~(137)Cs示踪法估算滇池流域土壤侵蚀

用13 7Cs示踪法探讨滇池流域的土壤侵蚀表明 ,不同利用方式农田的侵蚀量从 2 2 4t km2 yr(菜地 )～ 345 6t km2 yr(园地 )。与太湖地区相比 ,粗放的耕作方式也改变了当地农田的侵蚀排序。特别是土壤中的13 7Cs含量为 35 5～ 872Bq m2 ,比世界其他许多地区都低 ,却与青藏高原相邻地区的数值相近。原因可能是气候特点及远离核试验中心。经与其他方式所得结果比较可见 ,用13 7Cs示踪法研究滇池流域的中长期土壤侵蚀既简便快速又合理可行。     

基于GIS和RUSLE的滇池流域土壤侵蚀敏感性评价及其空间格局演变

土壤侵蚀是滇池流域重要的生态问题之一,掌握滇池流域土壤侵蚀敏感性的时空变化特征有助于水土保持工作的实施和改进。以降雨量、DEM、土壤类型和Landsat影像为数据源,选择降雨、土壤、坡度坡长、植被覆盖4个因子建立土壤侵蚀敏感性评价体系,对滇池流域进行土壤侵蚀敏感性评价。结果表明:滇池流域土壤侵蚀敏感性以轻度敏感和中度敏感为主。空间分布上,轻度敏感区主要分布在滇池周边。中度敏感区主要分布在滇池流域山地区域,地形陡峭。时间变化上,1999—2014年滇池流域土壤侵蚀敏感程度呈下降趋势。轻度敏感区域面积增加20.18%,中度敏感区域面积减少20.31%,轻度敏感区的增加来源于中度敏感区的转变,转变区域分布于滇池流域西北部和东南部。在土壤侵蚀敏感性影响因子中,降雨是影响滇池流域土壤侵蚀敏感性的关键因子。研究滇池流域土壤敏感性时空变化,识别滇池流域易发生土壤侵蚀的区域,有助于该区域水土保持措施实施、生态治理和土地利用优化。     

Fingerprinting the sources of suspended sediment delivery to a large municipal drinking water reservoir: Falls Lake, Neuse River, North Carolina, USA

Purpose

We employ a geochemical-fingerprinting approach to estimate the source of suspended sediments collected from tributaries entering Falls Lake, a 50-km² drinking water reservoir on the Neuse River, North Carolina, USA. Many of the major tributaries to the lake are on North Carolina’s 303(d) list for impaired streams, and in 2008, the lake was added to that list because of high values of turbidity, likely sourced from tributary streams.

Materials and methods

Suspended sediments were collected from four streams with a time-integrated sampler during high-flow events. In addition, composite sediment samples representing potential sources were collected from stream banks, forests, pastures, construction sites, dirt and paved roads, and road cuts within tributary basins. Radiocarbon dating and magnetic susceptibility measurements were used to determine the origin of stream bank alluvial deposits. Sediment samples were analyzed for the concentrations of 55 elements and two radionuclides in order to identify tracers capable of distinguishing between potential sediment sources. The relative sediment source contributions were determined by applying a Monte Carlo simulation that parameterized the geochemical tracer data in a mixing model.

Results and discussion

Radiocarbon and magnetic susceptibility measurements confirmed the presence of “legacy” sediment in the Ellerbe and New Light Creek valley bottoms. Mixing model results demonstrate that stream bank erosion is the largest contributor to the suspended sediment load in New Light Creek (62%), Ellerbe Creek (58%), and Little Lick Creek (33%), and is the second largest contributor in Lick Creek (27%) behind construction sites (43%).

Conclusions

We find that stream bank erosion is the largest nonpoint source contributor to the suspended sediment load in three of the four catchments and is therefore a significant source of turbidity in Falls Lake. The presence of legacy sediment appears to coincide with increased contributions from stream bank erosion in Ellerbe and New Light creeks. Active construction sites and timber harvesting were also significant sources of suspended sediment. Water quality mitigation efforts need to consider nonpoint-source contributions from stream bank erosion of valley bottom sediments aggraded after European settlement.     

