Reforestation Programs in Southwest China： Reported Success, Observed Failure, and the Reasons Why

Ever since the disastrous floods of 1998, the Chinese government has used the Natural Forest Protection and Sloping Land Conversion Programs to promote afforestation and reforestation as means to reduce runoff, control erosion, and stabilize local livelihoods. These two ambitious programs have been reported as large-scale successes, contributing to an overall increase in China’s forest cover and to the stated goals of environmental stabilization. A small-scale field study at the project level of the implementation of these two programs in Baiwu Township, Yanyuan County, Sichuan, casts doubt upon the accuracy and reliability of these claims of success; ground observations revealed utter failure in some sites and only marginal success in others. Reasons for this discrepancy are posited as involving ecological, economic, and bureaucratic factors. Further research is suggested to determine whether these discrepancies are merely local aberrations or represent larger-scale failures in reforestation programs.     

Pathfinder applications of arsenic, antimony and bismuth in geochemical exploration

The potential applications of As, Sb and Bi as pathfinder elements in geochemical exploration have been researched using a new, rapid technique for the simultaneous determination of the three elements. Following a warm hydrochloric acid sample leach, the volatile hydrides of the elements are generated and flushed into an inductively-coupled plasma linked to an emission spectrometer. The technique offers a combination of good analytical precision and detection limits of 100 ppb for each of the elements.The principal sulphide ore minerals commonly contain traces of As, Sb and Bi, and concentrations of more than 1% of any one of these have been found in some sulphide specimens. During sub-aerial oxidation of sulphides, any As, Sb and Bi present is released and forms dispersion patterns in the surficial environment. Geochemical surveys of localities in the United Kingdom have demonstrated that anomalous dispersion trains of these elements can be detected in the sediments of streams draining the mineralized localities. In a geochemical mapping programme covering 16,000 km² of central Nepal, over 3500 stream sediment samples were analyzed for As, Sb and Bi, and many known occurrences of Cu, Pb and Zn mineralization are reflected by As, Sb and Bi anomalies. However, bedrock lithology appears to be an important factor influencing Sb and Bi dispersion patterns.In the areas studied, some or all of the elements As, Sb and Bi produce stream sediment anomalies that compare favourably in terms of contrast and extent with the heavy metal expressions, even though none of the three elements have been reported as important constituents of the mineralization with which they occur.     

Spatial crime distribution and prediction for sporting events using social media

ABSTRACT

Sporting events attract high volumes of people, which in turn leads to increased use of social media. In addition, research shows that sporting events may trigger violent behavior that can lead to crime. This study analyses the spatial relationships between crime occurrences, demographic, socio-economic and environmental variables, together with geo-located Twitter messages and their ‘violent’ subsets. The analysis compares basketball and hockey game days and non-game days. Moreover, this research aims to analyze crime prediction models using historical crime data as a basis and then introducing tweets and additional variables in their role as covariates of crime. First, this study investigates the spatial distribution of and correlation between crime and tweets during the same temporal periods. Feature selection models are applied in order to identify the best explanatory variables. Then, we apply localized kernel density estimation model for crime prediction during basketball and hockey games, and on non-game days. Findings from this study show that Twitter data, and a subset of violent tweets, are useful in building prediction models for the seven investigated crime types for home and away sporting events, and non-game days, with different levels of improvement.     

Simulation of the size distribution and erosivity of raindrops and throughfall drops

This paper presents a model that simulates the size distribution and erosivity of raindrops and throughfall drops. It utilizes existing models of rainfall drop size distribution and fall velocity and combines them with newly collated evidence of throughfall drop size distributions. A sensitivity analysis reveals that the model is sensitive to parameters that are easily measured or estimated: rainfall intensity, the mean volume drop diameter of the intercepted throughfall, canopy cover, and canopy height. The results of the model may be used at two levels. Firstly, to calculate specifically the size and fall velocity of individual drops, parameters that are needed in studies examining the response of soil surfaces to forces applied by rainfall. Secondly, to produce erosivity indices, based on rainfall intensity but which take account of the effects of a vegetation canopy. The paper shows that while the kinetic energy of rainfall (E(0), J mm^?1 m^?2) may be calculated from an equation of the familiar form: the kinetic energy of throughfall under any canopy may be calculated by combining this equation with another that relates the energy of drops under a 100 per cent canopy cover (E(100)) and the canopy height: .     

