Evolution of the mid-channel bars in the middle and lower reaches of the Changjiang (Yangtze) River from 1989 to 2014 based on the Landsat satellite images: impact of the Three Gorges Dam

The mid-channel bars have long been identified as essential landforms in the large rivers of the world, and the significance of connectivity between morphology and flow-sediment dynamics has been intensively emphasized. In this study, remote sensing images and associated hydrological data from 1989 to 2014 were used to explore mid-channel bars evolution in the middle and lower reach of the Changjiang and their responses to the Three Gorges Dam (TGD), the world’s largest hydrological engineering. The results indicated that mid-channel bars, respectively, exhibited deposition and erosion in the flood and dry season in pre-TGD period, while mild deposition in flood season and deposition in dry season were found in post-TGD period. As a consequence, mid-channel bars area was characterized by ‘remarkable seasonal differences in pre-TGD period, mild seasonal pattern in post-TGD period’. The obvious shift in seasonal features could be attributed to the TGD operation in 2003. Specifically, flood duration decrease and sediment load reduction following TGD regulation suppressed the bars growth in flood season. TGD-induced variations in differences between sediment carry capacity and suspended sediment concentration resulted in the bars transformation in dry season. Meanwhile, the change trends of downstream mid-channel bars became weak as their locations’ distance to TGD increases because of the river adjustment and tributaries supplement. Moreover, mid-channel bars in different river patterns presented various change trends with the most remarkable variation being detected in goose-head-shaped river pattern. The results of this paper provide a theoretical basis for the river channel improvement in the middle and lower reaches of the Changjiang River.     

渤海湾盆地大歧口凹陷新生代构造演化与盆地原型

大歧口凹陷位于渤海湾盆地黄骅坳陷中北部,是中新生代叠合盆地中新生界沉积最厚的凹陷。本文基于大量二维、三维地震剖面和钻井资料,从凹陷主控断裂活动性、沉积沉降中心分布和构造格架等方面,侧重对大歧口凹陷新生代构造演化过程和原型盆地类型进行研究。认为:1)大歧口凹陷构造单元有4级,凹陷具有"东西分带、南北分块"的平面构造格局和北断南超箕状断陷的剖面结构。2)凹陷内断裂有4级,主要断裂的规模、活动期次和断裂活动具有演化的阶段性和空间的迁移性,典型构造带活动性具有由北往南迁移的特点。3)新生代期间整个大歧口凹陷的沉积沉降中心均在东部海域的歧口主凹内,但整体具有往南迁移的趋势。4)凹陷经历了拓展裂谷、拉分断陷、箕状断陷和碟状坳陷4个构造演化阶段,断陷阶段在整个构造演化时期意义重大,且具有走滑拉分特点。故认为大歧口凹陷原型盆地是一种"板内拉分盆地"。     

Ephemeral landform development following rapid coastal uplift in the southern orogen of Taiwan

Newly emerged landscapes above sea level are characterized by rapidly evolving geomorphic systems where the initial fluvial pattern adapts to a former submarine topography. Such an early formed fluvial system establishes drainage basins and unstable landforms that characterize high topographic asymmetry which are prone to fast removal or reorganization. Transitional landscapes might form depositional systems as lakes or ponds that subsequently are incised, captured and incorporated into drainage basins. In this study we focus on the recently emerged Hengchun Peninsula to survey its paleoenvironment evolution. Three drillings performed in the Gangkou basin with fieldwork revealed several indicators that reconstructed stages of the landscape reorganization. The major finding shows an ephemeral large lake in the central part of the Hengchun Peninsula that was drained to the Pacific c. 6000 bp . The lake belonged to an ephemeral lakeland that was created after the emergence of the peninsula. Currently, several areas as relict landforms indicate this stage of topography evolution that through high rates of incision and subsequent captures, transforms into drainage basins. Furthermore, two drillings show brackish waters at the present estuary of the Gangkou basin. These two different paleoenvironments today build one system – Gangkou catchment. Long-term uplift rates show that a hanging wall of the Hengchun Fault plays a significant role in the creation of a lakeland by tilting the peninsula's surface. The tilt impacts on asymmetrical emergence of the peninsula and catchment development. Our study shows that a new geomorphic system might create depositional ephemeral landforms (lakes) that represent phases of early topography evolution after emergence above a sea level that are subjected to instantaneous rearrangement and evolves through large-scale phases before it reaches a topographic steady-state.     

