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1.
地表风蚀导致的粉尘释放涉及全球变化研究的热点。自然条件下对粉尘释放的观测可以为风洞试验结果提供验证并为开发预测模型提供数据支撑与关键参数。本研究在河北坝上风蚀区,通过观测风蚀事件中农田近地表PM10浓度、垂直通量与流失通量,以及风速和风沙流强度的变化,探讨农田风蚀过程中的粉尘释放特征。结果表明：地表风蚀释尘对近地表粉尘浓度的影响随高度增大而逐渐减弱,各高度的粉尘浓度变化趋势与摩阻风速、输沙率变化趋势相同;粉尘垂直通量和流失通量与摩阻风速呈幂函数关系,与输沙率呈线性关系;农田土壤跃移颗粒的轰击效率α数量级为10-7m-1。 相似文献
2.
风蚀影响因子的敏感性试验 总被引：3，自引：0，他引：3
对风蚀模式的各重要影响因子进行了敏感性试验，结果表明：①随风力的增大，跃动沙粒的粒径范围迅速增大，从而会使更多、更大的尘粒因受到更强烈的撞击作用而释放于空中。但随土壤水分和植被覆盖度的增加，跃动沙粒粒径范围会变窄，较大的粒子很难被激发到空中。②各种土壤沙流通量及尘粒释放率随粒径的变化趋势Q(d)和F(d)与相应的地表土壤有效粒度分布Ps(d)具有相似的特征，说明前人用近地层沙尘粒度分布来代表地表土壤的有效粒度分布是合理的。③若以总沙流通量Q>0.5 g·m-1·s-1为风蚀过程开始发生的标准，在干燥、裸露的情况下，沙土、沙壤土、壤土、黏土和粉黏土表面发生风蚀的临界摩擦速度都约为0.3 m·s-1。相同风力条件下（u*=0.6 m·s-1），若地表干燥（w=0）并忽略小于0.1 g·m-1·s-1的总沙流通量，则抑制5种土壤发生风蚀的最小植被覆盖度分别约为：沙土0.35、沙壤土0.45、壤土0.45、黏土0.55、粉黏土0.55；若地表裸露，抑制风蚀发生的最小水分含量分别为：沙土0.15、沙壤土0.18、壤土0.3、黏土0.36和粉黏土0.33。④通常情况下沙土最不易起尘，它在各个粒径的尘粒释放率比其他土壤均约小3~5个量级。粉黏土最易起尘，且粒径较小，较容易传输到下游很远处。⑤总尘粒释放率F和总沙流通量Q随风力、地表条件的变化一般是同相的，即Q增大，F也会增大。⑥一般情况下F随摩擦速度u*的增大或植被覆盖度cf和土壤水分w的减小而增大；土壤拖曳系数sx和弹性压力垂直分量pye的增加会大大降低尘粒释放率。⑦通常风蚀情况下，5种土壤中粉黏土和沙壤土因聚合粒子破碎产生的尘粒释放率Fc最大，Fc随风力、地表条件变化的敏感度也最强；沙土的Fc最小，其对风力、地表条件的敏感度也最弱。 相似文献
3.
Wind tunnel test of the influence of moisture on the erodibility of loessial sandy loam soils by wind 总被引：3，自引：0，他引：3
Loessial sandy loam soils are the major soil categories in the northern Loess Plateau, China. Owing to a dry, windy climate and sparse surface cover, wind erosion is a serious problem and dust (sand) storms occur frequently. Soil moisture is one of the most important factors influencing resistance to wind erosion. The influence of moisture content on the erodibility of sandy loam soils was investigated through wind tunnel simulations. Results showed that the threshold velocity for soil particle movement by wind increases with increasing soil moisture by a power function. The intrinsic factor in the increase in soil resistance due to moisture content is the cohesive force of soil water. Cohesive forces of the film and capillary water are different; the influence of soil moisture on threshold velocity was shown to follow a step-like pattern. The wind erosion modulus of sandy loam was directly proportional to the cube of the wind velocity or the square of the effective wind velocity (V−Vt). There existed a negative exponential relationship between the wind erosion rate and soil moisture content. Initially, as soil moisture increased the decrease in the wind erosion rate was rather rapid. When the moisture content reached more than 4%, the rate of decrease in erosion slowed and became almost constant with successive increments of moisture. This suggests that different soil moisture contents can prevent wind erosion at different levels. Four percent soil moisture could only reduce the erodibility of the sandy loam soil by a small degree. 相似文献
4.
