scholarly journals Cosmogenic <sup>10</sup>Be in river sediment: where grain size matters and why

2018 ◽  
Author(s):  
Renee van Dongen ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Friedhelm von Blanckenburg
Keyword(s):  
Grain Size ◽  
River Sediment ◽  
Soil Layer ◽  
Sediment Provenance ◽  
Depth Interval ◽  
Sand Fraction ◽  
Size Dependent ◽  
Erosion Processes ◽  
Denudation Rates ◽  
Modelling Studies

Abstract. Concentrations of in situ-produced cosmogenic 10Be in river sediment are widely used to estimate catchment-average denudation rates. Typically, the 10Be concentrations are measured in the sand fraction of river sediment. However, the grain size of bedload sediment in most bedrock rivers cover a much wider range. Where 10Be concentrations depend on grain size, denudation rate estimates based on the sand fraction alone could potentially be biased. To date, knowledge about catchment attributes that may induce grain size-dependent 10Be concentrations is incomplete or has only been investigated in modelling studies. Here we present an empirical study on the occurrence of grain size-dependent 10Be concentrations and the potential controls of hillslope angle, precipitation, lithology and abrasion. We first conducted a study focusing on the sole effect of precipitation in four granitic catchments located on a climate-gradient in the Chilean Coastal Cordillera. We found that observed grain size dependencies of 10Be concentrations in the most-arid and most-humid catchments could be explained by the effect of precipitation on both the scouring depth of erosion processes and the depth of the mixed soil layer. Analysis of a global dataset of published 10Be concentrations in different grain sizes (n=62 catchments), comprising catchments with contrasting hillslope angles, climate, lithology and catchment size revealed a similar pattern. Lower 10Be concentrations in coarse grains (defined as negative grain size dependency) emerge frequently in catchments which likely have thin soil and where deep-seated erosion processes (e.g. landslides) excavate grains over a larger depth-interval. These catchments include steep (>25°), arid (<100 mm yr−1) and humid catchments (>2000 mm yr−1). Furthermore, we found that an additional cause of negative grain size dependencies may emerge in large catchments with long sediment travel distances (>2300–7000 m, depending on lithology) where abrasion and sediment provenance may lead to a grain size distribution that is not representative for the entire catchment. The results of this study can be used to evaluate whether catchment-average denudation rates are likely to be biased in particular catchments.

scholarly journals Cosmogenic <sup>10</sup>Be in river sediment: where grain size matters and why

2019 ◽  
Vol 7 (2) ◽  
pp. 393-410 ◽  
Author(s):  
Renee van Dongen ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Friedhelm von Blanckenburg
Keyword(s):  
Grain Size ◽  
River Sediment ◽  
Soil Layer ◽  
Depth Interval ◽  
Sand Fraction ◽  
Size Dependent ◽  
Erosion Processes ◽  
Denudation Rates ◽  
Modelling Studies ◽  
Scouring Depth

Abstract. Concentrations of in-situ-produced cosmogenic 10Be in river sediment are widely used to estimate catchment-average denudation rates. Typically, the 10Be concentrations are measured in the sand fraction of river sediment. However, the grain size of bedload sediment in most bedrock rivers covers a much wider range. Where 10Be concentrations depend on grain size, denudation rate estimates based on the sand fraction alone are potentially biased. To date, knowledge about catchment attributes that may induce grain-size-dependent 10Be concentrations is incomplete or has only been investigated in modelling studies. Here we present an empirical study on the occurrence of grain-size-dependent 10Be concentrations and the potential controls of hillslope angle, precipitation, lithology, and abrasion. We first conducted a study focusing on the sole effect of precipitation in four granitic catchments located on a climate gradient in the Chilean Coastal Cordillera. We found that observed grain size dependencies of 10Be concentrations in the most-arid and most-humid catchments could be explained by the effect of precipitation on both the scouring depth of erosion processes and the depth of the mixed soil layer. Analysis of a global dataset of published 10Be concentrations in different grain sizes (n=73 catchments) – comprising catchments with contrasting hillslope angles, climate, lithology, and catchment size – revealed a similar pattern. Lower 10Be concentrations in coarse grains (defined as “negative grain size dependency”) emerge frequently in catchments which likely have thin soil and where deep-seated erosion processes (e.g. landslides) excavate grains over a larger depth interval. These catchments include steep (> 25∘) and humid catchments (> 2000 mm yr−1). Furthermore, we found that an additional cause of negative grain size dependencies may emerge in large catchments with weak lithologies and long sediment travel distances (> 2300–7000 m, depending on lithology) where abrasion may lead to a grain size distribution that is not representative for the entire catchment. The results of this study can be used to evaluate whether catchment-average denudation rates are likely to be biased in particular catchments.

