SfM-MVS Photogrammetry for Splash Erosion Monitoring under Natural Rainfall     

Tomáš Laburda  Josef Krása  David Zumr  Jan Devátý  Michal Vrána  Nives Zambon  Lisbeth Lolk Johannsen  Andreas Klik  Peter Strauss  Tomáš Dostál 《地球表面变化过程与地形》2021,46(5):1067-1082

An understanding of splash erosion is the basis to describe the impact of rain characteristics on soil disturbance. In typical splash cup experiments, splashed soil is collected, filtered, and weighed. As a way to collect additional data, our experiments have been supplemented by a photogrammetric approach. A total of three soils were tested across three sites, one in the Czech Republic and two in Austria, all equipped with rain gauges and disdrometers to measure rainfall parameters. The structure from motion multiview stereo (SfM-MVS) photogrammetric method was used to measure the raindrops impact on the soil surface. The images were processed using Agisoft PhotoScan, resulting in orthophotos and digital elevation models (DEMs) with a resolution of 0.1 mm/pix. The surface statistics included the mean surface height (whose standard deviation was used as a measure of surface roughness), slope, and other parameters. These parameters were evaluated depending on soil texture and rainfall parameters. The results show a linear correlation between consolidation and splash erosion with a coefficient of determination (R²) of approximately 0.65 for all three soils. When comparing the change in soil volume with rainfall parameters, the best correlation was found with the maximum 30-minintensity (I₃₀), resulting in R² values of 0.48 (soil A, silt loam, 26% clay), 0.59 (soil B, silt loam, 18% clay), and 0.68 (soil C, loamy sand, 12% clay). The initial increase in the sample volume for the lowest splashed mass corresponds with the increase in the clay content of each of the soils. Soil A swells the most. Soil B swells less. Soil C does not swell at all and consolidates the most. We derived the relationship between the photogrammetrically measured change in surface height and the splash erosion (measured by weight) by accounting for the effect of the clay content.  相似文献   

Deciphering seismic and normal-force fluctuation signatures of debris flows: An experimental assessment of effects of flow composition and dynamics     

Tjalling de Haas  Amanda S. Åberg  Fabian Walter  Zhen Zhang 《地球表面变化过程与地形》2021,46(11):2195-2210

Debris flows are gravity-driven mass movements that are common natural hazards in mountain regions worldwide. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of debris flows. A remaining question is to what extent additional flow properties, such as grain-size distribution and flow depth can be inferred reliably from seismic data. Here, we experimentally explore the relation of seismic vibrations and normal-force fluctuations with debris-flow composition and dynamics. We use a 5.4 m long and 0.3 m wide channel inclined at 20°, equipped with a geophone plate and force plate. We show that seismic vibrations and normal-force fluctuations induced by debris flows are strongly correlated, and that both are affected by debris-flow composition. We find that the effects of the large-particle distribution on seismic vibrations and normal-force fluctuations are substantially more pronounced than the effects of water fraction, clay fraction, and flow volume, especially when normalized by flow depth. We further show that for flows with similar coarse-particle distributions seismic vibrations and normal-force fluctuations can be reasonably well related to flow depth, even if total flow volume, water fraction, and the size distribution of fines varies. Our experimental results shed light on how changes in large-particle, clay, and water fractions affect the seismic and force-fluctuation signatures of debris flows, and provide important guidelines for their interpretation.  相似文献   

Crystal structure of meteoritic schreibersites: determination of absolute structure     

Roman Skála  Ivana Císařová 《Physics and Chemistry of Minerals》2005,31(10):721-732

Minerals of the schreibersite–nickelphosphide series (Fe,Ni)₃P crystallize in the non-centrosymmetric space group . As a consequence, they can possess two different spatial arrangements of the constituting atoms within the unit cell, related by the inversion symmetry operation. Here, we present the crystal structure refinements from single crystal X-ray diffraction data for schreibersite grains from iron meteorites Acuña, Carlton, Hex River Mts. (three different crystals), Odessa (two different crystals), Sikhote Alin, and Toluca aiming for the determination of the absolute structure of the examined crystals. The crystals studied cover the composition range from ~58 mol% to ~80 mol% Fe₃P end-member. Unit-cell parameter a and volume of the unit cell V, as well as certain topological structural parameters tightly correlate with Fe₃P content. Unit-cell parameter c, on the other hand, does not show such strong correlation. Eight of the nine crystal structure refinements allowed unambiguous absolute structure assignment. The single crystal extracted from Toluca is, however, of poor quality and consequently the structure refinement did not provide as good results as the rest of the materials. Also, this crystal has only weak inversion distinguishing power to provide unequivocal absolute structure determination. Six of the eight unambiguous absolute structure determinations indicated inverted atomic arrangement compared to that reported in earlier structure refinements (here called standard). Only two grains, one taken from Odessa iron and the other from the Hex River Mts. meteorite, reveal the dominance of standard crystal structure setting.  相似文献   

