Micro-spectroscopic investigation of selenium-bearing minerals from the Western US Phosphate Resource Area     

Amy?L?Ryser  Daniel?G?StrawnEmail author  Matthew?A?Marcus  Jodi?L?Johnson-Maynard  Mickey?E?Gunter  Gregory?M?ller 《Geochemical transactions》2005,6(1):1

Mining activities in the US Western Phosphate Resource Area (WPRA) have released Se into the environment. Selenium has several different oxidation states and species, each having varying degrees of solubility, reactivity, and bioavailability. In this study we are investigating the speciation of Se in mine-waste rocks. Selenium speciation was determined using bulk and micro-x-ray absorption spectroscopy (XAS), as well as micro-x-ray fluorescence mapping. Rocks used for bulk-XAS were ground into fine powders. Shale used for micro-XAS was broken along depositional planes to expose unweathered surfaces. The near edge region of the XAS spectra (XANES) for the bulk rock samples revealed multiple oxidation states, with peaks indicative of Se(-II), Se(IV), and Se(+VI) species. Micro-XANES analysis of the shale indicated that three unique Se-bearing species were present. Using the XANES data together with ab initio fitting of the extended x-ray absorption fine structure region of the micro-XAS data (micro-EXAFS) the three Se-bearing species were identified as dzharkenite, a di-selenide carbon compound, and Se-substituted pyrite. Results from this research will allow for a better understanding of the biogeochemical cycling of Se in the WPRA.  相似文献   

Improving the spatial representation of soil properties and hydrology using topographically derived initialization processes in the SWAT model          下载免费PDF全文

Daniel R. Fuka  Amy S. Collick  Peter J.A. Kleinman  Daniel A. Auerbach  R. Daren Harmel  Zachary M. Easton 《水文研究》2016,30(24):4633-4643

Topography exerts critical controls on many hydrologic, geomorphologic and biophysical processes. However, many watershed modelling systems use topographic data only to define basin boundaries and stream channels, neglecting opportunities to account for topographic controls on processes such as soil genesis, soil moisture distributions and hydrological response. Here, we demonstrate a method that uses topographic data to adjust spatial soil morphologic and hydrologic attributes: texture, depth to the C‐horizon, saturated conductivity, bulk density, porosity and the water capacities at field (33 kpa) and wilting point (1500 kpa) tensions. As a proof of concept and initial performance test, the values of the topographically adjusted soil parameters and those from the Soil Survey Geographic Database (SSURGO; available at 1 : 20 000 scale) were compared with measured soil pedon pit data in the Grasslands Soil and Water Research Lab watershed in Riesel, TX. The topographically adjusted soils were better correlated with the pit measurements than were the SSURGO values. We then incorporated the topographically adjusted soils into an initialization of the Soil and Water Assessment Tool model for 15 Riesel research watersheds to investigate how changes in soil properties influence modelled hydrological responses at the field scale. The results showed that the topographically adjusted soils produced better runoff predictions in 50% of the fields, with the SSURGO soils performing better in the remainder. In addition, the a priori adjusted soils result in fewer calibrated model parameters. These results indicate that adjusting soil properties based on topography can result in more accurate soil characterization and, in some cases, improve model performance. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Infrastructure and climate change: a study of impacts and adaptations in Malawi,Mozambique, and Zambia     

Paul S. Chinowsky  Amy E. Schweikert  Niko L. Strzepek  Ken Strzepek 《Climatic change》2015,130(1):49-62

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Is Certification Associated with Better Forest Management and Socioeconomic Benefits? A Comparative Analysis of Three Certification Schemes Applied to Brazil Nuts in Western Amazonia   总被引：1，自引：0，他引：1  

Amy E. Duchelle  Karen A. Kainer  Lúcia H. O. Wadt 《社会与自然资源》2014,27(2):121-139

Nontimber forest product (NTFP) certification has potential to promote sustainable harvest and to bolster rural livelihoods. This research compares environmental and socioeconomic benefits of Brazil nut certification for 231 producers in 17 communities in the trinational border region of Bolivia, Brazil, and Peru during the 2006–2007 harvest. Specific objectives were: (1) to analyze differences in “best management practices” between certified and noncertified producers; (2) to identify socioeconomic benefits associated with certified nuts; and (3) to explore producer perceptions of nut certification. Organic and Fairtrade certification were associated with better postharvest practices and higher prices, while Forest Stewardship Council (FSC) certification was related to preharvest planning. Certification was viewed most positively in Bolivia, where producers gleaned financial and social benefits, moderately in Peru, and least positively in Brazil, where benefits were lower or nonexistent. Partnerships with cooperatives, donors, government, and nongovernmental organizations were essential to maximize conservation and development objectives.  相似文献   