Determination of denudation rates by the measurement of meteoric 10Be in Guadiana river sediment samples (Spain) by low-energy AMS

2018 ◽  
Vol 189 ◽  
pp. 227-235 ◽  
Author(s):  
S. Padilla ◽  
J.M. López-Gutiérrez ◽  
D.M.R. Sampath ◽  
T. Boski ◽  
J.M. Nieto ◽  
...  
Keyword(s):  
River Sediment ◽  
Low Energy ◽  
Sediment Samples ◽  
Denudation Rates

Grain-size-dependent gas-sensing properties of TiO2 nanomaterials

2015 ◽  
Vol 211 ◽  
pp. 67-76 ◽  
Author(s):  
B. Lyson-Sypien ◽  
M. Radecka ◽  
M. Rekas ◽  
K. Swierczek ◽  
K. Michalow-Mauke ◽  
...  
Keyword(s):  
Grain Size ◽  
Gas Sensing ◽  
Sensing Properties ◽  
Size Dependent ◽  
Gas Sensing Properties ◽  
Tio2 Nanomaterials

Controlling Grain Size in Oxide Ceramics for Optimization of Strength and Wear Resistance

2012 ◽  
Vol 715-716 ◽  
pp. 703-710
Author(s):  
W.M. Rainforth ◽  
P. Zeng ◽  
L. Ma
Keyword(s):  
Grain Size ◽  
Sliding Wear ◽  
Second Phase ◽  
Alumina Ceramics ◽  
Size Dependent ◽  
Mild Wear ◽  
Accumulation Mechanism ◽  
Wear Transition ◽  
Magnitude Increase ◽  
Zirconia Toughened Alumina

t is well known that alumina ceramics undergo a time dependent wear transition during sliding wear. The transition, which is associated with 1-2 orders of magnitude increase in specific wear rate, involves a change from mild wear to intergranular fracture. The transition is strongly grain size dependent, with the time to the transition decreasing with grain size. However, there is a minimum grain size that can be achieved in fully dense alumina using commercially viable processing. Alternative strategies for reducing grain size and increasing toughness are through the addition of a fine second phase, with SiC and ZrO2being the most promising. The resultant composite not only has finer grain size, but also exhibits additional toughening mechanisms. This paper reports on the microstructural control in alumina, zirconia toughened alumina and alumina-silicon carbide composites. The grain size and residual stress distribution are related to the damage accumulation mechanism that occur during frictional contact, in particular the surface specific dislocation activity.

scholarly journals Dark gray podzolized soils of the Chyzhykiv ridge: problems of degradation and protection

2019 ◽  
Vol 53 ◽  
pp. 85-96
Author(s):  
Volodymyr Haskevych ◽  
Nadiya Lemeha ◽  
Anastasiya Vishchur
Keyword(s):  
Soil Aggregates ◽  
Humus Content ◽  
Soil Layer ◽  
Research Area ◽  
Soil Protection ◽  
Anthropogenic Pressure ◽  
Degradation Processes ◽  
Erosion Processes ◽  
General Physical ◽  
Very High