Selection of coherent deposit-type locations and their application in data-driven mineral prospectivity mapping

Data-driven prospectivity mapping can be undermined by dissimilarity in multivariate spatial data signatures of deposit-type locations. Most cases of data-driven prospectivity mapping, however, make use of training sets of randomly selected deposit-type locations with the implicit assumption that they are coherent (i.e., with similar multivariate spatial data signatures). This study shows that the quality of data-driven prospectivity mapping can be improved by using a training set of coherent deposit-type locations. Analysis and selection of coherent deposit-type locations was performed via logistic regression, by using multiple sets of deposit occurrence favourability scores of univariate geoscience spatial data as independent variables and binary deposit occurrence scores as dependent variable. The set of coherent deposit-type locations and three sets of randomly selected deposit-type locations were each used in data-driven prospectivity mapping via application of evidential belief functions. The prospectivity map based on the training set of coherent deposit-type locations resulted in lower uncertainty, better goodness-of-fit to the training set, and better predictive capacity against a cross-validation set of economic deposits of the type sought. This study shows that explicit selection of training set of coherent deposit-type locations should be applied in data-driven prospectivity mapping.     

Microtextural constraints on the interplay between fluid–rock reactions and deformation

Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees of embrittlement during exhumation, depending on the extent to which fluid–rock reactions proceeded. At one site, graphitic schists preserve textural evidence for two metamorphic reactions that modified and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction involved net consumption of increasingly CO₂-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I microcracks. Fluid inclusion arrays within the microcracks show that increased from ∼0.1 to 0.6 during decompression from 4.75 to 2 kbar at a reference temperature of 500°C. Titanite consumption is most pronounced within transgranular Mode I microcracks, but microcracks do not crosscut products of this reaction; fluid consumption during reaction was coeval with the end of microcracking, at least on a local scale. At the other site, graphitic schists lack small-scale Mode I cracks as well as evidence for graphite consumption during decompression. SEM imaging shows that graphite is anhedral and pitted at the first site, but occurs in clusters of euhedral grains at the second site. Mass balance calculations demonstrate that rocks with partially consumed graphite were infiltrated by an externally derived, H₂O-rich fluid that drove subsequent graphite-fluid reaction. Evidence for similar fluid infiltration is absent at the second site. Variations in the degree of reaction progress indicate that fluid pathways and deformation style were heterogeneous on the scale of millimeters to kilometers during exhumation from mid-crustal depths.     

Subglacial comminution in the deforming bed: Inferences from SEM analysis

This study investigates the variations in erosional processes beneath Briksdalsbreen; a Norwegian valley glacier, with a thin coarse grained deforming bed. The subglacial zone was investigated in situ, close to the central glacial flow line (Site A) and close to the valley wall (Site B), via boreholes. The till was collected using two different sediment samplers and the bed was examined using a borehole video camera. In order to evaluate how representative borehole sampling was of the subglacial environment, the results from in situ subglacial samples were compared with random samples taken from an exposed subglacial surface in the glacier foreland, as well as a sample taken from the site after glacier retreat. The results indicated that the texture of the exposed subglacial surface was similar to in situ samples from subglacial Site B (close to the valley wall), and that the samples collected with the ‘small’ sediment sampler had the closest fit. SEM analysis revealed eroded quartz grains at both sites as a result of rotation (abrasion) and fracture. The samples from close to the valley wall were very poorly sorted, with evidence for rounding and preservation of pre-weathered surfaces, which suggest that a relatively simple pattern of erosion from crushing to rotation dominated. However, the till from the centre of the glacier was better sorted, more angular, and with few pre-weathered surfaces. We suggest that this results from a more complex glacial erosional history associated with greater strain and longer residence time within the deforming layer. When compared with other deformation tills, it was confirmed that there is a relationship between grain size and erosional style. Clay-rich tills show little comminution, fine sand-rich tills generate a significant silt component, whilst the coarse sand-rich tills at Briksdalsbreen showed complex deformational styles but no significant silt component.     

