Characteristics of Vegetation Carbon,Nitrogen, and C/N Ratio in a Tamarix chinensis Coastal Wetland of China     

Linping Xie  Baodong Wang  Ming Xin  Min Wang  Xiuping He  Qinsheng Wei  Xiaoyong Shi  Xia Sun 《洁净——土壤、空气、水》2019,47(9)

Variations in carbon (C) and nitrogen (N) of the vegetation in a Tamarix chinensis coastal wetland located in Laizhou Bay, China, are analyzed. It is found that T. chinensis accumulates more C and N than the surrounding herbs, and it allocates more C and N in the aboveground parts but less in the roots. Branches store more C, whereas leaves and flowers accumulate more N than other tissues. The C and N contents in the aboveground parts of T. chinensis are mainly influenced by pH, electrical conductivity (EC), water content, and clay content in the top 100 cm of soil as well as the distance from the sea. For the herbs, their C contents vary little in the supratidal zone, but they are higher than those in the intertidal zone. However, N contents in the herbs are higher in the aboveground parts and varied among different communities. The contents of C and N in the herbs are affected by EC, water content as well as the contents of organic C and total nitrogen (TN) in the top 10 cm of soil. The findings confirm that increasing the biomass of T. chinensis is an effective way to increase C sequestration in temperate coastal wetland.  相似文献   

CEDLES: a framework for plugin-based applications for earthquake risk prediction and loss assessment     

Long  Li  Zheng  Shansuo  Zhang  Yixin  Sun  Longfei  Zhou  Yan  Dong  Liguo 《Natural Hazards》2020,103(1):531-556

Natural Hazards - To evaluate the seismic risk and loss caused by an earthquake, many earthquake disaster loss assessment softwares have been developed. However, it is difficult to apply one...  相似文献   

煤层气井产出剖面测试技术及应用     

张雷  樊洪波  侯伟  张伟  郝帅  孙晓光 《吉林大学学报(地球科学版)》2020,50(2):617-626

现有常规油气井产出剖面测试方法在煤层气井中适应性较差，测试范围和测量工艺等存在局限性，施工成功率低。因此，本文对煤层气井产出剖面测试技术进行了整体的系统化设计和研发。通过紧凑的结构设计、高度集成，研发了一套可同时进行温度、压力、磁性定位、热式流量、探针持气率、微波持气、涡轮流量和超声流量等多参数测量的煤层气井测井仪，并研制了一套一次下井可进行多种测试技术测量的煤层气井产出剖面测试技术。同时提高了测试仪器的精度和抗干扰能力，开发了多任务多窗口的便携地面系统操作，并研制新型偏心测试井口应用于煤层气井，实现修井作业时不间断连续测试。该技术在鄂尔多斯盆地石楼北区块3口煤层气井进行了现场试验，取得精确、连续的测试数据。测试结果显示，石楼北区块8^#+9^#煤层为主力产气、产水层。  相似文献   

基于时间序列遥感数据的嵯岗国家沙化土地封禁保护成效评估     

田海静  孙涛  刘旭升  孔祥吉 《中国沙漠》2019,39(3):155-162

2013年中国启动实施了内蒙古自治区新巴尔虎左旗嵯岗国家沙化土地封禁保护区试点。本研究利用2001—2017年生长季NDVI数据分析了嵯岗封禁保护区及周边区域植被长势时空演变特征，分析了多年的生长季降水量和历年旱情，之后利用植被降水利用效率和NDVI残差趋势分析对保护成效进行了评估。结果表明：（1）封禁项目实施之前，封禁区内外植被长势变化趋势基本一致，而在项目实施后的2016、2017年，封禁区内NDVI距平明显高于封禁区外；（2）降水为影响该区域植被长势的主导气候因素，在封禁实施后的2015—2017年该区域连续3 a干旱，极大地限制了区域植被生长；（3）封禁区内植被降水利用效率和NDVI残差均呈现明显的增加趋势，而封禁区外变化不明显，说明封禁提升了植被的自我修复能力；（4）嵯岗封禁保护区由3个地块组成，其中嵯岗林场封禁效果比牧场八队和牧场十一队明显。国家沙化土地封禁保护措施有效促进了植被自我修复，提高了沙漠生态系统应对气候变化的能力。  相似文献   

