Differences in pathogen indicators between proximal urban and rural karst springs,Central Kentucky,USA     

Thomas M. Reed  Alan E. Fryar  Gail M. Brion  James W. Ward 《Environmental Earth Sciences》2011,64(1):47-55

Because of their architecture, karst aquifers are susceptible to contamination by fecal-derived pathogens. Previous studies have examined the behavior of bacterial indicators such as total coliforms (TC) and fecal coliforms (FC) in karst aquifers, but simple techniques for discriminating between human and non-human inputs are still needed. This study examines concentrations of TC, FC, atypical colonies (AC, which grow on the same media as TC), male-specific coliphage virus (MSP, an indicator of human feces), and nitrate at two springs in the Inner Bluegrass region of Kentucky (USA). Blue Hole Spring primarily drains the city of Versailles, whereas spring SP-2 drains pasture. Baseflow was monitored, usually biweekly, from December 2002 to March 2004, while storm flow was monitored in September 2003 and March 2004. At each spring, bacterial concentrations were highest in storm flow and lowest in “normal” baseflow (for which 72-h antecedent precipitation was negligible). Concentrations in baseflow tended to be highest during late spring and summer and lowest during autumn and winter. FC concentrations exceeded regulatory (contact) standards in storm-flow samples. For both storm flow and baseflow, AC concentrations were greater than TC, which in turn were greater than FC. Median AC and TC concentrations were greater in baseflow at Blue Hole than at SP-2. MSP was detected in most samples from Blue Hole but never at SP-2. The AC/TC ratio was typically <15 except for normal baseflow samples at Blue Hole, which is probably impacted by leakage from sanitary sewers, as suggested by MSP and nitrate results. Mobilization of sessile bacteria appears to reduce the AC/TC ratio during storm flow. Consequently, this ratio shows promise as a screening tool to identify sewage inputs in karst groundwater basins under baseflow conditions.  相似文献   

J. P. Smol and E. F. Stoermer (eds): The diatoms: applications for the environmental and earth sciences     

Jane M. Reed 《Journal of Paleolimnology》2011,46(1):167-169

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Preliminary results of the multisite time-series campaign on the sdB pulsator PG 1325+101     

R. Silvotti  A. Bonanno  A. Frasca  S. Bernabei  R. Janulis  R. Østensen  S.-L. Kim  B.-G. Park  J. Xiaojun  J. Guo  Z. Liu  M.D. Reed  R.S. Patterson  K.M. Gietzen  P.J. Clark  G.W. Wolf  Y. Lipkin  L. Formiggini  E. Leibowitz  T.D. Oswalt  M. Rudkin  K. Johnston 《Astrophysics and Space Science》2004,289(3-4):445-448

I present a model for the formation and evolution of a massive disk galaxy, within a growing dark halo whose mass evolves according to cosmological simulations of structure formation. The galactic evolution is simulated with a new 3D chemo-dynamical code, including dark matter, stars and a multi-phase ISM. We follow the evolution from redshift z = 4.85 until the present epoch. The energy release by massive stars and supernovae prevents a rapid collapse of the baryonic matter and delays the maximum star formation until redshift z ≈ 1. The galaxy forms radially from inside-out and vertically from top-to-bottom. The feedback of stars leads to turbulent motions and large-scale flows in the ISM. As one result the galactic disk is significantly enriched by chemical elements synthesized in bulge stars.  相似文献   

Wind signatures in the X-ray emission-line profiles of the late-O supergiant ζ Orionis     

David H. Cohen  Maurice A. Leutenegger  Kevin T. Grizzard  Catherine L. Reed  Roban H. Kramer  Stanley P. Owocki 《Monthly notices of the Royal Astronomical Society》2006,368(4):1905-1916

X-ray line-profile analysis has proved to be the most direct diagnostic of the kinematics and spatial distribution of the very hot plasma around O stars. The Doppler-broadened line profiles provide information about the velocity distribution of the hot plasma, while the wavelength-dependent attenuation across a line profile provides information about the absorption to the hot plasma, thus providing a strong constraint on its physical location. In this paper, we apply several analysis techniques to the emission lines in the Chandra High Energy Transmission Grating Spectrometer (HETGS) spectrum of the late-O supergiant ζ Ori (O9.7 Ib), including the fitting of a simple line-profile model. We show that there is distinct evidence for blueshifts and profile asymmetry, as well as broadening in the X-ray emission lines of ζ Ori. These are the observational hallmarks of a wind-shock X-ray source, and the results for ζ Ori are very similar to those for the earlier O star, ζ Pup, which we have previously shown to be well fit by the same wind-shock line-profile model. The more subtle effects on the line-profile morphologies in ζ Ori, as compared to ζ Pup, are consistent with the somewhat lower density wind in this later O supergiant. In both stars, the wind optical depths required to explain the mildly asymmetric X-ray line profiles imply reductions in the effective opacity of nearly an order of magnitude, which may be explained by some combination of mass-loss rate reduction and large-scale clumping, with its associated porosity-based effects on radiation transfer. In the context of the recent reanalysis of the helium-like line intensity ratios in both ζ Ori and ζ Pup, and also in light of recent work questioning the published mass-loss rates in OB stars, these new results indicate that the X-ray emission from ζ Ori can be understood within the framework of the standard wind-shock scenario for hot stars.  相似文献   

