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131.
Claire Rollion-Bard Dominique Blamart Grégory Tricot Jean-Pierre Cuif 《Geochimica et cosmochimica acta》2011,75(4):1003-1012
Dissolved boron in modern seawater occurs in the form of two species, trigonal boric acid B(OH)3 and tetrahedral borate ion . One of the key assumption in the use of boron isotopic compositions of carbonates as pH proxy is that only borate ions, , are incorporated into the carbonate. Here, we investigate the speciation of boron in deep-sea coral microstructures (Lophelia pertusa specimen) by using high field magic angle spinning nuclear magnetic resonance (11B MAS NMR) and electron energy-loss spectroscopy (EELS). We observe both boron coordination species, but in different proportions depending on the coral microstructure, i.e. centres of calcification versus fibres. These results suggest that careful sampling is necessary before performing boron isotopic measurements in deep-sea corals. By combining the proportions of B(OH)3 and determined by NMR and our previous ion microprobe boron isotope measurements, we propose a new equation for the relation between seawater pH and boron isotopic composition in deep-sea corals. 相似文献
132.
Nicolas Jeannée Eric Bardou Claire Faucheux Pascal Ornstein 《Mathematical Geosciences》2013,45(5):591-599
The Glacier Bonnard is a rock glacier located in the State of Valais, Switzerland. It overhangs a settlement and its slow downward constant creep constitutes an environmental hazard. It is therefore important to understand the glacier’s internal structure, particularly in terms of ice content, in order to evaluate its current global dynamic and future evolution. Following preliminary geophysical investigations, several boreholes have been drilled to measure the thickness of the glaciated mass and the vertical distribution of lithology and ice content. These new data are helpful in assessing the amount of ice within the Glacier Bonnard. Two geostatistical modeling approaches are considered: a direct modeling of ice content and an indirect approach linking together lithology and ice content by the use of the plurigaussian algorithm. Comparisons between these approaches are made in terms of ice content prediction and of global ice mass within the sampled area; they underline the benefit of the geostatistical modeling and particularly the advantages of the indirect approach. 相似文献
133.
Monitoring US agriculture: the US Department of Agriculture,National Agricultural Statistics Service,Cropland Data Layer Program 总被引:6,自引:0,他引:6
The National Agricultural Statistics Service (NASS) of the US Department of Agriculture (USDA) produces the Cropland Data Layer (CDL) product, which is a raster-formatted, geo-referenced, crop-specific, land cover map. CDL program inputs include medium resolution satellite imagery, USDA collected ground truth and other ancillary data, such as the National Land Cover Data set. A decision tree-supervised classification method is used to generate the freely available state-level crop cover classifications and provide crop acreage estimates based upon the CDL and NASS June Agricultural Survey ground truth to the NASS Agricultural Statistics Board. This paper provides an overview of the NASS CDL program. It describes various input data, processing procedures, classification and validation, accuracy assessment, CDL product specifications, dissemination venues and the crop acreage estimation methodology. In general, total crop mapping accuracies for the 2009 CDLs ranged from 85% to 95% for the major crop categories. 相似文献
134.