“It's Not Easy Being Green”: Environmental Advocacy and Policymaking in Chile     

Amy Risley 《社会与自然资源》2014,27(4):421-435

This article analyzes the collective action frames used by members of Chilean nongovernmental organizations (NGOs) while engaging in policy advocacy. The focus is a large-scale dam project along the Bío Bío River that generated controversy for more than a decade due to its impact on the environment and indigenous communities. It is argued that the environmental advocates’ reliance on certain frames hindered their ability to influence policymaking. They framed the neoliberal model as “pathologically” growth centered, unjust, and destructive. Additionally, advocates were besieged by counter frames portraying them as foes of modernization. Though compelling, the groups’ frames set them on a collision course with the policymaking establishment. In contrast, members of groups advocating for children used more effective discursive strategies and achieved a greater presence in policy debates. These arguments are supported with qualitative data collected primarily through interviews with NGO members, textual analysis of their documents, and news content analysis.  相似文献   

Development and application of a physically based landscape water balance in the SWAT model   总被引：1，自引：0，他引：1  

Eric D. White  Zachary M. Easton  Daniel R. Fuka  Amy S. Collick  Enyew Adgo  Matthew McCartney  Seleshi B. Awulachew  Yihenew G. Selassie  Tammo S. Steenhuis 《水文研究》2011,25(6):915-925

Watershed scale hydrological and biogeochemical models rely on the correct spatial‐temporal prediction of processes governing water and contaminant movement. The Soil and Water Assessment Tool (SWAT) model, one of the most commonly used watershed scale models, uses the popular curve number (CN) method to determine the respective amounts of infiltration and surface runoff. Although appropriate for flood forecasting in temperate climates, the CN method has been shown to be less than ideal in many situations (e.g. monsoonal climates and areas dominated by variable source area hydrology). The CN model is based on the assumption that there is a unique relationship between the average moisture content and the CN for all hydrologic response units (HRUs), and that the moisture content distribution is similar for each runoff event, which is not the case in many regions. Presented here is a physically based water balance that was coded in the SWAT model to replace the CN method of runoff generation. To compare this new water balance SWAT (SWAT‐WB) to the original CN‐based SWAT (SWAT‐CN), two watersheds were initialized; one in the headwaters of the Blue Nile in Ethiopia and one in the Catskill Mountains of New York. In the Ethiopian watershed, streamflow predictions were better using SWAT‐WB than SWAT‐CN [Nash–Sutcliffe efficiencies (NSE) of 0·79 and 0·67, respectively]. In the temperate Catskills, SWAT‐WB and SWAT‐CN predictions were approximately equivalent (NSE > 0·70). The spatial distribution of runoff‐generating areas differed greatly between the two models, with SWAT‐WB reflecting the topographical controls imposed on the model. Results show that a water balance provides results equal to or better than the CN, but with a more physically based approach. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Carbon–mineral interactions along an earthworm invasion gradient at a Sugar Maple Forest in Northern Minnesota     

Amy Lyttle  Kyungsoo Yoo  Cindy Hale  Anthony Aufdenkampe  Stephen Sebestyen 《Applied Geochemistry》2011

