Areas Of Severe Erosion Research Articles

Passive flow control of a Francis turbine operating in sand-laden rivers for mitigating sediment erosion

In a typical Francis turbine operating in sand-laden rivers, owing to its complicated geometry and variable operating conditions, vortex structures appear and cause severe erosion damage to turbine components. Here, we present a bioinspired method to mitigate severe sediment erosion on Francis turbines. The proposed method includes a passive flow control strategy using biomimetic convex domes for the inter-blade vortex, a major contributor to severe sediment erosion on the turbine runner. The effects of biomimetic convex domes on sediment erosion are investigated through numerical simulations and experiments. The results indicate that biomimetic convex domes significantly reduce the impact velocity and accretion rate of the particles, eventually reducing sediment erosion by at least 50 %. The mechanism underlying the effect of convex domes on sediment erosion is their inhibition of the development of the inter-blade vortex. The convex domes induce small-scale vortices from the blade boundary layer. When located in the nascent region of the inter-blade vortex, the small-scale vortex effectively inhibits its formation. Moreover, convex domes placed in severe erosion areas can accelerate the dissipation process of the inter-blade vortex.

Potential Reduction of Spatiotemporal Patterns of Water and Wind Erosion with Conservation Tillage in Northeast China

Conservational tillage (NT) is widely recognized globally for its efficacy in mitigating soil loss due to wind and water erosion. However, a systematic large-scale estimate of NT’s impact on soil loss reduction in Northeast, China’s primary granary, remains absent. This study aimed to investigate the spatial and temporal variability of soil erosion under NT compared to conventional tillage (CT) in the black soil region and to analyze the underlying mechanisms driving these erosions. The Revised Universal Soil Loss Equation (RUSLE) and the Revised Wind Erosion Equation (RWEQ) models were employed, incorporating previously published plot/watershed data to estimate the potential reduction of water and wind erosion by NT in this region. Results indicated that under CT practices, water- and wind-induced soil losses were widely distributed in the arable land of Northeast China, with intensities of 2603 t km−2 a−1 and 34 t km−2 a−1, respectively. Furthermore, the erosive processes of water and wind erosion were significantly reduced by 56.4% and 91.8%, respectively, under NT practices compared to CT. The highest efficiency in soil conservation using NT was observed in the mountainous regions such as the Changbai Mountains and Greater Khingan Mountains, where water erosion was primarily driven by cropland slopes and wind erosion was driven by the wind speed. Conversely, the largest areas of severe erosion were observed in the Songnen Plain, primarily due to the significant proportion of arable land in this region. In the plain regions, water-induced soil loss was primarily influenced by precipitation, with light and higher levels of erosion occurring more frequently on long gentle slopes (0–3°) than on higher slope areas (3–5°). In the temporal dimension, soil loss induced by water and wind erosion ceased during the winter under both tillage systems due to snow cover and water freezing in the soil combined with the extremely cold climate. Substantial reductions were observed under NT from spring to autumn compared to CT. Ultimately, the temporal and spatial variations of soil loss under CT and NT practices were established from 2010 to 2018 and then projected onto a cropland map of Northeast China. Based on this analysis, NT is recommended as most suitable practice in the southern regions of Northeast China for maintaining soil health and crop yield production, while its suitability decreases in the northern and eastern regions.