The spectral hardening associated with the westward travelling surge     

Åke Steen  Georg Gustafsson 《Planetary and Space Science》1981,29(9):1011-1017

Photometer recordings of auroral emissions from N⁺₂ and OI have demonstrated that the ratios between the emissions show a characteristic plateau just prior to the passage of a westward travelling surge. The plateau may be interpreted as a temporary (approx. 1 min) cessation in the spectral hardening of the precipitating particles associated with the surge. The characteristic energy of the plateau is about one keV above the level prior to the beginning of the surge. The results have been interpreted in terms of an instability that is switched on during the time of the plateau and then turned off when the electron density is increased above a certain limit.  相似文献   

Petrological evidence for crustal melting, unmixing, and undercooling in an alkali-calcic, high-level intrusion: the late Sveconorwegian Vinga intrusion, SW Sweden     

H. Årebäck  U. B. Andersson  J. Petersson 《Mineralogy and Petrology》2008,93(1-2):1-46

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Rb-Sr dating of alteration events in granitoids     

Frans E. Wickman  Göran Åberg  Beatriz Levi 《Contributions to Mineralogy and Petrology》1983,83(3-4):358-362

Veins and other effects of low-grade metamorphism are often found in igneous rocks. A method for dating such veins is proposed. It is based on the presence of Ca-bearing, Rb-free minerals in the veins and their aureoles. The method is applicable if five conditions are satisfied. The effects of low-grade metamorphism on Rb-Sr dating of the emplacement (extrusion) age are also studied. Veins and their aureoles in granitoid rocks from Central Sweden are used as a working example. Two groups of vein ages were found, 1600-1500 Ma and 1250-1100 Ma, which coincide with the two known periods of tensional movements in the region. The ratio ⁸⁷Sr/⁸⁶Sr in the aureoles and their neighbourhood at the time of vein formation (Sr(a)) shows several different patterns. One with constant Sr(a), independent of the distance to the vein, indicates complete homogenization at the time of alteration. Another shows an increase in Sr(a) close to the vein, indicating that it was rejuvenated. Furthermore, the Sr ratio might determine whether an alteration effect could be of deuteric origin or not: deuteric effects should be characterized by a Sr(a) value equal to the initial Sr-isotope ratio.  相似文献   

GHG mitigation of agricultural peatlands requires coherent policies   总被引：1，自引：0，他引：1  

Kristiina Regina  Arif Budiman  Mogens H. Greve  Arne Grønlund  Åsa Kasimir  Heikki Lehtonen 《Climate Policy》2016,16(4):522-541

As soon as peat soil is drained for agricultural production, the peat starts to degrade, which causes emissions to the atmosphere. In countries with large peatland areas, the GHG mitigation potential related to management of these soils is often estimated as the highest amongst the measures available in agriculture. Although the facts are well known, the policies leading to diminished emissions are often difficult to implement. We have analysed the reasons why the mitigation potential is not fully utilized and what could be done better in national implementation of climate policies. Four cases are used to illustrate the necessary steps to reach mitigation targets: determining the amount and properties of peat soils, estimating the potential, costs and feasibility of the mitigation measures, and selecting and implementing the best measures. A common feature for all of the cases was that national and international climate policies have increased the public interest in GHG emissions from peat soils and increased the pressure for mitigation. Basically the same factors restrict the implementation of mitigation measures in all countries with significant peat soil areas. The most important of these is lack of policy coherence, e.g. ignoring climate policies when planning land use or agricultural policies. We conclude that GHG mitigation is achieved only if other policies, especially national regulations and strategies, are in line with climate policies.

