Preface: Complexity (and simplicity) in landscapes     

Brad Murray  Mark A. Fonstad   《Geomorphology》2007,91(3-4):173

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Does the current Clean Development Mechanism (CDM) deliver its sustainable development claim? An analysis of officially registered CDM projects   总被引：1，自引：1，他引：1  

Christoph Sutter  Juan Carlos Parreño 《Climatic change》2007,84(1):75-90

This article presents an analytical framework for analyzing Clean Development Mechanism (CDM) projects in terms of their contribution to employment generation, equal distribution of CDM returns, and improvement of local air quality. It assesses 16 officially registered CDM projects with regard to whether they fulfill the two objectives required by the Kyoto Protocol: greenhouse gas emission reductions and contribution to sustainable development in the host country. While a large part (72%) of the total portfolio’s expected Certified Emission Reductions (CERs) are likely to represent real and measurable emission reductions, less than 1% are likely to contribute significantly to sustainable development in the host country. According to our analysis, there are currently no UNFCCC registered CDM projects that are likely to fulfill the Kyoto Protocol’s twofold objective of simultaneously delivering greenhouse gas (GHG) emission reduction and contributing to sustainable development.  相似文献   

Integrated application of 2D resistivity and electromagnetic methods to investigate a metallic-sulfide deposit in Soap Gulch,Montana. A case study     

Mohamed Khalil  Akpofure Orubu  Brad Rutherford  Marvin Speece  Fernando Santos  Mohammad Farzamian 《Arabian Journal of Geosciences》2018,11(23):764

Geoelectrical methods involving electrical resistivity tomography (ERT), self-potential (SP), frequency domain electromagnetic (FDEM), and very low frequency (VLF) methods have been used to provide valuable information in locating a known sulfide ore body in Soap Gulch, Montana. The study develops basis of comparison for the geophysical techniques employed. Ranges of resistivity along the area have been established using interpreted ERT which can help to understand the subsurface distribution of sulfides in the area. A sulfide body was delineated from the survey area corresponding to anomalously low resistivity values on the ERT section, negative SP, and high apparent current density zone in VLF. Depth to the localized ore zone ranges approximately from 10 to 20 m. FDEM data reflect the conductivity distribution of the shallow subsurface (less than 6 m deep); hence, the delineated sulfide zone had minimal contribution to FDEM measurements. The results of the study show that SP, VLF, and ERT methods provide significant information in localizing ore bodies. The survey revealed that the resistivity values obtained from ERT profile corroborate the FDEM, SP, and VLF from the area.  相似文献   

Numerical investigation of the effects of upwelling on harmful algal blooms off the west Florida coast     

Lyon W.J. Lanerolle  Michelle C. Tomlinson  Thomas F. Gross  Frank Aikman III  Richard P. Stumpf  Gary J. Kirkpatrick  Brad A. Pederson 《Estuarine, Coastal and Shelf Science》2006,70(4):599

The initiation of the toxic harmful algal bloom (HAB), Karenia brevis, along the west Florida coast has been associated with upwelling events. Upwelling processes may be responsible for the transport of nutrients or algae from deep offshore locations across the Florida shelf to the coast. The influence of coastal wind-driven upwelling on the onset and occurrences of K. brevis in this region was numerically investigated using Rutgers University's Regional Ocean Modeling System. Computations were carried out in an idealized model domain, a two-dimensional slice in the cross-shore and vertical directions. The surface forcing data used was from several offshore meteorological buoys. The motion of the algae was simulated using Lagrangian particles and a passive tracer. The numerical simulations of three K. brevis events in 2000–2002 showed that the particles respond (with upwelling/downwelling) to the along-shore wind stresses as expected and some upwelling was present during the events. Comparison of the passive tracer fields with measured fluorescence data exposed the model's sensitivity to the particular surface forcing data employed and the relatively more significant role played by surface forcing over initial conditions. The present model set-up constitutes a useful predictive tool for conditions conducive to the onset of HABs. It is planned to be used in a real-time mode to aid the NOAA HAB monitoring and forecasting system.  相似文献   

Scaling Agricultural Innovations: Pigeonpea in Malawi     

Brad G. Peter  Joseph P. Messina  April N. Frake  Sieglinde S. Snapp 《The Professional geographer》2018,70(2):239-250