Experimental Study of Sediment Erosion in Pelton Turbine Bucket

Abstract In hydroelectric power plants (HPPs), sediment-laden water flows through entire turbines, causing components to be damaged over time. Pelton turbine components serve abrasive erosion from particle hardness, and rough surface when subjected to high flow velocities and various jet impingement angles. In this study, an experiment was conducted to examine the erosion-prone areas of a small-scale Pelton turbine bucket under actual flow conditions. For the experiment, the Pelton bucket was painted with four distinct layers of paint: red, yellow, green, and blue. These layers served as indicators, helping us to visually track the erosion process. The setup was specifically designed to inject sediment upstream of the nozzle. It operated for a significant period of 0- 30 minutes, and every 5 minutes, the erosion pattern was noted with the nozzle fully open at 10 l/s and a net head of 6m with jet impingement angle 75°, 90°, and 105°. After operating for 0-30 minutes in sediment-laden flow conditions, a pattern of erosion was revealed, showing the hot spots (areas more susceptible to erosion) during the investigation at jet angles of 75°, 90°, and 105°. The most severe erosion areas are in the bucket domain, specifically at the splitter region and the deeper upper and lower parts of the brim. The erosion mechanism was influenced by the jet diameter and impingement angle on the bucket splitter. The experiment revealed that the outer regions of the bucket, where the flow was directed outward, suffered the most severe erosion, providing evidence of particle separation at high accelerations.

Investigation of erosion behavior of particle-fluid flow in offshore platform T-pipes

The process of viscous oil exploitation is often accompanied by small sand particles, which harms safety production and causing consequences such as erosion. T-shaped pipes are widely used in offshore platform, and its flow protection is very important for the safe operation. This work aims to investigate the particle trajectory and erosion ratio rule in viscous oil transportation by simulation, experiment and support vector machine (SVM) model. The sensitivity analysis and the orthogonal method results demonstrate that the erosion ratio (ER) of T-pipes is proportional to the water content, gas content and sand content. And the erosion ratio (ER) of T-pipes is inversely proportional to the viscosity. The water content has the greatest effect on the pressure drop (Δp). The viscosity value around 326.79 mPa s can significantly reduce the erosion ratio while maintaining a low-pressure drop. Meanwhile, SVM model is used to calculate the erosion ratio (ER) with the mean squared error (MSE) being 4.25 × 10−6 in the training set and 0.0002 in the test set. The most severe erosion area is located in the downstream branch symmetrically. The erosion mechanisms are impact deformation and sliding, that dominate the erosion distributions.

An improved method combined modified drag model and modified erosion model based on LES for solid-liquid multiphase flow and erosion with application in a 90° elbow

In various industrial processes, solid-liquid multiphase flows involving continuous carrier and discrete particle phases have erosion challenges. In this work, a modified drag model that considers the influence of turbulence intensity and a modified erosion model that considers the effect of low-angle impact are developed. An improved method combined modified drag model and modified erosion model based on LES is proposed for numerical simulation of solid-liquid multiphase flow and erosion. The commercial software ICEM for grid generation and ANSYS FLUENT for LES are used in the present work. In validation test of velocity distribution of solid-liquid multiphase flow in a vertical pipe, the mean relative error of the liquid phase pulsation velocity is 10.01 % for modified drag model, whereas the mean relative error is 16.11 % for original drag model. In validation test of the maximum erosion depth from a submerged impact test at a tilt angle of 45°, the relative error is 0.23 % for modified erosion model, while the relative error is 13.39 % for original erosion model. Then, the improved method is employed to compute the characteristics of solid-liquid flow and erosion in a 90° elbow. Particles have a significant influence on liquid flow in the shear layer area where the inner arch separation zone interacts with the main flow, and this influence is most pronounced at the position of r* = 0.3 at yd = 0.4D. At this position, particles result in 15.27 % reduction in liquid velocity and 8.75 % increase in turbulence intensity. The mean relative error of the elbow erosion rate by using the improved method is 16.95 %, whereas it is 31.34 % of the reference work. The erosion is affected by impact velocity, angle, and particle number, and the most significant parameter is the particle number in the severe erosion area.

