黄土高原南北样带不同土层土壤水分变异与模拟

为掌握黄土高原区域尺度土壤水分的时空分异特征及其影响因素,在黄土高原布设一条南北方向样带（N=86）,动态监测0~5 m剖面土壤含水率。采用经典统计学方法分析了土壤蓄水量的分布规律、变异特征及影响因素。结果表明:不同土层土壤水分均呈中等程度变异,并由南向北递减,样带0~5 m剖面平均土壤蓄水量为735 mm;随着土层深度的增加,土壤水分在空间上的变异增强,而在时间上的变异减弱,表明深层土壤水分具有较强的时间稳定性特征。干燥度、黏粒、归一化植被指数和坡度是影响区域土壤水分空间分布的主要因素,可作为一定置信水平上预测区域土壤水分空间分布状况的预测变量。     

陕北黄土区流域分水线土壤干层分布

陕北黄土区切沟密集,地形支离破碎,地形与植被共同作用下土壤水分状况较为复杂。通过长期定位观测深剖面土壤含水量,分析了流域分水线深层土壤水分时空动态及干层分布特征。研究结果表明:生长季0~3 m土层土壤水分亏缺,生长季后1.2 m以上土层亏缺水分得到补充,但该深度以下土壤水分含量未得到恢复,其中2.6~6.4 m深度范围缺水严重,流域分水线土壤水分含量出现明显的垂直分层现象;各观测点土壤含水量随深度的分布曲线、极值出现深度和干层深度范围不同,剖面干层随各分水线走向表现出不连续分布的特点;分水线干层平均起始深度为2.03 m,厚度为0.4~8 m,干层土壤含水量均值为9.03%,干层厚度与起始深度和干层土壤含水量均呈负相关关系。比较而言,陕北黄土高原干层发育严重程度较突出。相关研究结果可为流域土壤水资源分布及土壤水库功能评价提供理论依据。     

沟灌土壤湿润体空间矩特征参数估算模型

为进一步增加矩分析理论在研究沟灌土壤湿润体运移特性方面的实用性,采用数值模拟和理论分析相结合的方法,定量分析了土壤初始含水率、入渗水深、沟底宽和边坡系数等因素对沟灌自由入渗条件下土壤湿润体空间矩特征参数的影响,并建立了其与主要影响因素间的函数关系式。结果表明,土壤初始含水率、入渗水深和沟底宽对垂直向土壤水分分布的质量重心影响较大;水平向湿润锋的平均离散度主要受土壤初始含水率、入渗水深、沟底宽和边坡系数的影响,而垂直向对土壤初始含水率和入渗水深变化的敏感性较高;选取不同土壤质地对所建模型的可靠性进行了验证,结果表明所建模型估算不同入渗时刻的空间矩特征参数值与根据HYDRUS软件模拟结果所得计算值具有高度一致性,所有验证组合条件下两者相对误差绝对值均值均低于8.5%,且无显著性差异,说明所建模型估算沟灌土壤湿润体空间矩特征参数具有高度可靠性。研究结果可为沟灌灌水方案设计和管理提供理论基础和技术支撑。     

野外非饱和土壤中溶质运移的试验研究

通过在野外3×6m2面积上均匀入渗条件下非饱和土壤溶质运移试验,同时对8个点定时取样,得到170cm深度内土壤溶液浓度和含水量剖面分布.据此研究了小区域范围内土壤水分和溶质的运移特征,讨论了土壤水分和盐分分布的空间变异性和统计特征.研究结果表明,在本试验条件下,土壤溶液浓度剖面的空间变异性远大于土壤水分剖面.单一测点的取样结果不能代表区域的溶质运移特征.区域上溶质浓度的平均结果能反映溶质运移的基本规律.由于土壤结构等因素的影响,不动水体含量占土壤含水量的24%～39%.     

