HP special issue: Canadian geophysical union 2016          下载免费PDF全文

William Quinton  Daniel L. Peters 《水文研究》2018,32(4):459-461

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The occurrence and geochemistry of arsenic in groundwaters of the Newark basin of Pennsylvania     

Stephen C. Peters  Lori Burkert 《Applied Geochemistry》2008

Elevated As concentrations in groundwater in the eastern United States have been recognized predominantly in the accretionary geologic terranes of northern New England. A retrospective examination of more than 18,000 existing groundwater samples from the Pennsylvania Department of Environmental Protection (PA DEP) Drinking Water and Sampling Information System database indicates that elevated groundwater As concentrations occur throughout the northern half of the Piedmont Province of Pennsylvania. Chemical analyses of 53 samples collected in 2005 from drinking water wells in this area all had detectable As, and 23% of these samples contained elevated (>133 nmol/L or >10 μg/L) concentrations of As. Elevated concentrations of As in the groundwater samples were most common in the Mesozoic sedimentary strata composed of sandstone and red mudstone with interbedded gray shale, and gray to black siltstone and shale. Arsenic was typically not elevated in groundwater of diabase intrusions of the Newark Basin or in crystalline and calcareous aquifers to the north of the Newark Basin. Geochemical parameters such as pH and oxidation–reduction potential can indicate mobility mechanisms of As in some regions. In this area, measured groundwater conditions were predominantly oxidizing (Eh > +50 mV), and more than 85% of samples contained arsenate as the dominant As species. Variations in pH were strongly correlated to the As concentration, with highest As concentrations observed at pH values greater than 6.4. The original source of As is most likely the black and gray shales that contain some arsenian pyrite with groundwater concentrations likely to be controlled by adsorption/desorption reactions with Fe oxides in the red mudstone aquifer materials.  相似文献   

The contribution of atmospheric acid deposition to ocean acidification in the subtropical North Atlantic Ocean     

Nicholas R. Bates  Andrew J. Peters   《Marine Chemistry》2007,107(4):547-558

The absorption of anthropogenic CO₂ and atmospheric deposition of acidity can both contribute to the acidification of the global ocean. Rainfall pH measurements and chemical compositions monitored on the island of Bermuda since 1980, and a long-term seawater CO₂ time-series (1983–2005) in the subtropical North Atlantic Ocean near Bermuda were used to evaluate the influence of acidic deposition on the acidification of oligotrophic waters of the North Atlantic Ocean and coastal waters of the coral reef ecosystem of Bermuda. Since the early 1980's, the average annual wet deposition of acidity at Bermuda was 15 ± 14 mmol m^− 2 year^− 1, while surface seawater pH decreased by 0.0017 ± 0.0001 pH units each year. The gradual acidification of subtropical gyre waters was primarily due to uptake of anthropogenic CO₂. We estimate that direct atmospheric acid deposition contributed 2% to the acidification of surface waters in the subtropical North Atlantic Ocean, although this value likely represents an upper limit. Acidifying deposition had negligible influence on seawater CO₂ chemistry of the Bermuda coral reef, with no evident impact on hard coral calcification.  相似文献   

Nocdap results: On the relationship of extreme waves and currents for design of offshore structures     

R. Lee Gordon  Finn-Erik Dahl  David J.H. Peters 《Ocean Engineering》1985,12(4):293-308

Simultaneous wind, wave, and current data during 21 storms spanning four winters at Tromsøflaket (230 m depth) were analysed to determine joint probabilities of occurrence. Waves were measured with a Waverider Buoy, winds with a recording anemometer onboard a vessel and currents at up to five depths with Aandera RCM-4 current meters. Measured currents were filtered to separate tidal currents from residual currents. In most of the statistical analyses, the actual current profiles were replaced with a simplified “equivalent” profile (constant above 50 m depth) whose magnitude was chosen to give the same drag load on a single pile as the actual profile when both profiles were combined with wave orbital velocities. The data suggest that the equivalent current is weakly correlated with the wave height. Within the range of the data analysed, an in-line equivalent residual current of 30 cm sec⁻¹ is adequate for design drag force calculations.The data presented here are used to illustrate a procedure for data analysis and are not suitable for use as design criteria.  相似文献   

Correlative changes in metabolism and DNA damage in turbot (Scophthalmus maximus) exposed to benzo[a]pyrene     