艾比湖地区30多年来土壤侵蚀时空变化规律研究

以遥感与GIS为技术支撑,对新疆艾比湖地区1972-2005年土壤侵蚀进行了动态监测,并对33年来土壤侵蚀时空变化进行分析.研究结果表明.艾比湖地区的土壤侵蚀以风蚀为主.水蚀面积变化不大,风蚀区各强度面积变化明显.其时空变化特征:(1)侵蚀面积1977-2005年总体呈下降趋势,其中1992-2001年侵蚀面积减少显著,且以轻度和强度风蚀减少为主;其次是2001-2005年侵蚀面积减少明显.以中度和轻度风蚀减少为主.只有1972-1977年侵蚀面积有所增加.(2)侵蚀变化速度1977--2005年呈现总体下降,而且1990-2005年下降的速度趋快.(3)侵蚀强度趋于下降.水蚀各强度等级变化很小.风蚀各强度等级变化明显,以强度高的类型向强度较低类型转换为主.究其原因主要是20世纪90年代以来,由于艾比湖水面持续增大和国家一系列生态保护与建设工程的实施,使艾比湖周边风力侵蚀得到有效遏制,区域生态环境明显改善.     

基于USLE和GIS/RS的滇池流域土壤侵蚀研究

人类不合理的土地利用方式是水土流失发生的主要原因之一。研究滇池流域的土壤侵蚀现状,对于控制流域内生态环境恶化,建立良好的生态环境具有十分重要的意义。采用USLE模型并结合RS,GIS技术对滇池流域土壤侵蚀进行估算,分析不同坡度和不同植被类型对侵蚀的影响,同时提出了基于植被覆盖度的植被覆盖与作物管理因子计算方法。结果表明:滇池流域土壤侵蚀量为233.96万t,土壤侵蚀以中、轻度侵蚀为主,强烈以上侵蚀较弱。侵蚀主要发生在8°～35°的区域,灌木林地的侵蚀模数最大。在GIS支持下,通过土壤侵蚀模型进行定量评价,可高效、客观地反映土壤侵蚀情况,对减少流域内新增土壤侵蚀风险,控制非点源污染有着重要的参考价值。     

Soil degradation due to erosion under furrow irrigation

It is found that the differentiation and degradation of soil depend on surface slope, water flow rate, and furrow length. The development of irrigation erosion on irrigated areas results in the formation of three zones: erosion, stabilization, and accumulation. The high slopes of irrigated plots favor an intense erosion-accumulation process. Depending on the surface slope and the water flow rate, 0.48–19.40 t of soil is washed away from 1 ha. Irrigation erosion affects the density and porosity of soils, and erosion on the slope is enhanced during the differentiation of soil varieties. The texture of soils becomes coarser in the upper erosion region and finer in the aggraded varieties. On the basis of the quantitative assessment of soil erosion rate, the possible losses in dry matter, humus, and essential nutrients are calculated, as well as their removal with water flows.     

基于RS,GIS的滇池流域水土流失变化研究

滇池已被列入国家“三河三湖”治理的重点，也是云南省九大高原湖泊保护治理的重中之重。面源污染是滇池污染的主要原因，而水土流失则是面源污染的主要来源，占面源污染总量的80％；水土流失是导致滇池环境恶化的重要因素，防治水土流失是治理滇池的重要内容。在RS与GIS技术支持下，通过对1987年和2002年2期滇池流域TM数据的处理，分析流域内的水土流失分布、面积及强度变化，得出水土流失状况趋缓的结论；结合滇池流域森林覆盖和土地利用／覆盖动态变化数据，找出水土流失变化的主要原因是森林植被覆盖率的提高；提出了加速防护林体系建设、发展生态农业和加强法制宣传教育等水土保持建议。     

