共查询到19条相似文献，搜索用时 187 毫秒
1.
受大气降水、黄河水位断流、风暴潮和人类工程活动等因素影响,现代黄河三角洲滨海湿地生态水文环境极其脆弱和敏感。本文运用地下水数值模拟方法,通过构建滨海湿地水文模型,以氯离子作为模拟因子,预测滨海湿地地下水趋势性变化。计算结果显示,湿地水位和盐度对湿地生长和发育起控制作用;黄河持续断流和强烈风暴潮对湿地水质影响明显;当风暴潮引起增水幅度超过正常潮高的2.4m,会造成沿海低地特别是北部未受防潮大坝保护的滨海湿地淹没。 相似文献
2.
黄河三角洲滨海湿地健康条件评价 总被引：3，自引：0，他引：3
以黄河三角洲滨海湿地系统为研究对象,基于描述滨海湿地健康条件的4项功能,充分考虑滨海湿地生态地质环境系统的特征及其健康响应因素,建立了黄河三角洲滨海湿地健康条件评价的概念模型和指标体系。以统计监测和遥感数据为基础,采用RS和GIS技术,通过栅格化实现分区评价及其结果的优化整合,探讨了黄河三角洲滨海湿地健康的时空分布规律。结果显示：黄河三角洲滨海湿地现状健康条件处于健康的占14.2%,亚健康的占61.9%,一般病态的占23.9%;近期（2010－2015年）,河口三角洲湿地生境质量会逐步改善,向健康方向发展,而北部和南部部分滩涂区及神仙沟流路等局部地区在自然和人为因素的共同作用下,环境质量会有一定的降低;影响黄河三角洲滨海湿地健康条件的主要因素是全球气候变化背景下的区域水循环关键过程及其时空变化、湿地开发等人类负面干扰和黄河下游生态调度。应继续加大黄河下游生态调度的力度、积极实施生态修复工程,以促进黄河三角洲滨海湿地持续健康发展。 相似文献
3.
华南西部滨海湿地调查及主要成果 总被引：1，自引：1，他引：0
通过遥感、单波束测量、地质取样、海水取样、钻探、地下水采集与监测等多种调查手段及工作方法,首次在我国华南西部开展1∶10万滨海湿地地质调查与生态环境评价工作,对滨海湿地类型及分布、滨海海域地形地貌、沉积物环境质量、海水环境质量、生态地质演化、地下水化学要素进行综合分析与研究。项目系统查明了该区滨海湿地类型、分布、生态环境现状及其主要影响因素,对湿地生态地质环境质量进行了综合评价,构建了华南西部滨海湿地地质调查技术方法体系和生态地质环境综合评价体系,提出了滨海湿地保护和恢复的建议,为后续我国南方滨海湿地调查提供了示范。 相似文献
4.
海潮引起的滨海地区包气带气压周期性变化的数值模拟 总被引：2，自引：1，他引：1
滨海地区的地下水位由于海潮而上下波动, 这早已是为人熟知的事实.但是, 滨海地区包气带中气压也会随海潮的起伏而作周期性变化, 这一点却很少为人注意.如果地表由渗透性差的材料如水泥或沥青路面覆盖(这种情况在香港高度城市化的近海地区很常见), 海潮的起伏会产生幅度异常高的气压波动.在某些情形下, 足够高的气压会引起如路面拱起等工程问题.因此, 研究海潮引起的包气带气流, 不仅具有理论意义, 还对滨海地区土木工程有实际指导作用.以香港某滨海地区为例, 建立了该地区一剖面上水气两相流的二维数学模型, 并用TOUGH2程序进行了数值模拟.通过数值敏感度分析, 探讨了影响沥青路面下气压的主要水文地质因素.在根据该地区实际水文地质情况选取了适当的模型边界条件和模型参数后, 沥青路面下气压的数值模拟结果和观测数据吻合程度良好. 相似文献
5.
1961-2015年青藏高原降水量变化综合分析 总被引：2，自引：0，他引：2
降水量及其季节分配与降水形式变化一直是全球气候变化研究的热点之一。使用青藏高原72个气象站点1961-2015年的逐日降水量资料,基于趋势、波动特征和极端事件相结合的新视角,全面剖析了该地区近55年降水量的趋势、波动与极端事件变化。结果表明：（1）时间上,近55年青藏高原年降水量、年最大日降水量和一年中日降水量≥ 10 mm的天数分别以6.59 mm·（10a）-1、0.33 mm·（10a）-1和0.26 d·（10a）-1的速率显著增加,增幅分别达到36.2 mm、1.8 mm和1.4 d。（2）空间上,过去55年青藏高原绝大部分地区年降水量增加,不稳定性增强。但波动变化存在较大的地区差异,广大的中西部地区年降水量波动缓慢增强,而高原东部地区自北向南波动快速增强区与快速减弱区相间分布,极端降水强度与频数亦有类似的变化格局。（3）趋势、波动与极端变化三者组合预示,青藏高原东部的祁连山地区、柴达木盆地东部、青海湖流域与长江源区极端降水事件将明显增加,高原中西部地区发生强降水的可能性亦增加,而高原东南缘地区干旱事件将增多。 相似文献
6.