混合型缓冲砌块导热性能及其均匀性研究

混合型缓冲砌块作为高放废物地质处置库的缓冲屏障具有良好的导热性能。将高庙子(GMZ)膨润土和标准石英砂混合,依据正交试验原则,控制掺砂率Rs=30%,设置含水率变化为7.0%、11.0%、15.0%,干密度变化为1.60、1.70、1.80g/cm~3,采用半自动化液压机压制成大型缓冲砌块。对砌块进行切割分解,开展热传导试验,建立含水率和干密度与导热性能的关系,了解导热性能的空间分布特征。试验结果表明,随着含水率和干密度的增大,混合型缓冲砌块导热系数显著增大,大致呈线性关系,且平均值均大于国际原子能机构国际原子能机构(IAEA)推荐的导热系数下限值0.8 W/m·K,满足推荐要求;热扩散系数先略微减小再增大,总体也呈增大趋势。对混合型缓冲砌块导热系数的空间分布及均匀性分析发现,砌块四周边缘部位的导热系数比中间部位的波动略大,但总体差异性及非均匀性不明显。采用t检验法对混合型缓冲砌块导热系数均匀性进行检验,发现砌块满足均匀性检验条件,试样均匀。用Johansen模型从物理指标可以预测混合型缓冲砌块的导热系数,偏差在±10%以内。     

混合型缓冲砌块导热性能及其均匀性研究

混合型缓冲砌块作为高放废物地质处置库的缓冲屏障具有良好的导热性能。将高庙子（GMZ）膨润土和标准石英砂混合,依据正交试验原则,控制掺砂率Rs=30%,设置含水率变化为7.0%、11.0%、15.0%,干密度变化为1.60、1.70、1.80 g/cm~(3),采用半自动化液压机压制成大型缓冲砌块。对砌块进行切割分解,开展热传导试验,建立含水率和干密度与导热性能的关系,了解导热性能的空间分布特征。试验结果表明,随着含水率和干密度的增大,混合型缓冲砌块导热系数显著增大,大致呈线性关系,且平均值均大于国际原子能机构国际原子能机构（IAEA）推荐的导热系数下限值0.8 W/m · K,满足推荐要求;热扩散系数先略微减小再增大,总体也呈增大趋势。对混合型缓冲砌块导热系数的空间分布及均匀性分析发现,砌块四周边缘部位的导热系数比中间部位的波动略大,但总体差异性及非均匀性不明显。采用t检验法对混合型缓冲砌块导热系数均匀性进行检验,发现砌块满足均匀性检验条件,试样均匀。采用Johansen模型从物理指标可以预测混合型缓冲砌块的导热系数,偏差在±10%以内。     

喀斯特峰丛洼地不同植被类型土壤水分的空间异质性分析——以广西环江毛南族自治县西南峰丛洼地区为例

通过网格(5 m×5 m)取样,用地统计学方法研究了喀斯特峰丛洼地4个典型植被类型表层土壤（0～10 cm）水分的空间异质特征,探讨了其生态学过程和机制。结果表明,随着干扰强度的降低,植被产生了由农作物(Ⅰ)?人工林(Ⅱ)?次生林(Ⅲ)?原生林(Ⅳ)的变化,土壤水分显著提高,空间变异特征明显不同,Ⅰ、Ⅱ、Ⅲ和Ⅳ分别符合指数模型、高斯模型、指数模型和球状模型,块金值与基台值之比(C0/(C0+C))在0.269～0.500之间,具有中等的空间相关性,Ⅰ和Ⅳ土壤水分的空间结构相似,(C0/(C0+C))值较大,随机因素和自相关异质性各占50%,分维数D值较大,空间依赖性较小,Ⅱ和Ⅳ相反;农业耕作区土壤水分的空间延续范围较大,变程达252.9 m,其他3个植被类型的变程均较小(141.2～163.2 m);Kriging等值线图从不同位置和方向上清楚地表明Ⅰ和Ⅳ土壤水分的空间分布均呈凸型分布,Ⅱ呈单峰分布,Ⅲ呈凹型分布;影响土壤水分空间分布的因子很多,其中干扰通过对植被的调控发挥了关键作用,降低干扰是喀斯特峰丛洼地脆弱生态系统水资源改善、合理利用及生态恢复重建的重要举措。      

