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1.
本文首先提出了河流泥沙输移过程中泥沙中的钙镁矿物溶蚀消耗水体中的CO2并具有碳汇功能的观点。基于前人长江干流从源头到入海口和支流2003~2007年期间4次河流悬移质泥沙的化学元素组成和矿物组成资料,分析悬移质中CaO、MgO含量和方解石、白云石含量变化特征,定量计算了这些取样点悬移质泥沙的CO2总碳汇能力和非永久性、永久性碳汇能力,分析了不同碳汇能力沿程变化规律及其原因。碳汇计算结果表明:寸滩—大通河段1956~2000年期间泥沙输移过程中钙镁矿物溶蚀产生的总碳汇量、非永久性和永久性碳汇量分别为2572万t/a、1700万t/a和872万t/a。由于输沙量减少,寸滩站—大通站河段的总碳汇量、非永久性和永久性碳汇量2006~2019年期间较1956~2000年期间相应分别减少了1852万t、1224万t和872万t。三峡水库年均淤积量1. 145亿t,损失总碳汇量675. 6万t,相当于三峡电站减排二氧化碳8580万t的7. 9%。全球河流入海年输沙量126. 1亿t,以寸滩- 吴淞口河段碳汇功能0. 060 t/t计,总碳汇量7. 57亿t相当于全球岩石风化碳汇总量10. 56亿t CO2的71. 6%。河流泥沙输移过程中钙镁矿物溶蚀的碳汇量具有重要的作用,其溶蚀速率大于原地风化。  相似文献   
2.
高康  徐燕  胡天明  韩伶敏 《探矿工程》2021,48(1):112-119
季冻区草炭土是沼泽环境中植物残体在氧化分解作用下,堆积形成的含有大量未分解纤维残体的特殊土。草炭土纤维及其含量对其强度和变形特性具有重要影响,目前考虑纤维含量对草炭土强度和变形特性影响的本构关系研究还相对匮乏。K-G本构模型因其模型参数与土的体积模量和剪切模量能建立直接联系,因此在岩土工程非线性理论和数值计算分析方面广泛应用。以不同纤维含量的草炭土为研究对象,进行三轴剪切试验,研究了草炭土的应力应变曲线,得到了草炭土非线性K-G模型参数,分析了各模型参数随纤维含量的变化规律,建立了模型参数与纤维含量之间的线性函数关系。  相似文献   
3.
The study examines a water exploration and poverty alleviation project in Guyuan county. The study analyzes correlations between aquifers and multiple induced polarization (IP) parameters, including resistivity, polarizability, deviation, half decay time, water-bearing factors, and Kc, a new parameter refined in this study. Based on the study, the well was placed accurately, and its maximum water inflow reached 30 m3/h. Kc value highlights the rate of change at early stages of IP secondary field. Kc value served as a quick indicator in this groundwater prospecting and is validated in practice. Progress has been made in finding new parameters in exploring water with IP method. Thanks to the project, local people have access to water and poverty alleviation has scored some achievements.  相似文献   
4.
王晓艳 《中国沙漠》2019,39(4):168-176
2017年在秦岭黑河流域7个采样点进行地下水样品采集。通过综合分析、Gibbs图、Piper三角图、主要离子比值法、主成分分析法得出黑河地下水化学成分的特点、水化学类型及其成因。结果表明:阳离子的主要组成成分是Ca2+,HCO3-是阴离子的主要组成成分,黑河流域地下水化学类型为HCO3-- Ca2+和SO42--HCO3--Ca2+型。Gibbs图分析得出该地下水化学离子组成受岩石风化作用控制;Piper三角图、主要离子比值法、主成分分析及相关分析表明,地下水化学组分主要受方解石、白云岩等碳酸盐岩矿物的风化溶解,同时伴有硫酸溶解碳酸盐岩,受硅酸盐岩的溶解控制作用较小。  相似文献   
5.
Subsurface deformation is a driver for river path selection when deformation rates become comparable to the autogenic mobility rate of rivers. Here we combine geomorphology, soil and sediment facies analyses, and geophysical data of the Late Quaternary sediments of the central Garo-Rajmahal Gap in Northwest Bengal to link subsurface deformation with surface processes. We show variable sedimentation characteristics, from slow rates (<0.8 mm/year) in the Tista megafan at the foot of the Himalaya to nondeposition at the exposed surface of the Barind Tract to the south, enabling the development of mature soils. Combined subsidence in the Tista fan and uplift of the Barind Tract are consistent with a N-S flexural response of the Indian plate to loading of the Himalaya Mountains given a low value of elastic thickness (15–25 km). Provenance analysis based on bulk strontium concentration suggests a dispersal of sediment consistent with this flexural deformation—in particular the abandonment of the Barind Tract by a Pleistocene Brahmaputra River and the current extents of the Tista megafan lobes. Overall, these results highlight the control by deeply rooted deformation patterns on the routing of sediment by large rivers in foreland settings.  相似文献   
6.
