Contaminant plume classification system based on mass discharge   总被引：1，自引：0，他引：1  

Newell CJ  Farhat SK  Adamson DT  Looney BB 《Ground water》2011,49(6):914-919

Estimation of mass discharge has become an increasingly valuable analysis technique at sites with contaminated groundwater plumes. We propose a simple plume magnitude classification system based on mass discharge comprised of 10 separate magnitude categories, such as a "Mag 7 plume." This system can be a useful tool for scientists, engineers, regulators, and stakeholders to better communicate site conceptual models, prioritize sites, evaluate plumes both spatially and temporally, and determine potential impacts.  相似文献   

Some relationships between lithology,basin form and hydrology: a case study from the Thames basin,UK   总被引：1，自引：0，他引：1  

J. P. Bloomfield  S. H. Bricker  A. J. Newell 《水文研究》2011,25(16):2518-2530

The role of lithology in influencing basin form and function is explored empirically by investigating correlations between a range of catchment variables, where the spatial unit of analysis is not surface catchments but lithologically coherent groundwater units. Using the Thames basin, UK, as a case study, nine groundwater units have been identified. Values for 11 hydrological and geomorphological variables, including rainfall, drainage density, Baseflow Index, aquifer porosity, storage coefficient and log‐hydraulic conductivity, aquifer and drainage elevation, river incision, and hypsometric integral have been estimated for each of the groundwater units in the basin, and Pearson correlation coefficients calculated for all pairs of variables. Seven of the correlation coefficients are found to be significant at a confidence level of > 99%. Negative correlations between drainage density and log aquifer hydraulic conductivity, and between drainage density and river incision, and positive correlations between log‐hydraulic conductivity and river incision, log‐hydraulic conductivity and Baseflow Index, and between Baseflow Index and river incision are inferred to have consistent causal explanations. For example, incision of rivers into aquifers leads to relative increases in hydraulic gradients in the vicinity of rivers which, in turn, promotes the development of secondary porosity increasing both aquifer hydraulic conductivity and, hence, Baseflow Index. The implication of this interpretation is that the geomorphological evolution of basins is intimately linked to the evolution of hydraulic conductivity of the underlying aquifers. This is consistent with, and supports the notion of a coupled complexly evolving surface water‐groundwater system. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Factors Influencing Variability in Groundwater Monitoring Data Sets     

T.E. McHugh  L.M. Beckley  C.Y. Liu  C.J. Newell 《Ground Water Monitoring & Remediation》2011,31(2):92-101

“Random” variability in groundwater monitoring data sets reduces the ability to identify long‐term concentration trends. This, in turn, increases the time and cost required to evaluate the effectiveness of natural attenuation and other groundwater remedies. To better understand the factors influencing variability in groundwater monitoring results, we have analyzed three large groundwater monitoring data sets. For the three data sets, the long‐term trend in contaminant concentration in each well accounted for an average of 30% to 40% of the overall variation in contaminant concentration. Understanding the causes of the remaining variability would support the development of improved groundwater monitoring methods. All three data sets show large differences in the temporal monitoring records between individual wells (e.g., coefficient of variation for monitoring results from individual wells ranges from 0.08 to 4.6) indicating that well and aquifer factors are more important contributors to variability than sample collection and analysis factors. However, the depth to groundwater (R² = 0.020) and distance between water level and screened interval (R² = 0.049) accounted for only a portion of the differences in variability between wells and other aquifer characteristics evaluated and were not correlated with the observed variability in monitoring results. Unidentified factors were apparently much more important contributors to variability than these factors. The monitoring data sets exhibited two distinct timescales for variability: Time‐independent variability that was apparent even when wells were re‐sampled within a few days and a long‐term variability likely associated with the long‐term concentration trend. The observation of time‐independent variability suggests that frequent monitoring of contaminated monitoring wells serves primarily to characterize sources of variability unrelated to the long‐term trend of primary interest.  相似文献   

Timing of basin inversion on the Isle of Wight: New evidence from geophysical log correlation, seismic sections and lateral facies change in the Palaeogene Headon Hill Formation     