黄土高原沟壑区坡地土壤水分状态空间模拟

为掌握黄土高原沟壑区坡地土壤水分的空间分布特征及其影响因素,采用状态空间模型和经典线性回归方法对该区不同土层深度土壤含水率的分布进行模拟.结果表明,不同土层深度的土壤含水率呈中等程度变异,并与海拔高度、黏粒、粉粒、砂粒含量和分形维数具有显著的空间自相关和交互相关关系,可用于状态空间模拟分析.不同因素组合下的状态空间模拟效果均要优于线性回归方程,其中采用海拔高度、砂粒含量和分形维数的三因素状态空间方程模拟精度最高(R2=0.992).状态空间模拟方法可用于黄土高原坡面尺度不同土层深度土壤含水率的预测.     

黄河冲积平原灌溉入渗研究

黄河冲积平原面积广大,农田灌溉频繁,灌水量大,在地下水资源评价时对灌溉入渗系数取值困难。本文在现场灌溉入渗试验的基础上,分析包气带岩性及结构、水位埋深、灌溉水量对灌溉入渗系数的影响,总结提出了多种条件下灌溉入渗系数的取值范围。在单位灌水量40～60m3／亩和水位埋深小于4m、4～8m、大于8m的井灌区中,当包气带岩性为粉土、粉砂时,灌溉入渗系数可分别取值0．21～O．10、0．10—0．05、0．05～0;当包气带岩性夹有粉质粘土层时,灌溉入渗系数可分别取值0．15～0．09、0.09—0．05、0．05～0。在单位灌水量较大的渠灌区,灌溉入渗系数可按单位灌水量的增大倍数而增加,由此为黄河冲积平原区地下水补给量计算中灌溉入渗系数的确定提供了依据。     

甘肃黄土高原土壤水分气候特征

利用甘肃黄土高原42个气象站1961—2000年3～7月降水量和11个农业气象观测站逐年3～11月上旬的土壤重量含水率资料，分析了甘肃黄土高原土壤水分的地域和时间分布特征。结果表明：①甘肃黄土高原土壤水分从西南向东北减少，中部有一条从北向南的干舌，干旱中心在陇中北部，受六盘山的影响较大；②甘肃黄土高原分为7个气候区：陇中、陇东土壤严重缺水区，陇中、陇东土壤季节性缺水区，土壤水分适宜区，土壤水分湿润区和甘南高原土壤水分湿润区；③陇中北部和陇东北部土壤严重缺水区浅层土壤严重缺水主要出现在春季和春末夏初，深层土壤也常年处于缺水状态。季节土壤缺水区浅层主要缺水在5、6月份，深层土壤水分陇东高于陇中，适宜区和湿润区无明显土壤缺水时段。     

中国中、东部典型样区土壤和水体多样性关联分析

分别选取中国中、东部不同尺度典型样区为研究区域,将多样性理论与方法应用于水体空间分布多样性和土壤构成组分多样性评价中。计算了各研究区及其分区域内,以土属为基本单元的土壤构成组分多样性和2km×2km网格尺度下的水体空间分布多样性,并探索了两者之间的内在联系。研究结果表明:将多样性理论与研究方法应用于区域水资源的空间分布离散性评价具有可操作性;区域水体总面积变化与区域水体空间分布多样性变化之间具有一定的正相关关系,70%以上数据支持这一推断;区域水体比例与水体空间分布多样性之间并无绝对联系;水体和土壤研究数据均体现出分形特征及结构;区域土壤构成组分多样性与水体空间分布多样性之间存在负相关关系,大尺度区域下的相关系数R²约0.8。     

Spatial distribution of surface soil water content under different vegetation types in northwest Guangxi, China

