Corrosion of metal roof materials related to volcanic ash interactions     

Christopher Oze  Jim Cole  Allan Scott  Thomas Wilson  Grant Wilson  Sally Gaw  Samuel Hampton  Colin Doyle  Zhengwei Li 《Natural Hazards》2014,71(1):785-802

Metal roofing material is commonly used for residential and industrial roofs in volcanically active areas. Increased corrosion of metal roofing from chemically reactive volcanic ash following ash deposition post-eruption is a major concern due to decreasing the function and stability of roofs. Currently, assessment of ash-induced corrosion is anecdotal, and quantitative data are lacking. Here, we systematically evaluate the corrosive effects of volcanic ash, specifically ash leachates, on a variety of metal roofing materials (i.e. weathered steel, zinc, galvanized steel, and Colorsteel©) utilizing weathering chamber experiments and direct acid treatments. Weathering chamber tests were carried out for up to 30 days, and visual, chemical, and surface analyses did not definitively identify significant corrosion in any of the test roofing metal samples. Direct concentrated acid treatments with hydrochloric (HCl), sulphuric (H₂SO₄), and hydrofluoric (HF) acids demonstrate that roofing materials are chemically resilient. Our experimental results suggest that ash-leachate-related corrosion is a longer-term process (>1 month), potentially related to a multitude of factors including increased ash leachate concentrations, the dissolution of the glass matrix of the ash, moisture retention at the ash-surface boundary, and potential reactions involving photo-oxidation. Overall, corrosion is not a simple process related to the short-term release of acid and/or salt leachates from the ash surface, but a product of dynamic interactions involving ash and water at the surface of metal roofing material for extended periods.  相似文献   

The origin and evolution of the Klondike goldfields, Yukon, Canada     

Grant W. Lowey   《Ore Geology Reviews》2006,28(4):431

The world famous Klondike goldfields are located in the unglaciated part of west-central Yukon, Canada. Since their discovery over 100 years ago, they have produced an estimated 311 tonnes of gold, primarily from bench and creek placers that are fluvial in origin and range from Pliocene to Holocene in age. Historically, the placers are classified into three levels of gravel with four main units. These include the high-level White Channel Gravel (Pliocene), presently the most important gold-bearing unit, which sits nonconformably on an erosional bedrock surface (i.e., the ‘White Channel strath’) and is overlain and interbedded with the glaciofluvial Klondike Gravel (Pliocene); the intermediate-level gravel (Pleistocene), the least important economically; and the low-level gravel (Pleistocene–Holocene), historically the most important gold-bearing unit, but it has been mined three or four times now. The goldfields originated from the weathering and erosion of early Cretaceous, discordant mesothermal quartz veins, and the light grey color of the matrix of the White Channel Gravel is due mainly to weathering and diagenetic alteration by groundwater flow. The concentration of placer gold is related to a hierarchy of physical scales: at the lithofacies scale (metres), bed roughness determined sites of gold deposition; at the element scale (tens of metres), gravel bars were preferentially enriched in gold; at the reach scale (hundreds of metres), stream gradient was an important factor; at the system scale (hundreds of km), braided river environments transported large amounts of gold; and at the sequence scale (thousands of km), economic placers formed initially in the high-level White Channel Gravel and later in the intermediate-level and low-level gravel. The White Channel strath is interpreted as an erosional ‘tectonic’ terrace that formed during isostatic uplift and under conditions of dynamic equilibrium. The high-level White Channel Gravel and Klondike Gravel are interpreted as a depositional ‘climatic’ terrace that formed during a reversal in the tectonically induced downcutting, which is attributed to the initial and most extensive of the pre-Reid glaciations (3 Ma) in the Yukon. The intermediate-level gravel is interpreted as minor erosional ‘complex response’ terraces that formed during static equilibrium when there were pauses in valley-floor degradation, which are attributed to the subsequent and less extensive pre-Reid glaciations. The low-level gravel formed also during valley-floor degradation and may represent a return to dynamic equilibrium conditions. Hence, the dominant forcing mechanisms controlling the evolution of the goldfields were isostatically compensated exhumation and climatic change related to the repeated glaciation of the Yukon. In addition, the lowering of baselevel from high-level, to intermediate-level and finally to low-level gravel was accompanied by a decrease in accommodation space (as indicated by a decrease in gravel thickness), which resulted in an increase in the concentration of the placer gold.  相似文献   

Species identification and decay assessment of Late Pleistocene fragmentary vertebrate remains from Pin Hole Cave (Creswell Crags,UK) using collagen fingerprinting          下载免费PDF全文

