Total Erosion Research Articles

Clinically relevant radiographic progression in joint destruction in RA patients with abnormal MMP-3 or high levels of CRP despite 1-year treatment with infliximab

Objective: Identify the independently related factors of joint destruction progression in RA patients despite of infliximab treatment.Methods: The subjects were cases who underwent infliximab treatment for one year or longer in our department (n = 244). Patients in which modified total sharp score (mTSS), joint erosion (JE), and joint space narrowing (JSN) had advanced to the standard value (3.0) or more for one year were defined as mTSS- Clinically-Relevant-Rapid Progression (CRRP) (n = 20), JE-CRRP (n = 20), and JSN-CRRP (n = 23), and the respective related factors at baseline and week 54 were defined by multiple logistic regression.Results: The median disease duration was 24 months and median mTSS 9.0 at baseline. The median DAS28, CRP, and yearly progression of mTSS improved from 5.8 to 2.6, 1.2 to 0.1 mg/dL, and 4.4 to 0.0 point/year, respectively. The related factor in each of mTSS-CRRP, JE-CRRP, and JSN-CRRP was high CRP levels at baseline. At week 54, the related factor of mTSS-CRRP and JSN-CRRP was high MMP-3 titer; however, the related factor of JE-CRRP was high CRP levels.Conclusion: High CRP levels at baseline were an independent predictive factor of joint destruction advancement during infliximab treatment. Moreover, it was believed that abnormal MMP-3 at week 54 was the index for mTSS and JSN advancement, while high CRP levels were the index for JE advancement.

Assessment of wind and water erosion risk in the watershed of the Ningxia-Inner Mongolia Reach of the Yellow River, China

The watershed of the Ningxia-Inner Mongolia Reach of the Yellow River (NIMRYR) suffers from soil erosion by wind and water because of the wide distribution of deserts and arsenic sandstones in this region. The sediment generated by erosion fed into the Yellow River directly or by its tributaries, silting up the Yellow River and raising the elevation of the river bed. The silting of the Yellow River result in serious flood disasters in this watershed. Therefore, it is urgent to implement soil conservation projects to control wind and water soil erosion. To reach this objective, understanding the spatial and temporal variations of soil erosion in this watershed is very important. In this study, an assessment of soil erosion risk by wind and water was performed based on soil erosion models. The Integrated Wind Erosion Modeling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to estimate the wind erosion modulus in this watershed, and the water erosion modulus was estimated by the Revised Universal Soil Loss Equation (RUSLE). The results show that during 2000s, the wind erosion modulus ranged from 0 to 31,440.4t/km2/a, and the water erosion modulus was from 0 to 24,048.5t/km2/a. Moreover, the total soil erosion modulus by wind and water has ranged from 0 to 32,792.7t/km2/a. Due to the influence of regional weather and geomorphology, occurrences of wind and water erosion in this watershed are not identical in their spatial and temporal patterns. Based on the calculated soil erosion modulus, soil erosion risk was assessed according to the “Classification criteria for soil-erosion intensities” (SL190-2007). It was assumed that the areas with erosion intensity higher than slight were at risk of erosion; by this criterion, more than 34% of the total area of the watershed of the NIMRYR would be at erosion risk. Based on this estimation, it was also found that the NIMRYR watershed is not a region of wind–water erosion crisscross and that land-use conversions have a significant impact on soil erosion.

The soil leakage ratio in the Mudu watershed, China

Soil leakage in karst areas is an important geomorphic agent of environmental interest. There are several viewpoints concerning soil leakage ratios. One viewpoint states that the soil leakage ratio is high in karst regions, whereas others consider that it is very low. This paper’s objective is to describe the soil leakage phenomena qualitatively and quantitatively in the Chongqing Karst, China, by conventional methods such as monitoring runoff plots and paint traces drawn on piles and walls found within runoff plots, and by measuring the activity of the isotope 137Cs at small, medium, and large spatial scales. This paper’s results show that soil-filled karst cracks occurred at a small spatial scale with soil leakage ratios ranging from about 3% to about 34% at two abandoned quarries and six soil profiles with rock (karst) crack development. The soil leakage ratio was almost zero at the medium spatial scale. The soil leakage ratio was 4.50% and the surface-soil erosion ratio was 95.50% of the total soil erosion at the large spatial scale. It is concluded that soil leakage ratios in the study area were low at a large spatial scale, and that cracks in karst were filled with soil at small spatial scales. This paper’s results indicate that soil leakage phenomena vary depending on the processes acting at the small, medium, and large spatial scales.