The use of a new portable erosion measuring device for assessing the erodibility of the surface layers of flood embankments

When a river overtops its flood banks, water running down the landward side of the bank can rapidly erode the soil surface and scour the bank, sometimes leading to breaches and collapse. A covering of living vegetation, particularly grass, can reduce this risk of water erosion. As part of a project to assess the effectiveness of different management regimes on bank vegetation cover, direct measurements were required of the erodibility of the soil surface. A portable erosion measurement device (EMD) was developed by LAB Coastal with the support of the Environment Agency. This could direct water flowing at known velocities across areas of the flood banks, and it was used to test directly the erosion resistance of vegetated grass banks at three sites. The EMD gave a direct measure of the erodibility of a small sample of flood bank. While measurements of soil strength and assessments of vegetation cover were useful, they did not always correctly characterize the stability of the bank surface as measured directly by the EMD. The EMD and its use are described and the results obtained are discussed. The results indicate that flood banks need to be mown at least once a year to make them less vulnerable to erosion.     

基于DEM的抚仙湖流域土壤侵蚀综合分析

利用研究区地形图制作数字高程模型（DEM）,并由DEM提取坡度、坡向图,与土地利用类型、土壤侵蚀强度和抚仙湖历年水质（透明度、TN、TP平均值）等专题信息叠置,提取水土保持专题信息,并对提取结果进行应用分析,以确定抚仙湖流域不同土地利用类型和地形因子与侵蚀类型及侵蚀过程的关系。研究结果表明:抚仙湖的水质和流域的土地利用状况相关,抚仙湖流域土壤侵蚀方式具有明显的垂直分带性,土壤侵蚀强度受到土壤类型和植被覆盖状况的影响。不同坡向的侵蚀强度有明显差异,同时坡度不同是引起土壤侵蚀类型差异的主要因素。     

基于GIS/RS和USLE鄱阳湖流域土壤侵蚀变化

将空间信息技术（RS和GIS）和通用土壤流失方程（USLE）相结合对鄱阳湖流域土壤侵蚀量进行计算。分别利用1990年和2000年TM/ETM+影像分类得到两期土地利用/覆盖类型图,结合鄱阳湖流域数字高程模型（DEM）、土壤类型分布图和流域降雨资料分别获取USLE模型中各因子值的空间分布,最后计算流域2个年份的土壤侵蚀空间分布图。研究表明：鄱阳湖流域土壤侵蚀区域主要分布在赣江上游,信江上游,抚河上中游和修水上游地区;鄱阳湖流域1990年和2000年大范围土地经受着Ⅰ级微度与Ⅱ级轻度侵蚀,其侵蚀面积之和分别占流域面积的97.38%和97.30%;而流域产沙主要来源于Ⅱ级轻度侵蚀和Ⅲ级中度侵蚀,所占土壤侵蚀总量分别为58.16%和51.20%,其中中度以上等级的侵蚀对产沙量的贡献是不可忽视的;从1990年到2000年土壤侵蚀等级变化呈现了由中等级侵蚀（Ⅱ级轻度侵蚀和Ⅲ级中度侵蚀）向低等级（Ⅰ级微度侵蚀）和高等级侵蚀（Ⅴ级极强度和Ⅵ级剧烈侵蚀）的2个极端演化的趋势。鄱阳湖流域土壤侵蚀量从1990年到2000年增长幅度达6.3%;土壤平均侵蚀模数都约为1 100 t/(km2·a),属于Ⅱ级轻度侵蚀。分析2个年份的土地利用/覆盖变化,发现鄱阳湖流域湿地和农田面积减少,建筑用地增加均是造成土壤侵蚀量增加的因素,而降雨侵蚀力因子空间格局也对土壤侵蚀空间分布具有重要影响,最后提出了鄱阳湖流域水土保持规划措施。     

