崇明岛东滩湿地芦苇光合作用对土壤水盐因子的响应     

戚志伟  姜楠  高艳娜  李艳  王开运  张超 《湿地科学》2016,(4):538-545

2015年3~10月,在崇明岛东滩湿地设置7块采样地,以不同水盐条件下生长的芦苇(Phragmites australis)为材料,应用便携式光合系统分析仪(Li-6400),对芦苇的光响应特征进行实地测定,探讨芦苇光合过程对干旱和盐胁迫的响应机理。结果表明:1各月采样日的水位与土壤电导率显著负相关(n=420,p0.01),适当增加土壤水位,有利于降低土壤电导率,从而缓解植物盐胁迫伤害;28月21日的芦苇叶片净光合速率、蒸腾速率和气孔导度与水位显著正相关(n=42,p0.01),而与土壤电导率显著负相关(n=42,p0.01);胞间CO2浓度与水位和土壤电导率不相关。当水位高于-50 cm,净光合速率随着水位下降而降低,非气孔因素可能是净光合速率下降的主要原因;当水位低于-50 cm时,土壤电导率高于10 m S/cm,叶片蒸腾速率快速降低,水分利用效率不断提高,芦苇叶片以较低的净光合速率来适应干旱胁迫和盐胁迫;芦苇叶片通过降低最大净光合速率、暗呼吸速率、光补偿点和光饱和点等光合生理特征来适应干旱胁迫和盐胁迫;芦苇叶片净光合速率和最大净光合速率对土壤水盐因子具有高度相关性,可以作为土壤水盐胁迫程度的反应指标。因此,在芦苇快速生长阶段,合理调控水位,对芦苇光合作用具有重要意义。  相似文献   

中国“四纵四横”高铁网络可达性综合评估与对比   总被引：8，自引：1，他引：7  

姜博  初楠臣  修春亮  赵映慧  李晓庆  罗冲 《地理学报》2016,71(4):591-604

传统测算可达性的方法较为单一,缺乏多层面、多角度的综合研究和对比分析。基于时间、经济与重心视角利用可达性模型并结合ArcGIS 空间分析手段探究高铁通车前后沿线城市可达性的动态变化;利用综合变异系数、层级分析法和改进的哈夫模型分析高铁可达性空间演变特征及规律,构建高铁可达性评价体系并结合熵权法定量评估各高铁可达综合实力。研究表明：京广、京沪可达综合实力最强,沪昆、杭福深次之,沪汉蓉、哈大、青太再次之,郑西、兰新可达实力最弱;全国高铁可达性强弱变化呈明显地带性规律,东、中部高铁可达性强于东北,东北强于西部,纵向高铁强于横向;经济潜力的增加率明显高于加权平均旅行时间的减少率,可达性重心偏移驱使不同等时圈蔓延交叠;高铁以“核心—核心”逐步向“核心—网络”空间链接模式过渡,产生上海、北京、广州、深圳4 个高铁“国家服务中心”,天津、武汉、重庆等6 个“大区域服务中心”,形成“多中心”高铁服务格局以及日益庞大而复杂的高铁特质空间集群;高铁网络影响下的中国区域空间格局的渐变与重塑日趋复杂,“T”型轴带呈现出由空间极化向空间均衡转变,跨城流动性特征突显,加速空间对接与同城化进程。  相似文献   

Characteristics of groundwater flow field after land creation engineering in the hilly and gully area of the Loess Plateau   总被引：1，自引：0，他引：1  

Xiaoxi Yin  Luwang Chen  Jiandong He  Xiaoqing Feng  Wen Zeng 《Arabian Journal of Geosciences》2016,9(14):646

In order to study the degree of influence and control mechanism to groundwater flow field caused by land creation engineering in the hilly and gully area of the Loess Plateau, based on the geological and engineering conditions of the first stage project of Yan’an new district in China, numerical simulation of groundwater flow is carried out by the Feflow and GIS technologies. From the simulation, punning measure relatively reduces infiltration recharge and artificial gravel drain increases groundwater seepage. The basic characteristics of groundwater flow field is controlled by the old and new topographies in the whole study area, and artificial gravel drain plays an auxiliary role in accelerating groundwater drawdown upstream and promotes groundwater rise downstream. According to differences of groundwater level and declining percentages of hydraulic gradient in the main and secondary gullies, dewatering of artificial gravel drain in the secondary gully is more effective than that in the main gully, which will yet play an important role in the future. The study results will make contributions to understand groundwater response to land creation engineering and will be beneficial to take necessary measures to prevent collapse of loess and failure of building foundation in the hilly and gully area of the Loess Plateau.  相似文献   

