The synergistic effect of calcium on organic carbon sequestration to ferrihydrite   总被引：1，自引：0，他引：1  

Tyler D. Sowers  Jason W. Stuckey  Donald L. Sparks 《Geochemical transactions》2018,19(1):4

Sequestration of organic carbon (OC) in environmental systems is critical to mitigating climate change. Organo-mineral associations, especially those with iron (Fe) oxides, drive the chemistry of OC sequestration and stability in soils. Short-range-ordered Fe oxides, such as ferrihydrite, demonstrate a high affinity for OC in binary systems. Calcium commonly co-associates with OC and Fe oxides in soils, though the bonding mechanism (e.g., cation bridging) and implications of the co-association for OC sequestration remain unresolved. We explored the effect of calcium (Ca²⁺) on the sorption of dissolved OC to 2-line ferrihydrite. Sorption experiments were conducted between leaf litter-extractable OC and ferrihydrite at pH 4 to 9 with different initial C/Fe molar ratios and Ca²⁺ concentrations. The extent of OC sorption to ferrihydrite in the presence of Ca²⁺ increased across all tested pH values, especially at pH ≥ 7. Sorbed OC concentration at pH 9 increased from 8.72 ± 0.16 to 13.3 ± 0.20 mmol OC g^?1 ferrihydrite between treatments of no added Ca²⁺ and 30 mM Ca²⁺ addition. Batch experiments were paired with spectroscopic studies to probe the speciation of sorbed OC and elucidate the sorption mechanism. ATR-FTIR spectroscopy analysis revealed that carboxylic functional moieties were the primary sorbed OC species that were preferentially bound to ferrihydrite and suggested an increase in Fe-carboxylate ligand exchange in the presence of Ca at pH 9. Results from batch to spectroscopic experiments provide significant evidence for the enhancement of dissolved OC sequestration to 2-line ferrihydrite and suggest the formation of Fe–Ca-OC ternary complexes. Findings of this research will inform modeling of environmental C cycling and have the potential to influence strategies for managing land to minimize OM stabilization.  相似文献   

Quantifying land use influences on event-based flow frequency,timing, magnitude,and rate of change in an urbanizing watershed of the central USA     

Sean J. Zeiger  Jason A. Hubbart 《Environmental Earth Sciences》2018,77(3):107

There is a need for research that advances understanding of flow alterations in contemporary watersheds where natural and anthropogenic interactions can confound mitigation efforts. Event-based flow frequency, timing, magnitude, and rate of change were quantified at five-site nested gauging sites in a representative mixed-land-use watershed of the central USA. Statistically independent storms were paired by site (n = 111 × 5 sites) to test for significant differences in event-based rainfall and flow response variables (n = 17) between gauging sites. Increased frequency of small peak flow events (i.e., 64 more events less than 4.0 m³ s^?1) was observed at the rural–urban interface of the watershed. Differences in flow response were apparent during drier periods when small rainfall events resulted in increased flow response at urban sites in the lower reaches. Relationships between rainfall and peak flow were stronger with decreased pasture/crop land use and increased urban land use by approximately 20%. Event-based total rainfall explained 40–68% of the variance in peak flow (p < 0.001). Coefficients of determination (r²) were negatively correlated with pasture/crop land use (r² = 0.92; p = 0.007; n = 5) and positively correlated with urban land use (r² = 0.90; p = 0.008; n = 5). Significant differences in flow metrics were observed between rural and urban sites (p < 0.05; n = 111) that were not explained by differences in rainfall variables and drainage area. An urban influence on flow timing was observed using median time lag to peak centroid and time of maximum precipitation to peak flow. Results highlight the need to establish manageable flow targets in rapidly urbanizing mixed-land-use watersheds.  相似文献   

Can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate?     

Gorka Merino  Manuel Barange  Julia L. Blanchard  James Harle  Robert Holmes  Icarus Allen  Edward H. Allison  Marie Caroline Badjeck  Nicholas K. Dulvy  Jason Holt  Simon Jennings  Christian Mullon  Lynda D. Rodwell 《Global Environmental Change》2012,22(4):795-806

Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products.  相似文献   

Holocene alpine glaciation inferred from lacustrine sediments on northeastern Baffin Island,Arctic Canada     

Elizabeth K. Thomas  Jason Szymanski  Jason P. Briner 《第四纪科学杂志》2010,25(2):146-161