若干风蚀粉尘释放模型述评 总被引：6，自引：1，他引：6
粉尘气溶胶对大气、陆地和海洋多方面的影响促进了粉尘释放的模拟研究。Gillette和美国FPA的粉尘释放模型相对地比较简单，主要考虑了摩阻速度和土壤质地对粉尘释放的影响，没有考虑粉尘释放过程的微观机制；邵亚平和Alfaro等人的DPM粉尘释放模型都通过土壤粒度分布、粗糙度和起动摩阻速度等参数表达了地表特征对粉尘释放的影响，且都描述了粉尘释放的微观机制。20多年来粉尘释放的模拟研究取得了重要进展，主要表现在通过室内和野外实验证实了粉尘释放的主要机制为跃移颗粒的冲击，并分别从粉尘的结合能与跃移颗粒动能及跃移颗粒产生的弹坑体积角度来描述这个微观机制。然而所有的模拟工作只是从某一方面反映了粉尘释放过程，对粉尘释放机制还没有完全了解清楚，特别的是目前关于粉尘结合能研究还有很大的不确定性，这也是粉尘释放模型需要改进的地方。 相似文献
5.
The physics of the two processes (saltation and sandblasting) leading to fine mineral dust emissions by wind erosion in arid or semi-arid areas has been detailed and modeled. The combination of these two models has led to a physically explicit Dust Production Model (DPM). In this work, sensitivity tests are performed with the DPM to determine the nature of the main soil parameters that control dust emissions by sandblasting. It is found that the soil roughness length and the dry size distribution of the soil aggregates constituting the loose wind erodible fraction of the topsoil have the greatest influence on the soil potential for mineral dust production. Contrary to what is often assumed, soil texture is not a relevant parameter.In the light of these new findings, results of vertical flux measurements performed over a wide variety of sources in Niger and the US south west (14 soils) have been reanalyzed. Results show (1) that for the tested soils the DPM, and hence sandblasting, explain all dust emissions, and (2) that 13 of the 14 soils that had been selected a priori for their high potential for dust emissions contained a fine soil-aggregate component. This is consistent with the sensitivity tests indicating that the presence of such a component could enhance dust emissions by one order of magnitude. Finally, it can be concluded that most of the apparent scatter in the experimental results was in large part due to an inappropriate choice of soil parameters to interpret them. 相似文献
6.
粉尘释放是风蚀造成危害的一个重要过程。以农牧交错带沙区和非沙区农田土壤为研究对象,利用室内风洞模拟实验,实时监测了风蚀过程中释放的PM10,分析了PM10的动态变化特征,以深入认识土壤风蚀粉尘释放机理。结果表明：非沙区农田土壤风蚀强度远低于沙区农田,与风速呈指数函数关系;非沙区农田的土壤粉尘释放在不同风速下均以气流直接抬升模式为主,平均PM10通量与风速呈线性函数关系,最大PM10通量与风速呈幂函数关系;沙区农田的土壤粉尘释放在风速增大到一定程度后呈气流直接抬升和砂粒跃移冲击复合模式,最大PM10通量增加不明显,但平均PM10通量明显高于非沙区农田;对于沙区和非沙区农田而言,平均PM10通量与风蚀速率呈对数函数关系。 相似文献
7.
干旱半干旱地区是中国的农业后备战略基地,然而近年来该地区农田土壤风蚀现象严重,沙/尘释放量显著增大,威胁农业的可持续发展和生态系统平衡。目前绝大部分的天气和气候模式仅考虑了沙漠地表起沙,忽视退化农田的土壤风蚀起沙,导致起沙通量模拟存在很大的不确定性。对20世纪50年代以来干旱半干旱区农田土壤风蚀起沙特征及参数化做了详细的分析总结,回顾并梳理了干旱半干旱区农田土壤风蚀观测和数值模拟的研究脉络以及存在的问题,为提高农田起沙的模拟精度提供了有效参考,对中国干旱半干旱区农田土壤风蚀防治、土地荒漠化治理以及理解未来土地利用改变对大气污染的影响具有重要意义。 相似文献
8.