The results of the research of degradation of dark gray podzolized soils (Luvis Greyzemic Phaeozems) of the Chyzhykiv ridge are presented. The causes and consequences of this dangerous natural and anthropogenic phenomenon are analyzed. It has been established that the intensive agricultural use of soils caused the activation of water erosion processes, the development of physical degradation processes, which lead to soil compaction, deterioration of their general physical properties, and loss of humus. Degradation processes lead to a decrease in soil fertility and unprofitability of agriculture, worsen the ecological state of the environment. In the study of degradation processes and their consequences in dark gray podzolized soils, the following methods were used: comparative-geographical, comparative-profile, catena method, analytical, statistical. Soil field explorations were carried out after the growing season. The most dangerous among the degradation processes are erosion degradation, which leads to a decrease in the capacity of the soil profile and deterioration of the soil agrophysical properties. The results of the studies demonstrated that the capacity of the profile of poorly eroded soils decreased on average by 14.5 cm compared to the standard, in medium-eroded – by 28.3 cm, in highly-eroded – by 50.8 cm. Soils underwent erosion from low to very high (crisis) degree. Degradation processes of anthropogenic genesis caused a deterioration of the structural and aggregate state of the soils, which is manifested in a decrease in the content of agronomically valuable soil aggregates and the dominance of the sloping fraction. According to the research results, the content of agronomically valuable aggregates with a size of 10–0.25 mm in the arable soil layer is 18.65–33.86 %, which indicates a high and very high (crisis) level of degradation. Soils also undergo degradation due to re-compaction, which is manifested in an increase in the density of the structure and a decrease in the overall porosity of the soil. Long anthropogenic pressure on soils and erosion degradation processes have led to a decrease in humus content. In particular, in poorly eroded soils the humus content is 2.03 %, in medium-eroded soils – 1.45 %, in highly eroded – 1.06 %, which is 16.9–64.6 % less than the standard. Measures are proposed to minimize the degradation of the dark gray podzolized soils of the Chyzhykiv ridge, which consist in the application of anti-erosion measures and soil-protective methods of soil processing, conservation of heavily degraded lands. The introduction of basic and crisis monitoring of the state of soils in the research area is recommended. Key words: the Chyzhykiv ridge, dark gray podzolized soils, erosion, degradation, soil protection.

scholarly journals The role of unpaved roads in the formation of landslide processes (on the example of Voronezh region)

2020 ◽  
Vol 28 (1) ◽  
pp. 65-74
Author(s):  
Andrey N. Timofeev
Keyword(s):  
Soil Layer ◽  
Anthropogenic Activity ◽  
Unpaved Roads ◽  
Erosion Processes ◽  
Voronezh Region ◽  
Landslide Processes ◽  
Landslide Process ◽  
The Impact ◽  
Landslide Distribution

The article gives a brief description of the Voronezh region, provides data on the cause of landslides in its territory. The cyclical nature of landslide processes is noted, which in the region is on average 6-8 years. Attention is focused on anthropogenic activity, leading to the occurrence of creeping layers of the earth. The main causes of erosion processes are: significant plowing of the area (80%), which is not subject to the rules of anti-erosion agrotechnology; the irrational use of pastures and hayfields; an extensive gully-beam network. The role of temporary reservoirs formed in the ruts of unpaved roads, passing along the slopes and ravines, as a source of overmoistening of the soil layers and initiation of landslide processes is considered. The analysis of the landslide distribution over the territory of the Voronezh region and their dependence on the network of dirt roads is given. The areas of the Voronezh region were ranked by the number of landslide processes associated with the impact of a number of unpaved highways. Of the 32 districts of the region, according to this ranking, 12 are extremely dangerous, very dangerous and dangerous, and the same areas have a very extensive network of unpaved roads running near ravines, steep banks of rivers and ponds, where potentially flow of landslide processes. Dirt roads often have relatively deep ruts where melted or rainwater accumulates, forming local micro-ponds. Flowing to the waterproof layer, water saturates the soil layer, which can slide down the slope, forming a landslide process. It is necessary to predict the possibility of the occurrence of dangerous natural phenomena when laying automobile dirt roads.

scholarly journals Profile degradations of podzolic chernozem of the territory of Male Polissia

2017 ◽  
pp. 98-110
Author(s):  
Volodymyr Haskevych
Keyword(s):  
Physical Properties ◽  
Soil Layer ◽  
Vegetation Period ◽  
Soil Mass ◽  
Water Erosion ◽  
Soil Protection ◽  
Erosion Processes ◽  
Average Annual Loss ◽  
Study Results ◽  
Statistical Field