The interactions of organic matter and minerals contribute to the capacity of soils to store C. Such interactions may be controlled by the processes that determine the availability of organic matter and minerals, and their physical contacts. One of these processes is bioturbation, and earthworms are the best known organisms that physically mix soils. Earthworms are not native species to areas previously glaciated, and the introduction of earthworms to these regions has been associated with often dramatic changes in soil structure and geochemical cycles. The authors are studying C mineral interaction along an approximately 200 m long earthworm invasion transect in a hardwood forest in northern Minnesota. This transect extends from the soils where earthworms are absent to soils that have been invaded by earthworms for nearly 30–40 years. Pre-invaded soils have an approximately 5 cm thick litter layer, thin (～5 cm) A horizon, silt rich E horizon, and clay-rich Bt horizons. The A and E horizons formed from aeolian deposits, while the clay-rich Bt horizons probably developed from underlying glacial till. With the advent of earthworm invasion, the litter layer disappears and the A horizons thicken at the expense of the O and E horizons. In addition, organic C contents in the A horizons significantly increase with the arrival of earthworms. Simultaneously, measured mineral specific surface areas suggest that minerals’ capacities to complex the organic matter appear to be greater in soils with active earthworm populations. Based on the data from two end member soils along the transect, mineral specific surface areas in the A and E horizons are larger in the earthworm invaded soil than in the pre-invasion soil. Additionally, within < 5 a of earthworm invasions, A horizon materials are turned from single grain to a strong medium granular structure. While A horizon organic matter content and organic C-mineral complexation increase after earthworm invasion, they are also more vigorously mixed. This growing data set, when ultimately combined with ongoing measurements of (1) the population dynamics of earthworms along the invasion transect, (2) C-mineral association (via surface adsorption and physical collusion in mineral aggregates) and (3) dissolved organic C will show how and how much soil capacity to store C is affected by burrowing organisms, which are often the keystone species of given ecosystems.  相似文献   

Methodology for applying the Limits of Acceptable Change process to the management of recreational boating in the Balearic Islands, Spain (Western Mediterranean)     

Amy Diedrich  Pablo Balaguer Huguet  Joaquín Tintoré Subirana 《Ocean & Coastal Management》2011,54(4):341-351

The objective of this study is to propose a simple methodological approach, based on the Limits of Acceptable Change process, to support the formulation of management measures for recreational boating in bays. Management measures have been determined using statistical and geospatial analyses of data of biophysical characteristics, use, and user perceptions in a bay on the island of Mallorca. The results suggest that the optimal use level of the study site is being surpassed and a range of potential management options is provided. This methodology is applicable to additional management scenarios where balancing social and environmental needs is necessary and should be implemented as part of a broader Integrated Coastal Zone Management framework.  相似文献   

CFSv2 ensemble prediction of the wintertime Arctic Oscillation     

Emily E. Riddle  Amy H. Butler  Jason C. Furtado  Judah L. Cohen  Arun Kumar 《Climate Dynamics》2013,41(3-4):1099-1116

Lagged ensembles from the operational Climate Forecast System version 2 (CFSv2) seasonal hindcast dataset are used to assess skill in forecasting interannual variability of the December–February Arctic Oscillation (AO). We find that a small but statistically significant portion of the interannual variance (>20 %) of the wintertime AO can be predicted at leads up to 2 months using lagged ensemble averages. As far as we are aware, this is the first study to demonstrate that an operational model has discernible skill in predicting AO variability on seasonal timescales. We find that the CFS forecast skill is slightly higher when a weighted ensemble is used that rewards forecast runs with the most accurate representations of October Eurasian snow cover extent (SCE), hinting that a stratospheric pathway linking October Eurasian SCE with the AO may be responsible for the model skill. However, further analysis reveals that the CFS is unable to capture many important aspects of this stratospheric mechanism. Model deficiencies identified include: (1) the CFS significantly underestimates the observed variance in October Eurasian SCE, (2) the CFS fails to translate surface pressure anomalies associated with SCE anomalies into vertically propagating waves, and (3) stratospheric AO patterns in the CFS fail to propagate downward through the tropopause to the surface. Thus, alternate boundary forcings are likely contributing to model skill. Improving model deficiencies identified in this study may lead to even more skillful predictions of wintertime AO variability in future versions of the CFS.  相似文献   

An obsolete dichotomy? Rethinking the rural–urban interface in terms of food security and production in the global south     

Lerner AM  Eakin H 《The Geographical journal》2011,177(4):311-320

The global food system is coming under increasing strain in the face of urban population growth. The recent spike in global food prices (2007–08) provoked consumer protests, and raised questions about food sovereignty and how and where food will be produced. Concurrently, for the first time in history the majority of the global population is urban, with the bulk of urban growth occurring in smaller-tiered cities and urban peripheries, or ‘peri-urban’ areas of the developing world. This paper discusses the new emerging spaces that incorporate a mosaic of urban and rural worlds, and reviews the implications of these spaces for livelihoods and food security. We propose a modified livelihoods framework to evaluate the contexts in which food production persists within broader processes of landscape and livelihood transformation in peri-urban locations. Where and how food production persists are central questions for the future of food security in an urbanising world. Our proposed framework provides directions for future research and highlights the role of policy and planning in reconciling food production with urban growth.  相似文献