Fire Severity,Water Repellency Characteristics and Hydrogeomorphological Changes Following the Christmas 2001 Sydney Forest Fires     

R. A. SHAKESBY  C. J. CHAFER  S. H. DOERR  W. H. BLAKE  P. WALLBRINK  G. S. HUMPHREYS 《The Australian geographer》2003,34(2):147-175

Soil water repellency can enhance overland flow and erosion and may be altered by fire. The Christmas 2001 bushfires near Sydney allowed investigation of the relationship between fire severity, water repellency and hydrogeomorphological changes. For two sub-catchments with differences in fire severities in Nattai National Park, south-west of Sydney, this paper considers: (1) the links between fire severity based on SPOT image analysis and ground observation of fire severity and repellency; (2) the textural and organic/minerogenic characteristics of eroded sediment; and (3) erodibility, erosion and deposition of soils in both catchments. Ground surveys show that image analysis reflects well the degree of vegetation consumption by fire, but cannot adequately predict the degree of ground litter consumption, associated soil heating and repellency effects. Fire had varying effects on repellency, leaving it unchanged, destroying it or enhancing it, depending on the soil temperature reached. The main post-fire hydrogeomorphological changes have been widespread erosion and colluvial and alluvial deposition of topsoil in foot-slope locations and river systems, but only localised redistribution of the highly erodible, repellent sandy subsurface layer. The fire did not trigger major geomorphological change in the study area, but fires probably cause important topsoil and nutrient depletion and may also affect water quality.  相似文献   

新型砌块水土保持系统的应用研究   总被引：2，自引：0，他引：2  

耿灵生  巩向锋 《中国地质灾害与防治学报》2003,14(4):98-99,104

我国江河湖库众多，同时水土流失日趋严重，流失面积及速度已逐年增加。每年水库除险加固和河流治理等投资数百亿元，随着人们环保意识的加强，特别在近几年以长江和黄河为重点的堤防建设护岸工程中，联锁式砼砌块水土保持系统已逐渐成为我国水土保持领域中最重要的一种全新解决方案，被广泛采用。该系统既能有效防止水土流失、长久地防止坡面冲刷和保持坡体稳定，又能代替成本较高的常规护面，具有较广的推广应用前景。联锁式砼砌块水土保持系统是由多个独立的砼砌块相互啮合组合在一起的联锁矩阵，联锁式砼砌块铺面在各种动、静水条件下具有良好的整体稳定性，铺设于渗水土工布上。能有效保护土体不受水流冲刷和浸泡破坏。该系统在欧美已有多年的历史，是被工程实践证明了的性能卓越、经济实用、美观环保、可持续发展的水土保持系统，可广泛应用于河道和灌渠衬砌、沿海防潮堤、水库大坝边坡加固、铁路、高速公路边坡等防护和城市绿化工程。  相似文献   

陇东地区水土流失与地质作用初步分析          下载免费PDF全文

窦润吾 《甘肃地质》2003,12(1):92-96

陇东地区是黄河上游水土流失严重区 ,也是国家重点治理的地区之一。由于特殊的岩土体的存在 ,加重了这一地区水土流失作用的危害性。本文通过水土流失现象与地质作用的关系进行偿试性探讨 ,旨在从中找到防治水土流失的有效措施 ,开展治理工作  相似文献   

云南省癌死亡率与土壤环境中化学元素的关系   总被引：3，自引：0，他引：3  

曾昭华  曾雪萍 《云南地质》2003,22(4):395-402

癌病严重危害人类生命。研究表明：土壤环境中微量元素与肿病发生发展以及治疗相关，个别地区的地方病与元素含量关系密切。对土壤中元素含量研究证实：云南癌死亡率低于全国平均水平。文章详细讨论云南9种频发、52种常见癌症与元素的关系。  相似文献   

长江河源区的河水主要元素与Sr同位素来源   总被引：20，自引：1，他引：20  

赵继昌  耿冬青  彭建华  刘丛强  B.Dupre  J.Gaillardet  李文鹏  何庆成 《水文地质工程地质》2003,30(2):89-93,98

