Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface     

Corey D. Wallace  Audrey H. Sawyer  Rebecca T. Barnes 《水文研究》2019,33(3):405-413

Changes in streamflow and water table elevation influence oxidation–reduction (redox) conditions near river–aquifer interfaces, with potentially important consequences for solute fluxes and biogeochemical reaction rates. Although continuous measurements of groundwater chemistry can be arduous, in situ sensors reveal chemistry dynamics across a wide range of timescales. We monitored redox potential in an aquifer adjacent to a tidal river and used spectral and wavelet analyses to link redox responses to hydrologic perturbations within the bed and banks. Storms perturb redox potential within both the bed and banks over timescales of days to weeks. Tides drive semidiurnal oscillations in redox potential within the streambed that are absent in the banks. Wavelet analysis shows that tidal redox oscillations in the bed are greatest during late summer (wavelet magnitude of 5.62 mV) when river stage fluctuations are on the order of 70 cm and microbial activity is relatively high. Tidal redox oscillations diminish during the winter (wavelet magnitude of 2.73 mV) when river stage fluctuations are smaller (on the order of 50 cm) and microbial activity is presumably low. Although traditional geochemical observations are often limited to summer baseflow conditions, in situ redox sensing provides continuous, high‐resolution chemical characterization of the subsurface, revealing transport and reaction processes across spatial and temporal scales in aquifers.  相似文献   

Chronostratigraphy and lake-level changes of Laguna Cari-Laufquén, Río Negro, Argentina     

Alyson Cartwright  Jay Quade  Scott Stine  Kenneth D. Adams  Wallace Broecker  Hai Cheng 《Quaternary Research》2011,76(3):430-440

Evidence from shoreline and deep-lake sediments show Laguna Cari-Laufquén, located at 41°S in central Argentina, rose and fell repeatedly during the late Quaternary. Our results show that a deep (> 38 m above modern lake level) lake persisted from no later than 28 ka to 19 ka, with the deepest lake phase from 27 to 22 ka. No evidence of highstands is found after 19 ka until the lake rose briefly in the last millennia to 12 m above the modern lake, before regressing to present levels. Laguna Cari-Laufquén broadly matches other regional records in showing last glacial maximum (LGM) highstands, but contrasts with sub-tropical lake records in South America where the hydrologic maximum occurred during deglaciation (17–10 ka). Our lake record from Cari-Laufquén mimics that of high-latitude records from the Northern Hemisphere. This points to a common cause for lake expansions, likely involving some combination of temperature depression and intensification of storminess in the westerlies belt of both hemispheres during the LGM.  相似文献   

Development of the Global Earthquake Model’s neotectonic fault database   总被引：2，自引：0，他引：2  

Annemarie Christophersen  Nicola Litchfield  Kelvin Berryman  Richard Thomas  Roberto Basili  Laura Wallace  William Ries  Gavin P. Hayes  Kathleen M. Haller  Toshikazu Yoshioka  Richard D. Koehler  Dan Clark  Monica Wolfson-Schwehr  Margaret S. Boettcher  Pilar Villamor  Nick Horspool  Teraphan Ornthammarath  Ramon Zuñiga  Robert M. Langridge  Mark W. Stirling  Tatiana Goded  Carlos Costa  Robert Yeats 《Natural Hazards》2015,79(1):111-135

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Tertiary coal geology and stratigraphy of the Port Phillip Basin,Victoria     

G. R. Holdgate  S. J. Gallagher  M. W. Wallace 《Australian Journal of Earth Sciences》2013,60(3):437-453

Results from coal‐exploration drilling in the onshore part of the Port Phillip Basin, Victoria, have established stratigraphic and age correlations of the Lower Miocene Werribee Formation brown coal deposits at Bacchus Marsh to similar brown coals at Altona. The coal deposits occur in a northwest‐southeast structural depression (the Parwan Trough) that appears to be a southeast continuation of the Ballan Graben. Recent drilling for potential coal‐bed methane in the trough has provided new data on the deeper stratigraphy not penetrated by earlier drilling, including recognition of an Upper Cretaceous to Eocene Yaloak Formation coal‐bearing interval, similar to the Anglesea area, Ballan Graben and Lal Lal Basin. Up to 200 m of coal‐bearing sediment and minor volcanics underlie the Miocene coal measures. A marine facies transition takes place between the Miocene coal swamps of the Parwan Trough, through barrier sands west of Werribee, to carbonate facies near Geelong. To the south beneath Port Phillip Bay, a similar transition probably occurs between coal swamps of the Parwan Trough and fully marine carbonate environments of the contiguous Sorrento Graben. The palaeogeographical reconstructions suggest a similar coal‐to‐carbonate facies transition as in the adjacent onshore Gippsland Basin.  相似文献   

