Alkalinity production as an indicator of failure in steel slag leach beds treating acid mine drainage   总被引：1，自引：0，他引：1  

Natalie A. Kruse  Amy L. Mackey  Jennifer R. Bowman  Kimberly Brewster  R. Guy Riefler 《Environmental Earth Sciences》2012,67(5):1389-1395

Acid mine drainage is a serious environmental problem throughout mining regions of the US and around the world. In Appalachia, reuse of steel slag from steel production as a source of alkalinity for treatment of acid mine drainage has become a common practice. In these systems, dubbed steel slag leach beds, relatively clean surface water is percolated through a bed of steel slag to add large amounts of alkalinity to the water before mixing it with acidic, metalliferous mine water. These beds do not operate consistently and their failure mechanisms are poorly understood. Using the experience of Raccoon Creek watershed in southern Ohio, the alkalinity distribution of the discharge of six steel slag leach beds is compared. Two of these beds are still functional, one has been abandoned and three are operating poorly. The difference in alkalinity distribution between these beds suggests that a carbonate-dominated alkalinity system is an indicator of a poorly performing steel slag leach bed, while a more even distribution between hydroxide, carbonate and bicarbonate may point to more ideal operating conditions. In eight laboratory column experiments, this evidence was then expanded upon by testing different mixed media substrates (differing mixes of steel slag, wood chips and river gravel) to see which provided the most ideal alkalinity distributions. The columns that had steel slag mixed either with wood chips or wood chips and river gravel outperformed the column with slag only in terms of alkalinity distribution, perhaps due to microbial processes or increased hydraulic conductivity without significant added calcium or carbon that could drive calcium carbonate precipitation within the beds and causing them to fail.  相似文献   

Model insight into glacial–interglacial paleodust records     

Natalie Mahowald  Samuel Albani  Sebastian Engelstaedter  Gisela Winckler  Michelle Goman 《Quaternary Science Reviews》2011,30(7-8):832-854

We present a new method of analyzing model results to help identify the sensitivity of the location of different paleodust records to estimate local to regional scale variability of dust and climate variables. We use model simulations of global dust distribution from the last glacial maximum, preindustrial, current, and predicted future. The dust model has been previously shown to match available observational data for the current and last glacial maximum climate. Here, the model is compared to available source provenance data and is shown to agree with these limited observations. Using correlations and slopes across different time periods, the modeled relationships between deposition at specific observational sites and regional deposition and dustiness are shown. In addition, we evaluate the modeled relative slope of these cores to determine the location of paleodust sites that are especially easy to interpret as regional indicators of dustiness. Model predictions suggest that deposition in Antarctic ice cores is usually better than dust concentration to capture regional deposition and dustiness variability over glacial–interglacial time periods, in agreement with ice core interpretations. For Greenland, the model predicts a possible shift from dominantly wet deposition under modern conditions to dominantly dry deposition during glacial climate conditions indicating that deposition may be better suited to capture dustiness variability under LGM conditions in Greenland. The model also identifies specific regions that are not well covered by observations for glacial/interglacial or anthropocene dust variability. In addition, we evaluate the modeled relative slope of the location of these cores to determine regions that would provide ideal localities for pursuing records that would provide easily interpretable paleo-proxy records of regional dustiness.  相似文献   

Identification of the natural product 2,3,4,5-tetrabromo-1-methylpyrrole in Pacific biota, passive samplers and seagrass from Queensland, Australia     

Gaul S  Bendig P  Olbrich D  Rosenfelder N  Ruff P  Gaus C  Mueller JF  Vetter W 《Marine pollution bulletin》2011,62(11):2463-2468

Halogenated natural products (HNPs) are frequently detected in marine organisms. High HNP concentrations have previously been found in marine mammals from the Great Barrier Reef, Australia, including in the blubber of herbivorous dugongs (Dugong dugon). To identify the source of HNPs we initially focused on the analysis of Australian seagrass (Halophila ovalis) which serves as the principal food source for dugongs. GC/MS analysis of the seagrass indicated the presence of several organobromine compounds. One compound was identified as 2,3,4,5-tetrabromo-1-methylpyrrole (TBMP) by synthesis. Subsequent analysis of semipermeable membrane devices demonstrated that the photo-sensitive TBMP is widespread in the Great Barrier Reef (Queensland, Australia). The detection of larger TBMP concentrations in fish fillets from Chile and traces in mussels from New Zealand indicated that this potential HNP may be distributed throughout the Southern Pacific Ocean.  相似文献   

Simulated variations of eolian dust from inner Asian deserts at the mid-Pliocene, last glacial maximum, and present day: contributions from the regional tectonic uplift and global climate change     

Zhengguo Shi  Xiaodong Liu  Zhisheng An  Bingqi Yi  Ping Yang  Natalie Mahowald 《Climate Dynamics》2011,37(11-12):2289-2301