Impacts of vegetation restoration on soil erosion in the Yellow River Basin, China

Soil erosion is a serious and complex environmental problem, which directly leads to soil degradation and reduces land productivity. Analyzing the effect of vegetation restoration on soil erosion is the main way to quantitatively evaluate the contribution of vegetation restoration to soil erosion in semi-arid. This study utilized the RUSLE model and Geodetector method to quantitatively characterize the spatio-temporal dynamics of soil erosion and the contribution of FVC to erosion mitigation in the Yellow River Basin (YRB) since the implementation of the Grain for Green Project (GGP). The main findings are concluded as follows: (1) The fractional vegetation cover (FVC) in the YRB showed an overall increasing trend, with an average annual change rate of 0.006 a−1. (2) Soil erosion in YRB increased from 1999 to 2010, with a 10% increase in soil erosion intensity, and from 2010 to 2018, soil erosion improved significantly with a 31% decrease in soil erosion. The severe erosion areas were mainly concentrated in the Loess Plateau (LP) and the source area of the Yellow River (YR), which generally showed northeast-southwest banding changes. (3) FVC has a relatively stronger explanatory power for soil erosion in the YRB. FVC explained 5% of soil erosion, but the combination of FVC and land use, as well as the combination of FVC and slope, collectively explained 47% of soil erosion. The ecology of the YRB greatly benefits from the implementation of the GGP and other water conservation projects. But there are still necessities to formulate targeted soil and water conservation measures base on careful investigation of local conditions.

Spatiotemporal Variation in the Coupling Relationship between Human Activities and Soil Erosion—A Case Study in the Weihe River Basin

Studying the relationship between human activities and soil erosion on a regional scale is of great significance for macro-decision-making in soil erosion prevention and control. The entropy weight method and RUSLE model are used to analyze the spatiotemporal variation in human activity intensity (HAI) and soil erosion in the Weihe River Basin (WRB) from 2005 to 2020. Through geographic detectors and a four-quadrant model, the impact of various driving factors and the coupling degree of the human–land relationship are studied. The results showed: (1) During the past 15 years, the moderate, high, strong, and severe erosion areas in the WRB decreased by 9.88%, 35.89%, 45.17%, and 70.05%, respectively. The ratio of the historical sand transport modulus to the RUSLE model result is 0.83, indicating that the results obtained by the RUSLE model can be used for further analysis. (2) Slight and weak degrees account for 80% in the northwest region. The high and strong regions are mainly distributed in the Shaanxi section, accounting for 3% of the total basin. (3) The coupling between human activities and soil erosion is constantly strengthening, and the joint effect of pop and crop is the main reason for the slowdown and spatial differences in soil erosion. This indicates that the ecological environment became stable. These findings contribute by acting as references for soil and water conservation and management in the WRB to promote a harmonious relationship between humans and the environment.

Water erosion changes on the Qinghai-Tibet Plateau and its response to climate variability and human activities during 1982–2015

Climate variability and human activities cause changes in precipitation and underlying surface conditions, which are the main driving forces of changes in water erosion, especially in the Qinghai-Tibet Plateau (QTP). In this paper, the water erosion on the QTP from 1982 to 2015 was quantified by the Revised Universal Soil Loss Equation (RUSLE), and the response of water erosion changes to climate variability and human activities was investigated. The results indicated that the distribution of water erosion gradually decreased from south to north during 1982–2015. Areas of severe erosion were mainly distributed along the Yarlung Tsangpo River and in the western Hengduan Mountains. The years of the abrupt change in water erosion were 1989 and 2006. Compared to 1982–1989, the amount of water erosion was mitigated in both 1990–2006 and 2007–2015, with a 19.5% and 6.2% decrease, respectively. The contribution of human activities to the decrease in water erosion was 25.4% and 16.7% for each of these periods, respectively, and the contribution of climate variability to the increase in water erosion was 5.9% and 10.5%. However, water erosion increased by 16.5% from 2007 to 2015 compared to 1990–2006. The contribution of climate variability was 4.9% and the contribution of human activities 8.4%. The increase in water erosion due to human activities may be attributed to the construction of the Qinghai-Tibet Railway and associated human activities. It is therefore important to draw attention to the influence of human activities on the QTP on erosion, to prevent potential future risks. This study is the first attempt to research the relative contributions of variation in climate and human activities to changes in water erosion on the QTP. It would be beneficial for carrying out ecological environmental protection work on the QTP.

