Must critical state theory be revisited to include fabric effects?

Critical state (CS) is a physically observed state of granular materials at failure, based on which the critical state theory (CST) was founded. CST attempts to describe analytically the material response when CS failure occurs and constitutes the framework within which constitutive modeling techniques have been developed in the last half-century. The conditions of CST defined as necessary and sufficient to characterize CS do not include fabric orientation of material samples. In the present work, this absence of fabric is discussed in light of a newly developed anisotropic critical state theory (ACST) that enhances the classical CST by introducing an additional condition that fabric must satisfy at CS. The use of ACST framework in constitutive modeling is presented in a generic way, usable in conjunction with various constitutive models that comply with CST. Answers to some fundamental questions are attempted or suggested, e.g., as to whether the conditions of classical CST are necessary and sufficient for CS to occur, whether the ACST is simply a convenient supplement to CST or a necessary enhancement, and if the latter is true, the merits and open questions that arise. The presentation focuses on the justification and thoughts behind the proposed specific features of ACST, provides clarifications not made before, while several suggestions and disclaimers are made, and alternate approaches are proposed for further investigations on the subject matter.     

Will autogenic succession be sufficient to recover from vegetation cover loss or will soil condition need to be addressed in the arid lands of Kuwait?

Intervention is often required for the restoration of damaged arid ecosystems, particularly when the base environmental conditions are no longer suitable for autogenic recovery. Umm Nigga, in Kuwait, was damaged by overgrazing and destructive camping. It is unclear whether its restoration will require remediation of the soil conditions, or whether autogenic succession can occur once the area is fenced and released from this pressure. Thus, in this project, we assessed the current condition of the site by collecting soil samples and vegetation assessment within each ecosystem and determined suitable locations for the re-vegetation of native seeds and seedlings using geographical information system. Our results showed that the vegetation in the coastal portions of the ecosystem was not damaged. However, in the desert ecosystem locations, vegetation cover was very low and composed of very few species in the damaged areas but still, most soil nutrients were in supply similar to that in the control areas. We conclude that soil remediation and re-vegetation are, likely, not necessary to restore the damaged sites in any of these ecosystems. Rather, fencing alone will probably release the ecosystem. With these sites as a model, a conceptual framework is presented for arid ecosystem assessment and restoration planning.     

Flood risk analyses—how detailed do we need to be?

Applied flood risk analyses, especially in urban areas, very often pose the question how detailed the analysis needs to be in order to give a realistic figure of the expected risk. The methods used in research and practical applications range from very basic approaches with numerous simplifying assumptions up to very sophisticated, data and calculation time demanding applications both on the hazard and on the vulnerability part of the risk. In order to shed some light on the question of required model complexity in flood risk analyses and outputs sufficiently fulfilling the task at hand, a number of combinations of models of different complexity both on the hazard and on the vulnerability side were tested in a case study. The different models can be organized in a model matrix of different complexity levels: On the hazard side, the approaches/models selected were (A) linear interpolation of gauge water levels and intersection with a digital elevation model (DEM), (B) a mixed 1D/2D hydraulic model with simplifying assumptions (LISFLOOD-FP) and (C) a Saint-Venant 2D zero-inertia hyperbolic hydraulic model considering the built environment and infrastructure. On the vulnerability side, the models used for the estimation of direct damage to residential buildings are in order of increasing complexity: (I) meso-scale stage-damage functions applied to CORINE land cover data, (II) the rule-based meso-scale model FLEMOps+ using census data on the municipal building stock and CORINE land cover data and (III) a rule-based micro-scale model applied to a detailed building inventory. Besides the inundation depths, the latter two models consider different building types and qualities as well as the level of private precaution and contamination of the floodwater. The models were applied in a municipality in east Germany, Eilenburg. It suffered extraordinary damage during the flood of August 2002, which was well documented as were the inundation extent and depths. These data provide an almost unique data set for the validation of flood risk analyses. The analysis shows that the combination of the 1D/2D model and the meso-scale damage model FLEMOps+ performed best and provide the best compromise between data requirements, simulation effort, and an acceptable accuracy of the results. The more detailed approaches suffered from complex model set-up, high data requirements, and long computation times.     