Successful scaling of agricultural development strategies is fundamental to increased production and yields, yet targeting efforts frequently fail to fully consider the underlying biophysical drivers of agricultural marginality, particularly at fine spatial resolutions. We present a heuristic for intelligent targeting, utilizing remotely sensed information to identify the intersection between marginal conditions for performance of a staple crop and the optimal niche for technologies that improve crop performance. Here, we explore the geographic potential of maize diversification with pigeonpea, a crop with soil productivity enhancing properties. Overall, 79 percent of agricultural land in Malawi exhibits climate conditions optimal for pigeonpea cultivation and, in total, approximately 51 percent of Malawian maize-based farming is expected to receive some benefit from pigeonpea integration, with 9 percent receiving predictable and substantial benefits. These findings illustrate the geographic scaling potential of pigeonpea in Malawi and provide direction for informed pigeonpea deployment and market development across the country.  相似文献   

Discriminating assimilants and decoupling deep- vs. shallow-level crystal records at Mount Adams using 238U–230Th disequilibria and Os isotopes     

Brian R. Jicha  Clark M. Johnson  Wes Hildreth  Brian L. Beard  Garret L. Hart  Steven B. Shirey  Brad S. Singer 《Earth and Planetary Science Letters》2009,277(1-2):38-49

A suite of 23 basaltic to dacitic lavas erupted over the last 350 kyr from the Mount Adams volcanic field has been analyzed for U–Th isotope compositions to evaluate the roles of mantle versus crustal components during magma genesis. All of the lavas have (²³⁰Th/²³⁸U) > 1 and span a large range in (²³⁰Th/²³²Th) ratios, and most basalts have higher (²³⁰Th/²³²Th) ratios than andesites and dacites. Several of the lavas contain antecrysts (crystals of pre-existing material), yet internal U–Th mineral isochrons from six of seven lavas are indistinguishable from their eruption ages. This indicates a relatively brief period of time between crystal growth and eruption for most of the phenocrysts (olivine, clinopyroxene, plagioclase, magnetite) prior to eruption. One isochron gave a crystallization age that is ~ 20–25 ka older than its corresponding eruptive age, and is interpreted to reflect mixing of older and juvenile crystals or a protracted period of magma storage in the crust. Much of the eruptive volume since 350 ka consists of lavas that have small to moderate ²³⁰Th excesses (2–16%), which are likely inherited from melting of a garnet-bearing intraplate (“OIB-like”) mantle source. Following melt generation and subsequent migration through the upper mantle, most Mt. Adams magmas interacted with young, mafic lower crust, as indicated by ¹⁸⁷Os/¹⁸⁸Os ratios that are substantially more radiogenic than the mantle or those expected via mixing of subducted material and the mantle wedge. Moreover, Os–Th isotope variations suggest that unusually large ²³⁰Th excesses (25–48%) and high ¹⁸⁷Os/¹⁸⁸Os ratios in some peripheral lavas reflect assimilation of small degree partial melts of pre-Quaternary basement that had residual garnet or Al-rich clinopyroxene. Despite the isotopic evidence for lower crustal assimilation, these processes are not generally recorded in the erupted phenocrysts, indicating that the crystal record of the deep-level ‘cryptic’ processes has been decoupled from shallow-level crystallization.  相似文献   

Collateral consequences of the inhomogeneous distribution of short-lived radionuclides in the solar nebula     

Robert H. NICHOLS  Frank A. PODOSEK  Brad S. MEYER  Cristine L. JENNINGS 《Meteoritics & planetary science》1999,34(6):869-884