With accelerated melting of alpine glaciers, understanding the future state of the cryosphere is critical. Because the observational record of glacier response to climate change is short, palaeo‐records of glacier change are needed. Using proglacial lake sediments, which contain continuous and datable records of past glacier activity, we investigate Holocene glacier fluctuations on northeastern Baffin Island. Basal radiocarbon ages from three lakes constrain Laurentide Ice Sheet retreat by ca. 10.5 ka. High sedimentation rates (0.03 cm a^?1) and continuous minerogenic sedimentation throughout the Holocene in proglacial lakes, in contrast to organic‐rich sediments and low sedimentation rates (0.005 cm a^?1) in neighbouring non‐glacial lakes, suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation. The presence of varves and relatively high magnetic susceptibility from 10 to 6 ka and since 2 ka in one proglacial lake suggest minimum Holocene glacier extent ca. 6–2 ka. Moraine evidence and proglacial and threshold lake sediments indicate that the maximum Holocene glacier extent occurred during the Little Ice Age. The finding that glaciers likely persisted through the Holocene is surprising, given that regional proxy records reveal summer temperatures several degrees warmer than today, and may be due to shorter ablation seasons and greater accumulation‐season precipitation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Integrating downscaled CMIP5 data with a physically based hydrologic model to estimate potential climate change impacts on streamflow processes in a mixed‐use watershed          下载免费PDF全文

Michael G. Sunde  Hong S. He  Jason A. Hubbart  Michael A. Urban 《水文研究》2017,31(9):1790-1803

Climatic changes have altered surface water regimes worldwide, and climate projections suggest that such alterations will continue. To inform management decisions, climate projections must be paired with hydrologic models to develop quantitative estimates of watershed scale water regime changes. Such modeling approaches often involve downscaling climate model outputs, which are generally presented at coarse spatial scales. In this study, Coupled Model Intercomparison Project Phase 5 climate model projections were analyzed to determine models representing severe and conservative climate scenarios for the study watershed. Based on temperature and precipitation projections, output from GFDL‐ESM2G (representative concentration pathway 2.6) and MIROC‐ESM (representative concentration pathway 8.5) were selected to represent conservative (Δ_C) and severe (Δ_S) change scenarios, respectively. Climate data were used as forcing for the soil and water assessment tool to analyze the potential effects of climate change on hydrologic processes in a mixed‐use watershed in central Missouri, USA. Results showed annual streamflow decreases ranging from ?5.9% to ?26.8% and evapotranspiration (ET) increases ranging from +7.2% to +19.4%. During the mid‐21st century, sizeable decreases to summer streamflow were observed under both scenarios, along with large increases of fall, spring, and summer ET under Δ_S. During the late 21st century period, large decreases of summer streamflow under both scenarios, and large increases to spring (Δ_S), fall (Δ_S) and summer (Δ_C) ET were observed. This study demonstrated the sensitivity of a Midwestern watershed to future climatic changes utilizing projections from Coupled Model Intercomparison Project Phase 5 models and presented an approach that used multiple climate model outputs to characterize potential watershed scale climate impacts.  相似文献   

Application of a Bayesian model to infer the contribution of coalbed natural gas produced water to the Powder River,Wyoming and Montana          下载免费PDF全文

Jason M. Mailloux  Kiona Ogle  Carol D. Frost 《水文研究》2014,28(4):2361-2381

The Powder River Basin (PRB) of Wyoming and Montana contains significant coal and coal bed natural gas (CBNG) resources. CBNG extraction requires the production of large volumes of water, much of which is discharged into existing drainages. Compared to surface waters, the CBNG produced water is high in sodium relative to calcium and magnesium, elevating the sodium adsorption ratio (SAR). To mitigate the possible impact this produced water may have on the quality of surface water used for irrigation, the State of Montana passed water anti‐degradation legislation, which could affect CBNG production in Wyoming. In this study, we sought to determine the proportion of CBNG produced water discharged to tributaries that reaches the Powder River by implementing a four end‐member mixing model within a Bayesian statistical framework. The model accounts for the ⁸⁷Sr/⁸⁶Sr, δ¹³C_DIC, [Sr] and [DIC] of CBNG produced water and surface water interacting with the three primary lithologies exposed in the PRB. The model estimates the relative contribution of the end members to the river water, while incorporating uncertainty associated with measurement and process error. Model results confirm that both of the tributaries associated with high CBNG activity are mostly composed of CBNG produced water (70–100%). The model indicates that up to 50% of the Powder River is composed of CBNG produced water downstream from the CBNG tributaries, decreasing with distance by dilution from non‐CBNG impacted tributaries from the point sources to ~10–20% at the Montana border. This amount of CBNG produced water does not significantly affect the SAR or electrical conductivity of the Powder River in Montana. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Constraining Holocene 10Be production rates in Greenland     

Jason P. Briner  Nicolás E. Young  Brent M. Goehring  Joerg M. Schaefer 《第四纪科学杂志》2012,27(1):2-6

