Ecological implications of possible enteropneust faecal casts in tertiary deposits near castlepoint,New Zealand     

David J. Cullen 《新西兰海洋与淡水研究杂志》2013,47(3):283-290

Unusual “spiral” faecal casts from mid‐Tertiary beds of the Castlepoint area of North Island, New Zealand, are described and compared with modern enteropneust casts photographed at abyssal depths in the south‐west Pacific. Evidence suggests that the fossil casts originated in relatively shallow depths, and this discrepancy emphasises the caution required in the use of trace fossils for palaeoecological interpretations.  相似文献   

Modeling anthropogenic boron in groundwater flow and discharge at Volusia Blue Spring (Florida,USA)     

Erin M. Reed  Dingbao Wang  Steven J. Duranceau 《Hydrogeology Journal》2017,25(1):91-101

Volusia Blue Spring (VBS) is the largest spring along the St. Johns River in Florida (USA) and the spring pool is refuge for hundreds of manatees during winter months. However, the water quality of the spring flow has been degraded due to urbanization in the past few decades. A three-dimensional contaminant fate and transport model, utilizing MODFLOW-2000 and MT3DMS, was developed to simulate boron transport in the Upper Florida Aquifer, which sustains the VBS spring discharge. The VBS model relied on information and data related to natural water features, rainfall, land use, water use, treated wastewater discharge, septic tank effluent flows, and fertilizers as inputs to simulate boron transport. The model was calibrated against field-observed water levels, spring discharge, and analysis of boron in water samples. The calibrated VBS model yielded a root-mean-square-error value of 1.8 m for the head and 17.7 μg/L for boron concentrations within the springshed. Model results show that anthropogenic boron from surrounding urbanized areas contributes to the boron found at Volusia Blue Spring.  相似文献   

Dirt: The Erosion of Civilizations. David R. Montgomery, 2007, University of California Press,Berkeley, CA, 295 pp., $24.95 (hardcover)     

W. Cullen Sherwood 《Geoarchaeology》2008,23(3):420-422

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Is Our Ground Water Monitoring Strategy Illogical?     

Stephen J. Cullen  John H. Kramer  Lome G. Everett  Lawrence A. Eccles 《Ground Water Monitoring & Remediation》1992,12(3):103-107

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Vadose Zone Monitoring with the Neutron Moisture Probe     

John H. Kramer  Stephen J. Cullen  Lome G. Everett 《Ground Water Monitoring & Remediation》1992,12(3):177-187

The neutron moisture probe is widely applicable to vadose zone monitoring problems which require measuring variable moisture contents. Neutron data are proportional to hydrogen density (modified by local chemistry) and sensitive to wetting fronts as well as changing volumes of hydrocarbon liquids. They cannot, however, be used to confirm contaminant chemistry, nor to detect steady-state flow. Neutron data are amenable to statistical analysis, providing a measure of the significance of data variations. Detection of incipient moisture changes at numerous monitoring locations is more practical using raw neutron data than data calibrated for moisture content because calibrations suffer from uncertainties associated with soil heterogeneities. When properly applied, the neutron probe is an effective monitoring tool as illustrated by three example applications described in this paper: (1) neutron moisture logs are used to detect subtle lithologic changes and identify monitoring horizons; (2) sequential neutron data are used to track induced saturation at a soil flushing pilot study; and (3) neutron logs from a horizontal access tube beneath a waste facility are used to pinpoint moisture anomalies.  相似文献   

Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis   总被引：2，自引：0，他引：2  

P.N. Froelich  G.P. Klinkhammer  M.L. Bender  N.A. Luedtke  G.R. Heath  Doug Cullen  Paul Dauphin  Doug Hammond  Blayne Hartman  Val Maynard 《Geochimica et cosmochimica acta》1979,43(7):1075-1090

Pore water profiles of total-CO₂, pH, PO^3?₄, NO^?₃ plus NO^?₂, SO^2?₄, S^2?, Fe²⁺ and Mn²⁺ have been obtained in cores from pelagic sediments of the eastern equatorial Atlantic under waters of moderate to high productivity. These profiles reveal that oxidants are consumed in order of decreasing energy production per mole of organic carbon oxidized (O₂ > manganese oxides ~ nitrate > iron oxides > sulfate). Total CO₂ concentrations reflect organic regeneration and calcite dissolution. Phosphate profiles are consistent with organic regeneration and with the effects of release and uptake during inorganic reactions. Nitrate profiles reflect organic regeneration and nitrate reduction, while dissolved iron and manganese profiles suggest reduction of the solid oxide phases, upward fluxes of dissolved metals and subsequent entrapment in the sediment column. Sulfate values are constant and sulfide is absent, reflecting the absence of strongly anoxic conditions.  相似文献   