Abstract— The presence of several short-lived (now extinct) radionuclides in the early solar system demands that they were synthesized and added to preexisting solar system materials shortly (on a time scale on the order of the relevant radionuclide lifetime) before formation of solar system solids. For diverse reasons, it is often suggested that the solar system distributions of these radionuclides were radically heterogeneous, perhaps because of the late addition. Much attention has been given to the astrophysical circumstances that might govern the synthesis and distribution of these short-lived radionuclides, but comparatively little attention has been devoted to the distribution of cosynthesized isotopes. The focus of this paper is a systematic, quantitative evaluation of the collateral consequences in stable and long-lived isotopes that might be expected if short-lived radionuclides, in particular ²⁶Al or ⁵³Mn, were injected at their canonical levels and inhomogeneously distributed in the early solar system. We mix model massive star yields of Meyer et al. (1995) and Woosley and Weaver (1995) into a reservoir of cosmic composition, as tabulated by Anders and Grevesse (1989). To mitigate the effects of systematic deviations that may be present in these mixtures due to uncertainties in model stellar yields, we follow Timmes and Clayton (1996) and also mix into a “renormalized” proxy solar system composition computed from a galactic chemical evolution model based primarily on the stellar yields of Woosley and Weaver (1995). The results are very unfavorable to the likelihood of heterogeneously distributed ²⁶Al derived from supernova ejecta. If a massive star is invoked to account for ²⁶Al, its ejecta must have been rather uniformly distributed, as inferred from the lack of measured collateral anomalies in several elements, notably Ca, Cr, and Ni. Conversely, if ²⁶Al were indeed radically heterogeneously distributed, some other nucleosynthetic source more efficient at producing ²⁶Al is required. In principle, a similar statement applies to ⁵³Mn, but the situation is more complicated. The inferred anomalies at ⁵³Cr will depend not only on how much ⁵³Mn is added by a heterogeneous component, but also more sensitively on the contributions to the associated stable nuclides, ⁵³Cr, ⁵²Cr, and ⁵⁰Cr. Consideration of predicted collateral anomalies provides no direct support for heterogeneously distributed supernova-derived ⁵³Mn, but the required quantity of supernova contribution, and thus also the collateral anomalies, are much less for ⁵³Mn than for ²⁶Al. With allowance for model calculation uncertainties, it could be argued that anomalies collateral to heterogeneous ⁵³Mn might be small enough to have evaded detection.  相似文献   

Baseline Sediment Trace Metals Investigation: Steinhatchee River Estuary, Florida, Northeast Gulf of Mexico     

Candace A. Trimble  Ronald W. Hoenstine  A. Brad Highley  Joseph F. Donoghue  Paul C. Ragland 《Marine Georesources & Geotechnology》1999,17(2):187-197

This Florida Geological Survey U.S. Department of the Interior, Minerals Manage ment Service Cooperative Study provides baseline data for major and trace metal concentrations in the sediments of the Steinhatchee River estuary. These data are intended to provide a benchmark for comparison with future metal concentration data measurements. The Steinhatchee River estuary is a relatively pristine bay located within the Big Bend Wildlife Management Area on the North Central Florida Gulf of Mexico coastline. The river flows 55 km through woodlands and planted pines before emptying into the Gulf at Deadman Harbor. Water quality in the estuary is excellent at present. There is minimal development within the watershed. The estuary is part of an extensive system of marshes that formed along the Florida Gulf coast during the Holocene marine transgression. Sediment accretion rate measurements range from 1.4 to 4.1 mm yr on the basis of lead-210 measurements. Seventy-nine short cores were collected from 66 sample locations, representing four lithofacies: clay- and organic-rich sands, organic-rich sands, clean quartz sands, and oyster bioherms. Samples were analyzed for texture, total organic matter, total carbon, total nitrogen, clay mineralogy, and major and trace-metal content. Follow ing these analyses, metal concentrations were normalized against geochemical reference elements (aluminum and iron) and against total weight percent organic matter. Metals were also normalized granulometrically against total weight percent fines (0.062 mm). Concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) for all metals except mercury. Mercury concentrations were determined by cold-flameless atomic absorption spectrometry (AAS). Granulo metric measurements were made by sieve and pipette analyses. Organic matter was determined by two methods: weight loss upon ignition and elemental analysis (by Carlo-Erba Furnace) of carbon and nitrogen. X-ray diffraction was used to deter mine clay mineralogy. Trace-metal concentrations were best correlated when normalized with respect to sediment aluminum concentrations. Normalizations indicate that most major and trace-metal concentrations fall within 95 % prediction limits of the expected value. This finding suggests that little significant metal contamination occurred within this system prior to 1994 sediment sampling. Exceptions include lead, mercury, copper, zinc, potassium, and phosphorous. Lead and mercury are elements that generally enter this watershed through atmospheric deposition; thus, anomalous levels of these metals are not necessarily associated with activities within the watershed of the Steinhatchee River estuary. Anomalous concentrations of other metals such as zinc, copper, and phosphorous probably do originate within the Steinhatchee watershed. Copper failed to correlate well with any geochemical or granulometric normalizer, and this condition was not limited to a single facies or area within the estuary. This finding may indicate copper contamination in the system. Increased zinc and copper levels may be attributed to marine paints. Phosphorous levels also appeared to be elevated in a few locations in the two marsh facies sampled. This may be due to nutrient loading from two small communities, Jena and Steinhatchee, or from the application of this element in fertilizer to reduce moisture stress to young planted pines on tree farms within the watershed.  相似文献   

