Evaluating the hydrological and hydrochemical responses of a High Arctic catchment during an exceptionally warm summer          下载免费PDF全文

Daniel Lamhonwah  Melissa J. Lafrenière  Scott F. Lamoureux  Brent B. Wolfe 《水文研究》2017,31(12):2296-2313

The Arctic has experienced substantial warming during the past century with models projecting continued warming accompanied by increases in summer precipitation for most regions. A key impact of increasing air surface temperatures is the deepening of the active layer, which is expected to alter hydrological processes and pathways. The aim of this study was to determine how one of the warmest and wettest summers in the past decade at a High Arctic watershed impacted water infiltration and storage in deeply thawed soil and solute concentrations in stream runoff during the thaw period. In June and July 2012 at the Cape Bounty Watershed Observatory, we combined active layer measurements with major ion concentrations and stable isotopes in surface waters to characterize the movement of different runoff sources: snowmelt, rainfall, and soil water. Results indicate that deep ground thaw enhanced the storage of infiltrated water following rainfall. Soil water from infiltrated rainfall flowed through the thawed transient layer and upper permafrost, which likely solubilized ions previously stored at depth. Subsequent rainfall events acted as a hydrological flushing mechanism, mobilizing solutes from the subsurface to the surface. This solute flushing substantially increased ion concentrations in stream runoff throughout mid to late July. Results further suggest the importance of rainfall and soil water as sources of runoff in a High Arctic catchment during mid to late summer as infiltrated snowmelt is drained from soil following baseflow. Although there was some evaporation of surface water, our study indicates that flushing from solute stores in the transient layer was the primary driver of increased ion concentrations in stream runoff and not evaporative concentration of surface water. With warmer and wetter summers projected for the Arctic, ion concentrations in runoff (especially in the late thaw season), will likely increase due to the deep storage and subsurface flow of infiltrated water and subsequent flushing of previously frozen solutes to the surface.  相似文献   

In situ U–Pb rutile dating by LA-ICP-MS: <Superscript>208</Superscript>Pb correction and prospects for geological applications     

Thomas Zack  Daniel F. Stockli  George L. Luvizotto  Matthias G. Barth  Elena Belousova  Melissa R. Wolfe  Richard W. Hinton 《Contributions to Mineralogy and Petrology》2011,162(3):515-530

Rutile is a common accessory mineral that occurs in a wide spectrum of metamorphic rocks, such as in blueschists, eclogites, and granulites and as one of the most stable detrital heavy minerals in sedimentary rocks. The advent of rutile trace element thermometry has generated increased interest in a better understanding of rutile formation. This study documents important analytical advances in in situ LA-ICP-MS U/Pb geochronology of rutile: (1) Matrix matching, necessary for robust in situ dating is fulfilled by calibrating and testing several rutile standards (R10, R19, WH-1), including the presentation of new TIMS ages for the rutile standard R19 (489.5 ± 0.9 Ma; errors always stated as 2 s). (2) Initial common lead correction is routinely applied via ²⁰⁸Pb, which is possible due to extremely low Th/U ratios (usually <0.003) in most rutiles. Employing a 213 nm Nd:YAG laser coupled to a quadrupole ICP-MS and using R10 as a primary standard, rutile U/Pb concordia ages for the two other rutile standards (493 ± 10 Ma for R19; 2640 ± 50 Ma for WH-1) and four rutile-bearing metamorphic rocks (181 ± 4 Ma for Ivrea metapelitic granulite; 339 ± 7 Ma for Saidenbach coesite eclogite; 386 ± 8 Ma for Fjortoft UHP metapelite; 606 ± 12 Ma for Andrelandia metepelitic granulite) always agree within 2% with the reported TIMS ages and other dating studies from the same localities. The power of in situ U/Pb rutile dating is illustrated by comparing ages of detrital rutile and zircon from a recent sediment from the Christie Domain of the Gawler Craton, Australia. While the U/Pb age spectrum from zircons show several pronounced peaks that are correlated with magmatic episodes, rutile U/Pb ages are marked by only one pronounced peak (at ca 1,675 Ma) interpreted to represent cooling ages of this part of the craton. Rutile thermometry of the same detrital grains indicates former granulite-facies conditions. The methods outlined in this paper should find wide application in studies that require age information of single spots, e.g., provenance studies, single-crystal zoning and texturally controlled dating.  相似文献   

