Evaluating sampling efficiency when estimating sediment source contributions to suspended sediment in rivers by fingerprinting          下载免费PDF全文

Robin T. Clarke  Jean P. G. Minella 《水文研究》2016,30(19):3408-3419

A general method is proposed which measures the increase in uncertainty when sampling effort is reduced in sediment fingerprinting. The method gives quantitative measures of how reduced sampling of material in one of the source areas, and/or of suspended sediment in streams, increases the uncertainties in the proportions of sediment contributed from the sources. Because the proportions of sediment contributed by the source areas must add to one, standard errors of the estimated proportions cannot be used as the usual measures of uncertainty: the paper uses instead the volume of the joint 95% confidence region for the estimated proportions. The paper shows how the uncertainty in this volume changes as numbers of suspended sediment samples, and the numbers of samples collected from cropped fields, are reduced by successive steps from 24 (20, in the case of cropped fields) to 16, 12, 8, 4 and 2 samples. As expected, uncertainty increases rapidly as the number of samples – whether of suspended sediment or from cropped fields – is reduced drastically. The pattern of increasing uncertainty is similar both for reductions in suspended sediment sampling, and for reduced sampling from cropped areas. When the number of suspended sediment samples, and the number of samples from cropped fields, are reduced to the same values, the increase in uncertainty from fewer suspended sediment samples was always slightly greater than the increased uncertainty from the reduced sampling of cropped areas, although this finding took no account of differences in the costs of field sampling and laboratory analysis. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Prediction of topsoil properties at field-scale by using C-band SAR data     

《International Journal of Applied Earth Observation and Geoinformation》2020

Designing and validating digital soil mapping (DSM) techniques can facilitate precision agriculture implementation. This study generates and validates a technique for the spatial prediction of soil properties based on C-band radar data. To this end, (i) we focused on working at farm-field scale and conditions, a fact scarcely reported; (ii) we validated the usefulness of Random Forest regression (RF) to predict soil properties based on C-band radar data; (iii) we validated the prediction accuracy of C-band radar data according to the coverage condition (for example: crop or fallow); and (iv) we aimed to find spatial relationship between soil apparent electrical conductivity and C-band radar. The experiment was conducted on two agricultural fields in the southern Argentine Pampas. Fifty one Sentinel 1 Level-1 GRD (Grid) products of C-band frequency (5.36 GHz) were processed. VH and VV polarizations and the dual polarization SAR vegetation index (DPSVI) were estimated. Soil information was obtained through regular-grid sample scheme and apparent soil electrical conductivity (ECa) measurements. Soil properties predicted were: texture, effective soil depth, ECa at 0-0.3m depth and ECa at 0-0.9m depth. The effect of water, vegetation and soil on the depolarization from SAR backscattering was analyzed. Complementary, spatial predictions of all soil properties from ordinary cokriging and Conditioned Latin hypercube sampling (cLHS) were evaluated using six different soil sample sizes: 20, 40, 60, 80, 100 and the total of the grid sampling scheme. The results demonstrate that the prediction accuracy of C-band SAR data for most of the soil properties evaluated varies considerably and is closely dependent on the coverage type and weather dynamics. The polarizations with high prediction accuracy of all soil properties showed low values of σ_VV^o and σ_VH^o, while those with low prediction accuracy showed high values of σ_VV^o and low values of σ_VH^o. The spatial patterns among maps of all soil properties using all samples and all sample sizes were similar. In conditions when summer crops demand large amount of water and there is soil water deficit backscattering showed higher prediction accuracy for most soil properties. During the fallow season, the prediction accuracy decreased and the spatial prediction accuracy was closely dependent on the number of validation samples. The findings of this study corroborates that DSM techniques at field scale can be achieved by using C-band SAR data. Extrapolation y applicability of this study to other areas remain to be tested.  相似文献   

Micro‐sampling Lu–Hf geochronology reveals episodic garnet growth and multiple high‐P metamorphic events          下载免费PDF全文