Resolving the pulsations of subdwarf B stars: PG 0154+182, HS 1824+5745 and HS 2151+0857     

M. D. Reed  J. R. Eggen  A.-Y. Zhou  D. M. Terndrup  S. L. Harms  D. An  M. A. Hashier 《Monthly notices of the Royal Astronomical Society》2006,369(3):1529-1536

We continue our programme of extended single-site observations of pulsating subdwarf B (sdB) stars and present the results of extensive time-series photometry to resolve the pulsation spectra for use in asteroseismological analyses. PG 0154+182, HS 1824+5745 and HS2151+0857 were observed at the MDM Observatory during 2004 and 2005. Our observations are sufficient to resolve the pulsations of all three target stars. We extend the number of known frequencies for PG 0154+182 from one to six, confirm that HS 1824+5745 is a monoperiodic pulsator and extend the number of known frequencies to five for HS 2151+0857. We perform standard tests to search for multiplet structure, measure amplitude variations as pertains to stochastic excitation and examine the mode density to constrain the mode degree ℓ.  相似文献   

Performance of grass and eucalyptus riparian buffers in a pasture catchment,Western Australia,part 1: riparian hydrology     

Lucy A. McKergow  Ian P. Prosser  David M. Weaver  Rodger B. Grayson  Adrian E. Reed 《水文研究》2006,20(11):2309-2326

Rainfall takes many flowpaths to reach a stream, and the success of riparian buffers in water quality management is significantly influenced by riparian hydrology. This paper presents results from hydrometric monitoring of riparian buffer hydrology in a pasture catchment. Runoff processes and riparian flowpaths were investigated on two planar hillslopes with regenerating grass and E. globulus buffers. Surface runoff and subsurface flows (A‐ and B‐horizons) were measured for 3 years using surface runoff collectors, subsurface troughs and piezometers. Water volumes moving through the riparian buffers via the measured flowpaths were ranked B‐horizon ? surface runoff ≈ A‐horizon. Runoff volumes through the B‐horizon troughs were an order of magnitude greater than those recorded for the most productive surface runoff plots or the A‐horizon troughs. Subsurface runoff and saturation‐excess overland flow (SOF) were limited to the winter months, whereas infiltration‐excess overland flow (IEOF) can occur all year round during intense storms. Surface runoff was recorded on 33 occasions, mostly during winter (late May–early October), and total annual surface runoff volumes collected by the 20 unconfined (2 m wide) runoff plots varied between > 80 and < 20 m³. Subsurface flow only occurred in winter, and the 6 m wide B‐horizon subsurface troughs flowed above 1 l s^?1 continuously, whereas the A‐horizon troughs flowed infrequently (<6 days per year). In summer, surface runoff occurred as IEOF during intense storms in the E. globulus buffer, but not in the grass buffer. Observations suggest that surface crusting reduced the soil's infiltration capacity in the E. globulus buffer. During winter, SOF and seepage were observed in both buffers, but subsurface flow through the B‐horizon was the dominant flowpath. Key hydrologic differences between the grass and tree buffers are the generation of IEOF in the E. globulus buffer during intense summer storms, and the smaller subsurface runoff volumes and fewer flow days in the E. globulus buffer. Low surface runoff volumes are likely to limit the potential of these buffers to filter pollutants from surface runoff. High subsurface flow volumes and saturated conductivities are also likely to limit the residence time of water in the subsurface domain. Based on their hydrologic performance, the key roles of riparian buffers in this landscape are likely to be displacing sediment and nutrient‐generating activities away from streams and stabilizing channel morphology. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Performance of grass and eucalyptus riparian buffers in a pasture catchment,Western Australia,part 2: water quality     

Lucy A. McKergow  Ian P. Prosser  David M. Weaver  Rodger B. Grayson  Adrian E. G. Reed 《水文研究》2006,20(11):2327-2346