Intercropping with native perennial plants protects soil of arable fields in semi-arid lands

Surface run-off and erosion are the major contributors to soil degradation worldwide. These processes are especially severe in regions with sparse vegetation cover. A 2-year experiment was set up along an aridity gradient in Al-Khalil, Palestine, to quantify soil loss and water loss from arable fields and to test for the mitigating effect of native perennial filter strips in arable fields. Three useful native plant species were chosen as intercrops: Majorana syriaca, Salvia fruticosa and Salvia hierosolymitana. The water and soil losses were experimentally measured in all the treatments. The results showed that considerable amounts of water (223–288 m3) and soil (3.2–5.6 ton ha−1) are lost from the fields. However, both total run-off and erosion were strongly reduced when the annual crop was intercropped with strips of native perennial plants (NPPs). The filter strips reduced the run-off by 34–89% and soil loss by 45–94%. This effect was more pronounced at the drier part of the studied sites and during the drier season. Our study implies that using filter strips of NPPs is a beneficial strategy for reducing run-off and soil erosion in the semi-arid regions of east Mediterranean.

The characteristics of rill development and their effects on runoff and sediment yield under different slope gradients

Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore, total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the various indices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and -0.98, respectively, indicating that slope gradient is the major factor of affecting the development of rills. Furthermore, runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration, however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.

Comparison of species-rich cover crop mixtures in the Tokaj wine region (Hungary)

Intensive agricultural practices of past decades—such as mechanical cultivation on steep vineyard slopes—can endanger soil fertility. In addition, climate change scenarios predict heavier rainstorms, which can further accelerate soil degradation. Therefore, the use of cover crops in the inter-row has a special importance, particularly on steep slopes and in organic agriculture. A species-rich cover crop mixture helps not only in preventing erosion and providing easier cultivation, but has also positive effects on soil structure, soil fertility and ecosystem functions (Bauer et al. 2004; Hofmann et al. 2008). We began to develop and test several species-rich cover crop mixtures in spring of 2012 in Hungarian vine regions. During the experiments, three species-rich cover crop mixtures (Biocont-Ecovin mixture, mixture of legumes, mixture of grasses and herbs) were compared in vineyards of the Tokaj vine region. Each mixture was sown in three subsequent inter-rows at each site of the experiment. In the control blocks, unsown inter-rows and mechanically cultivated inter-rows were located subsequently next to each other. We studied weed control, yield quantity and must quality in every treatment. We found that the cover of weeds was lower in every treatment compared to the unsown control plots for 2013; thus, cover crops suppressed the weeds of the inter-rows effectively. Most examined indices of grapevines were not significantly affected by the applied cover crops. However, the yield loss results show that under Hungarian climate, the soil coverage in every second inter-row is more recommendable than subsequent seeding, where total erosion control is not required. The interest of the vine growers shows the importance of the topic; thus, we involved other wine regions of Hungary in our further experiments.

黄土高原水蚀风蚀交错带坡耕地土壤风蚀速率空间分布

Wind erosion is difficult to separate from the total erosion in the wind-water erosion crisscross region of the Loess Plateau, regardless of its spatial distribution. Water erosion also contributes to the total erosion. Water and wind erosions affect each other. The methods and techniques used in current research present the most significant limitation. Therefore, the methods and techniques of the field must be improved. A short-lived radionuclide—7Be—was used to trace wind erosion in this study. Surface soil samples (0–30 mm) were collected from two north-faced farmland slopes with sandy loam and clay loam using the transect approach in the Liudaogou Watershed. This study estimated the rates of soil–wind erosion, analyzed the spatial distribution pattern of soil-wind erosion, and discussed its implication to wind conditions and local microreliefs. Results showed that the average rate of wind erosion was 1560.81 t/(km2 a) on sandy loam slope A and 694.26 t/(km2 a) on clay loam slope B. The wind erosion rate decreased from top to bottom for both slopes. Soil particles were coarser, specific surface areas were smaller, and organic matter contents were lower in the surface layer (0–30 mm) after wind erosion than those before wind erosion. The isolines of the wind erosion rate visually showed the wind erosion distribution and indicated that the north wind was the effective resultant wind direction that caused soil loss. The variation in the shape of the isolines reflected the microreliefs of the slopes, and their variation degree denoted the influence degree and scope of microreliefs on wind erosion.