Experimental and simulation analysis of erosion law of crude gas production channel in underground coal gasification production wellhead

In underground coal gasification, crude gas carrying coal ash and cinder has a serious significant erosion effect on the gas extraction area of a wellhead device. To study the erosion of the wellhead device, based on the gas-solid two-phase flow theory, this study uses the discrete phase model to describe the kinematics and trajectories of discrete solid particles and uses the Reynolds-averaged Navier-Stokes equation to calculate the fluid dynamics of the continuous phase. This study determines the main erosion position and the maximum erosion angle range of the wellhead device through numerical analysis, as well as the influence of the changes in solid particle size, particle mass flow rate, and crude gas flow rate on the erosion rate, and predicts the service lifetime of the small four-way and side valve I. The gas-solid erosion experiment verified the maximum erosion angle of the wellhead device. The experimental results were consistent with the numerical analysis results. This study also proposes an optimization method of surfacing to reduce the erosion of gas-solid two-phase flow on wellhead devices. The results show that the inner walls of the small four-way and side valve I are the most eroded. Factors such as particle size, particle mass flow rate, and crude gas flow rate have a greater impact on the erosion rate of the device, and the particle size has the greatest impact. Surfacing the severely eroded area of the wellhead device can effectively reduce the erosion and wear of the wellhead device caused by the gas-solid two-phase flow. This study provides guidance for the reasonable prediction and effective protection of severe erosion areas of wellhead devices.

Numerical simulation of centrifugal pump impeller erosion caused by particles in lead–bismuth alloy

In order to study the influence of solid particles in lead–bismuth alloy on the safety of nuclear main pump, DPM (Discrete Phase Model) is used to calculate the wear rate of the impeller of nuclear main pump under different operating conditions. By comparing the erosion rate and the most severe erosion area under different working conditions, the most unfavorable operating conditions are obtained. The results show that the erosion of impeller caused by solid particles is the most serious when the inlet velocity of particles u is 0.4[Formula: see text]m/s and particle size D is 100[Formula: see text][Formula: see text]m. Under the small particle size, the impeller erosion concentrated on the suction side of the blade, and under the large particle diameter, the erosion concentrated on the pressure side, and the erosion is more serious. With the increase of solid particle velocity, the erosion of the impeller increases first and then decreases. The erosion severity of impeller and front and rear cover plates caused by solid particles is not consistent. The above research can provide guidance for the anti-wear design and safe operation of the nuclear main pump impeller.

Insights from size fractions to interpret the erosion-driven variations in soil organic carbon on black soil sloping farmland, Northeast China

Declines of soil organic carbon (SOC) and degradation of soil function are caused by long-term soil erosion and cultivation. Although the variations of bulk SOC have been extensively studied, the driving mechanisms of variations in SOC fractions, i.e., carbon in coarse particulate, fine particulate, and mineral-associated organic matter (CPOM-C, FPOM-C, and MAOM-C), and their relationship with soil erosion remain unclear on sloping farmland. In this study, two areas of farmland with different slope types (convex vs. straight) and reclamation periods (50 years vs. ≥100 years) in the black soil region of Northeastern China were chosen to explore the roles of soil erosion on the variations of SOC and their size fractions based on the 137Cs tracer technique. The results showed that the average net erosion rate of the straight slope was 2810.09 t km-2a-1 and the convex slope was 3801.71 t km-2a-1 with higher spatial variability. When compared with uncultivated land, SOC contents of convex and straight slopes have decreased by 13.58% and 35.18%, with a reduced rate of 0.089 g kg-1 a-1 and 0.116 g kg-1 a-1, respectively. Although the CPOM-C fraction showed the most significant relative decreases (over 73.24%), the absolute declines of MAOM-C were more significant, especially in the straight slope with a more extended cultivation period. The contributions of erosion to the SOC decreases on convex and straight slopes were 69.54% and 13.09%, respectively. Erosion exerted a significant influence on finer particles such as FPOM-C and MAOM-C. With increasing cumulative erosion, the absolute magnitude of each SOC fraction in soils decreased. But the proportion of MAOM-C increased, while FPOM-C and CPOM-C decreased. Overall, our findings demonstrated that soil erosion not only induced the loss of SOC fractions but also transformed the proportional distribution of their fractions, and then affected the functions of SOC. Moreover, the effects of tillage (i.e., an increase in microbial activity) on straight slopes are not negligible in farmland that has experienced long-term cultivation but relatively little erosion. Apart from erosion reduction in areas of severe erosion, appropriate fertilization for farmland with a long history of cultivation should also be adapted to achieve sustainable development of black soil resources.