Northern Tibetan Plateau uplift and global climate change are regarded as two important factors responsible for a remarkable increase in dust concentration originating from inner Asian deserts during the Pliocene?CPleistocene period. Dust cycles during the mid-Pliocene, last glacial maximum (LGM), and present day are simulated with a global climate model, based on reconstructed dust source scenarios, to evaluate the relative contributions of the two factors to the increment of dust sedimentation fluxes. In the focused downwind regions of the Chinese Loess Plateau/North Pacific, the model generally produces a light eolian dust mass accumulation rate (MAR) of 7.1/0.28?g/cm²/kyr during the mid-Pliocene, a heavier MAR of 11.6/0.87?g/cm²/kyr at present, and the heaviest MAR of 24.5/1.15?g/cm²/kyr during the LGM. Our results are in good agreement with marine and terrestrial observations. These MAR increases can be attributed to both regional tectonic uplift and global climate change. Comparatively, the climatic factors, including the ice sheet and sea surface temperature changes, have modulated the regional surface wind field and controlled the intensity of sedimentation flux over the Loess Plateau. The impact of the Tibetan Plateau uplift, which increased the areas of inland deserts, is more important over the North Pacific. The dust MAR has been widely used in previous studies as an indicator of inland Asian aridity; however, based on the present results, the interpretation needs to be considered with greater caution that the MAR is actually not only controlled by the source areas but the surface wind velocity.  相似文献   

Winter Diets of Immature Green Turtles (Chelonia mydas) on a Northern Feeding Ground: Integrating Stomach Contents and Stable Isotope Analyses     

Natalie C. Williams  Karen A. Bjorndal  Margaret M. Lamont  Raymond R. Carthy 《Estuaries and Coasts》2014,37(4):986-994

The foraging ecology and diet of the green turtle, Chelonia mydas, remain understudied, particularly in peripheral areas of its distribution. We assessed the diet of an aggregation of juvenile green turtles at the northern edge of its range during winter months using two approaches. Stomach content analyses provide a single time sample, and stable isotope analyses integrate diet over a several-month period. We evaluated diet consistency in prey choice over time by comparing the results of these two approaches. We examined stomach contents from 43 juvenile green turtles that died during cold stunning events in St. Joseph Bay, Florida, in 2008 and 2011. Stomach contents were evaluated for volume, dry mass, percent frequency of occurrence, and index of relative importance of individual diet items. Juvenile green turtles were omnivorous, feeding primarily on seagrasses and tunicates. Diet characterizations from stomach contents differed from those based on stable isotope analyses, indicating the turtles are not feeding consistently during winter months. Evaluation of diets during warm months is needed.  相似文献   

Reply to Comment by C. Gaucher et al. on "Chemostratigraphic constraints on early Ediacaran carbonate ramp dynamics,Río de la Plata craton,Uruguay" by Aubet et al. Gondwana Research (2012), Volume 22, Issues 3-4, November 2012, Pages 1073-1090     

Natalie R. Aubet  Ernesto Pecoits  Andrey Bekker  Murray K. Gingras  Horst Zwingmann  Gerardo Veroslavsky  Héctor de Santa Ana  Kurt O. Konhauser 《Gondwana Research》2013,23(3):1186-1188

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Nutrient density as a metric for comparing greenhouse gas emissions from food production     

Natalie A. Doran-Browne  Richard J. Eckard  Ralph Behrendt  Ross S. Kingwell 《Climatic change》2015,129(1-2):73-87

Dietary Guidelines for many countries recommend that people should eat ‘nutrient dense’ foods, which are foods with a high nutrient to energy ratio; and that people should limit their intake of saturated fat, added salt or added sugar. In addition, consumers and environmentalists increasingly want their food to be produced with a low impact on the environment, including reduced greenhouse gas emissions (GHGE), yet agriculture is a major source of CH₄ and N₂O emissions, as well as producing CO₂ emissions. Current research on GHGE from agriculture does not incorporate the nutritional value of the foods studied. However, the nutritional content of food is important, given the prevalence of malnutrition, including obesity (due to over-consumption of foods high in energy yet low nutritional density), and the negative health impacts they produce. This paper introduces the metric, emissions/unit nutrient density, and compares the results with three other metrics: emissions intensity (t CO₂e/t product), emissions/t protein and emissions/GJ. The food products examined are wheat flour, milk, canola oil, lean lamb, lean beef, untrimmed lamb and untrimmed beef. The metric t CO₂e/unit nutrient density was the preferred metric to use when examining GHGE from food production because it compares different types of products based on their nutritional value, rather than according to singular nutrients such as protein, or specific attributes such as product weight or energy content. Emissions/unit nutrient density has the potential to inform consumer choices regarding foods that have a higher nutritional content relative to the GHGE generated. Further analysis would be useful to develop and expand the use of this metric further.  相似文献   