Machine learning has achieved great success in many areas today. The lifting algorithm has a strong ability to adapt to various scenarios with a high accuracy, and has played a great role in many fields. But in astronomy, the application of lifting algorithms is still rare. In response to the low classification accuracy of the dark star/galaxy source set in the Sloan Digital Sky Survey (SDSS), a new research result of machine learning, eXtreme Gradient Boosting (XGBoost), has been introduced. The complete photometric data set is obtained from the SDSS-DR7, and divided into a bright source set and a dark source set according to the star magnitude. Firstly, the ten-fold cross-validation method is used for the bright source set and the dark source set respectively, and the XGBoost algorithm is used to establish the star/galaxy classification model. Then, the grid search and other methods are used to adjust the XGBoost parameters. Finally, based on the galaxy classification accuracy and other indicators, the classification results are analyzed, by comparing with the models of function tree (FT), Adaptive boosting (Adaboost), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Stacked Denoising AutoEncoders (SDAE), and Deep Belief Nets (DBN). The experimental results show that, the XGBoost improves the classification accuracy of galaxies in the dark source classification by nearly 10% as compared to the function tree algorithm, and improves the classification accuracy of sources with the darkest magnitudes in the dark source set by nearly 5% as compared to the function tree algorithm. Compared with other traditional machine learning algorithms and deep neural networks, the XGBoost also has different degrees of improvement.  相似文献   
7.
晋西北地区表层土壤粒度与地球化学元素组成   总被引:1,自引:1,他引:0  
对晋西北地区表层土壤的物质组成进行研究,可以明确其物质来源、沉积环境及化学风化特征。选择区内表层土壤(深度0、10、20 cm)及其附近的河流沉积物,进行粒度和化学元素组成测试。结果表明:(1)晋西北地区表层土壤粒度组成以黏土和粉沙为主,且有自地表向下粗颗粒组分含量增加的趋势。(2)常量化学元素组成以SiO2、Al2O3、CaO、Fe2O3为主,其余元素含量均较低。化学元素组成模式表明研究区内表层土壤物质与黄土高原腹地黄土有相同的物质源区,黄河河流沉积物对其贡献不大。(3)晋西北表层土壤的CIA值为52.70~57.89,平均54.06,说明它们的化学风化程度较低,处于早期的脱Na、Ca阶段。这是由于研究区地理位置比洛川更靠北,气温和降水量均低于洛川,降水量与兰州相差不大,但是年平均气温和年温差比兰州低。该研究明确了晋西北地区表层土壤的物质组成特征,为区域潜在沙漠化危害防治提供了数据支撑。  相似文献   
8.
Evapotranspiration (ET) is an important parameter in hydrologic processes and modelling. In agricultural watersheds with competing uses of fresh water including irrigated agriculture, estimating crop evapotranspiration (ETc) accurately is critical for improving irrigation system and basin water management. The use of remote sensing-based basal crop coefficients is becoming a common method for estimating crop evapotranspiration for multiple crops over large areas. The Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI), based on reflectance in the red and near-infrared bands, are commonly used for this purpose. In this paper, we examine the effects of row crop orientation and soil background darkening due to shading and soil surface wetness on these two vegetation indices through modelling, coupled with a field experiment where canopy reflectance of a cotton crop at different solar zenith angles, was measured with a portable radiometer. The results show that the NDVI is significantly more affected than the SAVI by background shading and soil surface wetness, especially in north–south oriented rows at higher latitudes and could lead to a potential overestimation of crop evapotranspiration and irrigation water demand if used for basal crop coefficient estimation. Relationships between the analysed vegetation indices and canopy biophysical parameters such as crop height, fraction of cover and leaf area index also were developed for both indices.  相似文献   
9.
本文建立了一种科研用室内珊瑚养殖中新生长珊瑚的培植方法,解决了养殖珊瑚中新生长珊瑚样品的培植和采集问题。按照所改进的珊瑚养殖技术和建立的新生长珊瑚的培植方法完成了在不同海水pH值环境下的珊瑚养殖实验,同时达到对养殖中研究参数控制的简化和有效地目的。测定了在养殖过程中各水化学参数的变化,获得了新生长的珊瑚样品,为利用硼同位素组成指示海洋环境的变化提供载体。  相似文献   
10.
Prehistoric rock art sites are endangered despite conservation efforts. The lack of scientific documentation regarding weathering agents affecting rock art and the absence of specific diagnostic protocols hinder the development of conservation strategies. The aim of this research was to investigate active deterioration processes in a granite petroglyph site located in Mougás (Galicia, NW Spain) by characterizing the granite, conducting a geotechnical study of the outcrop and describing and analysing the main weathering processes. Two main deterioration factors were identified. First, water favours block disjunction at the massif scale and causes pitting and surface erosion at the millimetre scale that affects the readability of the engravings. Second, high temperatures associated with wildfires cause mineral transformations that increase the susceptibility of the rock to weathering. Identifying deterioration factors is a first step in developing appropriate preventive conservation measures, which should aim to reduce rock contact time with water (technically affordable in the short term) and to reduce the probability of wildfire occurrence (technically more complex and possibly with longer‐term results). Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   
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