Using cesium-137 to quantify sediment source contribution and uncertainty in a small watershed

Knowledge of sediment provenance is critical for precision conservation planning and calibration of soil erosion models. The objectives are to evaluate the ability of 137Cs to apportion sediment source contributions, quantify uncertainty of the estimates, and estimate desirable sample numbers. We collected 50 surface soil samples from overland in a watershed (15.6km2), 28 subsoil samples from gully bank, and 43 sediment samples in channels. The 137Cs activity was measured by γ spectrometry. Proportion means were calculated by solving a linear mixing model. Uncertainty was estimated by the first-order approximation and Monte Carlo (MC) simulation. The 137Cs tracer was conservative in the fraction of <63μm. The 137Cs activities differed between sources in the whole watershed at P=0.05. The mean proportions of the <63μm fraction (relative error) predicted for the watershed using the mixing model were 0.42 (35%) for the overland source and 0.58 (25%) for the gully source, with a 95% confidence interval of ±0.145 for both. Overland source contributed most uncertainty to the proportion estimates, followed by sediment, with minimum from gully. The MC simulation predicted the same mean proportions, but with relative errors being <3% for both. Compared with the first-order approximation, MC underestimated uncertainty of the means due to the large sample number used in simulation. In general, 30 to 50 samples are needed for each source and sediment to generate reliable estimates using 137Cs. Estimated source proportions of the fine sediment may be converted to proportional contributions of total soil erosion by adjusting by particle sizes and sediment delivery ratio. No adjustment or weighting should be made directly to the mixing model unless conservativeness of the tracer is violated.

River bank erosion and channel evolution in sand-bed braided reach of River Chenab: role of floods during different flow regimes

Braided reaches of large rivers in alluvial plains show major morphological changes, particularly the external bank erosion, due to the flood events. This paper highlights the bank erosion and channel evolution induced by eleven different flood events in a 7-km long reach of the River Chenab, Pakistan. The impact of floods on river bank erosion and channel evolution is analyzed under low and high flow conditions. Flood-induced changes, for river’s external banks and channel evolution, were assessed by processing Landsat ETM+ images in ArcGIS tool, and their inter-relationship is evaluated through regression analysis. The results revealed that the major morphological changes were triggered by the flood events occurred during the high flow or Monsoon season (July–September), whereas the flood events of similar magnitude occurring during low flow season (October–March) did not induce such changes. Mostly, the erosion remained limited to the middle part of the reach, where the branch channel flows along the bank. The average annual bank erosion rates are much higher as compared with a global scale. Data analysis showed a strong correlation between the mean high flows and total bank erosion indicating that Monsoon seasonal flows and floods are responsible for bank erosion. The present study further identifies the river bank locations highly susceptible to erosion by developing the correlation between bank erosion and branch channel progression. Strong correlation for bank erosion could be established with the shift of branch channels position flowing along the banks in braided reaches of sand bed rivers. However, the presence of sand bars along the river banks resulted in reduced erosion that weakens this relationship. The findings of the present study can help develop better understanding about the bank erosion process and constitute a key element to inform and improve river bank management.