Telli-Karakoç F  Ruddock PJ  Bird DJ  Hewer A  Van Schanke A  Phillips DH  Peters LD 《Marine environmental research》2002,54(3-5):511-515

Juvenile turbot (Scophthalmus maximus) were injected intraperitoneally with either corn oil or 5 mg/kg benzo[a]pyrene (BaP) dissolved in corn oil and sampled I and 3 days after injection. After 1 day, no elevation of 7-ethoxyresorufin O-deethylase (EROD) activity was observed, however bile metabolites (BaP-7,8 dihydrodiol representing 70% of the total metabolites) and a single hepatic DNA adduct spot (0.47 adducts/10(8) nucleotides) identified by 32P-postlabelling were formed. No BaP metabolites or DNA adducts were observed in either control or carrier control fish. Fish sampled after 3 days reported 5-fold higher (P < 0.05) levels of EROD activity, a shift in the bile metabolite profile towards BaP phenol formation (1OH and 30H BaP comprising up to 60% of total metabolites detected) and the formation of two adduct spots (0.86 and 0.71 adducts/10(8) nucleotides). These results show that BaP can be metabolised and form hydrophobic DNA adducts in turbot without EROD elevation. Following EROD elevation, a shift in the profile of both BaP metabolites and BaP metabolite-DNA interactions occurs indicative of other oxidative processes.  相似文献   

Southeastern U.S. Vegetation Response to ENSO Events (1989–1999)     

Albert J. Peters  Lei Ji  Elizabeth Walter-Shea 《Climatic change》2003,60(1-2):175-188

El Niño/Southern Oscillation (ENSO) is considered one of the most powerful forces driving anomalous global weather patterns. Large-scale seasonal precipitation and temperature changes influenced by ENSO have been examined in many areas of the world. The southeastern United States is one of the regions affected by ENSO events. In this study, remote sensing detection of vegetation response to ENSO phases is demonstrated with one-kilometer biweekly Normalized Difference Vegetation Index (NDVI) data (1989–1999) derived from the Advanced Very High Resolution Radiometer(AVHRR). The impacts of three ENSO phases, cold, warm and neutral, on vegetation were analyzed with a focus on two vegetation cover types, two seasons and two geographic regions within the southeastern U.S. Significant ENSO effects on vegetation were found in cropland and forest vegetation cover types based on image and statistical analysis of the NDVI data. The results indicate that vegetation condition was optimal during the ENSO neutral phase for both agricultural and natural vegetation.  相似文献   

Experimental determination of activities in FeTiO3-MnTiO3 ilmenite solid solution by redox reversals     

A. Feenstra  Tjerk Peters 《Contributions to Mineralogy and Petrology》1996,126(1-2):109-120

 Solid solutions of (Fe,Mn)TiO₃ were synthesized, mostly at 0.10 X_Mn intervals, at 1 bar, 900°C and log f _{O 2} = –17.50. Analysis by EMP indicate an ideal stoichiometry for the Fe-Mn ilmenites with (Fe+Mn) = Ti = 1.000 when normalized to 3 oxygens. Their unit cell volume increases linearly with X_Mn. The composition of Fe-Mn ilmenite coexisting with metallic Fe and rutile was reversed at 1 bar, 700–900°C and fixed f _{O 2} in a gas-mixing furnace. Oxygen fugacity was controlled by mixing CO₂ and H₂ gas and was continuously monitored with an yttrium-stabilized zirconia electrolyte. Solution properties of Fe-Mn ilmenite were derived from the experimental data by mathematical programming (Engi and Feenstra, in preparation) including notably the results of Fe-Mn exchange experiments between ilmenite and garnet (Feenstra and Engi, submitted) and anchoring the standard state properties to the updated thermodynamic dataset of Berman and Aranovich (1996). The thermodynamic analysis resulted in positive deviations from ideality for (Fe,Mn)TiO₃ ilmenite, which is well described by an asymmetric Margules model with W^H _FeFeMn = –9.703 and W^H _FeMnMn = –23.234 kJ/mol, W^S _FeFeMn = –19.65 and W^S _FeMnMn = –22.06 J/(K·mol). The excess free energy for Fe-Mn ilmenite derived from the redox reversals is larger than in the symmetric ilmenite model (W^G _FeMn = +2.2 kJ/mol) determined by O'Neill et al. from emf measurements on the assemblage iron-rutile-(Fe,Mn)ilmenite. Received: 10 January 1996 / Accepted: 11 July 1996  相似文献   