Retrieving volume FeO and TiO_2 abundances of lunar regolith with CE-2 CELMS data using BPNN method     

Cai Liu  Hong-Yan Sun  Zhi-Guo Meng  Yong-Chun Zheng  Yu Lu  Zhan-Chuan Cai  Jin-Song Ping  Alexander Gusev  Shuo Hu 《天文和天体物理学研究(英文版)》2019,(5)

The volume FeO and TiO_2 abundances(FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs are retrieved with microwave sounder(CELMS) data from the Chang'E-2 satellite using the back propagation neural network(BPNN) method. Firstly, a three-layered BPNN network with five-dimensional input is constructed by taking nonlinearity into account. Then, the brightness temperature(TB) and surface slope are set as the inputs and the volume FTAs are set as the outputs of the BPNN network.Thereafter, the BPNN network is trained with the corresponding parameters collected from Apollo, Luna,and Surveyor missions. Finally, the volume FTAs are retrieved with the trained BPNN network using the four-channel TBderived from the CELMS data and the surface slope estimated from Lunar Orbiter Laser Altimeter(LOLA) data. The rationality of the retrieved FTAs is verified by comparing with the Clementine UV-VIS results and Lunar Prospector(LP) GRS results. The retrieved volume FTAs enable us to re-evaluate the geological features of the lunar surface. Several important results are as follows. Firstly, very-low-Ti(1.5 wt.%) basalts are the most spatially abundant, and the surfaces with TiO_2 5 wt.% constitute less than 10% of the maria. Also, two linear relationships occur between the FeO abundance(FA) and the TiO_2 abundance before and after the threshold, 16 wt.% for FA. Secondly, a new perspective on mare volcanism is derived with the volume FTAs in several important mare basins, although this conclusion should be verified with more sources of data. Thirdly, FTAs in the lunar regolith change with depth to the uppermost surface,and the change is complex over the lunar surface. Finally, the distribution of volume FTAs hints that the highlands crust is probably homogeneous, at least in terms of the microwave thermophysical parameters.  相似文献   

A feasible approach to predicting time-dependent bearing performance of jacked piles from CPTu measurements     

Li  Lin  Li  Jingpei  Sun  De’an  Gong  Weibing 《Acta Geotechnica》2020,15(7):1935-1952

Acta Geotechnica - In this paper, a simple but feasible approach is proposed to predict the time-dependent load carrying behaviours of jacked piles from CPTu measurements. The corrected cone...  相似文献   

The effectiveness of a pseudo-inverse extended Born operator to handle lateral heterogeneity for imaging and velocity analysis applications     

Abdullah Alali  Bingbing Sun  Tariq Alkhalifah 《Geophysical Prospecting》2020,68(4):1154-1166

Wave equation–based migration velocity analysis techniques aim to construct a kinematically accurate velocity model for imaging or as an initial model for full waveform inversion applications. The most popular wave equation–based migration velocity analysis method is differential semblance optimization, where the velocity model is iteratively updated by minimizing the unfocused energy in an extended image volume. However, differential semblance optimization suffers from artefacts, courtesy of the adjoint operator used in imaging, leading to poor convergence. Recent findings show that true amplitude imaging plays a significant role in enhancing the differential semblance optimization's gradient and reducing the artefacts. Here, we focus on a pseudo-inverse operator to the horizontally extended Born as a true amplitude imaging operator. For laterally inhomogeneous models, the operator required a derivative with respect to a vertical shift. Extending the image vertically to evaluate such a derivative is costly and impractical. The inverse operator can be simplified in laterally homogeneous models. We derive an extension of the approach to apply the full inverse formula and evaluate the derivative efficiently. We simplified the implementation by applying the derivative to the imaging condition and utilize the relationship between the source and receiver wavefields and the vertical shift. Specifically, we verify the effectiveness of the approach using the Marmousi model and show that the term required for the lateral inhomogeneity treatment has a relatively small impact on the results for many cases. We then apply the operator in differential semblance optimization and invert for an accurate macro-velocity model, which can serve as an initial velocity model for full waveform inversion.  相似文献   

Modelling of viscoacoustic wave propagation in transversely isotropic media using decoupled fractional Laplacians     

