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91.
92.
Pyritization of trace metals in estuarine sediments and the controlling factors: a case in Jiaojiang Estuary of Zhejiang Province,China 总被引:1,自引:0,他引:1
Siyuan Ye Edward A. Laws Qiang Wu Shaojun Zhong Xigui Ding Guangming Zhao Shaojun Gong 《Environmental Earth Sciences》2010,61(5):973-982
Three undisturbed sediment samples were collected from the intertidal zone of the Jiaojiang Estuary of Zhejiang Province,
China. The sediments were found to contain remarkably low concentrations of organic carbon (<0.6%) and acid volatile sulfide
(AVS) (<30 μmol g−1). The availability of these two substrates likely constrained sulfate reduction and pyritization of several trace metals,
respectively. This was especially true at one station where AVS concentrations in the upper 20 cm averaged less than 0.05 μmol g−1. Although the depth dependence of the degree of trace metal pyritization was generally consistent with expectations based
on redox conditions, depth profiles of reactive-metal and pyrite-metal concentrations in several cases revealed more complex
behavior and a positive correlation between reactive-metal concentrations and pore water metal concentrations. 相似文献
93.
本研究基于2001—2020年中分辨率成像光谱仪遥感产品,使用谐波分析重建完整作物生长过程植被指数变化曲线,对江苏省范围内水稻种植区域的收获期进行提取。同时利用Sen趋势分析与相关分析方法,研究水稻收获期时空动态变化趋势与影响因子。结果表明:利用谐波分析方法能够较好地重建作物生长期生理参数变化曲线,滤波值与原始值线性相关系数达到0.8;水稻收获期分布在9月中旬到12月上旬之间,2010年之后,10月中下旬之后占比增加,达到50%以上;部分地区水稻收获期呈现延迟趋势,南京北部、扬州、盐城北部地区为3 d·a-1及以上,泰州、南通等地区保持稳定,趋势绝对值低于1 d·a-1;9—11月降水日数与降水量均对水稻收获期有影响,10月降水量与收获期存在负相关,10、11月降水日数与收获期存在正相关。本研究的基于遥感的水稻收获期提取方法为大范围的水稻农业物候信息提取提供参考。 相似文献
94.
Crustal thickness beneath the Tanlu fault zone and its tectonic significance based on two-layer H-κ stacking 下载免费PDF全文
Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An in-depth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κ stacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vp/vs ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vp/vs ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to crustal thinning(caused by crustal extension)and the strong uplift of the mantle in eastern China.The isostatic gravity anomalies between the eastern and western parts of the TLFZ indicate that the fault zone plays a dominant role in controlling the development of the deep crustal structure.(3)Significant crustal thinning was observed beneath the eastern part of the boundary between the Jiangsu and Anhui provinces in the southern segment of the TLFZ,suggesting that this area is prone to lithospheric thinning of the North China Craton.Due to the subduction,compression,and retreat of the Paleo-Pacific Plate during the Yanshanian Period as well as the dehydration of subducting oceanic crust(within subduction zones),the asthenosphere and oceanic crust in eastern China partially melted,resulting in mantle enrichment.The basic magma from the mantle is accumulated at the base of the crust,leading to magmatic underplating.In areas with weak topography toward the east of the TLFZ,magma rises to the upper crust and surface,resulting in the enrichment of multiple'metal deposits in this area. 相似文献
95.
96.
QPSK作为一种抑制载波的抗干扰能力较强的四相移键控调制方式,被广泛应用于无线卫星通信中.同步(载波同步和符号同步)是解调过程中最核心的问题之一.采用基于软件无线电的思想,把尽可能多的通信功能用可升级、可替换的软件来实现.载波同步采用数字Costas环的方式,符号同步采用模平方谱线估计法来完成,并通过Matlab仿真验证结果的可行性.将仿真获得的参数结合硬件平台,最终在工程上实现了一款基于FPGA(现场可编程逻辑门阵列)的气象卫星解调器的设计. 相似文献
97.
我国南海海域海洋环境条件复杂且海水密度垂直层化现象显著,内孤立波活动频繁,因内孤立波而造成海洋开采平台破坏的案例屡见不鲜。依托水动力计算软件AQWA二次开发功能,采用Kdv方程,借助Fortran语言将深水半潜式平台立柱、浮箱、系泊系统3部分的内孤立波作用力叠加到外力项中,联合求解半潜式平台的6自由度动力响应特性。数值模拟结果表明,在内孤立波作用下,半潜式平台的运动及系泊线张力均受到了显著的影响。在不考虑系泊系统受内孤立波作用时,平台在纵荡和横荡方向上产生较大的漂移运动,最大偏移量较无内孤立波情况下增加了8倍;系泊线最大张力提高了17%,增加了系泊线断裂的风险。在考虑系泊系统受内孤立波作用时,平台的纵荡和横荡运动响应在原响应基础上继续提高15%,但是系泊线张力变化不大。内孤立波不同浪向下的平台纵荡和横荡响应相差也很明显;系泊系统合力在不同方向上的大小决定了平台不同方向上运动的大小。 相似文献
98.
