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141.
Peacock EE Hampson GR Nelson RK Xu L Frysinger GS Gaines RB Farrington JW Tripp BW Reddy CM 《Marine pollution bulletin》2007,54(2):214-225
Petroleum hydrocarbons persist in salt marsh sediments in Winsor Cove (Buzzards Bay, Massachusetts) impacted from the 1974 spill of No. 2 fuel oil by the barge Bouchard 65. Intertidal sediment cores were collected from 2001 to 2005 and analyzed for total petroleum hydrocarbons (TPHs). TPHs content was greatest (as high as 8.7 mg g(-1) dry weight) in the surface sediments and decreased with distance landward. Select samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) with values as high as 16.7 microg g(-1) for total naphthalenes and phenanthrenes/anthracenes. These remaining PAHs are mainly C(4)-naphthalenes and C(1)-, C(2)-, and C(3)-phenanthrenes/anthracenes revealing preferential loss of almost all of the naphthalenes and the parent compound phenanthrene. Inspection of the data indicates that biodegradation, water-washing and evaporation were major removal processes for many of the petroleum hydrocarbons in the marsh sediments. In addition, historical data and photographs combined with their recent counterparts indicate that erosion has physically removed these contaminants from this site. 相似文献
142.
Nelson L. Reginald O. C. St. Cyr Joseph M. Davila Douglas M. Rabin Madhulika Guhathakurta Donald M. Hassler 《Solar physics》2009,260(2):347-361
We conducted an experiment in conjunction with the total solar eclipse of 29 March 2006 in Libya that measured the coronal intensity through two filters centered at 3850 Å and 4100 Å with bandwidths of ≈?40 Å. The purpose of these measurements was to obtain the intensity ratio through these two filters to determine the electron temperature. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an eight inch, f/10 Schmidt Cassegrain telescope with a thermoelectrically-cooled CCD camera at the focal plane. Results show electron temperatures of 105 K close to the limb to 3×106 K at 1.3R ⊙. We describe this novel technique, and we compare our results to other relevant measurements. This technique could be easily implemented on a space-based platform using a coronagraph to produce global maps of the electron temperature of the solar corona. 相似文献
143.
This study was conducted under the USDA‐Conservation Effects Assessment Project (CEAP) in the Cheney Lake watershed in south‐central Kansas. The Cheney Lake watershed has been identified as ‘impaired waters’ under Section 303(d) of the Federal Clean Water Act for sediments and total phosphorus. The USDA‐CEAP seeks to quantify environmental benefits of conservation programmes on water quality by monitoring and modelling. Two of the most widely used USDA watershed‐scale models are Annualized AGricultural Non‐Point Source (AnnAGNPS) and Soil and Water Assessment Tool (SWAT). The objectives of this study were to compare hydrology, sediment, and total phosphorus simulation results from AnnAGNPS and SWAT in separate calibration and validation watersheds. Models were calibrated in Red Rock Creek watershed and validated in Goose Creek watershed, both sub‐watersheds of the Cheney Lake watershed. Forty‐five months (January 1997 to September 2000) of monthly measured flow and water quality data were used to evaluate the two models. Both models generally provided from fair to very good correlation and model efficiency for simulating surface runoff and sediment yield during calibration and validation (correlation coefficient; R2, from 0·50 to 0·89, Nash Sutcliffe efficiency index, E, from 0·47 to 0·73, root mean square error, RMSE, from 0·25 to 0·45 m3 s?1 for flow, from 158 to 312 Mg for sediment yield). Total phosphorus predictions from calibration and validation of SWAT indicated good correlation and model efficiency (R2 from 0·60 to 0·70, E from 0·63 to 0·68) while total phosphorus predictions from validation of AnnAGNPS were from unsatisfactory to very good (R2 from 0·60 to 0·77, E from ? 2·38 to 0·32). The root mean square error–observations standard deviation ratio (RSR) was estimated as excellent (from 0·08 to 0·25) for the all model simulated parameters during the calibration and validation study. The percentage bias (PBIAS) of the model simulated parameters varied from unsatisfactory to excellent (from 128 to 3). This study determined SWAT to be the most appropriate model for this watershed based on calibration and validation results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
144.