Bastnäsite-(Ce) at the Nkombwa Hill carbonatite complex, Isoka District, Northeast Zambia

Summary Within the Nkombwa Hill carbonatite complex, bastnäsite-(Ce), (Ce,La)CO₃F, has been identified as an abundant mineral in xenoliths hosted by late-stage ferrocarbonatite sills and dykes. Bastnäsite-(Ce) occurs as fibrous yellow crystals, about 1 µm in size, replacing monazite and in association with baryte, in a matrix of dolomite. In common with bastnäsite-(Ce) from other locations, the bastnäsite-(Ce) of Nkombwa Hill contains up to 70% RE₂O₃, almost entirely as light rare-earth oxides. However, Nkombwa Hill bastnäsite-(Ce) is relatively deficient in La and enriched in Pr and Nd.

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Bastnäsit-(Ce) im Nkombwa Hill Karbonatit-Komplex, Isoka-Distrikt, Nordost-Sambia

Zusammenfassung Im Karbonatit-Komplex von Nkombwa Hill kommt Bastnäsit-(Ce), (Ce-La) CO₃F, als eine weitverbreitete Komponente in Xenolithen in späten Ferrokarbonatit-Lagergängen und Gängen vor. Bastnäsit-(Ce) bildet faserige gelbe Kristalle in einer Matrix aus Dolomit, die ungefähr 1 µm groß sind, Monazit verdrängen und mit Baryt assoziiert sind. Ähnlich wie Bastnäsit von anderen Lokalitäten, enthält auch dieser bis zu 70% RE₂O₃ fast ausschließlich als Oxide der Leichten Seltenen Erden. Der Bastnäsite-(Ce) von Nkombwa Hill ist jedoch relativ verarmt an La und an Pr und Nd angereichert.

     

Fluid variability in 2 GPa eclogites as an indicator of fluid behavior during subduction

Fluid activity ratios calculated between millimeter- to centimeter-scale layers in banded mafic eclogites from the Tauern Window, Austria, indicate that variations in a _{H 2 O} existed between layers during equilibration at P approximately equal to 2GPa and T approximately equal to 625°C, whereas a _{CO 2} was nearly constant between the same layers. Model calculations in the system H₂O–CO₂–NaCl show that these results are consistent with the existence of different saturated saline brines, carbonic fluids, or immiscible pairs of both in different layers. The data cannot be explained by the exisience of water-rich fluids in all layers. The model fluid compositions agree with fluid inclusion compositions from eclogite-stage veins and segregations that contain (1) saline brines (up to 39 equivalent wt. % NaCl) with up to six silicate, oxide, and carbonate daughter phases, and (2) carbonic fluids. The formation of crystalline segregations from fluid-filled pockets or hydrofractures indicates high fluid pressures at 2 GPa; the record of fluid variability in the banded eclogite host rocks, however, implies that fluid transport was limited to local flow along individual layers and that there was no large-scale mixing of fluids during devolatilization at depths of 60–70 km. The lack of evidence for fluid mixing may, in part, reflect variations in wetting behavior of fluids of different composition; nonwetting fluids (water-rich or carbonic) would be confined to intergranular pore spaces and would be essentially immobile, whereas wetting fluids (saline brines) could migrate more easily along an interconnected fluid network. The heterogeneous distribution of chemically distinct fluids may influence chemical transport processes during subduction by affecting mineral-fluid element partitioning and by altering the migration properties of the fluid phase(s) in the downgoing slab.