Efficacy of bedrock erosion by subglacial water flow

Abstract. Bedrock erosion by sediment-bearing subglacial water remains little-studied; however, the process is thought to contribute to bedrock erosion rates in glaciated landscapes and is implicated in the excavation of tunnel valleys and the incision of inner gorges. We adapt physics-based models of fluvial abrasion to the subglacial environment, assembling the first model designed to quantify bedrock erosion caused by transient subglacial water flow. The subglacial drainage model consists of a one-dimensional network of cavities dynamically coupled to one or several Röthlisberger channels (R-channels). The bedrock erosion model is based on the tools and cover effect, whereby particles entrained by the flow impact exposed bedrock. We explore the dependency of glacial meltwater erosion on the structure and magnitude of water input to the system, the ice geometry, and the sediment supply. We find that erosion is not a function of water discharge alone, but also depends on channel size, water pressure, and sediment supply, as in fluvial systems. Modelled glacial meltwater erosion rates are 1 to 2 orders of magnitude lower than the expected rates of total glacial erosion required to produce the sediment supply rates we impose, suggesting that glacial meltwater erosion is negligible at the basin scale. Nevertheless, due to the extreme localization of glacial meltwater erosion (at the base of R-channels), this process can carve bedrock (Nye) channels. In fact, our simulations suggest that the incision of bedrock channels several centimetres deep and a few metres wide can occur in a single year. Modelled incision rates indicate that subglacial water flow can gradually carve a tunnel valley and enhance the relief or even initiate the carving of an inner gorge.

Soil losses due to carrot harvesting in south central Turkey

Harvest of root crops such as carrots (Daucus carota L.), sugar beets (Beta vulgaris L.), potatoes (Solanum tuberosum L.), and turnips (Brassica rapa) may cause significant losses of soil from croplands. The soil loss due to crop harvesting (SLCH) may be as severe as that by water, wind, and tillage erosion, but experimental data on SLCH, particularly due to carrot harvesting, are limited. Thus, we quantified soil losses due to carrot harvesting in the Konya Basin, south central Turkey, and discussed its implications for the sustainable management and conservation of croplands in the region. About 60% of carrot in Turkey is produced in the Konya Basin. During the harvest season in November 2013, carrot was harvested manually and mechanically at four representative locations and soil removed with the carrot roots was determined. Results showed that the mean annual soil loss was 22.4Mg−1ha−1 for manual and 14.0Mg−1ha−1 for machine harvesting. It is important to note that these large losses of soil due to carrot harvest occur every four years because carrot is grown in a four year rotation with other crops in the study region. Under manual harvesting, clay and soil organic matter content explained 76% of the variability in SLCH. Under machine harvesting, crop yield and the liquid limit of the soil explained 50% of the variability of SLCH. Overall, manual and machine harvests of carrot roots cause significant losses of soil, and can be an important contributor to the total soil erosion in the study region.

