Spatial evaluation of phosphorus retention in riparian zones using remote sensing data     

Guotao Dong  Shengtian Yang  Yunfei Gao  Juan Bai  Xuelei Wang  Donghai Zheng 《Environmental Earth Sciences》2014,72(5):1643-1657

Riparian zones act as important buffer zones for non-point source pollution, thus improving the health of aquatic ecosystems. Previous research has shown that riparian zones play an important role, and that land use has an important effect, on phosphorus (P) retention. A spatial basin-scale approach for analyzing P retention and land use effects could be important in preventing pollution in riparian zones. In this study, a riparian phosphorus cycle model based on EcoHAT was generated with algorithms from soil moisture and heat models, simplified soil and plant phosphorus models, plant growth models, and universal soil loss equations. Based on remote sensing data, model performance was enhanced for spatial and temporal prediction of P retention in the riparian zone. A modified soil and plant P model was used to simulate the soil P cycle of a riparian zone in a temperate continental monsoon climate in northern China. A laboratory experiment and a field experiment were conducted to validate the P cycle model. High coefficients of determination (R ²) between simulated and observed values indicate that the model provides reliable results. P uptake variations were the same as the net primary productivity (NPP) trends, which were affected by soil temperature and moisture in the temperate continental monsoon climate. Beginning in June, the monthly content increased, with the maximum appearing in August, when the most precipitation and the highest temperatures occur. The spatial distribution of P uptake rates from March to September showed that areas near water frequently had relatively high values from May to August, which is contrary to results obtained in March, April, and September. The P uptake amounts for different land uses changed according to expectation. The average monthly P uptake rates for farmlands and grasslands were more than those for orchards and lowlands, which had moderate P uptake rates, followed by shrubs and forests. The spatial distribution of soil erosion demonstrated that the soil erosion came primarily from high-intensity agricultural land in the western and central areas, while the northern and eastern study regions, which were less affected by human activity, experienced relatively slight soil erosion. From the point of view of P pollution prevention, the spatial structure of riparian zones and the spatial distribution of land use around the Guanting reservoir are thus not favorable.  相似文献   

A Study on Crack Damage Stress Thresholds of Different Rock Types Based on Uniaxial Compression Tests   总被引：7，自引：3，他引：4  

Lei Xue  Siqing Qin  Qiang Sun  Yuanyuan Wang  Lee Min Lee  Weichao Li 《Rock Mechanics and Rock Engineering》2014,47(4):1183-1195

When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress σ _cc, crack initiation stress σ _ci, crack damage stress σ _cd, and uniaxial compressive strength σ _ucs; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress σ _cd, its threshold, and a possible relationship between σ _cd and the uniaxial compressive strength. The σ _cd of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in σ _cd /σ _ucs between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average σ _cd /σ _ucs resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on σ _cd /σ _ucs. The ratio σ _cd/σ _ucs could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.  相似文献   

