Changes in water quality following tidal inundation of coastal lowland acid sulfate soil landscapes     

Scott G. Johnston  Richard T. Bush  Leigh A. Sullivan  Edward D. Burton  Douglas Smith  Michelle A. Martens  Angus E. McElnea  Col R. Ahern  Bernard Powell  Luisa P. Stephens  Steve T. Wilbraham  Simon van Heel 《Estuarine, Coastal and Shelf Science》2009

This study examines the remediation of surface water quality in a severely degraded coastal acid sulfate soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of acidified soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek acidification per given quantity of antecedent rainfall. Data also show considerable increase in soil pH (2–3 units) in formerly acidified areas subject to tidal inundation. This coincides with a decrease in soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale acid sulfate soil remediation strategy.  相似文献   

Statistical analyses of the effect of a drainage tunnel on landslide hydrogeological characteristics     

Dong-fei Wang  Hao-di Xu  Lei Wang  Xian Wu  Hong-yue Sun 《水文研究》2020,34(11):2418-2432

A high groundwater level is highly relevant to the slope instability. Drainage tunnel is an effective method for groundwater level control, but its effect on landslide hydrogeological characteristics is rarely discussed. This study analysed the changes of the landslide hydrogeological characteristics under the effect of a drainage tunnel by real-time monitoring of rainfall, groundwater level, and surface displacement. The trend and mutation of groundwater level are analysed by the Mann–Kendall test and the Mann–Kendall mutation test. The memory effect of groundwater in the landslide area was analysed using autocorrelation analysis. The response characteristics of groundwater level to rainfall were evaluated using cross-correlation analysis and mutual information theory. Variations of groundwater levels were further investigated based on hydrograph analysis. Results showed that the groundwater level had a downward trend from 2016 to 2017. The significant downward trend of groundwater levels began in August 2016. The memory effect of groundwater levels was longer under the effect of the drainage tunnel. Before the construction of the drainage tunnel, the response time of groundwater to rainfall was less than 3 hr and rainfall can generate dramatic groundwater level variations. After the drainage tunnel was completed, time lags can be observed in the groundwater response, and the variation of groundwater levels was smaller than before. A strong correlation was found between groundwater levels and the landslide movement. This study demonstrated that the drainage tunnel had effectively controlled the groundwater level in the landslide and ensured the stability of the landslide.  相似文献   

厦门湾水体中234Th的垂直分布及其时间变异特征     

陈飞舟  黄奕普  陈敏  刘广山  邱雨生 《台湾海峡》1999,18(3):259-265

１９９６年 ９～１０月在厦门湾上屿附近海域定点站连续６个航次测定了水柱中溶解态（ＤＴｈ）、颗粒态~(２３４)Ｔｈ（ＰＴｈ）和溶解态~２３８Ｕ,获得了~２３４Ｔｈ的时空分布图象。研究海域水柱中ＤＴｈ、ＰＴｈ和总~２３４Ｔｈ（ＴＴｈ）的放射性比度分别在０．８０～３．９５山／ｍ~３、１,９３～５．６５Ｂｑ／ ｍ~３和 ３．４７～９． １８Ｂｑ／ｍ~３之间,整个水柱中 ＤＴｈ、ＰＴｈ和ＴＴｈ均与~(２３８)Ｕ呈不平衡,其特征是~(２３４)Ｔｈ亏损,且亏损程度明显大于大洋水体。颗粒态~(２３４)Ｔｈ和总悬浮颗粒物（ＴＳＭ）在水体中的分布及其随时间的变化趋势相当一致,非生物过程可能对近岸海域水体中~(２３４)Ｔｈ的分布起着非常重要的作用。  相似文献   