Coastline dynamics in the extreme south of Brazil and their socio-environmental impacts

A coastal inflection of ∼45 km in the extreme south of Brazil demonstrates differences in coastline behavior with areas of deposition towards north and areas of severe erosion towards south, threatening coastal occupation. These areas are believed to be controlled by the sand wave behavior of the coastline with adjacent erosion and progradation areas that have relevant alongshore sediment transport imposed by S quadrant waves. In this study, we quantified the rates of change of coastline and described the erosion and deposition controls behind it, using ultra-high-resolution orbital images and UAV (unmanned aerial vehicle) orthomosaics obtained between 2005 and 2020 for three urbanized beach sectors within the area, i.e., the São Simão, Mostardense, and Lighthouse Beaches. The rates of change of coastline were calculated using the change polygon method. The results indicated total recession values > 40 m at the Mostardense and Lighthouse beaches corresponding to a rate of ∼3 m/y. Such values characterized the coastal erosive hotspots that have not been previously identified in the area. Future coastlines were projected from the estimated annual variation rates. Buildings previously destroyed or threatened by marine/wind processes were also mapped. A continuous high-resolution and high-frequency coastal monitoring approach for the area is essential for planning the future development of these beaches to minimize and possibly avoid environmental degradation.

Numerical investigation of the erosion behavior in blades of tidal current turbine

The blade erosion of a tidal current turbine can lead to significant energy losses and affect stall behavior. To maintain good performance and prevent turbine malfunction, it is important to determine the location and rate of blade erosion caused by particle impact. In this study, a computational fluid dynamics and discrete phase model (CFD–DPM) method is employed to study the erosion characteristics in blades subjected to multiphase flow. The fluid–particle interactions and the influence of turbulence on the particle trajectories are considered in the CFD–DPM model. The maximum erosion location and the average erosion rate are investigated under different particle diameters, particle concentrations, particle shape factors, and airfoil parameters. The fluid velocity, particle velocity, and particle trajectory are further analyzed to reveal the erosion mechanism under different influencing factors. The results show that while both the maximum erosion location and the average erosion rate depend upon particle independence (the greater the degree to which particles deviate from the fluid streamline, the better the particle independence), the latter is also related to the drag force exerted by the particle. For a tidal current turbine, erosion occurs first at the tip and leading edge of the blade, and the most severe erosion area is the blade tip. The erosion laws obtained in this work can provide guidance for erosion prediction, tidal current turbine field site selection, and blade optimization.

Study on sediment erosion of high head Francis turbine runner in Minjiang River basin

The Wenchuan earthquake greatly reduced the forest water conservation capacity along the banks of Minjiang River. With the intensified soil erosion and the rapid increasing sediment transport, the sediment erosion of hydraulic turbines running on the river has become more and more serious, especially of high head Francis turbines. In this study, the k-ε multiphase flow turbulence model was used to calculate the sediment-water flow of a high head Francis turbine with long and short blades in Minjiang River. The distribution pattern of sediment concentration (sediment volume fraction) on the blade surface shows that the sediment particles mainly gather on the outlet edge at 10% of the blade height on the suction surface of the long blade, while the sediment concentration on the surface of the short blade is small. The erosion of the 0Cr13Ni5Mo runner blade was tested by the flow around erosion method, and the erosion amount on the blade surface in the severe erosion area was obtained. Based on the test data of erosion and the numerical calculation results of sediment flow, a formula to calculate the sediment erosion rate of flow passage components with 0Cr13Ni5Mo material was given for turbines operating in Minjiang River. By using this formula, the sediment erosion of flow passage components in hydraulic turbines with 0Cr13Ni5Mo or similar materials operating in Minjiang River can be predicted.