基于近岸GPS RTK技术的潮位和波浪提取算法研究          下载免费PDF全文

党超群  齐占辉  李明兵  赵江涛 《海洋测绘》2016,(1):63-64

由于潮汐和波浪的周期相差甚远,对实时海面高程数据进行相应的低通和带通滤波即可提取潮位和波浪信息。通过对仿真的实时海面高程数据进行平滑滤波、中值滤波、小波滤波等低通滤波,以及椭圆、巴特沃斯等带通滤波结果分析表明:近岸GPS RTK技术可用于潮位和波浪同步测量;对于潮位信息的提取方面,平滑、中值、小波等低通滤波均能很好的提取出潮位信息,其中平滑滤波最佳,且工程中易于实现;对于波浪信息的提取方面,椭圆滤波、巴特沃斯、切比雪夫Ⅰ型等带通滤波均能很好提取出波浪信息。  相似文献   

Tectono–Thermal Evolution, Hydrocarbon Filling and Accumulation Phases of the Hari Sag, in the Yingen–Ejinaqi Basin, Inner Mongolia, Northern China     

YANG Peng  REN Zhanli  XIA Bin  TIAN Tao  ZHANG Yong  QI Kai  REN Wenbo 《《地质学报》英文版》2018,92(3):1157-1169

This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase,uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectonothermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY R_0% model, which is constrained by vitrinite reflectance(R_0) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a.105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43-45℃/km. The main hydrocarbon generation period ensued around 105.59-80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo-temperature was over 180℃.Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation(K_1 b) occurred primarily around 105.59-103.50 Ma with temperatures of 125-150℃. The second accumulation period observed in the Suhongtu Formation(K_1 s) occurred primarily around84.00-80.00 Ma with temperatures of 120-130℃. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono-thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation,which is the key reason for hydrocarbon filling and accumulation.  相似文献   

Timing of mineralization at the Shihu gold deposit in the middle segment of the Taihang Mountain,China     

Chao Chen  Shuyin Niu  Fang Wang  Fuxiang Zhang  Qinglian Zhang  Baojun Ma  Aiqun Sun  Jianzhen Zhang  Yaqi Cao  Xiaoqing Zhang 《中国地球化学学报》2018,37(1):80-89

The Shihu gold deposit, located in the middle-south section of the core of the Fuping mantle branch structure, is hosted in the Archean Fuping Group and adjacent to the quartz diorite porphyrite. The gold deposit is the only large gold deposit with reserves of more than 30 tons gold discovered in western Hebei Province so far. In order to constrain the timing of mineralization of this ore deposit, this paper focuses on the isotopic dating of zircon and pyrite. Zircons in gold-bearing quartz veins are magmatic in origin and no hydrothermal zircon has been found in such quartz veins, indicating that zircons were derived from the wall rocks. U–Pb ages of zircons fall mainly in the two domains: 2492 ± 82 and 136 ± 4 Ma, respectively, indicative of the contribution of the Fuping-Group TTG gneiss and Yanshanian igneous rocks, respectively. The Re–Os isotopic compositions of pyrites in the gold-bearing quartz veins yield an isochron age of 127 ± 31 Ma. Combined with other dating results, we suggest that the main metallogenic age of the Shihu gold deposit is 120–127 Ma.  相似文献   

容县压实花岗岩残积土的力学性质与微结构特性研究          下载免费PDF全文

王志兵  麦棠坤  齐程 《水文地质工程地质》2018,(5):101-101

选取广西容县花岗岩残积土为研究对象,取击实曲线上3个不同含水率对应的压实样（最佳含水率及干侧、湿侧,后两者对应的干密度相同）分别进行了直剪试验、扫描电镜观测（SEM）和压汞试验（MIP）,并从微观特征解释其力学性能的差异。结果表明:（1）花岗岩残积土在3种压实状态下具有相同应力-应变曲线形状,无明显峰值,抗剪强度在最佳状态时的最高,湿侧状态抗剪强度与干侧状态相近,3种状态下内摩擦角值差别较小,但黏聚力在最佳状态时最大,干侧和湿侧状态较最佳状态分别下降66.4%和43.1%;（2）花岗岩残积土在湿侧状态下普遍形成团聚体,团聚体之间呈架空结构,累积孔隙体积最大,为明显的双峰分布孔隙特征;在最佳状态下组构最密,高岭石片定向性排列;在干侧状态下高岭石片呈片架结构,累积孔隙体积最小;随着含水率的降低,土样双峰孔隙特征逐渐变得不明显;（3）花岗岩残积土在不同状态时的微观特性较好地解释其力学性质的差异。  相似文献   