目的:观察抗癌青黄汤联合羟基脲片治疗慢性髓系白血病(CML)慢性期毒热炽盛证的临床疗效。方法:将60例CML慢性期毒热炽盛证患者随机分为治疗组和对照组,每组各30例。对照组给予羟基脲片治疗,治疗组在对照组基础上加用抗癌青黄汤治疗。2组均以4周为1个疗程,治疗2个疗程后观察2组的综合疗效、白细胞计数、骨髓中不成熟粒细胞水平、中医证候积分以及不良反应。结果:总有效率治疗组为86.67%(26/30),高于对照组的70.00%(21/30),2组比较,差异有统计学意义(P<0.05);2组白细胞计数、骨髓中不成熟粒细胞水平、中医证候积分治疗前后组内比较及治疗后组间比较,差异均有统计学意义(P<0.05或P<0.01);不良反应发生率治疗组为13.33%(4/30),低于对照组的20.00%(6/30),组间比较,差异无统计学意义(P>0.05)。结论:抗癌青黄汤联合羟基脲片治疗CML慢性期毒热炽盛证疗效较佳,能改善患者临床症状和造血功能,值得临床推广应用。 相似文献
99.
Ma Yanyan Li Guangxue Ye Siyuan Zhang Zhiheng Zhao Guangming Li Jingyang Zhou Chunyan Ding Wenjie Yang Xin 《中国海洋湖沼学报》2010,28(6):1362-1370
The water and sediment discharge regulation (WSDR) project, which has been performed since 2002 before flood season every
year, is of great significance to the river management in China. Until 2007, six experiments have been fulfilled to evaluate
the effect of the project on the natural environment. To fill the gap of investigations, a study on flood and suspended sediment
transportation and channel changing along the distributary channel of the Huanghe (Yellow) River was conducted during the
WSDR project period in 2007. The lower channel was scoured rapidly and the channel became unobstructed gradually several days
after the flood peak water was discharged from the Xiaolangdi Reservoir. Within four days after the flood peak at 3 000 m3/s entered the distributary, the channel in the river mouth area was eroded quickly. Both the mean values of area and depth
of the main channel were tripled, and the maximum flood carrying capacity increased to 5 500 m3/s or more. Then, the river channel was silted anew in a very short time after completion of the WSDR. Favored by the WSDR
project, the river status in April 2008 became better than that of the year before. The adjustment ranges of main channel
parameters were about 30%, 10%, and 10% at sections C2, Q4, and Q7, respectively. The process of rapid erosion-deposition
was more active 15 km away in the channel from the river mouth due to the marine influence. It is reasonable for discharging
sediment at concentration peak from Xiaolangdi Reservoir at the end of the flood peak. As a result, the sediment peak reached
the river mouth about two days later than that of the water current. In addition, the WSDR project has improved the development
of the estuarine wetland. Wetland vegetation planted along the river banks restrained the water flow as a strainer and improved
the main channel stability. It is suggested to draw water at mean rate of 150 m3/s from the Huanghe River during flood periods, because at the rate the water in the wetland would be stored and replenished
in balance. Moreover, we believe that cropland on the river shoal of the lower Huanghe River should be replaced by wetland.
These activities should achieve the Huanghe River management strategy of “To concentrate flow to scour sediment, stabilize
the main channel, and regulate water and sediment”. 相似文献
100.
本文选择黄河三角洲大汶流自然保护区为研究对象,以多时相遥感影像,对土地利用类型进行解译分析。同时,以平均低潮线作为分析基线,提取海岸线变化信息。结果表明:1996-2009年研究区面积净增13.35km2。各种土地利用类型中滩涂所占面积最大,养殖池所占比例最小,但增幅明显。芦苇地面积后期增长迅速,指示研究区生态环境趋向转好。自然因素(黄河来水来沙量)和人类活动(黄河调水调沙工程,湿地恢复工程,滩涂规模开发以及人类开垦造田)是研究区土地利用类型变化的直接驱动力。1976-2009年研究区海岸净造陆面积217.14km2,沙嘴变幅为29.2km。黄河入海水沙量和滨海区的海洋潮流条件共同影响着海岸线的变迁。 相似文献