Spatial distribution of soil water erosion at Al-Hawiz Dam in Western Syria using CORINE model

Water erosion is one of the most important environmental problems that cause soil degradation in the areas of water basins in the Syrian coast. The present study aims at determining the spatial distribution of the risk of water erosion of the lands of Al-Hawiz Basin (Jableh region) using the CORINE model. The CORINE model is based on calculating all factors that affect water erosion: soil erosion factor, erosion factor, inclination factor, ground cover fac tor. The soil susceptibility factor for erosion was calculated by estimating both the soil texture, soil depth and gravity percentage for preparing a potential risk map. The feasibility of both the soil susceptibility factor map and the slope map prepared from the use of DEM and the value of the erosion factor were calculated using system technology Geographical information. Then the ground cover map was prepared and classified into two rows according to the degree of protection. The actual risk map was prepared from the seriousness of the potential danger map and the land cover map. The study showed that 12.79% of the studied area is under the control of severe erosion while 32.10% of which had an average risk of erosion, and the risk of erosion was low in the largest part of the area (55.11%). The areas of severe erosion have been concentrated in the central western region of Lake Al-Sadd. It has been shown that vegetation is the most influencing factor in erosion, as it worked to reduce the high risk of possible soil erosion by 50.83%.

Multiscale spatiotemporal characteristics of landscape patterns, hotspots, and influencing factors for soil erosion.

Soil erosion is an increasingly serious eco-environmental problem, and effective control of soil erosion is an important part of soil resource protection and ecological restoration. In this study, the multi-scale characteristics and influencing factors of soil erosion were analyzed in the Beijing-Tianjin-Hebei (BTH) region from 2000 to 2015. The results showed that the average soil erosion in the study area was 3500t/(km2·a), in which the severe erosion areas accounted for 10% of the total area. Although the total soil erosion rate decreased by 60% from 2000 to 2015, the rate of current soil erosion was higher than the soil loss tolerance. The severe erosion area had the highest aggregation index, making it the most suitable for centralized treatment. Meanwhile, the fractal dimension index of severe erosion showed a downward trend from 2000 to 2015. This decrease in complexity led to a more optimistic conservation situation. The hotspot areas overlapped with the relatively high erosion zones and were aggregated as three large patches in the northern, southwestern, and southern BTH regions. Soil erosion distribution depends on both anthropogenic activities and natural conditions. The slope factor, which reflects the impact of natural factors on soil erosion, was the most dominant factor on soil erosion from 2000 to 2010. Conversely, the land use factor, which is mainly controlled by humans, became the dominant factor in 2015. The distribution characteristics and influencing factors of soil erosion both had scale effects. As the scale decreased from city to town, the patches of high and severe erosion classes became more regular and aggregated, the hotspot area had the most concentrated and severe soil erosion rate at the town scale, and human impacts became dominant. Conservation targeting hotspot areas measured at the town scale, which was 20% of the total area, could reduce the total soil loss by 38%. For a region with a complex structure, the main influencing factors showed strong spatial dependence.

Measurement of erosion state and refractory lining thickness of blast furnace hearth by using three-dimensional laser scanning method

The three-dimensional (3D) model of erosion state of blast furnace (BF) hearth was obtained by using 3D laser scanning method. The thickness of refractory lining can be measured anywhere and the erosion curves were extracted both in the circumferential and height directions to analyze the erosion characteristics. The results show that the most eroded positions located below 20# tuyere with an elevation of 7700 mm and below 24#–25# tuyere with an elevation of 8100 mm, the residual thickness here is only 295 mm. In the circumferential directions, the serious eroded areas located between every two tapholes while the taphole areas were protected well by the bonding material. In the height directions, the severe erosion areas located between the elevation of 7600 mm to 8200 mm. According to the calculation, the minimum depth to ensure the deadman floats in the hearth is 2581 mm, corresponding to the elevation of 7619 mm. It can be considered that during the blast furnace production process, the deadman has been sinking to the bottom of BF hearth and the erosion areas gradually formed at the root of deadman.