东北黑土区埂带植物树莓栽培技术及其水土保持效益

[目的]分析树莓对土壤水分的影响及其水土保持和经济效益,为东北黑土区坡耕地水土流失综合治理提供新的水土保持埂带经济植物。[方法]在东北黑土区进行梯田埂和地埂栽植试验。[结果]树莓在埂带上具有良好的适应性,具有较好的保持土壤水分的作用。栽植第3a树莓小区土壤侵蚀量低于东北黑土区容许土壤流失量〔200t/(km2·a)〕,保水率达到86.6%以上。树梅在梯田埂上产值达17 200元/hm2,在地埂上产值达16 800元/hm2。[结论]树莓在埂带上水土保持效益显著,可以在东北黑土区埂带上栽植推广应用。     

Soil conservation on road embankments using palm‐mat geotextiles: field studies in Lithuania

The application of geotextile mats constructed from the palm leaves of Borassus aethiopum (Borassus) and Mauritia flexuosa (Buriti) was investigated in field experiments. The use of geotextiles caused improved soil moisture storage during dry summer periods on a steep (21–25°) roadside slope in Lithuania. The enhanced soil moisture under the Borassus and Buriti mats encouraged better root development of perennial grasses, increased the number and weight of earthworms and increased the dry biomass of perennial grasses by 50.5 and 18.2%, respectively, compared with a grassland control. The mean rate of water erosion from bare soil during the study period from 17/04/2007 to 11/12/2008 was 33.21 Mg/ha. The cover of palm‐mat geotextiles decreased soil losses from bare fallow soil by 94.8–91.1%. An erosion rate of 0.85 Mg/ha over this 21‐month period was measured on the slope under perennial grasses without geotextile cover. Application of geotextile cover on perennial grasses completely prevented soil erosion by water. Therefore, use of geotextiles has clear soil and water conservation benefits on industrial slopes susceptible to erosion. The use of geotextiles has multiple benefits including soil conservation, the improvement of plant growth conditions and the encouragement of earthworm populations.     

基于GIS和USLE的鄱阳湖流域土壤侵蚀敏感性评价

水土流失是鄱阳湖流域严重的生态环境问题。以USLE模型为基础,结合鄱阳湖流域自然环境特征,确定评价指标及其分级标准。运用GIS技术,实现研究区土壤侵蚀敏感性综合评价,揭示其流域空间分异特征及规律,并对流域土壤侵蚀产生的原因进行分析,提出了调控措施。研究表明：流域土壤侵蚀敏感性主要以中度和高度敏感为主,不敏感、轻度和极度敏感所占比例较少。从空间分布上来看,极敏感地区集中分布在赣东南部的宁都县和会昌县,赣中吉安县和泰和县,赣西北的万载县,赣东北的德兴市和上饶市;高度敏感地区主要分布在赣江、抚河、信江、饶河及修水这5条河流域中、上游河流两岸和鄱阳湖滨湖地区,以及坡度<25°的坡耕地、疏幼林地;中度敏感性地区分布面积最广,在整个流域内各地貌和用地类型(除水域外)上均有分布;轻度敏感性地区主要分布在赣西南的井冈山市、万安县、赣县、大余县一带,呈月牙形分布;不敏感地区以鄱阳湖及五河沿线向四周呈辐射状分布,还包括赣西北的拓林水库、赣西江口水库和赣东洪门水库等区域。     

Sediment and Phosphorous Fluxes Analysis in Aquia Creek,a Sub-watershed of the Chesapeake Bay Basin,VA, USA