中国北方干旱/半干旱区是全球主要的沙尘源区之一,风蚀造成的沙尘排放可导致大量的土壤有机质（SOM）与养分流失,并通过传输与沉降过程对其进行空间再分配,对空气质量、气候变化、植被生长及生物地球化学过程等具有重要影响。本文利用WRF/Chem（Weather Research Forecasting with Chemistry）v3.7.1大气化学传输模型,对1980—2015年间中国北方沙尘排放及其引起的SOM、全氮（TN）与全磷（TP）的时空变化过程进行了精细化模拟,探究了中国北方风蚀引起的SOM、TN与TP养分流失的时空变化特征。结果表明：① 1980—2015年来平均每年约有66.59 Tg的沙尘颗粒排放至大气;② 沙尘排放具有较大的时空差异,沙尘排放源区主要集中在新疆东部、内蒙古西部的巴丹吉林沙漠和腾格里沙漠等地区;③ 每年因沙尘排放引起的SOM、TN和TP流失量分别约为0.07 Tg、0.004 Tg和0.005 Tg;④ 1980—2015年间中国北方沙尘排放及其引起的SOM、TN与TP的流失量具有较强的年际波动,未呈现显著的趋势性变化特征。本研究对于认知风蚀在碳循环与养分循环过程中的作用,以及对深入了解中国北方的土地退化机理具有重要意义。 相似文献
9.
戈壁砾石覆盖度与风蚀强度关系实验研究 总被引：3，自引：1，他引：2
戈壁表面的砾石覆盖度对风沙物质的运移有不可忽略的影响,在极端干旱区砾石覆盖是防沙治沙的重要手段。通过风洞实验模拟了阿拉善戈壁区砾石覆盖度与风蚀强度的关系。结果表明,当因地表风化作用等产生的松散颗粒物被吹蚀后,不同地点、不同样品之间风蚀强度有明显的差异,因而砾石覆盖度与风蚀强度之间的相关关系并不显著;但数据标准化后则表明,当砾石覆盖度在40%以下时,随砾石覆盖度的增加风蚀强度也有所增大。戈壁地区的风沙运动中,在砾石覆盖度小于40%条件下,不同风速下风蚀强度的变异系数是不同砾石覆盖度下的风蚀强度的变异系数的2倍左右。在极端干旱的戈壁区,影响风蚀强度的因素十分复杂,砾石覆盖度增大不仅不能控制风蚀现象的发生,反而增强气流对地表的风蚀能力,这一因素可能是阿拉善高原戈壁区成为中亚强沙尘暴主要源地的重要原因之一。 相似文献
10.
The agricultural landscape in the semi-arid central Ebro Basin is changing from dry farming towards land abandonment. This study aims to describe quantitatively the influence of this land use change onto wind erosion susceptibility in this region. Additionally, the effects of tillage operations on wind erosion rates were evaluated. A portable wind tunnel was used to assess the relative sediment loss rates at three test sites near Zaragoza. Three different land use systems varying in crust disturbance level were investigated – (1) fallow land with undisturbed physical soil crusts, (2) simulated sheep trampling and (3) conventional tillage (dry farming).The results show that simulations on undisturbed crusted soils produce little soil loss. Consequently, wind erosion can be considered as negligible on these surfaces. Simulated sheep trampling during wind tunnel test runs produce 10 times higher sediment losses than simulations on undisturbed crusted soils. Highest sediment losses (50 times) were observed from rolled surfaces. Because of the ongoing extensification process, the distributions of physical soil crusts will most probably further increase. According to the results, this would lead to a reduction of wind erosion susceptibility in the central Ebro Basin depending on intensity and time of sheep pasturing and tillage. 相似文献
11.
《自然地理学》2013,34(5):381-400
Eolian erosion typically has not been considered a significant process on the humid southeastern coastal plain of the United States. A preliminary study of eolian erosion from an agricultural field was undertaken during the late winter of 2002 and early spring of 1999. During those times local agricultural practices leave fields bare while frontal systems produce frequent high wind events. Dust emissions were measured with two samplers; modified Wilson and Cooke passive dust traps and high-volume air samplers. Results of the study indicate that wind erosion is a significant process on agricultural fields of the North Carolina Coastal plain. Dust flux off of the field during the largest of five measured events was estimated as high as 126 kg/m with total losses of 3070 kg/ha. Atmospheric concentrations of suspended material were measured at 58,815 μgm-3. Sediment erosion was not evenly distributed across the field. Erosion was focused over soils that are better drained. Low levels of soil moisture did not eliminate erosion but instead produced pulses of sediment emission as sustained wind continually dried then activated sequential layers of the field surface. Soil moisture and topography appear to be the primary controls on spatial erosion differences and soil characteristics likely play a secondary role. 相似文献
12.
