Monitoring the evolution of irrigated areas with Landsat images using backward and forward change detection analysis in the Kou watershed,Burkina Faso

The Kou watershed is characterized by important water resources used for drinking, agriculture (especially in the irrigated areas), industry and the preservation of aquatic fauna and flora. For several decades, there has been increasing pressure on the Kou's water resources, partly because of the expansion of the irrigated agricultural areas. This study was conducted to examine this issue, focusing on one specific irrigated area. In order to monitor the expansion of irrigated areas in developing countries, a low-cost remote sensing method based on Landsat images and aerial photographs was developed. The method is based on maximum-likelihood classification, followed by backward and forward change detection analysis requiring agronomic expertise. Using pixel trajectory analysis, the method connects all pixels to their consecutive states in order to correct their current states. The study showed that the irrigated area has expanded by almost 70% over 20 years, with most of this expansion occurring in the past 10 years. The method, if validated, could be used to obtain better information on past occupation in the rural irrigated areas for which there is currently no archived data, making temporal analyses impossible.     

基于二期高分辨率遥感数据的巢湖矿区矿山地质环境及动态变化研究

高分辨率卫星如“IKONOS”“GEOEYE”等已经被应用于国民经济的诸多方面:例如监测土地利用状况、森林种植面积、农作物病虫害、找矿异常、荒漠化地质灾害等.由于矿产资源开采造成的占地面积逐年增加,且对生产、生活造成了巨大影响.因此矿业活动占地的监测工作与土地利用和灾害防治等息息相关.本文根据安徽省巢湖市非金属矿区的光谱特征对该地区的矿业活动占地变化进行遥感解译,实现了对2009年和2010年的矿业活动占地面积变化的监测:其中矿业活动占地面积保持不变的区域有138.08公顷,矿业活动占地面积总体增加了29.29公顷.     

Removal of K^＋, Na^＋, Ca^2＋, and M^g2＋ from saline-alkaline water using the microalga Scenedesmus obliquus

The capability ofScenedesmus obliquus to remove cations （K^＋, Na^＋, Ca^2＋, Mg^2＋） from saline- alkaline water was investigated at different salinities （0, 5, 10, 15, 20, 25） and carbonate alkalinities （0, 5, 10, 15, 20, 25, 30, 35 mmol/L）. K^＋, Na^＋, Ca^2＋, and Mg^2＋ in saline-alkaline water were efficiently removed by S. obliquus. The maximum removal of the cations （29.37 mg for K^＋, 185.85 mg for Na^＋, 23.07 mg for Ca^2＋, 66.14 mg for Mg^2＋） occurred at salinity 25. The maximum removal of K^＋ （2.28 mg）, Na＋ （6.62 mg）, Ca^2＋ （1.01 mg）, and Mg2＋ （0.62 mg） occurred at carbonate alkalinities of 25 mmol/L for K＊, 35 mmol/L for Na＋, 20 mmol/L for Ca2＋, and 25 mmol/L for Mf＋, respectively. Under a salinity stress, the concentration of Na＇ in S. obliquus increased significantly, while that of K~ decreased significantly. The concentrations of Ca^2＋ and Mg2＋ decreased as well. The ratios of K＋/Na~, Ca2＋/Na^＋, and Mg^2＋/Na^＋ were significantly lower in all salinity treatments than those of the control. Under alkaline stress, the concentrations of Nan and K＋ in S. obliquus decreased significantly and the ratios of K^＋/Na^＋, Ca2＋/Na^＋, and Mg^2＋/Na^＋ were significantly higher in all treatments than in the control. Moreover, the concentrations of Ca2＋ and Mg2＋ in S. obliquus at alkalinities of 5-10 mmol/L were significantly higher than those of the other treatments. The removal of Na＋ by S. obliquus mainly occurs through biosorption, and Mg^2＋ and Ca^2 ＋ were removed through both biosorption and bioaccumulation.     

Effect of cations on thermal properties of montmorillonite

Based on comparison and analysis on structural cations of montmorillonite in bentonite samples collected from several typical areas in Jilin Province, relationships among type and quantity of interlayer/tetrahedral/octahedral cations and temperature and activation energy of removal of bound and hydroxyl water were investigated. The results show that the interlayer cations not only play decisive roles on removal temperature of bound water, but also influence dehydroxylation temperature and activation energy of montmorillonite. Type of octahedral cations also has an effect on dehydroxylation process.     

Sensitivity of Salt-leached Clay Sediments in the Ariake Bay Area,Japan

This study aims to determine whether the principle that “divalent cation predominance in the pore water precludes quick clay development” applies to the Ariake Bay sediments. The chemical and geotechnical properties of an Ariake clay sediment are presented, and sensitivity is discussed with a focus on pore-water salinity and cation composition. In recent years, reduction of pore-water salinity has occurred due to permeation of river water through the sediments because of overpumping of groundwater. Sodium remains the dominant pore-water cation in an upper zone, whereas divalent cations are dominant in the deeper zone. Divalent cation domination in the deeper zone is ascribed to Ca release from nearby cement-stabilized sediments and to Mg increase in response to a change in river water quality. The upper zone's sensitivity ranged from 15 to 77, and the remolded strength was mostly <0.5 kPa, such that quick clay was present over much of its depth. In contrast, the deeper zone's sensitivity was <40, and its remolded strength exceeded 0.5 kPa; quick clay was not present despite the <2 g/L salinity. The absence of quick clay is ascribed to the high remolded strength caused by the pore-water divalent to monovalent cation ratio being greater than 0.25.     