Claire H. Jarvis Neil Stuart William Cooper 《International journal of geographical information science》2013,27(6):495-516
The wider uptake of GIS tools by many application areas outside GIScience means that many newer users of GIS will have high-level knowledge of the wider task, and low-level knowledge of specific system commands as given in reference manuals. However, these newer users may not have the intermediate knowledge that experts in GI science have gained from working with GI systems over several years. Such intermediate knowledge includes an understanding of the assumptions implied by the use of certain functions, and an appreciation of how to combine functions appropriately to create a workflow that suits both the data and overall goals of the geographical analysis task. Focusing on the common but non-trivial task of interpolating spatial data, this paper considers how to help users gain the necessary knowledge to complete their task and minimise the possibility of methodological error. We observe that both infometric (or cognitive) knowledge and statistical knowledge are usually required to find a solution that jointly and efficiently meets the requirements of a particular user and data set. Using the class of interpolation methods as an example, we outline an approach that combines knowledge from multiple sources and argue the case for designing a prototype ‘intelligent’ module that can sit between a user and a given GIS. The knowledge needed to assist with the task of interpolation is constructed as a network of rules, structured as a binary decision tree, that assist the user in selecting an appropriate method according to task-related knowledge (or ‘purpose’) and the characteristics of the data sets. The decision tree triggers exploratory diagnostics that are run on the data sets when a rule requires to be evaluated. Following evaluation of the rules, the user is advised which interpolation method might be and should not be considered for the data set. Any parameters required to interpolate the particular data set (e.g. a distance decay parameter for Inverse Distance Weighting) are also supplied through subsequent optimisation and model selection routines. The rationale of the decision process may be examined, so the ‘intelligent interpolator’ also acts as a learning tool. 相似文献
135.
We use two independent General Circulation Models (GCMs) to estimate surface winds at Titan’s Ligeia Mare (78° N, 250° W), motivated by a proposed mission to land a floating capsule in this ~500 km hydrocarbon sea. The models agree on the overall magnitude (~0.5–1 m/s) and seasonal variation (strongest in summer) of windspeeds, but details of seasonal and diurnal variation of windspeed and direction differ somewhat, with the role of surface exchanges being more significant than that of gravitational tides in the atmosphere. We also investigate the tidal dynamics in the sea using a numerical ocean dynamics model: assuming a rigid lithosphere, the tidal amplitude is up to ~0.8 m. Tidal currents are overall proportional to the reciprocal of depth—with an assumed central depth of 300 m, the characteristic tidal currents are ~1 cm/s, with notable motions being a slosh between Ligeia’s eastern and western lobes, and a clockwise flow pattern.We find that a capsule will drift at approximately one tenth of the windspeed, unless measures are adopted to augment the drag areas above or below the waterline. Thus motion of a floating capsule is dominated by the wind, and is likely to be several km per Earth day, a rate that will be readily measured from Earth by radio navigation methods. In some instances, the wind vector rotates diurnally such that the drift trajectory is epicyclic. 相似文献
136.
Stéphane Audry Henriette Ateba Bessa Jean-Pierre Bedimo Bedimo Jean-Loup Boeglin Laurie Boithias Jean-Jacques Braun Bernard Dupré Mikael Faucheux Christelle Lagane Jean-Christophe Maréchal Jules Remy Ndam-Ngoupayou Bernadette Nka Nnomo Justin Nlozoa Jean-Claude Ntonga Olivier Ribolzi Jean Riotte Emma Rochelle-Newall Laurent Ruiz 《水文研究》2021,35(5):e14138
Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modelling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented in the past 25 years, only a few are located in the humid Tropics despite the importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents, size of river systems, etc. Since 1994, weathering and erosion processes and fluxes have been investigated at both local (experimental watershed) and regional scales in the Nyong River Basin (Cameroon) which belongs to the Critical Zone Observatories network named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Cameroon are: (1) rainfall; (2) air temperature, air relative humidity, wind speed and direction, and global radiation; (3) stream and river water level; (4) pH, electrical conductivity, water temperature and suspended particulate matter (SPM) concentration; (5) major ion, alkalinity and dissolved organic carbon (DOC) concentrations. The dataset already contributed to describe the water partitioning in these tropical humid watersheds, to better understand the factors controlling chemical weathering and physical erosion in tropical ecosystems, particularly the role of organic matter. The dataset also contributed to calculate elemental weathering fluxes and saprolite production rate and to propose denudation rates on tropical cratonic landscapes. Hydrological modelling allowed quantification of the geographical water sources contributing to streamflow. DOC data were used to determine greenhouse-gas emissions and carbon budgets from African inland waters. However, long-term solute concentrations at the outlet of a small tributary of the Nyong River exhibit non-stationary behaviour over the last 26 years. The processes governing those fluctuations are not yet fully understood and might be related to changes in the hydrological regime, land-cover and land-use. The latter highlights the need for longer time-series and continued support for CZOs particularly in the humid tropics. 相似文献
137.