Seasonal reorganization of subglacial drainage inferred from measurements in boreholes     

Shulamit Gordon  Martin Sharp  Bryn Hubbard  Chris Smart  Brad Ketterling  Ian Willis 《水文研究》1998,12(1):105-133

The effect of the formation of a major subglacial drainage channel on the behaviour of the subglacial drainage system of Haut Glacier d'Arolla, Switzerland, was investigated using measurements of borehole water level and the electrical conductivity and turbidity of basal meltwaters. Electrical conductivity profiles were also measured within borehole water columns to identify the water sources driving water level changes, and to determine patterns of water circulation in boreholes. Prior to channel formation, boreholes showed idiosyncratic and poorly coordinated behaviour. Diurnal water level fluctuations were small and driven by supraglacial/englacial water inputs, even when boreholes were connected to a subglacial drainage system. This system appeared to consist of hydraulically impermeable patches interspersed with storage spaces, and transmitted a very low water flux. Drainage reorganization, which occurred around 31 July, 1993, in response to rapidly rising meltwater and rainfall inputs, seems to have involved the creation of a connection between an incipient channel and a well-established channelized system located further down-glacier. Once a major channel existed within the area of the borehole array, borehole water level fluctuations were forced by discharge-related changes in channel water pressure, although a diversity of responses was observed. These included (i) synchronous, (ii) damped and lagged, (iii) inverse, and (iv) alternating inverse/lagged responses. Synchronous responses occurred in boreholes connected directly to the channel, while damped and lagged responses occurred in boreholes connected to it by a more resistive drainage system. Pressure variations within the channel resulted in diurnal transfer of mechanical support for the ice overburden between connected and unconnected areas of the bed, producing inverse and alternating patterns of water level response. © 1998 John Wiley & Sons, Ltd.  相似文献   

Mineralogy and geochemistry of atypical reduction spheroids from the Tumblagooda Sandstone,Western Australia     

David C. M. Fox  Samuel C. Spinks  Robert L. Thorne  Milo Barham  Mehrooz Aspandiar  Joseph G. T. Armstrong  Tonguç Uysal  Nicholas E. Timms  Mark A. Pearce  Michael Verrall  Belinda Godel  Brad Whisson 《Sedimentology》2020,67(1):677-698

Reduction spheroids are small-scale, biogenic, redox-controlled, metal enrichments that occur within red beds globally. This study provides the first analysis of the compositionally unique reduction spheroids of the Tumblagooda Sandstone. The work aims to account for their composition and consequently improve existing models for reduction spheroids generally, which presently fail to account for the mineralogy of the Tumblagooda Sandstone reduction spheroids. Interstitial areas between detrital grains contained in the cores of these reduction spheroids are dominated by microplaty haematite, in addition to minor amounts of svanbergite, gorceixite, anatase, uraninite, monazite and illite. The haematite-rich composition, along with an absence of base metal phases and the vanadiferous mica roscoelite, makes these reduction spheroids notable in comparison to other global reduction spheroid occurrences. Analyses of illite crystallinity provide values for samples of the Tumblagooda Sandstone host rock corresponding to heating temperatures of ca 200°C. Consequently, while Tumblagooda Sandstone reduction spheroids formed via the typical metabolic processes of dissimilatory metal-reducing bacteria, the combination of a unique mineralogy and illite crystallinity analysis provides evidence of more complex late-stage heating and reoxidation. This has not previously been recognised in other reduction spheroids and therefore expands the existing model for reduction spheroid genesis by also considering the potential for late-stage alteration. As such, future reduction spheroid studies should consider the potential impact of post-formation modification, particularly where they are to be used as evidence of ancient microbial processes; such as in the search for early evidence of life in the geological record on Earth or other planets. Additionally, because of their potential for modification, reduction spheroids serve as a record of the redox history of red beds and their study could provide insights into the evolution of redox conditions within a given red bed during its diagenesis. Finally, this paper also provides insights into the relatively understudied diagenetic history of the Tumblagooda Sandstone; supplying the first reliable and narrow constraints on its thermal history. This has important implications for the thermal history of the Carnarvon Basin and its petroleum prospectivity more broadly.  相似文献