在黑龙江多宝山地区1：5万矿产远景调查及黑龙江省嫩江县霍龙门乡播根里金矿普查项目成果基础上,综合分析区域成矿规律和物化探异常特征,讨论其找矿潜力.1：5万化探异常特征显示以Au异常为主,Au强度较高,多达内带,并与Ag异常关系较密切.结合1：5万物探特征及遥感等信息,在研究区内圈定6处综合异常.其中,08XHt-3号异常中的Au-20异常面积为3.79 km2,异常最大值为43.1×10-9,平均值为7.53×10-9,达内带;08DHt-11号异常中的Au-47异常面积为2.157 km2,异常最大值为29.9×10-9,平均值为8.58×10-9,达内带.进一步开展的1：1万大比例尺物化探工作显示Au异常重现性好,与物探异常相吻合.其中圈定的BG12HtAu-22号金元素异常最大值为115.9×10-9,平均值为23.55×10-9,异常达到内带;BG12HtAu-42、43号金异常最大值分别为43.6×10-9、25.7×10-9,异常均达到中带.综合分析区域成矿规律、研究区成矿条件,结合物化探异常特征以及少量工程查证发现的1条金矿体和5条金矿化体,认为研究区具有较大的找矿潜力,值得继续开展进一步的查证工作. 相似文献
7.
通过1∶5万区域地质调查及典型剖面研究,在滇中禄劝地区二叠系峨眉山组顶部识别出一套厚约20～50 m不等的Nb、Co、Ga、Zr及REE超常富集层。富集层主要岩性为灰紫色泥岩、凝灰质泥岩、凝灰岩,局部夹杏仁状玄武岩。通过对禄劝万鲁布、撒角海一带的富集层刻槽分析显示,Nb2O5含量在82.4×10-6～120.1×10-6,平均值为100.3×10-6,大于风化壳型矿床一般工业指标80×10-6;Ga含量28.8×10-6～35.6×10-6,平均值为32.1×10-6,高于现行的Ga矿资源工业指标要求30×10-6;REE含量在360×10-6～510×10-6,平均值为440.6×10-6,接近风化壳型矿床一般工业指标500×10-6;并呈现出泥岩→凝灰质泥岩→凝灰岩关键金属含量依... 相似文献
8.
低密度地球化学填图具有采样水系级别高、工作覆盖面积广阔的特征，可有效追溯具有高金属含量的地球化学块体。本次研究以埃塞俄比亚1∶100万低密度地球化学填图数据为基础，通过对原始水系沉积物中Cu测试数据处理后，应用迭代剔除的方法，计算得出Cu的异常下限值为37×10-6。在此基础上，以37×10-6、42×10-6、47×10-6、52×10-6、59×10-6、66×10-6作为分级间隔，共圈定出地球化学块体3个、区域异常2个。通过参考相同成矿带中铜矿勘查研究程度较高的地球化学块体中已知铜矿床储量，计算出研究区的Cu块体成矿率为0.055%。本次以1 000 m岩块厚度估算出研究区内Cu的资源量为260万t。结合区域成矿地质条件分析，确定2号、3号、4号地球化学块体所在区域可作为开展进一步详细勘查工作的重点成矿远景区。 相似文献
9.
安徽沿江地区晚石炭世黄龙组白云岩广泛发育,主要为晶粒白云岩,其次是角砾白云岩和残余颗粒白云岩。地球化学分析表明,安徽沿江地区黄龙组白云岩中Fe、Mn、Sr、Na含量分别为:2 567×10-6(1 600×10-6～4 400×10-6)、353×10-6(166×10-6～742×10-6)、109.7×10-6(69.0×10-6～176.5×10-6)、288×10-6(100×10-6～700×10-6),稀土元素总量为7.29×10-6(2.56×10-6～20.82×10-6),ΣLREE/ΣHREE比值平均为3.07(1.16～10.17),经海水标准化后,显示LREE富集,HREE相对亏损,δCe平均为4.53(2.82～7.78),正异常显著,δEu平均为1.85(0.94～2.92),配分模式曲线显示白云岩化流体来自海水。白云岩中可见蒸发岩类或蒸发构造。综合分析认为该地区白云岩主要为准同生成因,部分为埋藏成岩成因,其中角砾白云岩为准同生成因,怀宁地区白云岩δEu平均为2.38(1.91～2.92),正异常显著,表明后期受到热液流体影响。 相似文献
10.