The chemical compositions of tephra shards are widely utilised in a myriad of disciplines, including volcanology, petrology, tephrochronology, palaeoecology and climate studies. Previous research has raised concerns over the possible chemical alteration of microscopic (<100 µm) volcanic glass shards through standard extraction procedures, such as the widely used acid digestion method. This study subjects 10 samples of well‐characterised volcanic glasses ranging from basalt to rhyolite to three common methods used in the extraction of volcanic material from lake sediments and peats. The major element geochemistry of each sample was analysed and compared with a control group. The results of this test indicate that basaltic and andesitic glasses are highly susceptible to chemical alteration, particularly to the concentrated corrosive materials used in acid and base digestion techniques. PERMANOVA analysis of the variation within groups suggests that the oxides most susceptible to variation are alkalis from groups I and II (K2O, Na2O, CaO, MgO) and SiO2, and the most stable oxides are Al2O3 and FeO. Felsic glasses are considerably less susceptible to alteration by both acidic (HCl, HNO3, H2SO4) and alkaline (KOH) digestions. Our findings have important implications for interpreting the geochemistry of volcanic glasses. Copyright © 2019 John Wiley & Sons, Ltd. 相似文献
138.
An essential component of ecosystem-based approaches in coastal zone management and the emerging field of marine planning are partnerships and collaborations between a range of multi-sector organisations and individuals. Ensuring that partnerships are effective is a priority for those responsible for planning and management in coastal and marine environments. Current partnership evaluation approaches, however, tend to view effectiveness as the cumulative end result of a set of variables acting in a linear process at a specific point in time. Given that governance and participation are acknowledged as non-linear and multifaceted processes, more reflective and nuanced approaches that take account of the dynamic, multidimensional and geographically embedded nature of the collaborative process are needed. This paper proposes a new framework for partnership evaluation based on policy narratives and indicators, and demonstrates the potential of the approach using three case studies of partnerships focused upon marine nature-based tourism. The insights from this research have direct relevance to the agencies and organisations responsible for delivering integrated coastal management, including marine spatial planning. 相似文献
139.
This paper presents how environmental concerns emanating outside the Common Fisheries Policy (CFP) are increasingly setting the stage for EU fisheries management. This is illustrated via what is termed the exogenous entrance of environmental concerns through the implementation of directives in EU policy. More endogenous entrance of environmental concerns occurs via stakeholder participation in Regional Advisory Councils (RACs) as well as market mechanisms, such as ecolabelling and traceability. This study discusses how these latter channels of environmental concern may have become a more potent and efficient way of reaching environmental goals, outside of the primacy of the CFP. 相似文献
140.
A model is proposed for determining the temporal and spatial patterns of anthropogenic heat fluxes in UK urban areas. It considers buildings, traffic, and metabolic heat flux sources and has been evaluated to a good accuracy against alternative data for the Greater Manchester area in the UK. Results are presented at spatial resolution of 200 ×?200 m although the model itself is scalable depending on data availability. In this paper, results are generated using a set of urban morphology units so that detailed and time-consuming accounting of individual building and road emissions is not required. The model estimates a mean heat emission of 6.12 Wm-2 across Greater Manchester, with values in the region of 10 Wm-2 for non central urbanized areas and 23 Wm-2 in city center areas. Despite this difference, the results are not described by a simple distance decay function, as has been reported for other cities, due to the influence of satellite towns and the influence of the road network. Buildings are the dominant emitter, contributing some 60% of total emissions across the city compared to around 32% for road traffic and 8% for metabolic sources. 相似文献