Geostatistical and statistical analyses were combined to examine the spatial distribution of soil water content under four vegetation types during the dry season, in the peak-cluster depression in the karst region in northwest Guangxi, southwest China. The soil water content significantly increased from farmland to plantation, secondary forest, and primary forest; whereas the variation coefficients, the sill (C ₀+C), and total spatial variance increased, although the range decreased. The spatial distribution of soil water content in the different vegetation types had a high spatial autocorrelation. Different models produced a best fit for the semivariograms of the four vegetation types. Elevation and slope position were the primary factors influencing the spatial distribution of soil water content, with other key factors differing between the four vegetation types. Moreover, even though different specific factors influenced soil water content in the four vegetation types, the correlations and degrees of associations between the soil water content and these various factors differed. Therefore, the corresponding strategies for rational usage and management of water resources should be different for the four vegetation types in this region.     

基于贝叶斯网络的地下水环境系统决策管理研究

应用贝叶斯网络解决地下水环境管理中具有不确定性的多目标决策问题,通过对决策变量氮肥施用量以及灌溉模式的调控,减少水中的硝酸盐含量,达到既能有效改善水环境又不至使农民经济利益受到损害的目标。通过分析具体的地下水环境管理系统中变量间的相互关系,构建描述变量间不确定性关系的贝叶斯网络模型,其中包括表示其依赖关系的有向无环图和表示其具体概率依赖程度的条件概率表。并在多个水环境管理目标均达到最优的前提下进行概率推理,得到决策变量氮肥施用量以及灌溉模式取不同值时目标变量的概率分布情况。最终确定出能使所有目标均达到最优的合理的水环境管理决策:(1)使用喷灌,将氮肥施用量控制在0.01~0.03 kg/m2;(2)使用漫灌,将氮肥施用量控制在0.01~0.02 kg/m2。     

Quantitative analysis of physical and geotechnical factors affecting methane emission in municipal solid waste landfill

The amount of methane that vent from landfills is dependent on the physical, chemical and biological components of the soil cover. Especially moisture content and temperature of the soil are known as the major controlling factors. In situ moisture content measurement is very critical because the moisture content of the soil continuously changes within minutes to hours as a result of change in temperature. The presented study used time domain reflectometry to measure in situ moisture content and analyzed moisture content, temperature and methane data of the landfill soil cover in a quantitative manner. Geotechnical factors including soil grain size and uniformity coefficient of the soil were analyzed and their influence on moisture content and methane emission was examined. The authors used kriging and polynomial regression methods to characterize the spatial distribution of moisture content and methane emission. Methane emission showed good temporal correlation with soil temperature, however, no significant relationship between moisture content and methane emission was observed. Spatial distribution of soil attributes was also analyzed to examine its effect on those variables. The spatial pattern of moisture content was quite similar to that of uniformity coefficient, C _u and that of clay content of the soil but strongly contrasted to that of methane emission.     

3D Property Modeling of Void Ratio by Cokriging

Void ratio measures compactness of ground soil in geotechnical engineering. When samples are collected in certain area for mapping void ratios, other relevant types of properties such as water content may be also analyzed. To map the spatial distribution of void ratio in the area based on these types of point, observation data interpolation is often needed. Owing to the variance of sampling density along the horizontal and vertical directions, special consideration is required to handle anisotropy of estimator. 3D property modeling aims at predicting the overall distribution of property values from limited samples, and geostatistical method can he employed naturally here because they help to minimize the mean square error of estimation. To construct 3D property model of void ratio, cokriging was used considering its mutual correlation with water content, which is another important soil parameter. Moreover, K-D tree was adopted to organize the samples to accelerate neighbor query in 3D space during the above modeling process. At last, spatial configuration of void ratio distribution in an engineering body was modeled through 3D visualization, which provides important information for civil engineering purpose.     