CFD analysis and field observation of tool erosion caused by abrasive waterjet fracturing

Abrasive waterjet (AWJ) fracturing has become an accepted horizontal multistage stimulation technique due to its flexibility and high efficiency of extensive fracture placement. The downhole tool failure of AWJ fracturing becomes an issue in the massive hydraulic fracturing because of high velocity and proppant erosion. This paper proposed a 3D computational fluid dynamics (CFD)-based erosion model by considering high-velocity waterjet impact, proppant shear erosion, and specific inner structure of hydra-jet tool body. The discrete phase approach was used to track the proppant transport and its concentration distribution. Field observation provides strong evidence of erosion patterns and mechanisms obtained from CFD simulation. The results show that the erosion rate has a space dependence in the inner wall of the tool body. The severe erosion areas are primarily located at the entries of the nozzle. Evident erosion patterns are found including a ‘Rabbit’s ear’ erosion at the upper-layer nozzles and a half bottom loop erosion at the lower-layer nozzles. Erosion mechanisms attribute to high flow velocity at the entry of nozzles and the inertia force of proppant. Sensitivity analysis demonstrates that the pumping rate is a primary factor contributing to erosion intensity.

Experiment and numerical simulation of sand particle erosion under slug flow condition in a horizontal pipe bend

Sand erosion is a common problem in oil and gas field development. An experimental facility was designed and used to study the sand erosion of pipe bend under slug flow. A detachable test pipe bend was designed to measure the weight loss at 36 discrete locations on the pipe bend before and after each experiment. A Computational Fluid Dynamics (CFD) based erosion prediction method was developed to get a further understanding of the erosion. The relationships among the gas and liquid distribution, the sand movement and the erosion profile were analyzed to explain the erosion mechanism. The most severe erosion area of the pipe bend occurs at the axial angle of the elbow between 67.5° and 90° and at the circumferential angle of the elbow between 45° and 90°. The erosion profiles of the pipe wall are dominated by three particle collision mechanisms, namely, micro-cutting, plowing and impact deformation.

Agricultural Expansion in the Brazilian Cerrado: Increased Soil and Nutrient Losses and Decreased Agricultural Productivity

While food and nutrition security are issues that national and international organizations are tackling, one of the central problems often overlooked is the essential role of soils in providing nutritious food. Soils are the base for food production and food security. However, the majority of soils are in fair and poor conditions, with the most significant threats being erosion and loss of nutrients. In this study, we estimate the potential of soil loss, agricultural productivity loss, and nutrient loss for Brazil’s most important agricultural region, the Brazilian Cerrado, for the years 2000 and 2012. For this, we applied the Revised Universal Soil Loss Equation (RUSLE) model integrated with a geographical information system (GIS) to estimate annual soil loss rate and agricultural productivity loss, and used total nitrogen and total phosphorus in soil to estimate the annual nutrient loss rate caused by soil loss. All model factors and data were obtained from the literature. The results show that agricultural expansion in the Brazilian Cerrado is increasing the area of severe erosion, occasioning agricultural productivity decrease and soil nutrient depletion. The annual soil loss rate increased from 10.4 (2000) to 12.0 Mg ha−1 yr−1 (2012). Agricultural productivity loss occurred in more than 3 million hectares of crops and silviculture in 2000 and in more than 5.5 million hectares in 2012. Severely eroded areas lost between 13.1 and 25.9 times more nutrients than areas with low and moderate soil loss rates. These findings show that government policy should be directed to ensure the sustainable use of soils, mainly in agriculturally consolidated regions of the Brazilian Cerrado.