轻非水相液体污染源区结构的影响因素数值分析          下载免费PDF全文

陶佳辉  施小清  康学远  徐红霞  吴吉春 《水文地质工程地质》2018,(6):132-132

轻非水相液体（light non-aqueous phase liquid,LNPAL）在地下介质中的运移分布与残余捕获受多种因素影响和控制。LNAPL污染场地概念模型中一般视LNAPL从地表泄漏后穿过包气带至潜水面。然而地下介质的非均质性与包气带含水量的空间变异分布可形成复杂的LNAPL污染源区结构,LNAPL可能无法到达潜水面,而在毛细水带蓄积。文章基于数值模型综合分析了LNAPL泄漏量、介质非均质性与含水量空间变异分布、潜水面周期性变化等多种因素对LNAPL污染源区结构的影响。研究表明:（1）当泄漏量较大时,LNAPL可运移至潜水面;（2）当泄漏量较小时,对于上粗下细的层状非均质条件,LNAPL可能在毛细水带边缘发生蓄积,无法到达潜水面;（3）包气带中黏土透镜体并非都是LNAPL运移的阻碍,LNAPL可以穿透低含水量的黏土透镜体,只有高含水量的黏土透镜体才对LNAPL的入渗有阻碍作用;（4）潜水面周期性变化将导致污染范围扩大。  相似文献   

大兴安岭呼中钼多金属矿床成矿流体特征及成矿机制          下载免费PDF全文

王升鹏  杨倩倩  齐忠友  陈晨  王童  钱鸿 《贵州地质》2018,35(2):118-124

大兴安岭呼中镇钼多金属矿床产于早白垩世碎裂花岗岩中,矿体形态似层状、脉状或透镜状。成矿阶段分为辉钼矿阶段、铜铅锌阶段、方解石阶段等3个阶段。本矿床中的包裹体主要有气液H_2O包裹体、气相H_2O包裹体、含子矿物H_2O包裹体,CO_2包裹体、CO_2-H_2O包裹体等五大类。辉钼矿阶段均一温度为209.2℃413.4℃,盐度ω(NaCleq)为0.53%16.53%,平均值7.3%,属中低盐度,成矿压力在53.3 68.5 MPa,相应的成矿深度为2 052 2 807 m;铜铅锌阶段为191.5℃351.0℃,盐度ω(NaCleq)为0.88%34.24%,平均值3.96%,属低盐度;方解石阶段207.2℃233.5℃,盐度ω(NaCleq)为3.55%4.18%,平均值3.77%,为低盐度。从辉钼矿阶段到铜铅锌阶段再到方解石阶段,温度及盐度逐渐降低。辉钼矿成矿压力在53.3 72.9 MPa,成矿深度为2 052 2 807 m。成矿过程中发生了CO_2-H_2O不混溶作用,这是导致辉钼矿沉淀的主要机制。矿床类型属中低温浅成热液型矿床。  相似文献   

地物化方法在航磁异常查证中的应用     

田宇  祁程  杨金政  沈正新  汪哲  张文峰 《地质与资源》2018,27(4):406-410

航磁异常查证是矿产勘查中的一个重要环节,其目的是通过地面查证,确定异常是否存在,追踪异常源,了解异常源所处的地质环境,对异常作出客观评价,提出进一步工作的建议,为后续资料解释提供依据.通过使用地物化综合方法对黑C-2011-02243号异常查证发现：地质剖面测量和土壤地球化学测量可在地表发现较好的找矿线索;高精度磁测及激电中梯测量则反映了深部地质体及矿化特征.依据查证结果认为,在进行航磁异常查证工作时,可优先进行剖面性的地质、高精度磁法及土壤地球化学测量工作;在分析上述测量结果的基础上安排剖面性的电法测量;如存在进一步找矿信息,可安排面积性物化探测量及工程验证工作.  相似文献