Andrew J. Newell  David J. Evans 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):868-882

Paleogene thickness patterns across the Bouldnor Syncline and Porchfield Anticline in the northwestern Isle of Wight have been deduced using outcrop information, borehole correlation, gamma-ray logs and seismic reflection data. The thickness patterns provide evidence for an early phase of basin inversion at around the Bartonian-Priabonian boundary (Late Eocene) in the Isle of Wight. Paleogene strata older than the Becton Sand Formation show little evidence for significant lateral changes in thickness, even though the boreholes are located at various structural positions around the Bouldnor Syncline and Porchfield Anticline. In contrast, both seismic reflection and borehole data provide evidence for marked thinning of Paleogene strata onto the Porchfield Anticline at around the level of the Becton Sand Formation and basal Headon Hill Formation (Totland Bay Member) which probably results from an episode of basin inversion and growth folding. The inversion event was relatively minor and short-lived and continues to point toward the main phase of the basin inversion being late Oligocene or younger. However, it still has important implications for understanding structural control on sedimentation patterns in the Headon Hill Formation, with the migration of sandy channelised depositional systems into the axis of the Bouldnor Syncline, and the sequence stratigraphic significance of the important Bartonian-Priabonian regression event, which may related to tectonics rather than global sea-level change.  相似文献   

Sexual productivity and spring intramarsh distribution of a key salt-marsh microbial secondary producer     

Steven Y. Newell  Jennifer Wasowski 《Estuaries and Coasts》1995,18(1):241-249

Phaeosphaeria spartinicola is known to be an important fungal (ascomycetous) secondary producer in the smooth-cordgrass (Spartina alterniflora) decomposition system of western Atlantic salt marshes, yet its degree of predominance among the ascomycete assemblages of salt marshes and the concentration of its sexual reproductive structures (ascomata) have been largely unknown. During May–June, we measured by direct microscopy the percent occupancy of leaf abaxial area and concentrations of ascomata in leaf blades of smooth cordgrass at three elevations in three drainage systems within the marshes of Sapelo Island, Georgia, United States. We also measured in water-saturation chambers the rates at which the ascomata expelled ascopoores (sexual propagules) out of decaying leaves from marsh sites containing or not containing shredder gastropods.P. spartinicola ascomata were found at averages of 36% to 93% of grid-circles (3-mm radius) on decaying leaf blades, with lower values at points directly adjacent to the leaf sheath, on leaves at earlier stages of decay, and at elevational subsites where shredder snails were more active. Marsh elevation had no effect of its own on percent occupation. No other species of ascomycetes were found at overall avarage frequencies greater than 3%. Average concentration of ascomata along the intervascular rows where they were located was 1 ascoma per 0.5 mm row (～1000 cm^?2 abaxial leaf surface, translating to production of 1.6×10⁷ ascomata m^?2 intermediate-height marsh per standing crop of living stems). The fraction of total fungal production allocated to ascomata is speculatively and crudely estimated at about 9%, without taking into account potential loss to invertebrate shredders. At sites with abundances of snails >-50 m^?2 peaks of ascospore expulsion (about 50–75 spores cm^?2 leaf h^?1, 3–5× the overall average rate) observed at snail-free sites were absent. Our measured rate of ascospore expulsion (averaged over snail-free and high-snail sites, and possibly an underestimate) translated to 6.5×10⁴ spores m^?2 marsh h^?1 for times of freshwater saturation of leaves, and one-third that value for times of saltwater wetting.  相似文献   

The dynamic cusp at low altitudes: a case study utilizing Viking,DMSP-F7, and Sondrestrom incoherent scatter radar observations     

J. Watermann  O. de la Beaujardière  D. Lummerzheim  J. Woch  P. T. Newell  T. A. Potemra  F. J. Rich  M. Shapshak 《Annales Geophysicae》1994,12(12):1144-1157

