- Geosciences, Vol. 8, Pages 359: Coupled Model of Bank Erosion and Meander Evolution for Cohesive Riverbanks
In this paper, a physics-based model that couples a bank erosion model with a meander evolution model is developed and evaluated. The physics-based bank erosion model considers the cantilever failure mechanism with slump blocks and decomposition effects. Moreover, bank accretion was considered using critical values of time required for landing, shear stresses and water depths. Two cases were tested. The first case consists of a hypothetical small-scale channel with cohesive riverbanks. Cross sections in the straight and curved part of the channel were compared to evaluate the curvature effect. Furthermore, the effect of the bank strength in the plan shape of the channel was tested in this case. The results show that the curvature increases the erosion rate in the outer bank and changes the cross-sectional profile by narrowing and widening the channel width. The plan shape of the channel changed as the bank strength was increased. In the second case, the model is compared with the River meander migration software (RVR meander) and the advantages and limitations of the model are discussed in terms of meander migration plan form and bank erosion processes. The results showed that the presented model is capable of simulating asymmetric bends.
- Geosciences, Vol. 8, Pages 358: Prediction of Holocene Mercury Accumulation Trends by Combining Palynological and Geochemical Records of Lake Sediments (Black Forest, Germany)
Forest vegetation plays a key role in the cycling of mercury (Hg) and organic matter (OM) in terrestrial ecosystems. Litterfall has been indicated as the major transport vector of atmospheric Hg to forest soils, which is eventually transported and stored in the sediments of forest lakes. Hence, it is important to understand how changes in forest vegetation affect Hg in soil and its biogeochemical cycling in lake systems. We investigated the pollen records and the geochemical compositions of sediments from two lakes (Schurmsee and Glaswaldsee) in the Black Forest (Germany) to evaluate whether long-term shifts in forest vegetation induced by climate or land use influenced Hg accumulation in the lakes. We were particularly interested to determine whether coniferous forests were associated with a larger export of Hg to aquatic systems than deciduous forests. Principal components analysis followed by principal component regression enabled us to describe the evolution of the weight of the latent processes determining the accumulation of Hg over time. Our results emphasize that the in-lake uptake of Hg during warm climate periods, soil erosion after deforestation and emissions from mining and other human activities triggered changes in Hg accumulation during the Holocene stronger than the changes caused by forest vegetation alone.
- Geosciences, Vol. 8, Pages 357: Using a Multi-Proxy Approach to Detect and Date a Buried part of the Hellenistic City Wall of Ainos (NW Turkey)
Throughout mankind’s history, the need to secure and protect the home settlement was an essential one. This holds especially true for the city of Ainos (modern Enez) in Turkish Thrace. Due to its continuous settlement history since the 7th/6th century BC, several different types of city walls were built—sometimes even on top of each other—several of which have been preserved over time. To decipher the construction style, the course and the age of a buried city wall segment in the southern part of the former city, a geoscientific multi-proxy approach including magnetic gradiometer (MG) and electrical resistivity tomography (ERT) measurements in combination with granulometrical, sedimentological and microfaunistical investigations on sediment cores was applied. We were able to (1) present reasonable arguments for its Hellenistic age; (2) reveal the course of this wall segment and extrapolate it further north into a less studied area; and (3) demonstrate that in this near-coastal area, the former swampy terrain had been consolidated for constructing the wall. Our multi-proxy approach serves as a valuable example for investigating buried structures in archaeological contexts, avoiding a less-economical, time-consuming, or even forbidden excavation.
- Geosciences, Vol. 8, Pages 356: Suitability of Boulder Marl and Marsh Clay as Sealing Substrates for Landfill Capping Systems—A Practical Comparison
The effects of compaction on soil shrinkage behavior need to be considered for engineering long-term durable mineral liners of landfill capping systems. For this purpose, a new three-dimensional laser scanning device was coupled with a mathematical-empirical model to simultaneously determine the shrinkage behavior of a boulder marl (bm) and a marsh clay (mc). Therefore, both materials were precompacted in 200 soil cores (100 cm3) on the basis of the Proctor test results with five different degrees of compaction (bm1-bm5; mc1-mc5). Thus, the shrinkage behavior, intensity, and tendency were determined during a standardized drying experiment. The volume shrinkage index was used to describe the pore size dependent shrinkage tendency and was classified as high to very high (11.3–17.7%) for the marsh clay and medium (5.3–9.2%) for the boulder marl. Additionally, only the boulder marl (bm2), compacted up to 88% of Proctor density, could be installed as landfill bottom liner in drier locations if the local matric potentials did not exceed the previously highest observed drying range (i.e. values below −300 hPa), to avoid crack formation and generation.