西秦岭印支期高Sr/Y花岗岩类的成因及动力学背景——以同仁地区舍哈力吉岩体为例   总被引：5，自引：4，他引：1  

黄雄飞  莫宣学  喻学惠  李小伟  杨梦楚  罗明非  和文言  于峻川 《岩石学报》2014,30(11):3255-3270

西秦岭印支期花岗岩类分布十分广泛,形成时代集中于248~234Ma和224~211Ma两个阶段.其中,夏河岩体(248~238Ma)和温泉岩体(223~216Ma)的部分样品被厘定为埃达克岩(Sr>400×10^-6,Yb<2×10^-6),指示陆壳厚度大于50km.本文对西秦岭同仁地区舍哈力吉岩体进行了锆石U-Pb定年、岩石学、地球化学和Sr-Nd同位素研究.舍哈力吉岩体主要由石英二长岩组成,同时含有许多暗色镁铁质微粒包体(MME).寄主岩中发育少量的钾长石巨晶,并且部分巨晶具有环斑结构.舍哈力吉石英二长岩化学成分比较均一,而且也显示出类似埃达克岩的一些地球化学特点,如富SiO₂(66.07%~67.52%)和Al₂O₃(14.85%~15.95%),高Sr(560×10^-6~692×10^-6),低Y(11.4×10^-6~12.9×10^-6)和Yb(0.99×10^-6~1.09×10^-6),并具有较高的(La/Yb)_N比值(27.8~34.3)和微弱的负Eu异常(δEu=0.77~0.95).锆石U-Pb测年结果为234.1±0.5Ma,表明其形成于印支早期.岩石为偏铝质、高钾钙碱性系列且K₂O/Na₂O>1,高Mg^#(59~60)、Cr(69.1×10^-6~81.2×10^-6)和Ni(31.6×10^-6~36.1×10^-6),以富集大离子亲石元素(Rb、Ba、Th、U)而相对亏损高场强元素(Nb、Ti、P)为特征,(⁸⁷Sr/⁸⁶Sr)_i=0.7075~0.7077,ε_Nd(t)=-6.3~-6.1,亏损地幔模式年龄为1.25~1.33Ga.舍哈力吉石英二长岩起源于石榴角闪岩相古老下地壳的部分熔融,之后经历了壳幔岩浆混合作用和以斜长石为主的分离结晶作用.寄主岩的环斑结构和相对一致的地球化学特征,很可能是高温幔源熔体对壳源富钾高黏度岩浆改造所导致的晶粥快速再活化的结果.西秦岭在印支早期可能并未经历显著的地壳加厚过程.西秦岭印支早期花岗岩类形成于活动大陆边缘局部伸展环境,可能与古特提斯洋壳俯冲极性的改变有关.  相似文献   

社会经济统计数据空间化研究进展   总被引：1，自引：0，他引：1  

郭红翔  朱文泉 《地理学报》2022,77(10):2650-2667

社会经济统计数据通常是以各级行政区为单位的汇总数据,它虽然能反映统计单元之间的差异但却不能反映统计单元内部的异质性,在实际应用中,无法满足统计任意区域内的社会经济数据的需求,而社会经济统计数据空间化则是有效解决该问题的一条重要途径。本文对现有社会经济统计数据的空间化方法、社会经济统计数据空间化过程所依赖的辅助数据、现有主要的社会经济空间化数据产品进行了归纳总结,并从空间化方法的制约因素和改进方向、新型辅助数据的探索和多源辅助数据的综合利用、高时空分辨率和高精度数据产品研发3个方面展望了社会经济统计数据空间化的未来发展趋势。研究结果可为社会经济统计数据空间化方法的选择与改进、辅助数据的选择与综合利用、社会经济空间化数据产品的选择与改进提供参考。  相似文献   

1992—2018年中国旱作农田土壤湿度的时空模式及气象驱动因素     

庄慧敏  张朝  程飞  张亮亮  何邦科 《地理学报》2022,77(9):2308-2321

土壤湿度作为影响陆气水热交换的重要变量,指示了干旱的演变特征。为揭示中国旱作农田土壤湿度的变化特征及其气象驱动要素,本文利用站点数据研究了1992—2018年中国旱作农田土壤湿度变化趋势的时间和空间特征,采用相关性、敏感性分析等方法探究了土壤湿度的驱动机制。结果表明：2001年中国旱作农田土壤湿度的变化趋势发生转折,土壤湿度年际变化普遍由下降趋势变为上升趋势,主要由夏季和秋季土壤湿度主导。而且土壤湿度的变化存在空间异质性,2001年后东北地区的土壤湿度在显著增加,而西南地区在显著下降。降水量和蒸散发的时空变化是土壤湿度趋势发生时空变化的主要原因,二者存在协同作用,北方地区由降水主导,南方地区由蒸散发主导。  相似文献   