Zhihao Qiao  Chengyu Sun  Jie Tang 《Geophysical Prospecting》2020,68(8):2400-2418

A new wave equation is derived for modelling viscoacoustic wave propagation in transversely isotropic media under acoustic transverse isotropy approximation. The formulas expressed by fractional Laplacian operators can well model the constant-Q (i.e. frequency-independent quality factor) attenuation, anisotropic attenuation, decoupled amplitude loss and velocity dispersion behaviours. The proposed viscoacoustic anisotropic equation can keep consistent velocity and attenuation anisotropy effects with that of qP-wave in the constant-Q viscoelastic anisotropic theory. For numerical simulations, the staggered-grid pseudo-spectral method is implemented to solve the velocity–stress formulation of wave equation in the time domain. The constant fractional-order Laplacian approximation method is used to cope with spatial variable-order fractional Laplacians for efficient modelling in heterogeneous velocity and Q media. Simulation results for a homogeneous model show the decoupling of velocity dispersion and amplitude loss effects of the constant-Q equation, and illustrate the influence of anisotropic attenuation on seismic wavefields. The modelling example of a layered model illustrates the accuracy of the constant fractional-order Laplacian approximation method. Finally, the Hess vertical transversely isotropic model is used to validate the applicability of the formulation and algorithm for heterogeneous media.  相似文献   

秦皇岛近岸海域潮间带砂质沉积物中微塑料和重金属污染特征   总被引：1，自引：0，他引：1  

陈月琴  罗维  孙聪慧  吴光红 《海洋学报》2020,42(4):113-121

基于密度分离原理，利用饱和NaCl溶液对秦皇岛近岸海域潮间带砂质沉积物中的微塑料进行了浮选和分离提取，采用显微红外光谱方法分析附着在滤膜上的微塑料颗粒形貌和材质。结合扫描电子显微镜?能谱仪(Scanning Electron Microscopy Energy Dispersive Spectrometer，SEM-EDS)对微塑料样品进行微观形貌观察及微区成分的分析。并采用地累积指数(Geo Accumulation Indexes，I_geo)和富集系数(Enrichment Factors，EF)分析砂质沉积物中重金属Hg、Cd和Pb污染水平和富集特点。分析砂质沉积物中烧失量(Loss on Ignition，LOI)、总有机碳(Total Organic Carbon，TOC)、总氮(Total Nitrogen，TN)以及碳氮的稳定同位素组成(δ13C和δ15N)，探讨有机质的可能来源。结果表明:秦皇岛近岸海域潮间带砂质沉积物中有纤维类、发泡类、薄膜类3种微塑料，以纤维类的微塑料为主。微塑料表层富集有Si、Al、Mg、Fe和Ca等元素。沉积物中Hg和Cd富集水平较高，Pb富集水平较低。沉积物TOC和TN含量较低，LOI为TOC的1.6倍，δ13C、δ15N和TOC/TN的数值范围均显示有机质以海洋浮游植物藻类等海源为主。  相似文献   

莱州湾大型底栖动物群落结构及其动态变化特征   总被引：1，自引：0，他引：1  

袁伟  王俊  左涛  牛明香  栾青杉  时永强  孙坚强 《海洋学报》2020,42(6):52-61

本文以莱州湾2009年夏季(8月)、秋季(10月)及2010年春季(5月)、夏季(8月)4个季节大型底栖动物资料为基础，对莱州湾大型底栖动物的种类组成、丰度、生物量、优势种进行了研究，同时与历史资料进行对比，探讨了莱州湾大型底栖动物的群落结构特征及动态变化。4个航次中共鉴定出大型底栖动物272种，其中包括环节动物多毛类122种，软体动物46种，甲壳动物64种，棘皮动物18种，鱼类9种，其他类13种。调查海域平均丰度为(1102.56 ± 216.32) ind./m2, 多毛类在丰度上占绝对优势；平均生物量为(28.16 ± 8.45) g/m2，软体动物占据优势。丰度和生物量空间分布规律具有很强的相似性，低值区位于莱州湾西部黄河口邻近海域，高值区位于渤海中部海域。丰度和生物量季节变化明显，夏季最高，秋季其次，春季最低。多毛类不倒翁虫(Sternaspis sculata)、寡鳃齿吻沙蚕(Nephthys oligobranchia)、紫壳阿文蛤(Alvenius ojianus)等是莱州湾调查海域的优势种。通过与历史资料的对比发现，莱州湾大型底栖动物种类组成及优势种类出现小型化的趋势。  相似文献