Comparing Lignin-Derived Phenols, δ13C Values, OC/N Ratio and 14C Age Between Sediments in the Kaoping (Taiwan) and the Kapuas (Kalimantan, Indonesia) Rivers

The Kaoping (Taiwan) and Kapuas (Indonesia) Rivers differ in hydrological cycle, topography and landscape. These differences strengthen the use of ¹⁴C dating, lignin-derived phenols, δ¹³C values and C/N ratios to determine the sources and diagenesis of surface sedimentary organic carbon (OC) in both rivers. The Kapuas River is surrounded by forest, resulting in sedimentary OC with a ¹⁴C age between 600 and 740 years, Λ (total lignin expressed as mg/100 mg OC) values from 0.94 to 3.70, δ¹³C values from −27.87 to −30.00‰, C/N ratios from 6.7 to 30.8, %OC from 0.63 to 9.24% and vanillic acid to vanillin ratio, (Ad/Al)v, values from 0.73 to 2.09, all of which indicate the presence of recent plant-derived organic matter. The tributaries and three locations upstream of the Kaoping River are also surrounded by forests, resulting in Λ values (0.51–4.80), δ¹³C values (−23.85 to −27.08‰), C/N ratios (14.1–28.7), %OC (1.01–7.86%) and (Ad/Al)v values (0.86–1.88), which are indicative of a terrestrial signal. No lignin oxidation products were detected in the mainstream of the Kaoping River or its coastal zone, hence the surface sediments OC with a ¹⁴C age between 4,915 and 15,870 years, enriched δ¹³C values (−23.30 and −26.54‰), lower C/N ratios (6.0–17.5) and lower %OC (0.15–2.24%) likely represent old rock and soil material. Massive floods during typhoons most probably cause plant materials from the Kaoping River and its coastal zone to be transported into the deep sea.     

黄姑鱼雌核发育的人工诱导及鉴定

采用紫外线（UV）灭活的同源精子通过冷休克抑制第二极体排放诱导黄姑鱼的雌核发育。黄姑鱼精子最适的灭活剂量为420 mJ/cm2,紫外照射剂量与黄姑鱼精子和卵子授精后的受精率及孵化率之间表现出明显的Hertwig效应。多次试验筛选的黄姑鱼雌核发育的最适条件为授精后2min在3℃处理8min。雌核发育仔鱼经形态学和流式细胞仪鉴定为二倍体。进一步利用10对微卫星分析了遗传物质在亲本和子代中的传递情况,结果表明雌核发育后代的等位基因完全来自于母本,没有父本基因参与;雌核发育后代在5个位点微卫星位点具有较高的重组率,使其与母本保持了高度同质性。     

Genetic diversity in two Japanese flounder populations from China seas inferred using microsatellite markers and COI sequences

Japanese flounder is one of the most important commercial species in China; however, information on the genetic background of natural populations in China seas is scarce. The lack of genetic data has hampered fishery management and aquaculture development programs for this species. In the present study, we have analyzed the genetic diversity in natural populations of Japanese flounder sampled from the Yellow Sea (Qingdao population, QD) and East China Sea (Zhoushan population, ZS) using 10 polymorphic microsatellite loci and cytochrome c oxidase subunit I (COI) sequencing data. A total of 68 different alleles were observed over 10 microsatellite loci. The total number of alleles per locus ranged from 2 to 9, and the number of genotypes per locus ranged from 3 to 45. The observed heterozygosity and expected heterozygosity in QD were 0.733 and 0.779, respectively, and in ZS the heterozygosity values were 0.708 and 0.783, respectively. Significant departures from Hardy-Weinberg equilibrium were observed in 7 of the 10 microsatellite loci in each of the two populations. The COI sequencing analysis revealed 25 polymorphic sites and 15 haplotypes in the two populations. The haplotype diversity and nucleotide diversity in the QD population were 0.746±0.072 8 and 0.003 34±0.001 03 respectively, and in ZS population the genetic diversity values were 0.712±0.047 0 and 0.003 18±0.000 49, respectively. The microsatellite data (F_st =0.048 7, P<0.001) and mitochondrial DNA data (F_st =0.128, P<0.001) both revealed significant genetic differentiation between the two populations. The information on the genetic variation and differentiation in Japanese flounder obtained in this study could be used to set up suitable guidelines for the management and conservation of this species, as well as for managing artificial selection programs. In future studies, more geographically diverse stocks should be used to obtain a deeper understanding of the population structure of Japanese flounder in the China seas and adjacent regions.     