重金属铜污染植被光谱响应特征研究   总被引：12，自引：1，他引：11  

朱叶青  屈永华  刘素红  陈圣波 《遥感学报》2014,18(2):335-352

重金属铜污染植被的反射光谱特性会发生明显改变。在本研究中,采用不同程度的铜污染土壤作为培养基质,选择春小麦、上海青两种农作物进行铜胁迫实验,获取了4个不同生育期、10个不同铜污染强度下的植被叶片的反射光谱,并采用铜污染叶片7个特征波段和光谱角的方法研究了铜污染叶片的光谱特征。结果表明,铜污染叶片光谱差异与作物时期和作物类型有关,可以采用叶片光谱角描述铜污染叶片与健康叶片的光谱差异。该方法只需与阈值做简单的比较,方法简便易行,而且对轻度及重度铜污染十分敏感。叶片光谱辐射传输模型反演结果表明铜污染叶片内部结构参数N明显变大,这也证明了铜污染使叶片内部结构更加散乱无序。在此基础上进一步建立了N与红肩处反射率值的线性关系,相关系数为0.978。本文为铜污染叶片光谱反射模型的建立提供了初步的数据基础与理论支持。  相似文献   

遥感影像大气校正通用查找表的设计与插值算法     

胡顺石  张立福  佘晓君  童庆禧 《遥感学报》2014,18(1):45-60

大气参数查找是遥感图像大气校正中一个重要的步骤。本文针对当前多数大气参数查找表普适性不强、查找表数据存储空间巨大、具体实施步骤不详细的问题,建立了一个通用化的多维大气参数查找表,其光谱分辨率为1 nm,并适用于多种遥感传感器。本文采用二进制文件方式存储查找表,并研究采用多维拉格朗日和多维反距离加权插值方法对输入参数进行插值。结果表明以二进制文件方式存储查找表,不但可以最大化地减少磁盘存储空间,还可以实现查找表数据快速随机读取;相对于多维反距离加权插值方法,多维拉格朗日插值方法的速度更快,精度更高,与MODTRAN4.0模型计算结果(真值)相比,它的误差仅为±1.0%左右。  相似文献   

地理图斑智能计算及模式挖掘方法研究     

骆剑承  吴田军  吴志峰  周亚男  郜丽静  孙营伟  吴炜  杨颖频  胡晓东  张新  沈占锋 《地球信息科学学报》2020,22(1):57-75

在大数据时代,高分辨率对地观测技术实现了对地球表层地理现象和地理过程最为真实、量化、全面覆盖又快速更新的数据化记录,可为地理空间认知研究的新发展奠定时空信息聚合与挖掘计算的基准。地理图斑是影像空间映射到地理空间中对于地理实体的抽象化表达,是构建地理场景和承载地理空间各类信息进而开展模式挖掘的最小单元。本文以地理图斑为基本对象,通过分析其中视觉模拟、符号推测等几类机器学习的协同计算机制,从空间、时间与属性等维度构建了集“分区分层感知”、“时空协同反演”、“多粒度决策”三者于一体的地理图斑智能计算模型,并以在贵州息烽县、广西江州区开展的农业种植结构制图与规划决策为应用案例,探索了地理图斑分布、生长以及功能3种模式的挖掘方法,并进一步设计了动态视角下开展图斑动力模式挖掘的研究思路。  相似文献   

Effects of mixing on the subduction of South Pacific waters identified by a simulated passive tracer and its adjoint     

Shan Gao  Tangdong Qu  Ichiro Fukumori 《Dynamics of Atmospheres and Oceans》2011,51(1-2):45-54

Effects of mixing on water mass subduction are analyzed in the South Pacific Ocean. Model simulations using a passive tracer and its adjoint are employed in conjunction with a particle tracking method to distinguish effects of mixing from those of advection. The results show that mixing processes can contribute to as much as 20% of the overall subduction rate in the South Pacific. Of this mixing contribution, about 30% can be attributed to meso-scale eddies, including their associated bolus transport, while the major part (70%) is due to other diabatic processes. The impact of mixing reaches its maximum near the Sub-Antarctic Front, accounting for nearly 30% of the total subduction rate. Consequently, estimates based on tracing particles or on advection alone may significantly underestimate the subduction rate in the South Pacific Ocean.  相似文献   

Using Red Edge Position Shift to Monitor Grassland Grazing Intensity in Inner Mongolia     

Jiajia Zheng  Fei Li  Xin Du 《Journal of the Indian Society of Remote Sensing》2018,46(1):81-88

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