Changes in beach gravel lithology caused by anthropogenic activities along the southern coast of Lake Michigan, USA     

Zoran Kilibarda  Nolan Graves  Melissa Dorton  Richard Dorton 《Environmental Earth Sciences》2014,71(3):1249-1266

The southern coast of Lake Michigan is the most urbanized and most densely populated area in the Great Lakes region. Development of steel mills, harbors, and municipalities in NW Indiana and in NE Illinois in the last century and a half altered the nearshore environment so much that native beach gravel (>8 mm) now exist only in the exhumed paleo-beach remnants from the Nipissing Phase (~4,500 years ago) of Lake Michigan. Native gravel, collected from paleo-beach remnants at Mount Baldy Dune and Beach House Blowout, contain predominantly beach shingle, very platy siltstones (71–78 %), with secondary crystalline pebbles (18 %) in the east, and carbonate pebbles (12 %) in the west. A large amount of anthropogenic fill (steel industry waste, waste from power generating plants, construction debris, railroad, and road fill) has been added since the late 1800s to fill Lake Michigan and expand industrial land. Four areas of major coastal structures—Michigan City Pier and Breakwater, Burns Harbor Pier and Breakwater, Gary Works Pier, and Indiana Harbor Peninsula—altered the natural littoral drift and created four independent sectors on Indiana’s coast—Northeastern, Eastern, Central, and Western—between which no natural transfers of coarse sediments occur. Downdrift from the coastal structures, severe beach erosion has prompted extensive beach nourishment with non-native sandy gravel. Four distinct populations of modern beach gravel now exist along Indiana’s coast of Lake Michigan: (1) native gravel with diluted beach nourishment influence, (2) native gravel with a minor industrial influence, (3) compact gravel of nourished origin, and (4) anthropogenic gravel of industrial origin. Native gravel with diluted nourishment influence is found in the western, downdrift areas of the Northeastern (from Long Beach to Washington Park Beach) and Eastern Sectors (from eastern Indiana Dunes State Park to western Dune Acres) and contains up to 40 % compact carbonate and crystalline pebbles in addition to native beach shingle. Native gravel with minor industrial influence is found in the Central Sector of Indiana’s coast (from central Ogden Dunes to Marquette Beach) and contains predominantly beach shingle, platy clastic lithology, but also up to 30 % of chert and other pebbles released by industry. Compact gravel of nourished origin contains 60–90 % of carbonate and crystalline pebbles, and is found in the eastern, updrift areas of the Northeastern (Michiana Beach and Duneland Beach) and Eastern Sectors (from Crescent Beach to the western Beverly Shores). Anthropogenic gravel of industrial origin contains 70–90 % compact chert and slag and is found in every beach of the Western Sector and in the westernmost beach of the Central Sector. Streams draining into southern Lake Michigan generally contain little coarse sediment except in their channels near the roads and railroads, where angular to subangular anthropogenic pebbles predominate (70–90 %). However, streams have very little influence on gravel lithology along the coast because they seldom discharge anthropogenic gravel into Lake Michigan. Recent changes in gravel lithology along the southern Lake Michigan coast may affect changes in nearshore benthic flora and fauna as well as algal and bacterial blooms during warm summer months.  相似文献   

Testing the Response of Mycenaean Terracotta Figures and Vessels to Earthquake Ground Motions     

Klaus‐G. Hinzen  Melissa Vetters  Tatiana Kalytta  Sharon K. Reamer  Ursula Damm‐Meinhardt 《Geoarchaeology》2015,30(1):1-18