Michael Buckley  Virginia L. Harvey  Andrew T. Chamberlain 《Boreas: An International Journal of Quaternary Research》2017,46(3):402-411

Ancient bone remains are widely utilized when investigating vertebrate biodiversity of past animal populations but are often so highly fragmented that the majority of specimens cannot be identified to any meaningful taxonomic level. Recently, high‐throughput methods for objective species identification using collagen peptide mass fingerprinting have been created to overcome this with the added indication that they could also offer a means of relative ageing through decay measurement. Here we explore both species identification and decay measurements for the Pin Hole Cave ‘microfaunal’ assemblage, the site that has been designated as a representative for Marine Oxygen Isotope Stage 3 in Britain in terms of its suite of mammalian fauna. We explore the technique's potential to corroborate the faunal diversity established previously by macroscopic studies and evaluate the decay measurements across the species boundary. The results support that the analysis of fragmentary remains by collagen fingerprinting can yield a more diverse set of fauna, and offer additional information relating to taphonomy, than the analysis of morphologically intact bones on their own. However, although useful for identifying likely contaminations of an assemblage, there was an unexpected decrease in the decay measurements observed for some megafauna compared with much younger microfauna, indicating that other factors need to be carefully monitored before it could be used as a relative ageing technique in Quaternary deposits.  相似文献   

Nekton Use of Flooded Salt Marsh and an Assessment of Intertidal Creek Pools as Low-Tide Refuges     

Dennis M. Allen  Virginia Ogburn-Matthews  Paul D. Kenny 《Estuaries and Coasts》2017,40(5):1450-1463

Patterns of nekton occurrence on the salt marsh surface at high tide and in an adjacent intertidal creek pool at low tide were used to investigate movements of nekton in an intertidal basin. Paired collections were made in North Inlet estuary, SC on 67 dates over 9 years. Comparisons of high- and low-tide total abundance indicated that what remained in the creek pool at low tide was representative of the nekton on the flooded marsh. Of the 64 taxa collected, the same 8 species ranked in the top 10 in both the high- and low-tide collections. Abundances of most resident species were positively correlated with the area of marsh flooded, but mummichog (Fundulus heteroclitus), the most abundant resident, was not. Abundances of young-of-the-year transient species were not related to the extent of tidal flooding. Some transient species used the flooded marsh but did not occupy the pool at low tide, and others found in the pool did not use the marsh. Differences in abundance, biomass, and length between the marsh and pool collections indicated differences in the tendency of species and life stages to retreat downstream of the pool to the subtidal channel. Proportionately more of the nekton that were present on the flooded marsh left the intertidal basin when large changes in temperature and salinity occurred between high and low tides. More transients left the basin following higher tides, but more residents did not. The results demonstrate a wide range of taxonomic and ontogenetic patterns among nekton using intertidal salt marsh basins and the underappreciated importance of intertidal creek pools as alternative low-tide refuges.  相似文献   

Photosynthesis and Growth of Temperate and Sub-Tropical Estuarine Phytoplankton in a Scenario of Nutrient Enrichment under Solar Ultraviolet Radiation Exposure     

Virginia E. Villafañe  Marco J. Cabrerizo  Gilmar S. Erzinger  Paula Bermejo  Sebastian M. Strauch  Macarena S. Valiñas  E. Walter Helbling 《Estuaries and Coasts》2017,40(3):842-855

We compared the responses of two estuarine phytoplankton communities, one from a temperate (Chubut River estuary (CH), Argentina) and one from a sub-tropical site (Babitonga Bay (BB), Brazil), in a scenario of nutrient enrichment under solar ultraviolet radiation (UVR) exposure. Seawater samples were exposed in microcosms to two nutrients, ambient vs. enriched, and two radiation conditions, with and without UVR, and exposed to solar radiation for 4 days. We evaluated the short- (PSII photochemistry, during 90 min light and 90 min dark cycles, before and after the , whereas in BB, nutrient effects prevailed. Such differences were related to the previous light history of the cells and to the ambient nutrient status. After acclimation, an overall improvement of the photosynthetic performance was observed at both sites, either by reducing the relative inhibition or by increasing the recovery of the effective photochemical quantum yield. Interactive effects of UVR and nutrients on growth at CH were antagonistic, while at BB, no differences were observed between the interactive and the sum of effects. Part of the differences in the mid-term observed responses can be attributed to taxonomic changes, with the CH community dominated by diatoms throughout the experiment, but with a shift from a diatom to a flagellate-dominated community in BB. Temperature differences between both sites might have favored higher growth rates and flagellates dominance in BB under the nutrient enriched conditions.  相似文献   