降雨能量对东北典型黑土区土壤溅蚀的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 降雨能量对东北典型黑土区土壤溅蚀的影响 DOI: 10.5846/stxb201412312613 作者: 作者单位: 中国科学院 水利部 水土保持研究所,中国科学院 水利部 水土保持研究所,西北农林科技大学 资源环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41571263） Effects of raindrop kinetic energy on splash erosion in the typical black soil region of Northeast China Author: Affiliation: Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources,Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:溅蚀特征研究可揭示溅蚀发生机理，而现有研究大多用溅蚀量来表征溅蚀特征，不能全面准确地反应溅蚀作用过程。为此，基于改进的试验土槽进行室内模拟降雨试验，研究降雨能量对坡面不同方向溅蚀量及溅蚀过程的影响。试验设计包括2种降雨强度（50 mm/h和100 mm/h）和10个降雨能量，其中10个降雨能量是通过2种降雨强度（50 mm/h和100 mm/h）和5个雨滴降落高度（3.5，5.5，7.5，9.5、11.5 m）来实现的。结果表明：在相同降雨强度下，坡面总溅蚀分量均随降雨能量的增加而增大。次降雨坡面溅蚀量均为向下坡最大，其次为侧坡溅蚀量，而向上坡溅蚀量最小。当降雨强度由50mm/h增加至100mm/h时，坡面向上坡溅蚀量增加2.3-5.0倍，向下坡溅蚀量增加1.7-5.1倍，侧坡溅蚀量增加1.9-4.3倍，总溅蚀量增加1.9-4.5倍，净溅蚀量增加1.2-6.4倍。对于不同降雨能量处理，坡面溅蚀率均表现为坡面产流前随降雨历时的增加而递增，产流后迅速达到峰值，之后逐渐减小并趋于稳定。定量分析了各溅蚀分量、总溅蚀量、净溅蚀量与降雨能量的关系，提出了溅蚀发生的降雨能量阈值，发现雨滴溅蚀发生的临界能量为3-6 J m-2 mm-1，且向上坡溅蚀量，向下坡溅蚀量，净溅蚀量和总溅蚀量皆与降雨能量呈幂函数关系，而侧坡溅蚀量与降雨能量呈二次多项式关系。 Abstract:Splash erosion is an important form of soil erosion caused by the impact of raindrops. Raindrop kinetic energy is the principal factor that affects splash erosion, and studies on splash characteristics can reveal splash erosion mechanics. However, current studies only characterize the amount of splash erosion, which cannot accurately and comprehensively reflect the splash processes. Therefore, this study examines the effects of raindrop kinetic energy on splash erosion processes and on the amount of splash erosion from different directions on a hillslope. The experimental treatments included two rainfall intensities (50 and 100 mm/h) and 10 rainfall kinetic energies that were obtained with a combination of the two rainfall intensities and five raindrop falling heights (3.5 m, 5.5 m, 7.5 m, 9.5 m, 11.5 m); the slope gradient was set at 10°. In the experiment, all treatments were replicated twice. The soil used in this study was a Mollisol (USDA system of Soil Taxonomy), containing 3.3% sand, 76.4% silt, and 20.3% clay. The tested soil was collected from 0-20 cm depth in the Ap horizon of a maize field in Liujia Town (44°43'N, 126°11'E), Yushu City, Jilin Province, located in the center of the Mollisol region in Northeast China. This study was completed in the rainfall simulation laboratory of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling City, China. A side-sprinkle rainfall simulator was used to apply rainfall and a soil pan was specially designed to measure both splash and sheet erosion. Results showed that directional splash erosion increased with the increase of raindrop kinetic energy for a given rainfall intensity. However, at each individual rainfall, the amount of splash erosion was in the order of downslope > lateral slope > upslope.When rainfall intensity increased from 50 to 100 mm/h, the total splash and net splash erosion increased 1.9-4.5 and 1.2-6.4 times, respectively; splash erosion on the upslope, downslope, and lateral slope were enhanced 2.3-5.0, 1.7-5.1, and 1.9-4.3 times, respectively. For all rainfall kinetic energies, splash erosion rate gradually increased with rainfall duration; when runoff occurred, splash erosion rate reached the maximum value, and then gradually decreased until reaching a steady state. According to the relationships between directional, total, and net splash erosion and rainfall kinetic energy, the critical energy for splash erosion initiation was 3-6 J m-2 mm-1. Splash erosion increased with an increase in raindrop kinetic energy above the critical value. Furthermore, the relationship between raindrop kinetic energy and upslope, downslope, total, and net splash erosion was expressed by power function, while raindrop kinetic energy had a quadratic polynomial relationship with lateral splash erosion. 参考文献 相似文献 引证文献

Erosion–corrosion interaction of Fe–B alloy in flowing zinc

The effect of erosion angle on the erosion–corrosion interaction of Fe–3.5 wt-%B alloy in flowing zinc was investigated. The total erosion–corrosion rate decreased linearly, whereas the pure erosion rate fluctuated slightly with increasing erosion angle, which was strongly dependent on the erosion–corrosion interaction. At an erosion angle of 0°, liquid zinc corrosion damaged the sample surface and facilitated erosion, which in turn increased corrosion via the removal of corrosion products. As the erosion angle increased, corrosion products accumulated and Fe2B flaked and cracked in front of the erosion interface, which resulted, in turn, in increased obstruction to the diffusion of liquid zinc. Accordingly, the erosion–corrosion interaction was reduced, thereby resulting in a low material loss at high erosion angles.

Histopathological studies on epizootic ulcerative syndrome in some fishes from Demra, Dhaka

Histopathological studies of early and late stages of Epizootic Ulcerative Syndrome infected fishes from three natural ponds at Demra, Dhaka. Five different types of freshwater wild fishes such as Anabas testudineus, Channa punctatus, Colisa fasciatus, Mystus vittatus and Puntius ticto were collected from August, 2009 to December, 2010. In this study, a prevalence of ~ 64% (322/500) was recorded. Channa punctatus was found to be the most infected fish among the examined fishes. Petechia haemorrhages and moderate necrosis with melanomacrophages and multinucleated giant cells without fungal hyphae were pronounced in the early stages in the muscles. Moderate to severe necrosis friable tissues possessing trailing fungal hyphae associated with fungal, protozoan and bacterial infection may have caused denuding or total erosion of the affected tissues. Extensive ulcers and high mortality were prominent in the late stages of infection. Cystic granulomas associated with multinucleated giant cells often engulfing fungal hyphae were the most characteristic features at the late stages in EUS affected fish. Other observations made were muscle degeneration, surrounding perforated muscle fibres and frequent degeneration of the blood vessel walls. However, the causative link between EUS and the observed histopathological features needs to be further elucidated.Bangladesh J. Zool. 43(1): 121-130, 2015