适用于河北坝上地区的农田风蚀经验模型 总被引：5，自引：4，他引：1
目前,中国缺少一种被广泛认可、普遍适用于中国自然条件的农田风蚀模型。本研究利用多年的野外风沙观测数据和风洞模拟实验结果,建立了一种基于河北坝上地区自然环境的农田风蚀经验模型。该模型涵盖风力侵蚀因子、粗糙干扰因子和土壤抗蚀因子三大风蚀影响因子,包括起沙风速、地表粗糙度、土壤可蚀性和土壤含水率四大风蚀影响要素,可对各种农田地表的风蚀量进行定量计算和预测。应用该模型对坝上地区2013年风蚀季农田风蚀量进行定量计算。结果表明,翻耕耙平地的平均风蚀量为39.45 t·hm-2·a-1,莜麦留茬地的平均风蚀量为14.08 t·hm-2·a-1,与采用其他方法得到的结果比较接近。在更广泛地区对模型进行验证和修订,促进该风蚀模型与“3S”技术融合是下一步的重点工作。 相似文献
13.
利用遥感综合分析西风引导气流与地形对沙尘运移路径的影响 总被引：2，自引：7，他引：2
沙尘暴的发生受大气环流、地表状况、降雨的影响，还受到局部地区地形的影响。一次规模较大的沙尘暴过程，沙尘可以从蒙古国和我国西部沙源地输送到我国东部、韩国、日本乃至夏威夷、美国西海岸。中日亚洲沙尘暴ADEC项目对亚洲沙尘暴的起沙、传输和降落的运行机制已经作了深入的研究，并建立了亚洲沙尘暴的数值模拟系统。本文以影响北京地区的沙尘暴事件为例，利用遥感技术，综合DEM地形数据和地面实测数据分析西风引导气流和地形对沙尘运移路径影响，将MODIs影像数据和DEM地形数据以及地面观测站点实测数据相结合，进行综合分析，结果表明在一次沙尘暴过程中，沙尘在运移过程中的运移路径明显地受到西风引导气流、沙尘粒子自然沉降规律以及局部地形的影响，要预防(减少)北京地区的沙尘暴仅仅作好北京地区的生态环境建设是不够的，加强北京周边地区，尤其是张家口地区、官厅水库库区及库区周围地区的生态环境建设尤为重要。 相似文献
14.
L.-Y. Liu X.-Y. Li P.-J. Shi S.-Y. Gao J.-H. Wang W.-Q. Ta Y. Song M.-X. Liu Z. Wang B.-L. Xiao 《Journal of Arid Environments》2007,68(4):611-623
Wind erosion and desertification are severe problems in China's farming-pastoral ecotone. In this study, wind erodibility of five major soils in both uncultivated and simulated cultivated conditions, were determined through wind tunnel tests at nine wind speeds ranging from 10 to 26 m s−1. The average wind erosion rate (g m−2 min−1) under the uncultivated condition (q0) for the five soils could be set in the order: chestnut soil (28.5)>brown soil (24.8)>sierozem (21.8)>chernozem (19.9)>fixed sandy soil (11.4). The highest natural wind erosion might take place in the semi-arid steppe zone where the Chestnut soils predominate. Cultivation can significantly accelerate wind erosion, the mean wind erosion rate under the cultivated condition (qc) for all five soils was 743.7 g m−2 min−1 in the following order: sandy soil (3313.2)>brown soil (227.2)>chernozem (221.8)>sierozem (85.1)>chestnut soil (81.2). For both the uncultivated and cultivated soil samples, the relationship between wind erosion rate (q) and wind speed (U) could be expressed in general as q=A eBU (A and B are constant coefficients). There was a critical wind speed for each soil type except for the sandy soil. Below the critical wind speed, cultivation reduced wind erosion rate possibly due to soil clodiness and roughness effects. Above the critical speed, cultivation greatly intensified wind erosion rates due to the break down of the original soil structure. The critical wind speed measured at 20 cm above the soil surface was 20 m s−1 for the brown soil, 14 m s−1 for chernozem and the chestnut soils, and 10 m s−1 for the sierozem. Among the five tested soils, the high wind erosion rate of the cultivated sandy soil showed its extreme sensitivity to cultivation, possibly because of the structureless nature of the loose sand. The “effect of cultivation on wind erosion” index, η (=qc/q0), increased exponentially with the increase of wind speed, indicating that under higher wind speed conditions, cultivation could result in more severe wind erosion. 相似文献
15.