长江源区河水化学成分来自雨雪、蒸发盐岩、碳酸盐岩和硅酸盐岩。主要支流楚玛尔河、北麓河的主要阳离子为Na 、Ca2 和Mg2 ,占阳离子总量的97%以上.Ca Na,Mg Na,K Na的比值较低,87Sr 86Sr为0 709180±20～0 710280±11,河水成分以蒸发岩类溶解为主。发源于唐古拉山北坡的长江源头,及其支流主要阳离子为Ca2 ,Mg2 ,Na 占阳离子总量的97%以上,Ca Na,Mg Na,K Na的比值较楚玛尔河等河流高,87Sr 86Sr为0 708954±20～0 710455±18,表现为以碳酸盐岩和硅酸盐岩的溶解为主。计算表明,长江河源区河水中主要化学成分来自蒸发岩中Na 和Cl-,在河流水化学成分中占比例最大,长江河水中Cl-含量从河源区向下游明显逐渐减小,反应出河源区高寒干旱环境下河流蒸发岩的化学侵蚀作用较强的特征。  相似文献   

干旱半干旱地区农田土壤NO3-N深层积累及其影响因素   总被引：7，自引：0，他引：7  

郭胜利  张文菊  党廷辉  吴金水  郝明德 《地球科学进展》2003,18(4):584-591

以长期试验资料为基础,着重分析了干旱半干旱地区农田系统中施肥、作物、降水、耕作措施以及土壤类型和特性对产生土壤NO3-N深层积累的影响.分析发现,氮肥的过量施用和400～800 mm降水量偏低是导致干旱半干旱地区土壤NO3-N积累在100～300 cm土层的主要因素.随着氮肥用量的增加,NO3-N深层积累显著增加;氮磷配施有助于降低其积累量.不同作物对氮素的吸收利用效率也是影响NO3-N深层积累的因素,作物之间的轮作方式会有效降低NO3-N深层积累;休闲期种植合理植物可有效降低NO3-N深层积累.NO3-N深层积累主要产生在质地较重的土壤上,带正电荷粘土矿物对NO3-N吸附是导致热带土壤中NO3-N积累的主要因素.深入研究深层积累NO3-N的生物有效性、迁移变化机理、与作物根系之间的关系以及对土壤性状和环境的影响具有重要意义.  相似文献   

SOIL CONSERVATION EFFICIENCY OF DIFFERENT MODELS CONVERTING FROM STEEP FARMING SLOPE PLOTS IN YA''''AN, SICHUAN, CHINA     

Yulin DENG  Yan PENG  Yukuan WANG  Zongting YANG Institute of Mountain Hazards  Environment  Chinese Academy of Sichuan  P. R. China  College of Forestry  Horticulture of Sichuan Agricultural University  Sichuan  P. R. China. Water Resources Administration in Ya''''an  Sichuan  P. R. China. 《国际泥沙研究》2003,18(4)

Converting farming slope land into artificial forestland or grassland is a major measure of soil/water conservation. Five conversion practices, namely, 1) a control plot still tilled with a crop (maize), 2) a folder grass-growing plot seeded with Lolium perenne , 3) a young alder tree-growing plot, 4) a pear orchard plot and 5)a bamboo plot intercropped with folder grass, were monitored to compare the soil conservation efficiency of those changes in Ya'an, Sichuan for 3 years between September 1998 and August 2001. Results showed that the 5 designed converting models functioned differently in erosion control. The most effective model was bamboo groves intercropped with folder grass (Lolium perenne). The folder grass (Lolium perenne) growing model was more effective than the pure pear orchard model. The least effective model was the young alder tree-growing slope, which was even less effective than the control (a slope without converted cultivation). Meanwhile, changes in the soil's physical properties r  相似文献   

Acoustic and electromagnetic properties of soils saturated with salt water and NAPL     

Jos M. Carcione  Gza Seriani  Davide Gei 《Journal of Applied Geophysics》2003,52(4):177-191