Streamlined islands and the English Channel megaflood hypothesis

Recognising ice-age catastrophic megafloods is important because they had significant impact on large-scale drainage evolution and patterns of water and sediment movement to the oceans, and likely induced very rapid, short-term effects on climate. It has been previously proposed that a drainage system on the floor of the English Channel was initiated by catastrophic flooding in the Pleistocene but this suggestion has remained controversial. Here we examine this hypothesis through an analysis of key landform features. We use a new compilation of multi- and single-beam bathymetry together with sub-bottom profiler data to establish the internal structure, planform geometry and hence origin of a set of 36 mid-channel islands. Whilst there is evidence of modern-day surficial sediment processes, the majority of the islands can be clearly demonstrated to be formed of bedrock, and are hence erosional remnants rather than depositional features. The islands display classic lemniscate or tear-drop outlines, with elongated tips pointing downstream, typical of streamlined islands formed during high-magnitude water flow. The length-to-width ratio for the entire island population is 3.4±1.3 and the degree-of-elongation or k-value is 3.7±1.4. These values are comparable to streamlined islands in other proven Pleistocene catastrophic flood terrains and are distinctly different to values found in modern-day rivers. The island geometries show a correlation with bedrock type: with those carved from Upper Cretaceous chalk having larger length-to-width ratios (3.2±1.3) than those carved into more mixed Paleogene terrigenous sandstones, siltstones and mudstones (3.0±1.5). We attribute these differences to the former rock unit having a lower skin friction which allowed longer island growth to achieve minimum drag. The Paleogene islands, although less numerous than the Chalk islands, also assume more perfect lemniscate shapes. These lithologies therefore reached island equilibrium shape more quickly but were also susceptible to total erosion. Our observations support the hypothesis that the islands were initially carved by high-water volume flows via a unique catastrophic drainage of a pro-glacial lake in the southern North Sea at the Dover Strait rather than by fluvial erosion throughout the Pleistocene.

Impact of a binary size distribution on particle erosion due to an impinging gas plume

Solid particles of nonuniform sizes exhibit behaviors not seen in monodisperse distributions. Following a previous study of monodisperse particles, the goal of this study is to investigate effects of a binary‐size distribution on erosion of lunar soil from a rocket landing. The discrete element method is used to examine near‐field (near impingement) and far‐field behavior. For near‐field simulations, small particles preferentially collide with large particles from below, due to a difference in velocity caused by gas forces, which is analogous to behavior for entrainment in gas‐solid fluidized beds. These collisions cause vertical momentum transfer from small to large particles that affects species and total erosion flux. For far‐field simulations, collisions result in an increase in vertical dispersion (binary) and a reduction in maximum horizontal velocity (binary and monodisperse). These results have implications on the most appropriate modeling framework to use for predictions over large distances utilizing wide size distributions. © 2015 American Institute of Chemical Engineers AIChE J, 62: 984–995, 2016

Radiometric dating and temperature history of banded iron formation–associated hematite, Gogebic iron range, Michigan, USA