- Geosciences, Vol. 8, Pages 355: Recession and Ice Surface Elevation Changes of Baranowski Glacier and Its Impact on Proglacial Relief (King George Island, West Antarctica)
Glacial forefields areas are dynamic landscapes, and due to the glacier frontal position changes, they are sensitive to climatic fluctuations. The results of the analysis of aerial photos, satellite imagery, archival maps, and terrestrial laser scanning surveys are presented. These investigations reveal that the ice surface decreased during the period 1989–2001, when almost the entire current forefield was already uncovered. Moreover, it is shown that, since 1969, there has been a relationship between the changes in air temperature and the changes of the annual front position rate of Baranowski Glacier. Specifically, the results demonstrate that during the cooling observed for the Antarctic Peninsula Regions since 2000, there is a deceleration of the recession rate and ice surface elevation changes of Baranowski Glacier. It is also shown that the fluctuation of the areal extent of the glacier as well as ice surface elevation changes are closely associated with proglacial relief. Moreover, it is shown that the difference in the retreat of the northern and southern tongue of the glacier can be explained by the presence of relatively warm water in the shallow bay, which can enhance the melting process of the northern part. In addition, existence of long flutes and crevasse fill ridges on the analyzed forefield of Baranowski Glacier suggest that the former episodes of its surge, which could happen at least in the northern part of the forefield and middle part of the southern forefield of the glacier.
- Continental soil drivers of ammonium and nitrate in Australia
Continental soil drivers of ammonium and nitrate in Australia Juhwan Lee, Gina M. Garland, and Raphael A. Viscarra Rossel SOIL, 4, 213-224, https://doi.org/10.5194/soil-4-213-2018, 2018 Soil nitrogen (N) is an essential element for plant growth, but its plant-available forms are subject to loss from the environment by leaching and gaseous emissions. Still, factors controlling soil mineral N concentrations at large spatial scales are not well understood. We determined and discussed primary soil controls over the concentrations of NH4+ and NO3− at the continental scale of Australia while considering specific dominant land use patterns on a regional basis.
- Refining physical aspects of soil quality and soil health when
exploring the effects of soil degradation and climate change on
biomass production: an Italian case study
Refining physical aspects of soil quality and soil health when exploring the effects of soil degradation and climate change on biomass production: an Italian case study Antonello Bonfante, Fabio Terribile, and Johan Bouma SOIL Discuss., https//doi.org/10.5194/soil-2018-30,2018 Manuscript under review for SOIL (discussion: open, 0 comments) This study is restriced to soil physical aspects of soil quality and – health with the objective to define procedures with worldwide rather than only regional applicability, reflecting modern developments in soil physical research and focusing on important questions regarding possible effects of soil degradation and climate change.
- Physical, chemical, and mineralogical attributes of a representative group of soils from the eastern Amazon region in Brazil
Physical, chemical, and mineralogical attributes of a representative group of soils from the eastern Amazon region in Brazil Edna Santos de Souza, Antonio Rodrigues Fernandes, Anderson Martins De Souza Braz, Fábio Júnior de Oliveira, Luís Reynaldo Ferracciú Alleoni, and Milton César Costa Campos SOIL, 4, 195-212, https://doi.org/10.5194/soil-4-195-2018, 2018 The study refers to a survey of the attributes of the main soil classes of the state of Pará, an eastern Amazon region in Brazil. These soils have good potential for agricultural use under natural conditions. In this study we observed that the soils are predominantly kaolinitic, but have relatively low aluminum and organic matter contents, with huge textural variability. The results enable a better understanding of eastern Amazonian soils, whose area reaches more than 1.2 million km2.
- Using deep learning for Digital Soil Mapping
Using deep learning for Digital Soil Mapping José Padarian, Budiman Minasny, and Alex B. McBratney SOIL Discuss., https//doi.org/10.5194/soil-2018-28,2018 Manuscript under review for SOIL (discussion: open, 0 comments) Digital soil mapping has been widely used as a cost-effective method for generating soil maps. DSM models are usually calibrated using point observations and rarely incorporate contextual information of the landscape. Here, we use convolutional neural networks to incorporate spatial context. We used as input a 3D stack of covariate images to simultaneously predicting organic carbon content at multiple depths. The model reduced the error by 30 % compared with conventional techniques.
- Dynamic modelling of weathering rates – Is there any benefit over steady-state modelling?
Dynamic modelling of weathering rates – Is there any benefit over steady-state modelling? Veronika Kronnäs, Cecilia Akselsson, and Salim Belyazid SOIL Discuss., https//doi.org/10.5194/soil-2018-25,2018 Manuscript under review for SOIL (discussion: final response, 2 comments) Weathering rates in forest soils are important for sustainable forestry, but can't be measured. In this paper, we have modelled weathering with the often used PROFILE model, as well as with the dynamic model ForSAFE, better suited in a changing climate, with changing human activities, but never before tested for weathering calculations. We show that ForSAFE gives comparable weathering rates as PROFILE, but that it shows the variation in weathering with time and is good for scenario modelling.