Can pyrolysis-GC/MS be used to estimate the degree of thermal alteration of black carbon?

Very little is known about the macromolecular properties of biomass combustion residues referred to as black carbon (BC). Pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS) was performed on: (i) peat from Spain at 400–1200 °C to investigate the effect of charring on pyrolysis fingerprint and (ii) natural charcoal from Laos in order to link molecular information to published chemical and reactivity parameters. Confirming earlier Py-GC/MS studies, the BC in the artificially charred peat and the natural charcoal produced predominantly benzene, toluene, C₂-benzenes, PAHs and benzonitriles. Furthermore, some charcoal samples produced significant amounts of phenols, methoxyphenols, carbohydrate markers, n-alkanes and n-alkenes upon pyrolysis, reflecting non-charred and weakly charred biomass. A series of pyrolysis product ratios related to the degree of dealkylation of the pyrolysis products (benzene/toluene, naphthalene/C₁-naphthalenes, C₁-naphthalenes/C₂-naphthalenes, benzofuran/C₁-benzofurans and benzonitrile/C₁-benzonitrile) increased with increasing artificial charring (peat) and, for the natural charcoal, these ratios were in accordance with established chemical and reactivity parameters related to charring intensity from other methods: proportion of aromatic C obtained from solid state ¹³C nuclear magnetic resonance spectroscopy (NMR), the proportion of charred material as estimated from NMR in conjunction with a molecular mixing model (NMR–MMM) and the resistance to acid dichromate oxidation. The alkyl side chains of aromatic pyrolysis products are probably inherited from short chain aliphatic C chains that cross link the predominantly aromatic building blocks of BC, and these linkages seem to disappear with increasing charring intensity. Thus, the degree of thermal alteration of BC can be discerned from the pyrolysis fragmentation pattern.     

Can the vapour phase be neglected to estimate bulk salinity of halite bearing aqueous fluid inclusions?

The bulk salinity cannot be directly obtained from the dissolution temperatures of halite in highly saline fluid inclusions that contain solid, liquid, and vapour at room temperature. At least two of the following independent parameters must be determined to estimate the bulk composition and density of these inclusions: 1. dissolution temperature of halite in the presence of vapour; 2. total homogenization temperature of liquid and vapour; and 3. volume fraction of the vapour phase. A new V ^m -x diagram for phase stabilities in the H₂O-NaCl system has been constructed to obtain these bulk fluid properties from inclusions that homogenize liquid and vapour phase at higher temperatures than dissolution of halite.     

“One needs to be very brave to stand all that”: Cycling,rational dress and the struggle for citizenship in late nineteenth century Britain

The article discusses changing ideas around citizenship through an analysis of first person accounts of women cyclists in Rational Dress in late nineteenth century Britain. A close reading of personal correspondence provides a sense of how it felt to cycle while dressed in new mobility costumes, such as bloomers, in urban and suburban English landscapes. Such attired and independently mobile women affirmed or unsettled onlooker’s understandings of how middle and upper class women should look and act in public. Some viewers subjected them to verbal and often physical assault. Others, in awe of their socio-technical sophistication were more supportive. Taking a ’bloomer point of view’ provides a unique socio-material way of gaining a deeper understanding of what enabled and also inhibited women’s claims to citizenship and freedom of movement, especially at a time when women were not citizens in a legal sense. I argue that through these richly described accounts we gain insightful glimpses into how individual sensory, embodied and political experiences collectively illuminate the becoming of ’citizen’ as it relates to mobility, gender and landscape.     

Can shells of freshwater mussels (Unionidae) be used to estimate low summer discharge of rivers and associated droughts?