Policy relevance

Agricultural peat soils could be used to help reach GHG mitigation goals in many countries, but the full potential of mitigation of peat soils is not used. Although peatland cultivation inevitably leads to loss of the whole peat layer and high emissions, there are few incentives or regulation to effectively minimize these losses. This article discusses the possibilities to reduce GHG emissions from agricultural peat soils, with specific emphasis on the barriers of implementing mitigation measures nationally. The lessons learned from the selected cases emphasize the role of all policy makers and their cooperation in planning coherent policies for achieving the goals determined by climate policies.  相似文献   

An integrated geophysical study of arsenic contaminated area in the peninsular Thailand     

K. Wattanasen  Sten-Åke Elming  W. Lohawijarn  T. Bhongsuwan 《Environmental Geology》2006,51(4):595-608

Geophysical surveys were carried out in an arsenic contaminated area, in the Ron Phibun District in southern Thailand. Here, tin and associated minerals, i.e. arsenopyrite and pyrite, have been extracted from granites and natural processes and the mining activities led to arsenic contamination in the environment. Electrical resistivity and self-potential (SP) were used to define the distribution of arsenic contamination in the groundwater. Resistivities of 25–100 Ωm and a positive SP anomaly of 66.0 mV were observed in an area where the arsenic content in auger water at 3.5–5.0 m depths was high, 0.5–5.0 mg/l. Integrated interpretation of resistivity, seismic refraction, GPR and gravity data gave a clear image of subsurface shallow structures (< 30 m depths). There was a good correlation between the resistivity and the gravity data. A subsurface rise was found, which possibly acts as a naturally buried dam, separating a high-contaminated area from a low contaminated area.  相似文献   

Mapping and clustering the adoption of carbon pricing policies: what polities price carbon and why?     

Jakob Skovgaard  Sofía Sacks Ferrari  Åsa Knaggård 《Climate Policy》2019,19(9):1173-1185

Carbon pricing, including carbon taxes and emissions trading, has been adopted by different kinds of polities worldwide. Yet, beyond the increasing adoption over time, little is known about what polities – countries as well as sub- and supranational entities – adopt carbon pricing and why. This paper explores patterns of adoption (both implemented policies and those scheduled to be) through cluster analysis, with the purpose of investigating factors that could explain polities’ decisions to adopt carbon pricing. The study contributes empirically by studying carbon taxes and emissions trading together and by ordering the polities adopting carbon pricing into clusters. It also contributes theoretically, by exploring constellations of variables that drive the adoption of carbon pricing within individual clusters. We investigated 66 adopted policies of carbon pricing, which were divided into five clusters: early adopters, North-American subnational entities, Chinese pilot provinces, second-wave developed polities, and second-wave developing polities. The analysis indicates that the reasons for adopting carbon pricing have shifted over time. While international factors (climate commitments or influences from polities within the same region) are increasingly salient, domestic factors (including crises and income levels) were more important for the early adopters.

Key policy insights

• Carbon pricing has become a global mainstream policy instrument.

• Economic and fiscal crises provide windows of opportunity for promoting carbon pricing.

• The international climate regime can support the adoption of carbon pricing through mitigation commitments and international financial and technical assistance.

• Learning between polities from the same region is a useful tool for promoting carbon pricing.

• Carbon intensive economies tend to prefer emissions trading over carbon taxes.

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Shallow-water tidal analysis at Sharm Obhur,Jeddah, Red Sea     

V.?R.?ShamjiEmail author  T.?C.?Vineesh 《Arabian Journal of Geosciences》2017,10(3):61

Comprehensive field data was collected at Sharm Obhur. This data was processed and analyzed using different harmonic analysis techniques during the period of 2013. Since the measurement of the data was from a shallow-water creek, the data was full of noise and hence was filtered using the MATLAB code. Harmonic analysis techniques such as IOS and Admiralty methods were used for deriving major and minor tidal constituents. The variability in the shallow-water constituents and their selective amplifications were studied with derived constituents. The tidal regime classifications using form factor were carried out by using derived tidal constituents as applied and have been effectively tested in the field condition. The form factor study also shows the mixed semidiurnal nature of the tide in the creek and has been verified with field conditions. The contribution of sea-level variations of shallow-water constituents, Zo, was investigated and analyzed. The study has great practical potential for sea-level variation study and hydrographic-related applications in this region.  相似文献