Trace element and major ion concentrations and dynamics in glacier snow and melt: Eliot Glacier,Oregon Cascades     

Sarah K. Fortner  W. Berry Lyons  Andrew G. Fountain  Kathleen A. Welch  Natalie M. Kehrwald 《水文研究》2009,23(21):2987-2996

We present concentrations of environmentally available (unfiltered acidified 2% v/v HNO₃) As, Cu, Cd, Pb, V, Sr, and major ions including Ca²⁺, Cl^?, and SO₄^2? in a July 2005 and a March 2006 shallow snow profile from the lower Eliot Glacier, Mount Hood, Oregon, and its proglacial stream, Eliot Creek. Low enrichment factors (EF) with respect to crustal averages suggests that in fresh March 2006 snow environmentally available elements are derived primarily from lithogenic sources. Soluble salts occurred in lower and less variable concentrations in July 2005 snow than March 2006. Conversely, environmentally available trace elements occurred in greater and more variable concentrations in July 2005 than March 2006 snow. Unlike major solutes, particulate‐associated trace elements are not readily eluted during the melt season. Additionally, elevated surface concentrations suggest that they are likely added throughout the year via dry deposition. In a 1‐h stream sampling, ratios of dissolved (<0·45 µm) V:Cl^?, Sr:Cl^?, and Cu:Cl^? are enriched in the Eliot Stream with respect to their environmentally available trace element to Cl^? ratios in Eliot Glacier snow, suggesting chemical weathering additions in the stream waters. Dissolved Pb:Cl^? is depleted in the Eliot Stream with respect to the ratio of environmentally available Pb to Cl^? in snow, corresponding to greater adsorption onto particles at greater pH values. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Stakeholder objective preferences in Australian Commonwealth managed fisheries     

Sean Pascoe  Wendy Proctor  Chris Wilcox  James Innes  Wayne Rochester  Natalie Dowling 《Marine Policy》2009,33(5):750-758

Fisheries management is increasingly involving a wide range of stakeholders in the decision making process. However, in most fisheries, the set of management objectives are poorly defined, and the implicit importance placed on these objectives may vary considerably both between and within different stakeholder groups. This may lead to conflicts within management advisory groups where members from different stakeholder groups view potential management outcomes substantially differently, and inconsistencies in decision making when changes in stakeholder representation take place. In this paper, the institutional structure of fisheries management in Australia and the roles the different organisations play in shaping fisheries management plans are detailed. An explicit hierarchy of management objectives is developed in collaboration with key managers and policy makers. A large survey of stakeholders involved in Australian Commonwealth fisheries management was undertaken to determine stakeholder preferences relating to these objectives. The results highlight the differences in perspectives regarding the relative importance of the multiple objectives of fisheries management. While on average stakeholder preferences generally correspond with their expected preference set, the results also indicate that there is generally low coherence within stakeholder groups.  相似文献   

Comparing modeled and observed changes in mineral dust transport and deposition to Antarctica between the Last Glacial Maximum and current climates   总被引：1，自引：0，他引：1  

Samuel Albani  Natalie M. Mahowald  Barbara Delmonte  Valter Maggi  Gisela Winckler 《Climate Dynamics》2012,38(9-10):1731-1755

Mineral dust aerosols represent an active component of the Earth’s climate system, by interacting with radiation directly, and by modifying clouds and biogeochemistry. Mineral dust from polar ice cores over the last million years can be used as paleoclimate proxy, and provide unique information about climate variability, as changes in dust deposition at the core sites can be due to changes in sources, transport and/or deposition locally. Here we present results from a study based on climate model simulations using the Community Climate System Model. The focus of this work is to analyze simulated differences in the dust concentration, size distribution and sources in current climate conditions and during the Last Glacial Maximum at specific ice core locations in Antarctica, and compare with available paleodata. Model results suggest that South America is the most important source for dust deposited in Antarctica in current climate, but Australia is also a major contributor and there is spatial variability in the relative importance of the major dust sources. During the Last Glacial Maximum the dominant source in the model was South America, because of the increased activity of glaciogenic dust sources in Southern Patagonia-Tierra del Fuego and the Southernmost Pampas regions, as well as an increase in transport efficiency southward. Dust emitted from the Southern Hemisphere dust source areas usually follow zonal patterns, but southward flow towards Antarctica is located in specific areas characterized by southward displacement of air masses. Observations and model results consistently suggest a spatially variable shift in dust particle sizes. This is due to a combination of relatively reduced en route wet removal favouring a generalized shift towards smaller particles, and on the other hand to an enhanced relative contribution of dry coarse particle deposition in the Last Glacial Maximum.  相似文献