Influence of soil texture on the binding energies of fine mineral dust particles potentially released by wind erosion 总被引：1，自引：0，他引：1
Stphane C. Alfaro 《Geomorphology》2008,93(3-4):157-167
Models of the two aeolian processes (saltation and sandblasting) that lead to emission of fine dust particles (PM20) by wind erosion in arid and semi-arid areas have been combined to form the so-called ‘Dust Production Model’ (DPM). In this model, the size dependent binding energies of PM20 embedded within the wind-erodible loose soil aggregates or in the soil surface itself are key input parameters. Indeed, their values condition at the same time the intensity of emissions and their initial size distribution. Previous comparisons of vertical mass fluxes measured on-field with the model predictions suggest that these energies might be relatively independent of soil texture and also probably composition. Because this would greatly facilitate application of the DPM at regional or global scale, the objective of this work is to check experimentally the veracity of this result. The strategy that has been designed for this has involved selecting four natural soil samples collected in various source areas of the world and covering a wide range of textures and compositions. Then, these soil samples have been used to perform carefully controlled wind erosion simulations in a wind tunnel. During the experiments, which were carried out at different wind speeds with each soil, the horizontal flux (Fh) of saltating soil aggregates has been monitored. At the same time, number concentrations (Ci) of PM20 released by the sandblasting process were recorded in the 6 size classes of an optical size analyzer. Thus, the efficiency of the sandblasting process (defined as the ratio of Ci to Fh) could be determined for each of these size classes. Analysis of the results obtained in similar saltation conditions shows that for the four tested soils, and within the range of contents in clay and other components favoring aggregation (mostly organic matter and carbonates), the influence of soil composition and texture on binding energies of the PM20 particles within soil aggregates is at best a second order effect that can be neglected in large scale modeling of wind erosion by the DPM. 相似文献
16.
17.
威连滩冲沟砂黄土的风蚀与降雨侵蚀模拟实验 总被引：3，自引：0，他引：3
通过风洞与模拟降雨实验，研究了风力与降雨对青海省贵南县威连滩冲沟砂黄土的复合侵蚀作用。实验得出：①风蚀后的降雨使砂黄土表面在风干过程中形成了一层较为坚硬的结壳，增大了土壤的抗蚀性，降低了第二次风洞实验后期的风蚀率;②土壤水分与人为扰动是影响土壤风蚀的两个重要因素。当土壤水分较小时，风蚀率受人为扰动影响巨大;当土壤水分较大时，人为扰动对土壤风蚀的影响较小;③在持续降雨的实验条件下，砂黄土的产流、产沙量随着雨强的变化而改变。这种变化与表土的侵蚀率、可蚀性物质的多少、土壤水分以及土壤的入渗率等都有很大的关系。 相似文献
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风蚀作用下的土壤碳库变化及在中国的初步估算 总被引：12，自引：2，他引：10
土壤有机碳库储量巨大且在表层富集 ,而风力侵蚀具有巨大的卷挟起沙、搬移输运和空间再分配能力 ,对土壤有机碳库的演变具有重要影响。在风力侵蚀作用下 ,风蚀发生地、风蚀土壤输运途中以及风蚀土壤沉降地的土壤有机碳库有着不同的变化过程。基于质量平衡原理 ,可以建立土壤有机碳流失及各路径碳输移量估算的模型。依据第二次全国遥感侵蚀调查以及第二次全国土壤普查数据 ,在GIS支持下 ,分析了中国土壤有机碳库以及风力侵蚀的空间格局 ,并计算得到风力侵蚀作用下中国土壤有机碳库储量变化以及各路径碳输移量。研究表明 ,我国因风力侵蚀造成的土壤有机碳流失量约为 5 9 76× 10 6 tC/yr,风蚀所致CO2 排放约为 2 9 88× 10 6 tC/yr;风蚀所致的土壤有机碳流失主要发生在中国西北部的干旱半干旱的农区和牧区 相似文献
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阿拉善高原东南部干涸湖盆沉积物粒度特征 总被引：1，自引：1，他引：0
干涸湖盆是西北干旱区广泛分布的地貌类型,也被认为是重要的沙尘源区,但目前对该类地表的土壤风蚀过程与特征研究较少。干涸湖盆沉积物和植被盖度的空间差异性导致沙尘释放过程和风蚀过程具有时空差异性。为了探讨干涸湖盆的土壤风蚀特征,选择阿拉善高原东南部的干涸湖盆为研究区域,沿主风向（西北-东南）方向,选择4个区域,野外实地收集湖相沉积物和灌丛沙丘样品,进行粒度特征分析。结果表明：（1）干涸湖盆地表沉积物粒度存在明显的空间差异性,一方面反映了物源的差异性,另一方面反映了风蚀过程的差异性。（2）受植被和风程长度的影响,上风向和下风向风蚀较弱,而中部地区风蚀最大。 相似文献