在农业生态环境地球化学调查与评价中,植物的化学组成是重要的直接指标,因此对植物样品元素含量进行准确测定具有重要意义.本研究的主要目的是开发一种利用电感耦合等离子体发射光谱(ICP-OES)测定植物样品中多元素的分析方法,同时不需要在光谱测定之前进行费力而繁琐的样品前处理.采用微波消解、电热板消解及超声消解3种方法处理植物样品,利用ICP-OES分别测定植物样品中Ca、Cr、Cu、Fe、Mg、Mn、Ni、Pb、Sr、Zn等10种元素的含量,并对3种方法的消解效果进行比较.结果表明：3种方法的检出限分别为0.042×10-6～0.239×10-6、0.046×10-6～0.237×10-6、0.026×10-6～0.232×10-6;测定待测元素的相对标准偏差均低于10%;相对误差分别为-11%～+13.8%,-22.1%～+8.7%,-13.3%～+8.9%.其中超声消解表现出更低的检出限和较好的准确度,满足DD2005-03《生态地球化学评价样品分析技术要... 相似文献
11.
Paul Harris Chris Brunsdon Martin Charlton Steve Juggins Annemarie Clarke 《Mathematical Geosciences》2014,46(1):1-31
Outlier detection is often a key task in a statistical analysis and helps guard against poor decision-making based on results that have been influenced by anomalous observations. For multivariate data sets, large Mahalanobis distances in raw data space or large Mahalanobis distances in principal components analysis, transformed data space, are routinely used to detect outliers. Detection in principal components analysis space can also utilise goodness of fit distances. For spatial applications, however, these global forms can only detect outliers in a non-spatial manner. This can result in false positive detections, such as when an observation’s spatial neighbours are similar, or false negative detections such as when its spatial neighbours are dissimilar. To avoid mis-classifications, we demonstrate that a local adaptation of various global methods can be used to detect multivariate spatial outliers. In particular, we account for local spatial effects via the use of geographically weighted data with either Mahalanobis distances or principal components analysis. Detection performance is assessed using simulated data as well as freshwater chemistry data collected over all of Great Britain. Results clearly show value in both geographically weighted methods to outlier detection. 相似文献
12.
Surendra P. Verma Leonides Javier Orduña-Galván Mima Guevara 《Geostandards and Geoanalytical Research》1998,22(2):209-234
A new computer programme was written in programming language TURBOC, which enables us to apply a procedure involving seventeen statistical tests (a total of sixty five single or multiple outlier versions of these tests) for outlier detection in univariate sample at a high confidence level of 99% (significance level α= 0.01). The outlying observations should be evaluated first for technical reasons and then rejected manually from the data base until no more outliers are detected and the final statistical parameters are computed from the remaining data. This programme has been used successfully to process two reference material data bases: WS-E from England and Soil-5 from Peru. The final mean values for WS-E are more reliable (characterized by smaller standard deviations and narrower confidence limits) than those obtained earlier using a different statistical approach. The application of a large number of statistical tests to Soil-5 also resulted in smaller standard deviation values for most elements than the method involving a limited number of such tests. For WS-E, some laboratories seem to have produced multiple data that were detected as statistical outliers. A close analysis of the distribution of outliers as a function of laboratory, country and analytical method leads to a technical justification for these outlying observations, probably in terms of inadequate QA/QC practices. Use of geochemical criteria indicates that the new mean values in WS-E might be closer to the "true" concentrations. This procedure of outlier detection and elimination is therefore recommended in the study of the existing RM. 相似文献
13.
马氏距离是一种多元异常识别方法,目前已有多种基于马氏距离的异常识别方法。笔者选择青海省东昆仑东段1∶50万水系沉积物测量数据,对比常规马氏距离、基于最小方差行列式(FMCD)的稳健马氏距离、基于校正的最小方差行列式的稳健马氏距离(Adaptive)和基于协中值的稳健马氏距离(Comedian)4种方法在识别Cu、Co、Cr、Ni、V、Fe,Cd、Cu、Mo、Pb、Zn、Ag和Au、As、Sb三种组合异常中的应用效果。结果显示,基于Comedian方法识别的异常效果最好,而常规方法识别的异常效果最差,因此Comedian方法是该区最有效的多元异常识别方法。 相似文献
14.