Coincident multi-instrument magnetospheric and ionospheric observations have made it possible to determine the position of the ionospheric footprint of the magnetospheric cusp and to monitor its evolution over time. The data used include charged particle and magnetic field measurements from the Earth-orbiting Viking and DMSP-F7 satellites, electric field measurements from Viking, interplanetary magnetic field and plasma data from IMP-8, and Sondrestrom incoherent scatter radar observations of the ionospheric plasma density, temperature, and convection. Viking detected cusp precipitation poleward of 75.5○ invariant latitude. The ionospheric response to the observed electron precipitation was simulated using an auroral model. It predicts enhanced plasma density and elevated electron temperature in the upper E- and F-regions. Sondrestrom radar observations are in agreement with the predictions. The radar detected a cusp signature on each of five consecutive antenna elevation scans covering 1.2 h local time. The cusp appeared to be about 2○ invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2○ during this time, possibly influenced by an overall decrease in the IMF B_z component. The radar plasma drift data and the Viking magnetic and electric field data suggest that the cusp was associated with a continuous, rather than a patchy, merging between the IMF and the geomagnetic field.  相似文献   

Modes of variability of global sea surface temperature,free atmosphere temperature and oceanic surface energy flux     

Wenjie Hu  Reginald E. Newell  Zhong-Xiang Wu 《Climate Dynamics》1994,10(8):377-393

Monthly mean sea surface temperature (SST), free air temperature from satellite microwave sounding units (MSU) and oceanic surface energy fluxes are subjected to empirical orthogonal function (EOF) analysis for a common decade to investigate the physical relationships involved. The first seasonal modes of surface solar energy flux and SST show similar inter-hemispheric patterns with an annual cycle. Solar flux appears to control this pattern of SST. The first seasonal mode of MSU is similar with, additionally, land-sea differences; MSU is apparently partly controlled by absorption of solar near-infrared radiation and partly by sensible heat from the land surface. The second and third seasonal eigenvector of SST and solar flux exhibit semi-annual oscillations associated with a pattern of cloudiness in the subtropics accompanying the translation of the Hadley cell rising motion between the hemispheres. The second seasonal mode of MSU is dominated by an El Niño signal. The first nonseasonal EOFs of SST and solar flux exhibit El Niño characteristics with the solar pattern being governed by west-to-east translation of a Walker cell type pattern. The first non-seasonal EOF of MSU shows a tropical strip pattern for the El Niño mode, which is well correlated with the latent heat fluxes in the tropical east Pacific but not in the tropical west Pacific. Two possible explanations are: an increase in subsidence throughout the tropical strip driven by extra evaporation in the tropical east Pacific and consequent additional latent heat liberation; a decrease of meridional heat flux out of the tropics.  相似文献   

OASIS: A Graphical Decision Support System for Ground-Water Contaminant Modeling     

Charles J. Newell  John F. Haasbeek  Philip B. Bedient 《Ground water》1990,28(2):224-234

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Discrete wetland groundwater discharges revealed with a three-dimensional temperature model and botanical indicators (Boxford,UK)     

Andrew R. House  James P. R. Sorensen  Daren C. Gooddy  Andrew J. Newell  Ben Marchant  J. Owen Mountford  Peter Scarlett  Peter J. Williams  Gareth H. Old 《Hydrogeology Journal》2015,23(4):775-787

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Bacterial response to presence of eukaryote inhibitors in water from a coastal marine environment     

S.Y. Newell  B.F. Sherr  E.B. Sherr  R.D. Fallon 《Marine environmental research》1983,10(3):147-157

A method involving chemical (cycloheximide, thiram) inhibition of protozoan bacterivores was applied in an attempt to estimate marine bacterioplanktonic growth rates. The inhibitors were capable of preventing growth of marine protozoan bacterivores at concentrations which did not inhibit growth of marine bacterial assemblages. Use of the predator-inhibition method with incubated water samples from a nearshore marine environment indicated that protozoan grazing control of the size of bacterial standing crop was quite variable with time and site. The apparent degree of control ranged from non-existent to complete. As a means of estimating bacterial generation times, the predator-inhibition method gave results more closely aligned with those of a dividing-cells technique than a [³H]thymidine technique.  相似文献