In the late 1970s, the hypothesis originated that earthquakes played a decisive role in the decline of the Mycenaean civilization at the end of the Late Bronze Age. The late excavator of Tiryns in the Argolid/Greece, Klaus Kilian, presented evidence for earthquake‐related damage to Mycenaean structures and considered four terracotta figures and two ceramic vessels lying on a floor of a potential cult room (later 12th century B.C.) in the Lower Citadel as “earthquake victims.” The broken figures were confined to a small area on the cult room's floor in front of a bench. We assess the archaeological data and test the plausibility of earthquake‐induced toppling of the objects with engineering seismological models. Dimensions and physical properties of the models were taken from the originals. In our simulations the models are virtually placed on a bench, and are exposed to earthquake ground motions based on records from recent Greek earthquakes. We test the artifacts’ toppling behavior and compare the final position of the fallen objects with the original find spots. Statistical analysis of 74,250 model calculations with highly varied ground motion parameters and bench heights reveal only a small probability that the find situation of the objects was caused by an earthquake.  相似文献   

Climate change beliefs, concerns, and attitudes toward adaptation and mitigation among farmers in the Midwestern United States     

J. Gordon Arbuckle Jr.  Linda Stalker Prokopy  Tonya Haigh  Jon Hobbs  Tricia Knoot  Cody Knutson  Adam Loy  Amber Saylor Mase  Jean McGuire  Lois Wright Morton  John Tyndall  Melissa Widhalm 《Climatic change》2013,117(4):943-950

A February 2012 survey of almost 5,000 farmers across a region of the U.S. that produces more than half of the nation’s corn and soybean revealed that 66 % of farmers believed climate change is occurring (8 % mostly anthropogenic, 33 % equally human and natural, 25 % mostly natural), while 31 % were uncertain and 3.5 % did not believe that climate change is occurring. Results of initial analyses indicate that farmers’ beliefs about climate change and its causes vary considerably, and the relationships between those beliefs, concern about the potential impacts of climate change, and attitudes toward adaptive and mitigative action differ in systematic ways. Farmers who believed that climate change is occurring and attributable to human activity were significantly more likely to express concern about impacts and support adaptive and mitigative action. On the other hand, farmers who attributed climate change to natural causes, were uncertain about whether it is occurring, or did not believe that it is occurring were less concerned, less supportive of adaptation, and much less likely to support government and individual mitigative action. Results suggest that outreach with farmers should account for these covariances in belief, concerns, and attitudes toward adaptation and mitigation.  相似文献   

The current status of lightning safety knowledge and the effects of lightning education modes on college students     

Melissa C. K. Phillips  Thomas W. Schmidlin 《Natural Hazards》2014,70(2):1231-1245

Lightning is a natural hazard occurring frequently within the United States causing injury, damage, and death. To avoid this hazard, citizens need to self-mitigate their risk by taking action. The level of lightning safety knowledge must be known to determine if citizens have the tools to mitigate their risk. No studies have previously explored the status of lightning safety knowledge or the best way to educate about lightning safety. Therefore, the research community is unaware if citizens understand their risk and have the knowledge to mitigate their risk, or if current safety programs are effectively educating citizens. This study distributed two surveys to college students in Florida, Ohio, and Colorado. Following the pre-mode survey, students were shown videos, given brochures, or both with lightning safety information. A follow-up survey was then distributed. Participants were found to have a moderate level of lightning safety knowledge. Study areas of variable risk as well as past death rates were not found to affect the rate of knowledge. The presence of education programs were not affected by the variable risk. Misunderstood areas of lightning safety knowledge were associated mostly with the lightning and thunder relationship as well as safety before and after a thunderstorm. The education modes involving a video were the most effective at increasing knowledge. Gender displayed minor differences in gaining of lightning safety knowledge.  相似文献   

Spatial and Temporal Variation in Brackish Wetland Seedbanks: Implications for Wetland Restoration Following <Emphasis Type="Italic">Phragmites</Emphasis> Control     

Eric L. G. Hazelton  Rebekah Downard  Karin M. Kettenring  Melissa K. McCormick  Dennis F. Whigham 《Estuaries and Coasts》2018,41(1):68-84