H. Cheng  X. C. Liu  J. D. Vervoort  D. Wilford  D. D. Cao 《Journal of Metamorphic Geology》2016,34(4):363-377

We present Lu–Hf dates from multiple growth zones within two large garnet porphyroblasts by a micro‐sampling method. A single eclogite sample, taken from the Huwan shear zone in the Hong'an orogen, was investigated with Lu–Hf geochronology by micro‐sampling and traditional bulk separation methods. The sample contains a few large garnet porphyroblasts up to several centimetres in diameter and a second major population of smaller (0.1–2.0 mm) garnet porphyroblasts, comprised of dark cores and pale rims. Elemental compositions and mineral inclusions in the garnet appear consistent with two garnet generations. Lu–Hf dates (c. 400–264 Ma) were determined from twelve micro‐sawed garnet sections from two large garnet porphyroblasts. These Lu–Hf dates overlap with age peaks defined by 115 SIMS zircon U–Pb analyses from the same eclogite sample. Bulk analyses of smaller garnet separates define a minimum date of c. 306 Ma and a maximum date of c. 252 Ma for the dark cores and pale rims respectively. These Lu–Hf dates were interpreted to bracket the period of garnet growth and the broad interval from c. 400 to 264 Ma is best explained by protracted and episodic garnet growth, which may require that these rocks experienced two subduction cycles that were initiated during the Devonian and terminated in the Triassic.  相似文献   

锂电池电动冲击取样钻机及其配套工具的研制          下载免费PDF全文

岳永东  谭春亮  卢倩  郭强  林广利 《探矿工程》2022,49(3):44-50

冲击钻进取样是支撑生态地质调查中松散地层优质高效、原状无污染取样的有效手段,但目前常见的便携式冲击取样钻机采用汽油机驱动,不能较好地适应安全生产与绿色勘查的发展要求。鉴于此,本文研制了一种以锂电池作为动力源的便携式电动冲击取样钻机及配套工具,详细介绍了钻机的电动冲击器、控制器、锂电池动力源及配套的取样器、锂电池液压起拔器的设计选型过程,并开展了钻机取样试验。实践证明该钻机及配套工具轻便可靠,可以实现5 m以浅松散地层的安全、高效、零碳排取样,是践行绿色勘查理念、推动浅层钻探装备电动化升级的有益尝试。  相似文献   

地表基质钻探取样技术方法与应用研究     

苏兴涛  冉灵杰  祝强  冯跃文  张永兴  张思源  孙小艳 《地质论评》2023,69(6):2239-2246

地表基质取样是开展地表基质层调查必不可少的工作环节,笔者等在浅地表层钻探技术的基础上,结合浅覆盖区矿产勘查、地球化学勘查、区域地质填图、环境调查、工程勘查、考古调查等领域钻探技术应用现状,根据不同地表景观及基质类型条件下的钻探取样需求,梳理了岩石、砾质、土质、泥质等地表基质钻探取样技术要点,研发了电动背包式钻机、Ф60/40mm单管冲击钻进、Ф50mm双管冲击钻进、Ф208mm中空螺旋钻进等取样器具及配套钻进工艺,在北京、内蒙古巴彦淖尔、浙江宁波、西藏那曲等地区开展了野外试验应用,通过获取满足要求的样品,很好的揭示了地层信息及物质组成,进一步在实践中提出了不同种类地表基质钻探取样技术方法,为建立自然资源调查监测体系及地表基质层调查工作提供钻探技术支撑。  相似文献   

草原浅覆盖区浅钻取样技术的研究与应用          下载免费PDF全文

卢猛  何远信  宋殿兰  谭春亮  赵洪波 《探矿工程》2015,42(11):1-6

为实现草原浅覆盖区快速揭露,并最大限度减少对环境的破坏,采用浅层钻探取样技术揭穿第四系,采取残坡积层及基岩层样品,用于浅钻金属矿产地球化学勘查、浅覆盖区地球化学立体填图及代替槽探的工作中。研究了干旱半干旱草原浅覆盖区浅钻取样技术方法组合。该方法在花敖包特铅锌矿及东乌旗地区的应用表明,通过灵活合理地调整钻探装备及钻进工艺方法,可以顺利地采取目的层样品。  相似文献   