Decline in global surface water quality around the world is closely linked to excess sediment and nutrient inputs. This study examined sediment and phosphorus fluxes in Aquia Creek, a fourth-order sub-watershed of the Chesapeake Bay located in Stafford, Virginia. The Revised Universal Soil Loss Equation (RUSLE), sediment delivery ratio (SDR), field sediment traps, bank erosion pins, and LIDAR data, combined with historical aerial images, were used in quantifying rill and inter-rill erosion from the basin, as well as internally generated sediments. Stream water and stream bank soils were analyzed for phosphorus. RUSLE/SDR modeling estimates a basin total sediment flux of 25,247 tons year^?1. The greatest calculated soil losses were in deciduous forests and cropland areas, whereas medium and high-intensity developed areas had the least soil loss. Cut-bank erosion ranged from 0.2 to 27.4 cm year^?1, and annual bank sediment fluxes were estimated at 1444 Mg, with a corresponding annual mass of phosphorous of 13,760 kg year^?1. The highest bank loss estimates were incurred along reaches draining urban areas. Stream water total phosphorous levels ranged from 0.054 μg g^?1 during low flows to 134.94 μg g^?1 during high discharge periods in autumn and spring. These results show that stormwater management practices in urban areas are limiting runoff water and soil contact, reducing surficial soil loss. However, the runoff acceleration due to expansion of impervious surfaces is progressively increasing the significance of intrinsic sediment and phosphorous sources by exacerbating stream bank erosion and resuspension of internally stored sediments.     

Testing of the hydromechanical prediction model of soil erosion under the conditions of Georgia

A hydromechanical model for predicting water (rain-induced) soil erosion was tested on the experimental plots of the Research Institute of Tea and Subtropical Crops in Zendidi village (the Ajara Autonomous Republic) and the Sabashvili Institute of Soil Science, Agrochemistry, and Melioration in Khevi and Kitskhi villages (Upper Imeretia, Western Georgia). A comparison of factual and predicted values of rain-induced erosion for the plots with permanent black fallow showed that the model overestimated the average annual soil loss for the yellow-brown strongly eroded soil in Zendidi village by 23.22 t/ha (133%). This value ranged in different years from 18 to 1052%. For the plots with corn, the predicted value of annual erosion was by 16.94 t/ha higher than the factual value (overestimation of 488%). A comparison of factual and predicted values of rainfall erosion for the plots under sprinkling irrigation also showed that the predicted soil loss was higher than the factual one by 4.14–30.40 t/ha for corn, 6.76–11.14 t/ha for winter wheat, and 15.75–24.12 t/ha for the plots with stubble of winter wheat and barley. Thus, the hydromechanical model for predicting water erosion inadequately describes it under the conditions of Western Georgia and has to be refined.     

基于CSLE和抽样调查的泰国土壤水蚀评价

通过对泰国区域土壤侵蚀的定量评价,掌握泰国土壤水蚀特征,以期为泰国土壤侵蚀防控和相关研究提供技术和数据支撑。采用CSLE模型,基于30 m分辨率区域侵蚀因子综合运算完成泰国土壤水蚀速率计算(地图代数法制图),基于亚米级分辨率抽样调查完成抽样单元水蚀速率计算,再以抽样单元计算结果为参考,对地图代数制图结果进行直方图匹配,最终获得研究区土壤水蚀速率专题图。结果表明:(1)直方图匹配制图结果既保留了原有的空间分布特征,又具有准确的统计特征。(2)泰国平均土壤水蚀速率为687.9 t/(km²·a),是全球平均土壤水蚀速率的2.4倍,个别地区达到1 000 t/(km²·a)以上(占面积13.2%,占侵蚀总量72.0%),与全球平均水蚀速率相比,土壤水蚀较为严重,0.6%的区域年侵蚀量约占研究区侵蚀总量的21.5%,局部侵蚀剧烈。(3)在各土地利用类型中,耕地水蚀最为严重,平均水蚀速率高达1 020.2 t/(km²·a),水蚀速率>2 500 t/(km²·a)的热点地区84.1%区域为耕地。由此可知,泰国局部区域的土壤水蚀较为剧烈,耕地对区域水土流失的贡献较大。     