海洋酸化之时间序列研究进展     

曲宝晓  宋金明  李学刚 《海洋通报》2020,39(3):281-290

本文简要总结了海洋酸化时间序列研究的主要方法，重点综述了时间序列研究在揭示海洋酸化长期变化方面的重要进展。大气中 CO2 不断溶解进入海洋，导致海水 pH 与碳酸钙饱和度 （Ω） 降低，这一过程即为海洋酸化。海洋酸化时间序列研究主要关注 pH 与Ω的实时、动态、长期变化。在海洋酸化时间序列研究中，pH 一般通过锚泊浮标所搭载的传感器现场获得，而Ω则需借助相关参数间接计算得到。目前全球共有 21 套正在运行的锚泊浮标，分别布设在大洋、近岸和珊瑚礁等海域，记录了近十几年来全球典型区域海洋酸化的长期变化过程。受上升流、生产力、陆源输入等因素的协同影响，近岸海域的酸化现象极具季节/年际变化，pH 和Ω 的变化范围较大，分别为 7.780~8.723，1.07~9.25。大洋的 pH 变化范围为 7.890~8.238，珊瑚礁的 pH 变化范围为 7.837~8.273，大洋的Ω变化范围为 1.93~4.19，珊瑚礁的Ω 变化范围为 2.06~5.22。海洋酸化时间序列研究表明，受人为活动与气候变化的共同影响，北半球近岸典型海域的Ω在冬季和春季已出现低于生物耐受阈值的现象，将产生十分严重的生态危害，需要尽快采取应对措施。  相似文献   

基于有色噪声模型的GPS速度场精度与时间序列长度相关性研究     

张风霜  畅柳 《地震》2017,37(1):92-102

利用2010—2015年陆态网络GPS连续观测站的三维站坐标时序资料, 在采用最大似然估计MLE方法计算得到云南地区GPS基准站三维站坐标分量最优噪声模型的基础上, 进一步定量对比分析了有色噪声和白噪声模型下陆态网络GPS连续站速度场稳定性与时间序列长度的关系。 结果表明: 在闪烁噪声模型下, 中国大陆大部分地区GPS连续站1 a时段的速度不确定度大。 而随着时间的逐年累积, 闪烁噪声模型下的速度不确定度与同时段白噪声模型下的差异逐步减小, 闪烁噪声模型下3～4 a时段的速度不确定度与同时段白噪声模型的差异小于0.2 mm。 研究说明在有色噪声模型下要获得高精度的速度场需要3～4 a的观测数据, 白噪声模型下GPS速度场精度可靠可信的前提是采用不少于3～4 a的数据。  相似文献   

潮汐和植被物候影响下的潮间带湿地遥感提取   总被引：1，自引：0，他引：1  

智超  吴文挺  苏华 《遥感学报》2022,26(2):373-385

潮间带湿地具有重要的生态和经济价值,但受到全球变化影响,发生大面积退化甚至丧失.掌握潮间带湿地的时空分布特征,对海岸带资源的科学管理具有重要意义.由于受到多云多雨天气和潮汐动态淹没的影响,单时相遥感数据难以获取完整的潮间带湿地信息.因此,本研究开发了一种基于时序遥感指数的潮间带湿地分类算法,并以福建省亚热带海岸带为例,...  相似文献   