Landscape controls on long‐term runoff in subhumid heterogeneous Boreal Plains catchments          下载免费PDF全文

Kevin J. Devito  Kelly J. Hokanson  Paul Adrian Moore  Nicholas Kettridge  Axel E. Anderson  Laura Chasmer  Chris Hopkinson  Maxwell C. Lukenbach  Carl A. Mendoza  Julienne Morissette  Daniel L. Peters  Richard Michael Petrone  Uldis Silins  Brian Smerdon  James Michael Waddington 《水文研究》2017,31(15):2737-2751

We compared median runoff (R) and precipitation (P) relationships over 25 years from 20 mesoscale (50 to 5,000 km²) catchments on the Boreal Plains, Alberta, Canada, to understand controls on water sink and source dynamics in water‐limited, low‐relief northern environments. Long‐term catchment R and runoff efficiency (RP^?1) were low and varied spatially by over an order of magnitude (3 to 119 mm/year, 1 to 27%). Intercatchment differences were not associated with small variations in climate. The partitioning of P into evapotranspiration (ET) and R instead reflected the interplay between underlying glacial deposit texture, overlying soil‐vegetation land cover, and regional slope. Correlation and principal component analyses results show that peatland‐swamp wetlands were the major source areas of water. The lowest estimates of median annual catchment ET (321 to 395 mm) and greatest R (60 to 119 mm, 13 to 27% of P) were observed in low‐relief, peatland‐swamp dominated catchments, within both fine‐textured clay‐plain and coarse‐textured glacial deposits. In contrast, open‐water wetlands and deciduous‐mixedwood forest land covers acted as water sinks, and less catchment R was observed with increases in proportional coverage of these land covers. In catchments dominated by hummocky moraines, long‐term runoff was restricted to 10 mm/year, or 2% of P. This reflects the poor surface‐drainage networks and slightly greater regional slope of the fine‐textured glacial deposit, coupled with the large soil‐water and depression storage and higher actual ET of associated shallow open‐water marsh wetland and deciduous‐forest land covers. This intercatchment study enhances current conceptual frameworks for predicting water yield in the Boreal Plains based on the sink and source functions of glacial landforms and soil‐vegetation land covers. It offers the capability within this hydro‐geoclimatic region to design reclaimed catchments with desired hydrological functionality and associated tolerances to climate or land‐use changes and inform land management decisions based on effective catchment‐scale conceptual understanding.  相似文献   

Intra-community implications of implementing multiple tsunami-evacuation zones in Alameda,California     

Jeff Peters  Nathan Wood  Rick Wilson  Kevin Miller 《Natural Hazards》2016,80(2):975-995

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Quantifying fracture geometry with X-ray tomography: Technique of Iterative Local Thresholding (TILT) for 3D image segmentation     

Hang Deng  Jeffrey P. Fitts  Catherine A. Peters 《Computational Geosciences》2016,20(1):231-244

This paper presents a new method—the Technique of Iterative Local Thresholding (TILT)—for processing 3D X-ray computed tomography (xCT) images for visualization and quantification of rock fractures. The TILT method includes the following advancements. First, custom masks are generated by a fracture-dilation procedure, which significantly amplifies the fracture signal on the intensity histogram used for local thresholding. Second, TILT is particularly well suited for fracture characterization in granular rocks because the multi-scale Hessian fracture (MHF) filter has been incorporated to distinguish fractures from pores in the rock matrix. Third, TILT wraps the thresholding and fracture isolation steps in an optimized iterative routine for binary segmentation, minimizing human intervention and enabling automated processing of large 3D datasets. As an illustrative example, we applied TILT to 3D xCT images of reacted and unreacted fractured limestone cores. Other segmentation methods were also applied to provide insights regarding variability in image processing. The results show that TILT significantly enhanced separability of grayscale intensities, outperformed the other methods in automation, and was successful in isolating fractures from the porous rock matrix. Because the other methods are more likely to misclassify fracture edges as void and/or have limited capacity in distinguishing fractures from pores, those methods estimated larger fracture volumes (up to 80 %), surface areas (up to 60 %), and roughness (up to a factor of 2). These differences in fracture geometry would lead to significant disparities in hydraulic permeability predictions, as determined by 2D flow simulations.  相似文献