Susan W.S. Millar & Frederick E. Nelson 《Geografiska Annaler: Series A, Physical Geography》2001,83(3):145-156
Samples of macrofabric data obtained from colluvial deposits near the late-Wisconsinan glacial margin display widely divergent characteristics. Those from highly weathered and jointed sandstone plot as girdle distributions. Samples from red colluvium of early-Wisconsinan age form moderately strong clusters. Fabrics from shallow depth in medium-textured brown colluvium of late-Wisconsinan age generally have modes aligned with the local slope but are weak, and appear to have been modified by frost heaving. Clasts in the basal layers of an overlying loess unit were emplaced by frost heaving from the brown colluvium and have very weak or uniform fabrics. Particle shape exerts an influence on fabric strength in the brown colluvium, with samples composed of more elongated clasts displaying stronger fabrics. Fabrics from near-surface deposits show generally weaker shape and strength characteristics and higher inclinations than those at depth. Calculated seasonal frost penetration is consistent with the depth to which weaker, more steeply inclined fabrics are found. Sampling in relict periglacial deposits should be performed only below the level of disturbance by seasonal frost. 相似文献
145.
Optical absorption spectra obtained on glasses quenched from sodium silicate melts show Mn3+ to be the dominant species for melts heated in air and Mn2+ to be the dominant species for melts heated at Po2 = 10?17 bar. The absorption spectrum of Mn3+ consists of an intense band at 20,000cm?1 with a 15,000cm?1 satellite possibly arising from the Jahn-Teller effect. The independence of the spectrum from melt composition and the high band intensity is offered as evidence for a distinct Mn3+ complex in the melt. The spectrum of Mn2+ is weak and many expected bands are not observed. A two-band luminescence spectrum from Mn2+ has been tentatively interpreted as due to Mn2+ in interstitial sites in the network and Mn2+ coordinated by non-bridging oxygens. 相似文献
146.
147.
148.
Flat-bottomed depression 50–150 m in diameter and 60–80 cm deep occur in the floor of Norton Sound, Bering Sea. These large
erosional bedforms and associated current ripples are found in areas where sediment grain size is 0.063–0.044 mm (4–4.5 φ),
speeds of bottom currents are greatest (20–30 cm/s mean speeds under nonstorm conditions, 70 cm/s during typical storms),
circulation of water is constricted by major topographic shoals (kilometers in scale), and small-scale topographic disruptions,
such as ice gouges, occur locally on slopes of shoals. These local obstructions on shoals appear to disrupt currents, causing
separation of flow and generating eddies that produce large-scale scour. Offshore artificial structures also may disrupt bottom
currents in these same areas and have the potential to generate turbulence and induce extensive scour in the area of disrupted
flow. The size and character of natural scour depressions in areas of ice gouging suggest that large-scale regions of scour
may develop from enlargement of local scour sites around pilings, platforms, or pipelines. Consequently, loss of substrate
support for pipelines and gravity structures is possible during frequent autumn storms. 相似文献
149.
Information about the transfer of pollutants from adult aquatic animals to their progeny is relatively unknown. The present study was designed to measure the transfer of metals from adults to eggs of the American oyster. Two groups of oysters containing significantly different levels of copper and cadmium were induced to spawn, the eggs were collected and trace metal contents measured. The eggs from both groups of oysters contained the same amount of copper, while cadmium levels were below detectable limits in both groups of eggs. Silver, lead, and zinc concentrations also were determined. The concentrations of these metals were similar for both groups of adults and eggs; thus, no conclusion could be made about the transfer of these three metals from adults to eggs of oysters. 相似文献
150.
GeoJournal - From a human ecological perspective, research was undertaken on interactions between Lake Erie fisheries and offshore petroleum (gas) development from 1913 to summer, 1981. In an... 相似文献