Shuo Zheng Yu-Xin Zhu Dian-Qing Li Zi-Jun Cao Qin-Xuan Deng Kok-Kwang Phoon 《地学前缘(英文版)》2021,12(1):425-439
Various uncertainties arising during acquisition process of geoscience data may result in anomalous data instances(i.e.,outliers)that do not conform with the expected pattern of regular data instances.With sparse multivariate data obtained from geotechnical site investigation,it is impossible to identify outliers with certainty due to the distortion of statistics of geotechnical parameters caused by outliers and their associated statistical uncertainty resulted from data sparsity.This paper develops a probabilistic outlier detection method for sparse multivariate data obtained from geotechnical site investigation.The proposed approach quantifies the outlying probability of each data instance based on Mahalanobis distance and determines outliers as those data instances with outlying probabilities greater than 0.5.It tackles the distortion issue of statistics estimated from the dataset with outliers by a re-sampling technique and accounts,rationally,for the statistical uncertainty by Bayesian machine learning.Moreover,the proposed approach also suggests an exclusive method to determine outlying components of each outlier.The proposed approach is illustrated and verified using simulated and real-life dataset.It showed that the proposed approach properly identifies outliers among sparse multivariate data and their corresponding outlying components in a probabilistic manner.It can significantly reduce the masking effect(i.e.,missing some actual outliers due to the distortion of statistics by the outliers and statistical uncertainty).It also found that outliers among sparse multivariate data instances affect significantly the construction of multivariate distribution of geotechnical parameters for uncertainty quantification.This emphasizes the necessity of data cleaning process(e.g.,outlier detection)for uncertainty quantification based on geoscience data. 相似文献
15.
松辽盆地中二叠统哲斯组发育一套暗色泥岩、灰色砂砾岩与灰岩沉积组合,灰岩中产海相腕足类和双壳类化石。由于受钻井进尺和取心资料限制,前人对盆地覆盖区晚古生代地层及其沉积环境研究较少。对采自松辽盆地杜101井、杜103井剖面哲斯组的白云质灰岩进行了系统的稳定同位素和微量元素、稀土元素分析,首次获取了盆地覆盖区中二叠统灰岩元素地球化学资料。测试结果显示碳同位素δ13CPDB值一般>0(均值为1.68‰),氧同位素δ18OPDB值全部<-15‰(均值为-19.98‰),碳、氧稳定同位素关系图解显示二者呈正相关关系,表明白云岩化作用对灰岩同位素改造作用明显。稀土元素(REE+Y)总量为56.88×10-6~143.72×10-6,均值为108.92×10-6,PAAS标准化后显示具有轻稀土相对于中稀土和重稀土亏损、δEu(均值0.94,最大值1.57)负异常、δCe(均值0.87,最大值1.06)普遍负异常和相对高的Y/Ho均值(均值34.59)等特点,与正常海相具有大体相同的稀土元素配分模式;而微量元素Ba(均值281.55×10-6)、Zn(均值71.91×10-6)、Y(均值17.44×10-6)、Zr(均值117.75×10-6)和Rb(均值66.84×10-6)等元素含量整体较高,Sr/Ba(均值2.91)、Th/U(均值2.75)、V/Cr(均值1.45)和V/(V+Ni)(均值0.66)等比值适中,指示研究区哲斯组沉积时期主体为一种频繁受陆源碎屑混染作用影响的碳酸盐台地或滨海岸环境。 相似文献
16.
美国海岸带自然资源与生态损害评估及修复工作对中国的启示 总被引：1，自引：0，他引：1
海岸带是位于海陆结合部的复杂环境系统,是人类活动最集中的地区。中国大陆海岸线约18000km,涉及沿海11个省,由于经济社会高速发展,海岸带地区的人口、资源、环境矛盾日益突出,面临海岸带资源无序开发、水土污染、滨海湿地退化、海岸侵蚀、地面沉降等一系列生态环境与灾害地质问题,已成为影响生态文明建设的主要问题之一。因此中国持续加大海岸带生态环境保护力度,并提出实施重要生态系统保护和修复重大工程、强化湿地保护和修复等政策措施。美国国家海洋和大气管理局主导的海岸带损害评估及修复计划已实施了近30年,并取得了显著效果,其完善的法律制度体系、规范的损害评估和修复程序、数据集成管理和共享应用等成功经验值得学习借鉴。建议加快完善中国海岸带生态环境损害评估与修复的技术方法体系和制度体系、有序开展海岸带自然资源和生态环境调查、加强海岸带及滨海湿地等重要生态系统的演化和修复技术研究与示范,并构建统一的海岸带基础调查数据库、建立海岸带监测预警体系。 相似文献
17.
