SST) data over the last 20 years is also presented. The first mode of interannual variability exhibits a quasi-uniform structure and is related to the inverse winter North Atlantic Oscillation (NAO) index. Regarding the vertical structure, most cool and warm anomalies are generated at the surface, with the strongest ones penetrating down to 700 m and lasting up to 5 years. The complete heat budget from 1965 to 2004 is presented, including the contributions of vertical transport, freshwater flux and surface elevation. Interannual anomalies are mainly generated by the surface heat flux, while oceanic transports may become more important at longer time scales.  相似文献