Newly developed techniques were used to characterize the age, origin, and temperature history of coarse hematite contained in high-grade iron ore. Three botryoidal specimens from two different mines in the Gogebic iron range near Ironwood, Michigan (USA), yielded (U-Th)/^(21)Ne ages concordant with plateau ^4He/^3He ages. These data reveal that while two of the specimens grew at ca. 772 ± 41 Ma, the third formed 300 m.y. later (453 ± 14 Ma). ^4He/^3He polydomain thermochronometry indicates hematite formation at >80 °C for the older specimens and ∼60 °C for the younger. Fe mobilization and recrystallization in open cavities at 3–5 km subsurface has occurred episodically or possibly continuously over hundreds of millions of years despite a quiescent tectonic setting throughout this interval. While the analyzed specimens are distinct from typical Fe ore, their ages along with structural relationships constrain the onset of iron enrichment to between 1060 and 770 Ma. Cooling of ∼0.5 °C/m.y. ensued between ca. 800 and ca. 550 Ma, declining to ∼0.1 °C/m.y. for the last 550 m.y. These data suggest an erosion rate of ∼6 m/m.y. and ∼5 km of total erosion of the Superior Upland province through the Phanerozoic, and limit unroofing associated with Pleistocene glaciation to <1 km.

Erosion of synchronization: Coupling heterogeneity and network structure

We study the dynamics of network-coupled phase oscillators in the presence of coupling frustration. It was recently demonstrated that in heterogeneous network topologies, the presence of coupling frustration causes perfect phase synchronization to become unattainable even in the limit of infinite coupling strength. Here, we consider the important case of heterogeneous coupling functions and extend previous results by deriving analytical predictions for the total erosion of synchronization. Our analytical results are given in terms of basic quantities related to the network structure and coupling frustration. In addition to fully heterogeneous coupling, where each individual interaction is allowed to be distinct, we also consider partially heterogeneous coupling and homogeneous coupling in which the coupling functions are either unique to each oscillator or identical for all network interactions, respectively. We demonstrate the validity of our theory with numerical simulations of multiple network models, and highlight the interesting effects that various coupling choices and network models have on the total erosion of synchronization. Finally, we consider some special network structures with well-known spectral properties, which allows us to derive further analytical results.

Soil losses due to potato harvesting: a case study in western Turkey

AbstractHarvesting of potato (Solanum tuberosum L.) may cause soil losses, but the magnitude of such losses has not been widely documented. We quantified the amount of soil lost with the mechanical harvesting of potatoes in 39 fields in western Turkey in 2013. The amount of soil lost was 1.81 Mg/ha/harvest and increased with increased gravimetric water content and plant density. The cost to replace nutrients lost with soil was about US$3 per hectare. Overall, soil loss due to potato harvesting is an important component of total erosion in the study region.

Late Cenozoic evolution of high-gradient trough mouth fans and canyons on the glaciated continental margin offshore Troms, northern Norway—Paleoclimatic implications and sediment yield

Trough mouth fans contain information about the evolution of high-latitude continental margins, including rates of glacial sedimentation and hinterland erosion. Here, the late Cenozoic evolution of high-gradient trough mouth fans and canyons on the Troms margin, northern Norway, is reconstructed. Paleocanyons were active prior to the Quaternary glaciations. Glaciomarine and glaciofluvial conditions prevailed between ca. 2.7 Ma and ca. 1.5 Ma, and ice sheets possibly reached the paleo–shelf break at least once. The minimum average sedimentation rate of this period was 0.22 m/k.y. From ca. 1.5 Ma to ca. 0.7 Ma, the glaciations intensified, and fast-flowing ice streams reaching the shelf break were established in the cross-shelf troughs. Subglacial deformation till was deposited at the outer shelf and later reworked by debris flows and turbidity currents. The Fennoscandian Ice Sheet started to route much of its ice mass to the north and south of the study area, and so the Troms margin possibly was a low-ice-flow sector from this time, with a minimum average sedimentation rate of 0.15 m/k.y. During the last ca. 0.7 m.y., ice streams continued to traverse the troughs, while sluggish-flowing ice prevailed on the banks. A minimum average sedimentation rate of 0.14 m/k.y. is estimated for this period. The minimum total erosion and erosion rate for the Quaternary are 50–140 m and 0.02–0.05 m/k.y., respectively. Compared with previous studies from other areas, this implies up to one order of magnitude variation in average glacial erosion rates along the western sector of the Fennoscandian–Barents Sea ice sheets. This is interpreted to be due to the size and bedrock composition of the catchment areas and the timing of ice growth and ice-sheet dynamics. In addition, the steep preglacial continental slope promoted high sediment flow velocity for the glacigenic sediments, causing much of the debris flows to transform into turbidity currents, which efficiently transported sediments across the slope and thereby maintained its steep gradient.