Surendra P. Verma 《Geostandards and Geoanalytical Research》1997,21(1):59-75
A totally objective procedure involving sixteen statistical tests (a total of thirty four single or multiple outlier versions of these tests) for outlier detection and rejection in a univariate sample is applied to a data base of sixty four elements in a recently issued international geochemical reference material (RM), a microgabbro PM-S from Scotland. This example illustrates the relative importance and usefulness of these tests in processing modern geochemical data for possible outliers and obtaining mean concentration and other statistical parameters from a final normal sample of univariate data. The final mean values are more reliable (characterized by smaller standard deviations and narrower confidence limits) than those obtained earlier using an accommodation approach (robust techniques) applied to this data base. Very high quality (certified value equivalent, cve) mean data are now obtained for eleven elements as well as high quality recommended values (rv) for thirty three elements in PM-S. Earlier work using the accommodation approach failed to establish even one cve value for any of the sixty four elements compiled here. The present procedure of outlier detection and elimination is therefore recommended in the study of RMs 相似文献
18.
如何快速准确地建立老红砂剖面年代学标尺或区域年代学框架,是在实践中有待解决的问题。而标准生长曲线法(SGC)在减少样品测试时间、提高测年仪器的测试效率方面具有独特的优势,因此在内陆黄土及沙漠沉积年代测定中得到了广泛应用。在福建和海南海岸带老红砂分布区采集了4个剖面的测年样品共计20个,应用单片再生剂量法(SAR)及SGC法进行定年研究。结果表明: (1)福建和海南海岸带老红砂样品释光(OSL)信号均以快组分为主,在信号积分通道前0.64 s 快组分的信号占据总体信号的80%以上,适合使用SAR及SGC方法测年;其快、中组分光电离截面分别为: 福建老红砂2.62×10-17 cm2和3.24×10-18 cm2,海南老红砂2.66×10-17 cm2和3.51×10-18 cm2; 2个区域样品的IRSL(红外激发释光信号)/OSL信号比值表明,较老样品的红外释光信号明显高于较年轻的样品,这可能是受到长石包裹体的影响,但其比值均小于10%,符合SAR与SGC测试要求。 (2)SGC法在华南海岸地区老红砂OSL年代学研究中具有较好的适用性,不同样品之间的剂量生长曲线存在着相似的增长模式,可以建立标准生长曲线; 但福建与海南老红砂样品之间的标准生长曲线具有较大的差异,因此在较大区域范围内运用标准生曲线法应当谨慎小心。 相似文献
19.
Surendra P. Verma Lorena Díaz-González Rosalinda González-Ramírez 《Geostandards and Geoanalytical Research》2009,33(1):29-49
Numerous studies report geochemical data on reference materials (RMs) processed by outlier-based methods that use univariate discordancy tests. However, the relative efficiency of the discordancy tests is not precisely known. We used an extensive geochemical database for thirty-five RMs from four countries (Canada, Japan, South Africa and USA) to empirically evaluate the performance of nine single-outlier tests with thirteen test variants. It appears that the kurtosis test (N15) is the most powerful test for detecting discordant outliers in such geochemical RM databases and is closely followed by the Grubbs type tests (N1 and N4) and the skewness test (N14). The Dixon-type tests (N7, N8, N9 and N10) as well as the Grubbs type test (N2) depicted smaller global relative efficiency criterion values for the detection of outlying observations in this extensive database. Upper discordant outliers were more common than the lower discordant outliers, implying that positively skewed inter-laboratory geochemical datasets are more frequent than negatively skewed ones and that the median, a robust central tendency indicator, is likely to be biased especially for small-sized samples. Our outlier-based procedure should be useful for objectively identifying discordant outliers in many fields of science and engineering and for interpreting them accordingly. After processing these databases by single-outlier discordancy tests and obtaining reliable estimates of central tendency and dispersion parameters of the geochemical data for the RMs in our database, we used these statistical data to apply a weighted least-squares linear regression (WLR) model for the major element determinations by X-ray fluorescence spectrometry and compared the WLR results with an ordinary least-squares linear regression model. An advantage in using our outlier procedure and the new concentration values and uncertainty estimates for these RMs was clearly established. 相似文献