Declining water quality on the south coast of Western Australia has been linked to current agricultural practices. Riparian buffers were identified as a tool available to farmers and catchment managers to achieve water quality improvements. This study compares 10 m wide regenerating grass and Eucalyptus globulus buffer performance. Surface and subsurface water quality were monitored over a 3‐year period. Nutrient and sediment transport were both dominated by subsurface flow, in particular through the B‐horizon, and this may seriously limit the surface‐runoff‐related functions of the riparian buffers. Riparian buffer trapping efficiencies were variable on an event basis and annual basis. The grass buffer reduced total phosphorus, filterable reactive phosphorus, total nitrogen and suspended sediment loads from surface runoff by 50 to 60%. The E. globulus buffer was not as effective, and total load reductions in surface runoff ranged between 10 and 40%. A key difference between the grass and E. globulus buffers was the seasonality of sediment and nutrient transport. Surface runoff, and therefore sediment and nutrient transport, occurred throughout the year in the E. globulus buffer, but only during the winter in the grass buffer. As a consequence of high summer nutrient and sediment concentrations, half the annual loads moving via surface runoff pathways through the E. globulus buffer were transported during intense summer storms. This study demonstrates that grass and E. globulus riparian buffers receiving runoff from pasture under natural rainfall can reduce sediment and nutrient loads from surface runoff. However, in this environment the B‐horizon subsurface flow is the dominant flowpath for nutrient transport through the riparian buffers, and this subsurface flow pathway carries contaminant loads at least three times greater than surface runoff. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Discovery of a New Multiperiodic δ Scuti Variable Star     

A.-Y. Zhou  D. An  J. R. Eggen  M. D. Reed  D. M. Terndrup  S. L. Harms 《Astrophysics and Space Science》2006,305(1):29-36

We report on the discovery of a new short-periodic pulsating variable star in the field of the pulsating sdB star KPD 2109+4401. The star was observed on 10 consecutive nights. Based on the light curves, we detect three pulsation frequencies at 10.308, 4.023 and 11.075 cycle d⁻¹ with amplitudes of 11.1, 4.3 and 4.2 milli-magnitudes, respectively. Using the existing data from other sky surveys, we estimate a spectral type of late F and other atmospheric parameters. Then we discuss the observational properties of the star. Finally it is classified to be a new low-amplitude multiperiodic δ Scuti star. A future interest addressed is to accurately determine the star's spectral type and then to judge a possible link to γ Doradus-type pulsation.  相似文献   

A framework to assess the vulnerability of California commercial sea urchin fishermen to the impact of MPAs under climate change     

Cheryl Chen  David López-Carr  Barbara Louise Endemaño Walker 《GeoJournal》2014,79(6):755-773

This paper describes the development of a Livelihood Vulnerability Index (LVI) that estimates the relative ability of California commercial sea urchin fishermen to cope with the change associated with proposed marine protected areas. A key goal in establishing marine protected areas is to maximize conservation benefits while minimizing the potential negative impacts to local fishing communities. However, current impact analyses largely assume a linear relationship between percent of fishing area or revenue lost with the magnitude of impact to fishermen. The LVI described in this paper aims to provide an additional dimension to impact analyses in which the adaptive capacity of individual fishermen is examined to estimate the differential abilities of fishermen to cope with the loss of fishing areas or revenue. This paper advances vulnerability assessments as it develops a novel framework for identifying and measuring drivers of vulnerability for understudied fishing populations whose livelihoods depend upon marine resources. This vulnerability assessment is intended to inform the design of marine protected areas by enabling researchers to incorporate the adaptive capacity of fishermen into socioeconomic impact analyses. The LVI was developed for the California commercial sea urchin fishery in the context of proposed marine protected area networks develop through the California Marine Life Protected Act planning process. As climate change advances there is an increasing need to identify vulnerable and resilient populations and ways to bolster adaptive capacity given the environmental and economic changes ahead.  相似文献   

Chemical dispersant effectiveness testing: influence of droplet coalescence     

Sterling MC  Bonner JS  Ernest AN  Page CA  Autenrieth RL 《Marine pollution bulletin》2004,48(9-10):969-977

Thermodynamic and kinetic investigations were performed to determine the influence of coalescence of chemically dispersed crude oil droplets in saline waters. For the range of pH (4-10) and salinity (10 per thousand, 30 per thousand, 50 per thousand ) values studied, zeta-potential values ranged from -3 to -10 mV. As the interaction potential values calculated using Derjaguin-Landau-Verway-Overbeek (DLVO) theory were negative, the electrostatic barrier did not produce significant resistance to droplet coalescence. Coalescence kinetics of premixed crude oil and chemical dispersant were determined within a range of mean shear rates (Gm = 5, 10, 15, 20 s(-1)) and salinity (10 per thousand, 30 per thousand ) values. Coalescence reaction rates were modeled using Smoluchowski reaction kinetics. Measured collision efficiency values (alpha = 0.25) suggest insignificant resistance to coalescence in shear systems. Experimentally determined dispersant efficiencies (alpha = 0.35) were 10-50% lower than that predicted using a non-interacting droplet model (alpha = 0.0). Unlike other protocols in which the crude oil and dispersant are not premixed, salinity effects were not significant in this protocol. This approach allowed the effects of dispersant-oil contact efficiency eta(contact) to be separated from those of water column transport efficiency (eta(transport)) and coalescence efficiency (eta(coalescence)).  相似文献