Electrical, seismic, and electromagnetic methods can be used for noninvasive determination of subsurface physical and chemical properties. In particular, we consider the evaluation of water salinity and the detection of surface contaminants. Most of the relevant properties are represented by electric conductivity, P-wave velocity, and dielectric permittivity. Hence, it is important to obtain relationships between these measurable physical quantities and soil composition, saturation, and frequency. Conductivity in the geoelectric frequency range is obtained with Pride's model for a porous rock. (The model considers salinity and permeability.) White's model of patchy saturation is used to calculate the P-wave velocity and attenuation. Four cases are considered: light nonaqueous phase liquid (LNAPL) pockets in water, dense nonaqueous phase liquid (DNAPL) pockets in water, LNAPL pockets in air, and DNAPL pockets in air. The size of the pockets (or pools), with respect to the signal wavelength, is modeled by the theory. The electromagnetic properties in the GPR frequency range are obtained by using the Hanai–Bruggeman equation for two solids (sand and clay grains) and two fluids (LNAPL or DNAPL in water or air). The Hanai–Bruggeman exponent (1/3 for spherical particles) is used as a fitting parameter and evaluated for a sand/clay mixture saturated with water.Pride's model predicts increasing conductivity for increasing salinity and decreasing permeability. The best-fit exponent of the Hanai–Bruggeman equation for a sand/clay mixture saturated with water is 0.61, indicating that the shape of the grains has a significant influence on the electromagnetic properties. At radar frequencies, it is possible to distinguish between a water-saturated medium and a NAPL-saturated medium, but LNAPL- and DNAPL-saturated media have very similar electromagnetic properties. The type of contaminant can be better distinguished from the acoustic properties. P-wave velocity increases with frequency, and has dissimilar behaviour for wet and dry soils.  相似文献   

Neuzeitlicher Schadstofftrend: Polycylische aromatische Kohlenwasserstoffe (PAK) in aquatischen und terrestrischen Sedimenten     

Hubert Hellmann 《洁净——土壤、空气、水》2003,31(2):85-96

A Recent Contamination Trend: Polycylic Aromatic Hydrocarbons (PAHs) in Aquatic and Terrestrial Sediments Concentrations of polycylic aromatic hydrocarbons (PAHs) measured in aquatic sediments of small, medium‐sized or very large inland lakes, of estuaries as well as in terrestrial sediments from Germany, the UK, Finland, and the USA were plotted in 10 trend curves over the period from 1800 to 1990. The segments of the bore cores were dated for their deposition age. For comparability of the results, the trend is preferentially shown by the guide parameter fluoranthene. Until the 19th century, a constant background value of C_Fluo = 10…50 μg/kg was observed in all regions. Then a steep increase in concentration followed, reaching in the aquatic sediments a maximum in the period 1940 to 1965, while the individual fluoranthene values ranged widely from 90 to 2400 μg/kg. In several regions, a more or less distinct decrease superseded this maximum, although this development did not appear in terrestrial sediments, in one estuary, and in remote forest lakes in Finland. The trend curves reflect the atmospheric deposition of PAHs in airborne dust and in some cases the import through runoff via rivers. Thus, the sediment profiles depict the development of air pollution by pyrogenic contaminants over more than a century. Sediment profiles from rivers can be used only with a high degree of reservation, because of the irregularity and low representativity of the sedimentation.  相似文献   

The importance of plant root characteristics in controlling concentrated flow erosion rates   总被引：3，自引：0，他引：3  

G. Gyssels  J. Poesen 《地球表面变化过程与地形》2003,28(4):371-384

While it has been demonstrated in numerous studies that the aboveground characteristics of the vegetation are of particular importance with respect to soil erosion control, this study argues the importance of separating the influence of vegetation on soil erosion rates into two parts: the impact of leaves and stems (aboveground biomass) and the influence of roots (belowground biomass). Although both plant parameters form inseparable constituents of the total plant organism, most studies attribute the impact of vegetation on soil erosion rates mainly to the characteristics of the aboveground biomass. This triggers the question whether the belowground biomass is of no or negligible importance with respect to soil erosion by concentrated flow. This study tried to answer this question by comparing cross‐sectional areas of concentrated flow channels (rills and ephemeral gullies) in the Belgian Loess Belt for different cereal and grass plant densities. The results of these measurements highlighted the fact that both an increase in shoot density as well as an increase in root density resulted in an exponential decrease of concentrated flow erosion rates. Since protection of the soil surface in the early plant growth stages is crucial with respect to the reduction of water erosion rates, increasing the plant root density in the topsoil could be a viable erosion control strategy. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献