RIVER-WATER POLLUTION IN NORWAY: SOME REGIONAL ENVIRONMENTAL POLICY IMPLICATIONS*     

Lawrence M. Sommers  Bradley T. Cullen 《The Professional geographer》1982,34(2):208-219

This paper presents a systematic method of classifying water quality and identifies factors influencing the water quality of Norwegian rivers. Water quality and potential-pollution indices are developed for selected Norwegian drainage basins. The lowest-quality water is in the Mandals and Auli drainage areas, but the Glomma-Gudbrandsdal-Mjosa-Vorma system has the greatest pollution potential. Thus even in a waterrich country such as Norway, water policy is a major concern.  相似文献   

Process-based snowmelt modeling: does it require more input data than temperature-index modeling?   总被引：4，自引：0，他引：4  

M. Todd Walter  Erin S. Brooks  Donald K. McCool  Larry G. King  Myron Molnau  Jan Boll 《Journal of Hydrology》2005,300(1-4):65-75

Modeling snow hydrology for cold regions remains a problematic aspect of many hydro-environmental models. Temperature-index methods are commonly used and are routinely justified under the auspices that process-based models require too many input data. To test this claim, we used a physical, process-based model to simulate snowmelt at four locations across the conterminous US using energy components estimated from measured daily maximum and minimum temperature, i.e. using only the same data required for temperature-index models. The results showed good agreement between observed and predicted snow water equivalents, average R²>0.9. We duplicated the simulations using a simple temperature-index model best fitted to the data and results were poorer, R²<0.8. At one site we applied the process-based model without substantial parameter estimation, and there were no significant (=0.05) differences between these results and those obtained using temperature-estimated parameters, despite relatively poorly predicted specific energy budget components (R²<0.8). These results encourage the use of mechanistic snowmelt modeling approaches in hydrological models, especially in distributed hydrological models for which landscape snow distribution may be controlled by spatially distributed components of the environmental energy budget.  相似文献   

A Systematic Approach to Designing a Multiphase Unsaturated Zone Monitoring Network     

Stephen J. Cullen  John H. Kramer  Jon R. Luellen 《Ground Water Monitoring & Remediation》1995,15(3):124-135

A systematic approach is presented for the design of a multiphase vadose zone monitoring system recognizing that, as in ground water monitoring system design, complete subsurface coverage is not practical. The approach includes identification and prioritization of vulnerable areas: select ion of cost-effective indirect monitoring methods that will provide early warning of contaminant migration: selection of direct monitoring methods for diagnostic confirmation; identification of background monitoring locations; and identification of an appropriate temporal monitoring plan. An example of a monitoring system designed for a solid waste landfill is presented and utilized to illustrate the approach and provide details of system implementation. The example design described incorporates the use of neutron moisture probes deployed in both vertical and horizontal access tubes beneath the lcachate recovery collection system of the landfill. Early warning of gaseous phase contaminant migration is monitored utilizing whole-air active soil gas sampling points deployed in gravel- filled trenches beneath the subgrade. Diagnostic confirmation of contaminant migration is provided utilizing pore- liquid samplers. Conservative tracers can be used to distinguish between chemical species released by a landfill from those attributable to other (e.g. off-site) sources or present naturally in the subsurface. A discussion of background monitoring point location is also presented.  相似文献   

Vadose Zone Monitoring: Experiences and Trends in the United States     

Stephen J. Cullen 《Ground Water Monitoring & Remediation》1995,15(3):136-143

The vadose zone is the portion of the geologic profile above a perennial aquifer. Inclusion of mandatory vadose zone monitoring techniques as an approach to aquifer protect ion was first proposed under the Resource Conservation and Recovery Act in the United States in 1978 and has since received increasing acceptance at federal and stale levels. The goals of a vadose zone characterization and monitoring effort are to establish background conditions, identify contaminant transport pathways, identify the extent and degree of existing contamination, establish the basis for monitoring network design, measure the parameters needed in a risk assessment, and provide detection of contaminant migration toward ground water resources. The benefits of vadose zone monitoring include early warning of contaminant migration, potential reduction of ground water monitoring efforts, reduction of contaminant spreading and volume, and reduced time and cost of remediation once a contaminant release occurs. Vadose zone characterization and monitoring techniques should be considered as critical hydrologic tools in the prevention of ground water resource degradation.  相似文献