黄土高原关键带全剖面土壤水分空间变异性

土壤水分是黄土高原关键带水循环、地下水补给和植被恢复的关键因素。为揭示黄土高原关键带黄土整个剖面的土壤水分空间变化特征,通过土芯钻探的方式获取了黄土高原关键带5个典型样点（杨凌、长武、富县、安塞和神木）从地表到基岩的土壤水分样品,采用经典统计学和地统计学相结合的方法分析了剖面土壤水分的分布规律、变异特征及空间结构。结果表明:黄土高原关键带剖面土壤水分从南往北,土壤平均含水量由高变低;5个样点的土壤水分均为中等变异,随着深度由40 m增加到200 m,土壤水分变异性变弱,且样点之间的土壤含水量差异降低;地统计学分析表明样点的半方差函数能被理论模型较好地拟合（杨凌除外）,指数模型能够描述大部分样点深剖面的空间变异结构。相关结果有助于了解黄土高原深层土壤水分状况及分布规律,对于黄土高原土壤水资源估算和区域植被恢复具有重要价值。     

黄土高原北部坡面尺度土壤饱和导水率分布与模拟

为探明黄土高原北部坡面土壤饱和导水率(K_s)空间分布特征,为土壤水文过程模拟与预测提供理论依据,采用经典统计学和地统计学的空间变异分析方法,分析了坡面尺度土壤K_s的空间变异特征,并用一阶自回归状态空间模型对K_s的空间分布进行了模拟.研究区坡面尺度K_s的变异为中等程度变异,具有中等程度空间依赖性,变程为42 m.K_s与容重、砂粒、粉粒和黏粒含量在不同滞后距离下均具有自相关关系和交互相关关系.容重和土壤颗粒是影响坡面K_s空间分布的主要因素.状态空间模拟结果表明,基于容重和土壤颗粒的状态空间方程可以很好地解释坡面K_s的变异状况(R2>0.9).一阶自回归状态空间模型可用于田间条件下坡面尺度K_s分布特征的预测.     

农田土壤水分和盐分的空间变异性及其协同克立格估值

通过对一块面积为1hm2麦田内的98个观测点取样分析,测定了两个时期的土壤水分和盐分含量。结果表明两个时期的土壤含水量均服从正态分布,底层盐分均服从对数正态分布,而表层的盐分分布具有不确定性。两个时期土壤水分和盐分的变异系数分别属于弱变异和中等变异强度。通过结构分析,发现两个时期的水分和盐分均在一定范围内存在空间相关性。对两个时期土壤水分和盐分空间分布的动态变化进行了比较,同时采用CoKriging方法进行估值,与Kriging法相比,其估计方差减少百分数最大达到了136.3%。     

An integrated assessment of soil erosion dynamics with special emphasis on gully erosion in the Mazayjan basin,southwestern Iran

Soil erosion by water is a significant problem in arid and semi-arid areas of large parts of Iran. Water erosion is one of the most effective phenomena that leads to decreasing soil productivity and pollution of water resources; especially, in the Mazayjan watershed in the southwest of Fars Province gully erosion contributes to the sediment dynamics in a significant way. Consequently, the intention of this research is to identify the different types of soil erosion processes acting in the area and to assess the process dynamics in an integrative way. Therefore, we applied GIS and satellite image analysis techniques to derive input information for the numeric models. For sheet and rill erosion the Unit Stream Power-based Erosion Deposition Model (USPED) was utilized. The spatial distribution of gully erosion was assessed using a statistical approach, which used three variables (stream power index, slope, and flow accumulation) to predict the spatial distribution of gullies in the study area. The eroded gully volumes were estimated for a 7-year period by fieldwork and Google Earth high-resolution images. Finally the gully retreat rates were integrated into the USPED model. The results show that the integration of the SPI approach to quantify gully erosion with the USPED model is a suitable method to qualitatively and quantitatively assess water erosion processes. The application of GIS and stochastic model approaches to spatialize the USPED model input yields valuable results for the prediction of soil erosion in the Mazayjan catchment. The results of this research help to develop an appropriate management of soil and water resources in the southwestern parts of Iran.