基于非线性时序分析的三峡支流浮游植物因果响应     

何孟奇  闪锟  王兰  杨柳  李哲  尚明生 《湖泊科学》2023,35(2):507-518

水华的频发已成为当前三峡水库最为突出的生态环境问题之一。尽管水动力调控叠加上温度变暖和营养负荷增加会诱导水华暴发强度和频率增加,但仍缺乏有效的方法框架去利用野外观测数据评估环境因子与浮游植物间的因果关联。本研究以三峡水库澎溪河监测数据为例,采用非线性时序分析的建模框架来量化浮游植物的因果响应规律。数据来自于2007年6月至2018年9月澎溪河流域的高阳平湖和汉丰湖两个观测点,其中包含了水文、气象和水质及叶绿素a等11种变量。首先,利用奇异谱分析(SSA)分离了叶绿素a和环境因子的低维确定性动力学信号;其次,采用收敛交叉映射(CCM)方法检验了叶绿素a与环境因子间的因果关联。结果显示:(1)气象因子、支流流量、水温、三峡大坝水位和上游调节坝水位是影响高阳平湖叶绿素a时序变化的重要因素;(2)总氮、总磷为代表的营养盐只在汉丰湖观测点中表现出与叶绿素a的因果关系,且总氮较之于总磷对叶绿素a变化影响更为显著;(3)CCM结果与传统的皮尔森相关性分析及格兰杰因果检验比较,证实非线性时序分析方法在分析浮游植物的因果响应上更具优势。本研究为水生态系统的因果建模提供了研究范例,也为推动利用长期观测数据...  相似文献   

中国中部六省预期寿命时序加密估算研究     

李畅  王安丽  龚胜生  孙攸宁 《地理学报》2020,75(10):2269-2280

年龄组死亡率是利用年龄分组人口数据计算预期寿命的关键参数,而非采样年份的统计年鉴中年龄分组死亡率缺失导致无法计算预期寿命。针对该问题,本文将人口普查数据与统计年鉴数据融合,首次提出一种基于拉格朗日插值的中国省级预期寿命时间序列加强密集度（时序加密）的算法,以解决非采样（即未进行人口普查或1%人口抽样调查）年份省级预期寿命的估算问题。以中国中部六省为例,在所选取年份省级预期寿命估算实验中,绝对精度表明年龄分组人口比例线性插值计算的精度明显高于人口比例抛物线插值和直接插值算法的精度,故为推荐算法。本研究为高时间分辨率下省级预期寿命值的获取提供了一个新的可行思路,为分省较精确地进行预期寿命趋势分析奠定基础。  相似文献   

Object-based image analysis supported by data mining to discriminate large areas of soybean     

Carlos Antonio da Silva Junior  Marcos Rafael Nanni  José Francisco de Oliveira-Júnior  Everson Cezar  Paulo Eduardo Teodoro  Rafael Coll Delgado 《International Journal of Digital Earth》2019,12(3):270-292

This research aimed to analyze the possibility to estimate and automatically map large areas of soybean cultivation through the use of MODIS (Moderate-Resolution Imaging Spectroradiometer) images. Two major techniques were used: GEOgraphic-Object-Based Image Analysis (GEOBIA) and Data Mining (DM). In order to obtain the images, the segmentation algorithm implemented by Definiens Developer was used. A decision tree (DT) was created from a training set previously prepared. Time-series of images from the MODIS sensor aboard the Terra satellite were acquired in order to represent the wide variation of the vegetation pattern along the soybean crop cycle. The time-series data were used only for the CEI index. Furthermore, to compare the results obtained from GEOBIA, the slicing technique was used at the CEI level. After the training, the DT was applied to the vegetation indices generating the thematic map of the spatial distribution of soybean. In accordance with the error matrix and kappa parameter analysis, tests for statistical significance were created. Results indicate that the classification achieved by Kappa coefficients is 0.76. In short, the obtained results proved that combining vegetation indices and time-series data using GEOBIA return promising results for mapping soybean plantation on a regional scale.  相似文献   

藏北地区三种时序NDVI重建方法与应用分析   总被引：8，自引：0，他引：8  

宋春桥  游松财  柯灵红  刘高焕 《地球信息科学学报》2011,13(1):133-143

遥感植被指数时间序列数据集,已广泛应用于陆地生态环境变化监测与模拟、植被覆盖动态变化分析、植被物候特征识别与信息提取等多方面的研究.但其因受遥感器采集与传输过程、大气条件、地面状况等诸多因素的影响,时序NDVI数据包含各种噪声,因此研究者们发展了一系列时间序列曲线重建方法.本文对近年来提出或改进的重建算法原理、优缺点进...  相似文献