The article presents the results of the study of Male Polissia podzolic chernozems profile degradation. The causes and consequences of this dangerous natural and man-made phenomenon resulting in changes in the habitus of soils, losses of soil mass and humus, deterioration of general physical properties and structural and aggregate composition, decrease in soil fertility and agriculture unprofitability on the slopes have been analysed. In the study of the profile degradation of podzolic chernozems, the following methods have been used: comparative-geographical, comparative-profile, soil-catena, analytical, and statistical. Field studies were conducted after the vegetation period. According to the study results, the thickness of the profile of weakly eroded podzolic chernozems, in comparison with non-eroded types, decreased by 17.0–35.5% as compared to the standard, which corresponds to satisfactory and pre-crisis condition, in medium eroded soils - by 32.2–63.4%, the degree of degradation is estimated as pre-crisis, crisis and catastrophic. In the highly eroded types, the thickness of the soil layer decreased by 47.8–74.9%, which indicates a high and very high (crisis) level of profile degradation. Erosion soil loss compared to the standard in weakly eroded podzolic chernozems is 1245.0-3744.6 t/ha, in medium eroded soil – 6762.4-8321.0 t/ha, and in highly-eroded soil – 8874.0-11595.0 t/ha. It has been established that chernozems as a result of water erosion from one hectare of weakly eroded podzolic, on average 39.47–118.70 tons of humus was eroded, 214.36-237.98 tons was eroded from medium eroded ones, and 240.49-267.84 tons from highly eroded soils. The average annual loss of humus is from 0.23-0.68 t/ha in weakly eroded types to 1.37-1.53 t/ha in highly eroded podzolic chernozems. Erosion processes result in deterioration of physical properties of soils. The use of dense and low-humus plumage horizons for plowing causes compaction of soils and deterioration of structure. Minimization of podzolic chernozem profile degradation in Male Polissia is possible provided that the system of anti-erosion measures, especially the conservation of highly eroded soils, the introduction of soil protection methods for soil cultivation, optimization of the structure of crop areas, ban on cultivated crops on slopes more than 3° steep, consolidation of small areas in larger arrays are applied. It is also necessary to introduce a system of basic and crisis monitoring over the condition of eroded soils. Key words: Male Polissia, podzolic chernozems, profile degradation, water erosion, humus, soil conservation.

scholarly journals Sourse degradation - global environmental problem

2017 ◽  
pp. 63-70 ◽  
Author(s):  
Myroslav Voloshchuk
Keyword(s):  
Soil Degradation ◽  
Agricultural Land ◽  
Arable Land ◽  
Soil Layer ◽  
Organic Fertilizers ◽  
Economic Losses ◽  
Complex Situation ◽  
Erosion Processes ◽  
Fertile Soil ◽  
Catchment Areas

Based on generalization of literary sources, normative legal, stock materials and experimental data, the complex situation of soil degradation is highlighted. Different types and intensity of the manifestation of soil degradation, their distribution and characteristics are described. The threatening situation of manifestation of degradation processes in some regions of Ukraine is shown, among which soil erosion occupies the leading place. More than 4.5 million hectares are occupied by medium and strongly ground soils, including 68 thousand hectares completely lost their humus horizon. Particularly large areas of eroded soils are distributed on arable land in the Vinnytsia, Luhansk, Donetsk, Odesa, Chernivtsi and Ternopil regions, where the average annual ground wash is 24.5–27.8 t/ha with a tolerance of 2.5–3.7 t/ha. As a result of erosion processes from the total area of agricultural land, about 500 million tons of fertile soil layer is washed out on average annually, which contains about 24 million tons of humus, 0.96 million tons of nitrogen, 0.68 million tons of phosphorus and 9.4 million tons of potassium equivalent to 320–333 million tons of organic fertilizers, and ecological and economic losses due to erosion exceed 9 billion UAH. Flat soil was associated with linear erosion. The main indicators characterizing the degree of damage to land by linear erosion are the density of ravines, the distance and area between them, the slope, the properties of soils and rocks, the morphometric parameters of the ravines and their catchment areas. According to various estimates, the area of land affected by linear erosion in the country increases by 5–10 thousand ha annually. The effect of the ravines on the complete destruction of the land, deformation of the soil cover is highlighted. Information on various types of soil pollution by poison chemicals, industrial waste is given. According to the prediction of scientists in such a situation, 120–150 years on the planet can destroy the fertile soil layer. Key words: erosion, dehumidification, pollution, waterlogging, acidity, degraded land.

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