Glacial to interglacial changes in ocean chemistry     

Wallace S. Broecker 《Progress in Oceanography》1982,11(2):151-197

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Altered feeding habits and strategies of a benthic forage fish (Fundulus heteroclitus) in chronically polluted tidal salt marshes     

Goto D  Wallace WG 《Marine environmental research》2011,72(1-2):75-88

Responses in feeding ecology of a benthic forage fish, mummichogs (Fundulus heteroclitus), to altered prey resources were investigated in chronically polluted salt marshes (the Arthur Kill-AK, New York, USA). The diet niche breadth of the AK populations of mummichogs was significantly lower than that of the reference population, reflecting reduced benthic macroinfaunal species diversity. Most of the AK populations also had 2-3 times less food in their gut than the reference population. This disparity in gut fullness among the populations appeared to be partly due to ingested prey size shifts; some of the AK populations ingested fewer large prey than the reference population. Furthermore, benthic assemblages were strongly associated with sediment-associated mercury; gut fullness of the AK populations also significantly decreased with increasing mercury body burdens. These results indicate that chronic pollution may have directly (chemical bioaccumulation) and indirectly (reduced prey availability) altered the feeding ecology of mummichogs.  相似文献   

People helping turtles, turtles helping people: Understanding resident attitudes towards sea turtle conservation and opportunities for enhanced community participation in Bahia Magdalena, Mexico     

Jesse Senko  Andrew J. SchnellerJulio Solis  Francisco Ollervides  Wallace J. Nichols 《Ocean & Coastal Management》2011,54(2):148-157

In Pacific Mexico, all five sea turtle species have declined over the past century due to intense overexploitation of meat and eggs, fisheries bycatch, and degradation of marine and nesting habitats. One of the most heavily impacted areas has been the Baja California peninsula, where sea turtle populations remain historically low despite existing conservation measures that include a complete moratorium on the use of sea turtles, over three decades of widespread protection of nesting beaches, and in-water monitoring of sea turtles at coastal foraging areas. We recognize the need for alternative sea turtle conservation strategies that rely on increased participation of civil society and Mexican citizens. The purpose of this paper was to identify resident attitudes towards sea turtle conservation and opportunities for enhanced community participation in Bahia Magdalena, a region in Baja California Sur, Mexico experiencing high levels of sea turtle poaching and bycatch in fisheries. Through semi-structured interviews we found that while residents were overwhelmingly interested in participating in sea turtle conservation, peer pressure and conflict within the community presented major challenges. The majority of residents indicated that sea turtle voluntourism would have a positive impact on their community. Economic incentives and increased protection for sea turtles were mentioned as benefits of sea turtle voluntourism, whereas peer pressure, difficulty obtaining permits and producing effective marketing materials, and doubt about direct economic benefits were cited as constraints. We discuss our results in terms of opportunities, challenges, and recommendations for improving community-focused sea turtle conservation throughout the region.  相似文献   

Bioenhancement of cadmium transfer along a multi-level food chain     

Seebaugh DR  Goto D  Wallace WG 《Marine environmental research》2005,59(5):77-491

Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus.  相似文献   

Dispersion of naturally occurring ions in groundwater from various rock types in a portion of the San Pedro river basin, Arizona     

D. E. Wallace  L. R. Cooper 《Journal of Hydrology》1970,10(4):391-405

The groundwater in an alluvial basin in southern Arizona was analyzed for concentrations of Ca⁺⁺, Mg⁺⁺, Na⁺, and Cl⁻, ions.

The variety of rock types in the area, plus the undisturbed state of the groundwater basin, make comparative rock mineralization-groundwater ionization interpretations possible. Ionic dispersion in groundwater eminating from source areas composed of differing rock types is plotted as isogram maps. These isolated areas of differing mineral composition each exhibit a unique ionic contribution to groundwater. The ion concentrations in groundwater were then used as naturally occurring tracers to determine source areas of recharge and to delineate subsurface barriers to the normal basin flow net. Ion dispersion plots reveal the carbonates of the Dragoon Mountains to be a major contributor of Ca⁺⁺ and Mg⁺⁺ to the deep alluvial portion of the basin. Cl⁻ dispersion patterns show the granitic intrusives of the Tombstone Hills produce a barrier effect in the normal flow pattern of the basin as well as being a contributor of Cl⁻ to groundwater.  相似文献   

Structural analysis of compactive deformation in the incoming sedimentary section of the Hikurangi Subduction Margin, New Zealand:results from IODP 375 expedition     

Maomao Wang  Philip Barnes  Julia Morgan  Rebecca E Bell  Ake Fagereng  Heather M Savage  Demian M Saffer  Laura M Wallace  Katerina E Petronotis  Shipboard Scientists 《《地质学报》英文版》2018,92(Z1):157-157

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