Heavy metals in tropical Lake Kariba,Zimbabwe

Metal mining is carried out in the drainage basin of Lake Kariba, Zimbabwe. In an attempt to assess the distribution of heavy metals in the lake ecosystem, the concentrations of chromium (Cr), cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn), and selenium (Se) were analysed in the following ecosystem components at different locations in the lake; water, sediment, aquatic macrophytes, mussels, and carnivorous and herbivorous fish. Concentrations were generally in the same range as in other temperate and tropical aquatic ecosystems, except for Pb and Cd, which were higher in marcrophytes and fish from the lake. Apart from Cd, there were no signs of biomagnification and the highest levels of metals were found in the macrophytes and sediments. While metal contamination in fish is probably a combination of uptake from the food and an equilibrium with the surrounding water, the levels in macrophytes appear to be determined mainly by uptake from the sediment through the roots.     

永定河典型生态护岸措施下坡面产流产沙试验研究

为实现永定河北京段沙质河道生态修复,通过野外径流小区放水冲刷试验,在3种放水流量(0.5,1.0,1.5 m~3/h)、坡度10°、5种护岸材料(生态袋、椰丝植生毯、三维土工网、松木桩、卵石)下分析不同生态护岸坡面的水动力学特性、产流产沙状况。结果表明:(1)3种放水流量下5种护岸材料布设坡面的平均流速均小于裸坡,5种护岸材料平均径流流速均表现为卵石松木桩三维土工网生态袋椰丝植生毯。5种生态护岸材料弗劳德数均小于1,雷诺数均小于500。(2)生态护岸措施有效减少产流,产流量随时间均呈对数显著增加,5种生态护岸材料平均径流拦截率表现为松木桩卵石三维土工网椰丝植生毯生态袋。(3)随放水流量的增大坡面产沙率增大,各生态护岸措施均能有效减少产沙量,各护岸措施的泥沙拦截效果随着放水流量增大显著降低。研究结果对永定河不同河段岸坡治理、生态护岸材料选择、永定河绿色廊道建设有重要意义,也对定量评价不同护岸材料下坡面的减水减沙效益提供参考。     

东北黑土区坡耕地水蚀与风蚀速率的定量区分

用137Cs含量测定和USLE水蚀预报模型,研究了东北黑土区2块坡耕地的水蚀与风蚀速率,结果表明:直型坡耕地和凸型坡耕地的年均侵蚀速率分别为3054和3548t.km2.a-1;由于坡向的不同,2块坡面的风蚀速率分别为631和1155t.km2.a-1,即研究区每年约有0.5～1.0mm的表层土壤被风吹蚀掉,风蚀分别占总侵蚀的20.7%和32.6%;而水蚀仍为研究区主要的侵蚀方式,2块坡面的水蚀速率分别占总侵蚀的79.3%和67.4%。因此,东北黑土区坡耕地水土流失的防治要充分考虑水和风的不同影响,综合治理。     

土壤生物工程在北京河流生态恢复中的应用研究

为了研究土壤生物工程措施在河流生态修复中效果,选择北京怀九一渡河段裸露坡岸为研究对象,针对该河段坡面存在着溅蚀,面蚀,沟蚀及侧渗侵蚀等土壤侵蚀现象,采用扦插、生物垫和梢捆3种土壤生物工程措施对河流岸坡进行治理,分别对施工4个月、8个月后植物的生长特征、稳固岸坡效果进行了调查观测,结果表明:在不同土壤生物工程措施下,成活金丝柳的生长情况均达到较高水平,但在以水分、覆土过厚等制约因素下,金丝柳的生长表现出明显差异;扦插措施根系扎根深,易成活,对深层土壤的加固作用良好;土壤生物工程施工后河流岸坡植物快速恢复,生物多样性增加。最后总结了北京地区土壤生物工程施工以及后期管理防护中的注意问题,以期为北京地区河流的生态治理提供一定的技术指导和理论支持。