Ground motion record simulation for structural analysis by consideration of spectral acceleration autocorrelation pattern

A novel approach is introduced to generate simulated ground motion records by considering spectral acceleration correlations at multiple periods. Most of the current reliable Ground Motion Record(GMR) simulation procedures use a seismological model including source, path and site characteristics. However, the response spectrum of simulated GMR is somewhat different when compared with the response spectrum based on recorded GMRs. More specifi cally, the correlation between the spectral values at multiple periods is a characteristic of a record which is usually different between simulated and recorded GMRs. As this correlation has a signifi cant infl uence on the structural response, it is needed to investigate the consistency of the simulated ground motions with actual records. This issue has been investigated in this study by incorporating an optimization algorithm within the Boore simulation technique. Eight seismological key parameters were optimized in order to achieve approximately the same correlation coeffi cients and spectral acceleration between two sets of real and simulated records. The results show that the acceleration response spectra of the synthetic ground motions also have good agreement with the real recorded response spectra by implementation of the proposed optimized values.     

基于垂向一阶导数与解析信号比值的欧拉反演方法

常规欧拉反褶积法中构造指数的选取以及分散解存在较多的问题,提出了基于联立垂向一阶导数与解析信号的欧拉齐次方程的RDAS-Euler反演方法。该方法可以更为精确的估计场源的范围及埋深,且不需考虑构造指数N的影响,避免了因构造指数不当而引起的反演误差。通过对单一地质体及组合地质体模型的实验证明本文方法能有效地完成目标体的反演工作,反演结果与理论值之间的误差小于10%,且相对于常规欧拉反褶积法更加稳定准确,能够更好的得到地质体边界及深度信息。将RDAS-Euler法应用于黑龙江省虎林盆地实测布格重力异常数据,获得了丰富的断裂信息,说明RDASEuler法增强了对断裂平面位置的识别能力。     

膨润土中蒙脱石含量测试新方法研究

对于某一特定的膨润土矿,蒙脱石含量与阳离子交换容量呈正相关,以此为依据提出了一种确定蒙脱石含量的新方法——纯样品指标标定法。对山东莱西、潍坊两地膨润土矿的实际测定结果显示,利用纯样品指标标定法确定蒙脱石含量取得了较满意的结果,说明此方法具有较大的使用价值。该方法考虑了膨润土中杂质、蒙脱石层间可交换阳离子类型及端面电荷对测定结果的影响,推荐以钠基土为试样,在pH=4的条件下采用加权法测定蒙脱石含量。     

振荡交换-抽滤淋洗结合凯氏定氮法快速测定土壤中的阳离子交换量

测定土壤阳离子交换量(CEC)的行业标准方法(LY/T1243—1999)是采取离心分离结合手工蒸馏进行滴定,耗时长、操作繁琐。为了缩短反应时间,提高检测效率,本文利用乙酸铵对酸性和中性土壤进行处理,用氯化铵-乙酸铵对石灰性土壤进行处理,应用振荡和抽滤装置快速交换和清洗阳离子,通过全自动凯氏定氮仪对吸附的铵根离子进行测定,由此计算CEC值。结果表明:在最佳的振荡和蒸馏时间、滴定酸浓度、指示剂配比等实验条件下,一个批次样品(100件)的分析流程仅需要12h,比传统方法检测时间缩短近80%。经国家标准物质验证,测定结果与推荐值相符,5次测定的相对标准偏差均小于1. 5%。本方法免去了多次离心分离操作,解决了待测成分损失、CEC测定值偏低的问题,提高了检测效率和准确度,较林业标准方法的成本低,可操作性强,适用于土壤环境质量评价、地区土壤抽样调查等大批量土壤样品分析。     

Upper Pleistocene‐Holocene geomorphic changes dictating sedimentation rates and historical land use in the valley system of the Chifeng region,Inner Mongolia,northern China

This study focuses on the late Quaternary landscape evolution in the Chifeng region of Inner Mongolia, China, its relations to the history of the Pleistocene‐Holocene loess accumulation, erosion and redeposition, and their impact on human occupation. Based on 57 optically stimulated luminescence (OSL) ages of loess sediments, fluvial sand and floodplain deposits accumulated on the hill slopes and floodplains, we conclude that during most of the Pleistocene period the region was blanketed by a thick layer of aeolian loess, as well as by alluvial and fluvial deposits. The loess section is divided into two main units that are separated by unconformity. The OSL ages at the top of the lower reddish loess unit yielded an approximate age of 193 ka, roughly corresponding to the transition from MIS 7 to 6, though they could be older. The upper gray loess unit accumulated during the upper Pleistocene glacial phase (MIS 4–3) at a mean accumulation rate of 0·22 m/ka. Parallel to the loess accumulation on top of the hilly topography, active fans were operating during MIS 4–2 at the outlet of large gullies surrounding the major valley at a mean accumulation rate of 0·24 m/ka. This co‐accumulation indicates that gullies have been a long‐term geomorphic feature at the margins of the Gobi Desert since at least the middle Pleistocene. During the Holocene, the erosion of the Pleistocene loess on the hills led to the burial of the valley floors by the redeposited sediments at a rate that decreases from 3·2 m/ka near the hills to 1–0·4 m/ka¹ in the central part of the Chifeng Valley. This rapid accumulation and the frequent shifts of the courses of the river prevented the construction of permanent settlements in the valley floors, a situation which changed only with improved man‐made control of the local rivers from the tenth century AD. Copyright © 2010 John Wiley & Sons, Ltd.