Tectonics and Seismicity of the Yarlung Tsangpo Grand Canyon Region

The Yarlung Tsangpo Grand Canyon region is located in the frontal zone of the eastern Himalayan syntaxis, where neo-tectonics and seismicity are intensive and closely related to each other. In the region, two sets of fault structures have developed, striking NNE-NE and NWW-NW, respectively. Investigation shows that they differ markedly in terms of scope, property, active times and intensity. The NWW-NW trending faults are large in size, and most are thrust and thrust strike-slip faults, formed in earlier times. The NEE-NE-strike faults are relatively small in size individually, with concentrated distribution, constituting the NNE-trending shear extensional fault zone, which is relatively younger with evident late Quaternary activities. Strong earthquakes occur mainly in the areas or zones of intensive differential movement of the Himalayas, e.g. along the deep and large fault zones around the crustal blocks. Most earthquakes of M≥7.0 are closely related to tectonics, where large-scale Holocene active faults are distributed with complicated fault geometry, or the faults of multiple directions intersect. Among them, earthquakes of M≥7.5 have occurred on the NW and NE-trending faults with a greater strike-slip component in the fault tectonic zones.     

Intermediate-depth earthquakes beneath the Pamir-Hindu Kush Region:Evidence for collision between two opposite subduction zones

We employed a double-difference algorithm(hypoDD)to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964?2003 reported by the International Seismological Center(ISC).The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt.Based on this feature and other evidences,we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zon...     

黄河口湿地潜在溢油污染生态风险评估

黄河口有着我国典型的新生湿地生态系统,生态环境非常脆弱,极易受到陆源和海洋污染事故的影响。本文针对黄河口附近海上油田的开发和运输带来的潜在溢油风险,结合溢油污染概率模型以及河口的生态脆弱性,对黄河口湿地潜在溢油污染风险进行评估。在河口水动力模拟的基础上,采用随机情景模拟法选取300种风和潮流组合作为溢油模拟的强迫条件,分别模拟溢油后72 h和720 h的污染结果,并统计黄河口湿地受溢油污染影响的最大概率和最短时间,采用环境敏感指数表征湿地对溢油污染的敏感程度、危害后果指数量化表征其危害程度及风险矩阵量化风险高低。结果表明黄河口国家公园受潜在溢油污染概率较大,危害后果指数值为29,处于较高危害等级,属于中风险区;河口岸线受潜在溢油污染概率较小,危害后果指数值均小于1,溢油危害后果低,属于低风险区。     

Thyroid cancer incidence in China between 2005 and 2009

Thyroid cancer (TC) incidence has significantly increased worldwide in recent decades, with large differences between urban and rural areas. However, studies on Chinese TC incidence are limited. Research on the relationship between TC incidence and industry activities is also rare. In this work, data from 31 cancer registry cities in China between 2005 and 2009 were used to reveal the trend of TC incidence, compare the incidence among different cities, and analyze the relationship of TC incidence with socioeconomic factors. During the five-year period, TC incidence in China increased by 49.5 % from 3.21/100,000 to 4.80/100,000, with a female–male ratio of 3 and an urban–rural ratio of 2.5. The increase of TC incidence in more developed cities was significant, but it was not in less developed cities. People living in cities with higher secondary industry output had a higher risk of developing TC. The government and scientific community should pay sufficient attention to the rapidly increasing incidence of TC and to industry activities.