The absence of a production rate calibration experiment on Greenland has limited the ability to link ¹⁰Be exposure dating chronologies of ice‐margin change to independent records of rapid climate change. We use radiocarbon age control on Holocene glacial features near Jakobshavn Isbræ, western Greenland, to investigate ¹⁰Be production rates. The radiocarbon chronology is inconsistent with the ¹⁰Be age calculations based on the current globally averaged ¹⁰Be production rate calibration data set, but is consistent with the ¹⁰Be production rate calibration data set from north‐eastern North America, which includes a calibration site nearby on north‐eastern Baffin Island. Based on the best‐dated feature available from the Jakobshavn Isbræ forefield, we derive a ¹⁰Be production rate value of 3.98 ± 0.24 atoms g a^?1, using the ‘St’ scaling scheme, which overlaps with recently published reference ¹⁰Be production rates. We suggest that these ¹⁰Be production rate data, or the very similar data from north‐eastern North America, are used on Greenland. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A Spatial Variant of the Basic Reproduction Number for the New Orleans Yellow Fever Epidemic of 1878     

Andrew Curtis  Jacqueline W. Mills  Jason K. Blackburn 《The Professional geographer》2007,59(4):492-502

A spatial variant of the basic reproduction number (R₀), here defined as the number of subsequent deaths attributed to an initial mortality, can be used to identify geographic variation within an epidemic. A spatial R₀ was calculated at the neighborhood level, here defined by a 50‐m buffer surrounding an index case, for mortality data from the 1878 yellow fever epidemic of New Orleans. The highest number of secondary mortalities linked to a neighborhood index case was twelve, with a further eighty‐seven extrapolated morbidity cases. Results also highlight the importance of multideath residences and cultural contacts in neighborhood‐level disease spread.  相似文献   

A spatial perspective for predicting enrollment in a regional pharmacy school     

Ke Chen  Jason Kennedy  John M. Kovacs  Chunhua Zhang 《GeoJournal》2007,70(2-3):133-143

Having the ability to predict enrollment is an important task for any school’s recruiting team. The purpose of this study was to identify significant factors that can be used to predict the spatial distribution of enrollments. As a case study, we used East Tennessee State University (ETSU) pharmacy school, a regional pharmacy school located in the Appalachian Mountains. Through the application of a negative binomial regression model, we found that the most important indicators of enrollment volume for the ETSU pharmacy school were Euclidean distance, probability (based on competing pharmacy schools’ prestige, driving distance between schools and home and tuition costs), and the natural barrier of the Appalachian Mountains. Using these factors, together with other control variables, we successfully predicted the spatial distribution of enrollments for ETSU pharmacy school. Interestingly, gender also surfaced as a variable for predicting the pharmacy school’s enrollment. We found female students are more sensitive to the geographic proximity of home to school.  相似文献   

Volcanoes of the Tibesti massif (Chad,northern Africa)     

Jason L. Permenter  Clive Oppenheimer 《Bulletin of Volcanology》2007,69(6):609-626

The Tibesti massif, one of the most prominent features of the Sahara desert, covers an area of some 100,000 km². Though largely absent from scientific inquiry for several decades, it is one of the world’s major volcanic provinces, and a key example of continental hot spot volcanism. The intense activity of the TVP began as early as the Oligocene, though the major products that mark its surface date from Lower Miocene to Quaternary (Furon (Geology of Africa. Oliver & Boyd, Edinburgh (trans 1963, orig French 1960), pp 1–377, 1963)); Gourgaud and Vincent (J Volcanol Geotherm Res 129:261–290, 2004). We present here a new and consistent analysis of each of the main components of the Tibesti Volcanic Province (TVP), based on examination of multispectral imagery and digital elevation data acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Our synthesis of these individual surveys shows that the TVP is made up of several shield volcanoes (up to 80 km diameter) with large-scale calderas, extensive lava plateaux and flow fields, widespread tephra deposits, and a highly varied structural relief. We compare morphometric characteristics of the major TVP structures with other hot spot volcanoes (the Hawaiian Islands, the Galápagos Islands, the Canary and Cape Verdes archipelagos, Jebel Marra (western Sudan), and Martian volcanoes), and consider the implications of differing tectonic setting (continental versus oceanic), the thickness and velocity of the lithosphere, the relative sizes of main volcanic features (e.g. summit calderas, steep slopes at summit regions), and the extent and diversity of volcanic features. These comparisons reveal morphologic similarities between volcanism in the Tibesti, the Galápagos, and Western Sudan but also some distinct features of the TVP. Additionally, we find that a relatively haphazard spatial development of the TVP has occurred, with volcanism initially appearing in the Central TVP and subsequently migrating to both the Eastern and Western TVP regions. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.  相似文献