This paper examines if shell oxygen isotope ratios (δ¹⁸O_ar) of Unio sp. can be used as a proxy of past discharge of the river Meuse. The proxy was developed from a modern dataset for the reference time interval 1997–2007, which showed a logarithmic relationship between discharge and measured water oxygen isotope ratios (δ¹⁸O_w). To test this relationship for past time intervals, δ¹⁸O_ar values were measured in the aragonite of the growth increments of four Unio sp. shells; two from a relatively wet period and two from a very dry time interval (1910–1918 and 1969–1977, respectively). Shell δ¹⁸O_ar records were converted into δ¹⁸O_w values using existing water temperature records. Summer δ¹⁸O_w values, reconstructed from δ¹⁸O_ar of 1910–1918, showed a similar range as the summer δ¹⁸O_w values for the reference time interval 1997–2007, whilst summer reconstructed δ¹⁸O_w values for the time interval 1969–1977 were anomalously high. These high δ¹⁸O_w values suggest that the river Meuse experienced severe summer droughts during the latter time interval. δ¹⁸O_w values were then applied to calculate discharge values. It was attempted to estimate discharge from the reconstructed δ¹⁸O_w values using the logarithmic relationship between δ¹⁸O_w and discharge. A comparison of the calculated summer discharge results with observed discharge data showed that Meuse low-discharge events below a threshold value of 6 m³/s can be detected in the reconstructed δ¹⁸O_w records, but true quantification remains problematic.     

Metallic Reserves of Submarine Manganese Nodules to be Estimated and Harnessed Prudently: Evidence from China’s Jiaolong Manned Submersible

Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876,research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown,spherical or massive Mn-bearing ores,deposits of which are found on the sea bottom.The nodules are a mixture of silicate and insoluble potassium permanganates (also with sub-Ti,Fe and Na permanganates) that contain more than 30 kinds of metallic elements,among which those of greatest economic interest are Mn (27-30％),Ni(1.25-1.5％),Cu(1-1.4％),Co(0.2-0.25 ％),Fe,Si,and Al,with minor amounts of Ca,Na,K,Ti,B,H and O.     

Instructions to authors

The Chinese Journal of GEOCHEMISTRY is published quarterly and edited by a distinguished editorial committee under the auspices of the Institute of Geochemistry, Chinese Academy of Sciences, and published by Science in China Press and Springer.     

Instructions to authors

The Chinese Journal of GEOCHEMISTRY is published quarterly and edited by a distinguished editorial committee under the auspices of the Institute of Geochemistry,     

Instructions to authors

The Chinese Journal of GEOCHEMISTRY is published quarterly and edited by a distinguished editorial committee under the auspices of the Institute of     

Instructions to authors

The Chinese Journal of GEOCHEMISTRY is published quarterly and edited by a distinguished editorial committee under the auspices of the Institute of Geochemistry, Chinese Academy of Sciences, and published by Science in China Press and Springer.     

Metal ions bound to colloids from database to field systems

Nowadays, environmental problems related to soil pollution with heavy metals are numerous, therefore, it is important to understand metal behavior in aquatic sediments and soils and to appreciate their transfer. The fate of the metals in the environment is closely related to their interactions with the major reactive compartments （organic matter, iron and manganese oxides, clays）. The objective of this work is to develop an approach based on the combination of several models to study metal ion speciation in different environmental systems. Models used to describe the interactions of metals with the main reactive phases in the soil are CD-MUSIC （amorphous and crystallized iron oxides）, NICA-Donnan （organic matter and manganese oxides）, and cationic ion exchange model （clays）. Firstly, this work implies the definition of generic parameters to describe the interactions of the studied metals with iron and manganese oxides, a part of this information is missing in the literature. Then, after the validation of the approach by comparison with analytical results, this multi-surface model is applied to test sites corresponding to a soil and to two riverine environments. These new models give good predictions of the behavior of major and trace metal ions even in heterogeneous system characteristics of the natural environment. The measured free metal concentrations in the solution are in agreement with those obtained from model calculations.