羌塘盆地天然气水合物钻探试验井取样技术与施工实践          下载免费PDF全文

吴纪修  李宽  薛倩冰  李鑫淼  梁健  李小洋  张永勤 《探矿工程》2015,42(6):6-10

羌塘盆地天然气水合物钻探试验井工程位于羌塘盆地西北部,海拔4998～5100 m。羌塘盆地是青藏高原年平均地温最低、冻土层相对较厚的地区,所处的水文地质及工程地质环境极其复杂,多年冻土层经反复冻胀融沉,地层破碎。另外,该处地层节理、裂隙、小断层和地下水极其发育,施工条件十分恶劣和困难。从取心钻具结构改进、钻头设计、冲洗液配方以及钻孔结构等方面总结了近年在羌塘盆地实施天然气水合物钻探试验井工程的实践和经验,为未来高海拔地区天然气水合物及其他矿产资源勘探提供参考。  相似文献   

伸缩叠合型柔性(袋)管取心内管的研究与应用          下载免费PDF全文

汪发文  邬学农  徐俊  方波  叶慧 《探矿工程》2015,42(1):49-54

为解决刚性取心管采取岩心扰动度、水分保真度、取心率难以满足业主及设计部门要求的问题,研制了伸缩叠合型柔性(袋)管取心内管。通过分析比较柔性取心内管轴向和径向2种折叠方式对取心效果的影响,选用了轴向折叠方式的柔性取心内衬管。柔性取心内管的材质选用添加玻璃纤维丝的聚乙烯塑料。辅之配套使用高胎体底喷钻头、单向性罩爪簧的钻进工艺。通过在4种典型钻探项目中的试验,样品的扰动度＜5%,水分保真度＞95%,取心率达到了80%～95%。实践证明,应用伸缩式叠合型柔性（袋）管取心内管的三重管钻取特殊心样等原状样品,保真度高,采取率高,取心效果良好,有较好的推广应用价值。  相似文献   

考虑地形遮蔽影响的电磁传播算法与可视化研究     

张宗佩  万刚  李锋  刘婧 《测绘工程》2015,(4):41-45

采用规则格网数据(DEM)建立虚拟地理环境,并设定研究平面和电磁设备的空间位置,通过三角图元求交算法确定电磁波与地形是否存在遮蔽情况,从而计算得到受地形遮蔽影响的电磁场数据;采用颜色混合技术和优化处理的体绘制技术,将抽象的电磁场数据映射到可见的不同颜色值,形成直观、形象的可视化效果。  相似文献   

光释光测年法——综述及进展   总被引：4，自引：1，他引：3  

张克旗  吴中海  吕同艳  冯卉 《地质通报》2015,34(1):183-203

光释光(OSL)测年是对沉积物最后一次曝光(或热)事件年代的测定,其测试对象主要为石英和长石。自20世纪80年代该方法提出以来,在国内外得到了广泛的应用。但国内不少地学工作者对该技术的原理与测年方式了解十分有限,为了使应用者能更好、更全面地了解和使用这一方法,对OSL测年法及其近年来的国内外主要研究进展进行了回顾,重点对OSL测年法的基本原理、样品采集及实验室前处理过程、等效剂量(De)值的测定方式、环境剂量率的计算,以及影响测年结果可靠性的重要因素等进行了全面介绍、分析和探讨。同时,对近年来国内外关于De值测定方法与技术上的进展及已经获得较可信年龄的相关方法等进行了总结分析,并对OSL可能测年的范围和影响结果可靠性的一些潜在因素,以及对获得100ka~1Ma间的年龄新的释光信号研究方法等进行了介绍和探讨。  相似文献