Chesapeake Bay tidal wetlands are experiencing a broad-scale, aggressive invasion by the non-native, clonal grass Phragmites australis. The grass is often managed with herbicides in efforts to restore native plant communities and wildlife habitat. Management efforts, however, can act as a disturbance, resulting in increased light availability, potentially fostering reinvasion from soil seedbanks. If native vegetation establishes quickly from seedbanks, the site should have greater resiliency against invasion, while disturbed sites where native plants do not rapidly establish may be rapidly colonized by P. australis. We surveyed the soil seedbank of three vegetation cover types in five Chesapeake Bay subestuaries: areas where P. australis had been removed, where P. australis was left intact, and with native, reference vegetation. We determined the total germination, the proportion of the seedbank that was attributable to invasive species, the richness, the functional diversity, and the overall composition of the seedbanks in each of the cover types (i.e., plots). After 2 years of herbicide treatment in the P. australis removal plots, vegetation cover type impacted the total germination or the proportion of invasive species in the seedbank. In contrast, we also found that seedbank functional composition in tidal brackish wetlands was not influenced by vegetation cover type in most cases. Instead, plots within a subestuary had similar seedbank functional composition across the years and were composed of diverse functional groups. Based on these findings, we conclude that plant community recovery following P. australis removal is not seed-limited, and any lack of native vegetation recruitment is likely the result of yet-to-be-determined abiotic factors. These diverse seedbanks could lead to resilient wetland communities that could resist invasions. However, due to the prevalence of undesirable species in the seedbank, passive revegetation following invasive plant removal may speed up their re-establishment. The need for active revegetation will need to be assessed on a case-by-case basis to ensure restoration goals are achieved.  相似文献   

The Role of Decorative Features in the Endurance of Vernacular Architecture in Kinnaur,Himachal Pradesh,India          下载免费PDF全文

Melissa Malouf Belz 《Geographical review》2015,105(3):304-324

The remote Himalayan region of Kinnaur in northwestern India is known for its carved wooden homes with decorative features. Relatively recent environmental policies have prompted limitations on wood collection. This, coupled with an increase in access to modern building materials, has resulted in dramatic changes in vernacular housing styles. Landscape analysis and interviews reveal that house form, building methods, and construction materials are all changing. However, decorative features are among the last remaining characteristics of the traditional house. This paper argues that small‐scale architectural features are a significant part of an enduring vernacular landscape and allow a region to preserve traditional styles and identity, while also moving forward as a modernizing society.  相似文献   

Magnesium Isotopic Compositions of International Geological Reference Materials          下载免费PDF全文

Fang‐Zhen Teng  Wang‐Ye Li  Shan Ke  Wei Yang  Sheng‐Ao Liu  Fatemeh Sedaghatpour  Shui‐Jiong Wang  Kang‐Jun Huang  Yan Hu  Ming‐Xing Ling  Yan Xiao  Xiao‐Ming Liu  Xiao‐Wei Li  Hai‐Ou Gu  Corliss K. Sio  Debra A. Wallace  Ben‐Xun Su  Li Zhao  Johnnie Chamberlin  Melissa Harrington  Aaron Brewer 《Geostandards and Geoanalytical Research》2015,39(3):329-339

Magnesium isotopic compositions are reported for twenty‐four international geological reference materials including igneous, metamorphic and sedimentary rocks, as well as phlogopite and serpentine minerals. The long‐term reproducibility of Mg isotopic determination, based on 4‐year analyses of olivine and seawater samples, was ≤ 0.07‰ (2s) for δ²⁶Mg and ≤ 0.05‰ (2s) for δ²⁵Mg. Accuracy was tested by analysis of synthetic reference materials down to the quoted long‐term reproducibility. This comprehensive dataset, plus seawater data produced in the same laboratory, serves as a reference for quality assurance and inter‐laboratory comparison of high‐precision Mg isotopic data.  相似文献   

Modeling the impacts of climate change on nitrogen losses and crop yield in a subsurface drained field   总被引：1，自引：0，他引：1  

Zhaozhi Wang  Zhiming Qi  Lulin Xue  Melissa Bukovsky  Matthew J. Helmers 《Climatic change》2015,129(1-2):323-335

  相似文献