Space use by Rhabdosargus holubi in a southern African estuary,with emphasis on fish movements and ecosystem connectivity     

GN Grant  RH Bennett  TS Murray  AK Whitfield 《African Journal of Marine Science》2017,39(2):135-143

Twenty-one juvenile Cape stumpnose Rhabdosargus holubi (140–190 mm fork length) were tagged with internal acoustic transmitters in the lower, middle and upper reaches of the Kowie Estuary, South Africa. The movements of each fish were continually monitored from October 2014 to February 2015 using 22 stationary data-logging acoustic receivers situated at approximately equidistant intervals along the length of the estuary (21 km). Juvenile R. holubi spent the greatest proportion of time within the estuarine environment (83%), with the sea (16%) and riverine (1%) environments used to a much lesser extent. Within the estuarine environment, tagged individuals showed high levels of residency and fidelity to their capture and release sites; however, the degree of residency was dependent on the position of the release site, with batches in the upper and lower reaches exhibiting different space-use patterns. When larger juvenile R. holubi migrated back to the sea for the next phase of their life cycle, they generally did not return to the estuarine environment, thus indicating a permanent ontogenetic shift in habitat use with the onset of sexual maturity. This contribution to our understanding of the ecology of a ubiquitous estuarine fish further highlights the importance of estuarine habitats as nursery areas that require effective management.  相似文献   

Carolina Bay geoarchaeology and Holocene landscape evolution on the Upper Coastal Plain of South Carolina     

Mark J. Brooks  Barbara E. Taylor  John A. Grant 《Geoarchaeology》1996,11(6):481-504

Surface water on the mainly dry, upland interfluves of the Upper Coastal Plain of South Carolina occurs currently as a sporadic distribution of shallow ponds held within Carolina bays and other small, isolated basins. At seven bays on the U.S. Department of Energy's Savannah River Site on the Upper Coastal Plain of South Carolina, we investigated Holocene changes in bay morphology, ecology, and prehistoric human activity. At Flamingo Bay, we employed archaeological survey and testing, shovel and auger testing, sediment analysis, and ground-penetrating radar to document stratigraphy and chronology of the sand rim on the eastern side of the bay. Artifact assemblage indicate changes in intensity of human use of the bay. Radiocarbon dates from a sediment core establish time scales for depositional processes at the center of the basin. Ground-penetrating radar data from the other bays indicate that the stratigraphy of all seven bays is broadly similar. We conclude that: (1) Significant modification of the bays, including rim development and basin infilling, occurred during the Holocene; (2) ponds on the early Holocene landscape were larger and more permanent than at present; (3) early Holocene climate, as indicated by both depositional processes and human activity, was not characterized by prolonged periods of extremely dry conditions; and (4) fluvial-centric models of terminal Pleistocene—early Holocene human adaptations require revision to include intensive use of isolated upland ponds. © 1996 John Wiley & Sons, Inc.  相似文献   

Dietary niche separation of three Late Pleistocene bear species from Vancouver Island,on the Pacific Northwest Coast of North America     

Cara Kubiak  Vaughan Grimes  Geert Van Biesen  Grant Keddie  Mike Buckley  Reba Macdonald  M. P. Richards 《第四纪科学杂志》2023,38(1):8-20

Competition between taxa related to climate changes has been proposed as a possible factor in Pleistocene megafaunal extinctions, and here we present isotope evidence of the diets of three co-existing bear species [black bear (Ursus americanus), brown bear (Ursus arctos), and the now extinct short-faced bear (Arctodus simus)] from a locale in western North America dating to the Late (Terminal) Pleistocene (~14.5–11.7 ka). The three bear species were found at several sites on Vancouver Island, on the western coast of Canada. To examine the chronological overlap and niche partitioning between these species of bear, we used direct radiocarbon dating, stable isotope analysis and ZooMS proteomic identification methods. Here we present new radiocarbon evidence from Terminal Pleistocene U. americanus, U. arctos and A. simus from several sites on the island, along with both bulk collagen and compound-specific isotope data for these species. Radiocarbon dates confirm the chronological overlap of Arctodus and both Ursus species in the montane regions of the island at the end of the Pleistocene. Stable isotope data reveal niche differentiation between these species, with U. americanus occupying a distinctly lower trophic position than the other two taxa.  相似文献