威海沿岸海域潮汐特征分析          下载免费PDF全文

邹曙光  刘李钊 《海洋开发与管理》2018,35(5):83-86

文章主要选取国家海洋局成山头海洋环境监测站1996—2016年的潮位、潮差月值资料,利用线性回归法,对威海沿岸海域近21年来的潮汐特征进行分析。结果表明:威海沿岸海域近21年的平均潮位、最高潮位、最低潮位、平均潮差、最大潮差整体上均呈上升的变化趋势,但气候倾向率各不相同,分别是2.57cm/(10a)、5.872cm/(10a)、4.137cm/(10a)、1.017cm/(10a)、2.604cm/(10a)。  相似文献   

不同盐度对文蛤(Meretrix meretrix)呼吸代谢及体内酶活性的影响     

白奕天  丁天扬  李东东  聂鸿涛  闫喜武 《海洋科学》2018,42(6):123-131

为研究不同盐度对文蛤呼吸代谢的影响,本实验设置5个盐度(‰)梯度(11、18、25、32、39),检测不同盐度对文蛤(Meretrixmeretrix)耗氧和排氨的影响,以及文蛤的外套膜、鳃、肝胰腺三种组织中乳酸脱氢酶和Na+/K+-ATP酶活性的变化。结果表明:随着盐度的不断升高,文蛤耗氧率先升后降再升,在盐度18时达到最大值;排氨率先升后降,在盐度32时达到最大值。随着盐度不断升高和胁迫时间延长,文蛤的肝胰腺中乳酸脱氢酶活力总体呈先升高后下降再升高的趋势(P0.05),酶活力在盐度39时为最高;随着盐度不断升高和胁迫时间延长,文蛤的外套膜中Na+/K+-ATP酶活力总体呈先下降再升高后下降的趋势(P0.05),在盐度32时为最高;文蛤的外套膜和鳃中乳酸脱氢酶活力以及鳃和肝胰腺中Na+/K+-ATP酶活力受盐度影响不显著(P0.05),酶活力变化也多呈现"W"形的变化趋势。研究结果为文蛤的人工养殖提供参考。  相似文献   

Terrestrial discharge influences microbioerosion and microbioeroder community structure in coral reefs     

SA Mwachireya  M Carreiro-Silva  BE Hartwick  TR McClanahan 《African Journal of Marine Science》2018,40(1):25-42

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m^?2 y^?1 (SEM) and 134.7 g CaCO₃ m^?2 y^?1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO₃ m^?2 y^?1), which was almost double that in the pristine reef (69.5 g CaCO₃ m^?2 y^?1) and the mangrove-fringed reef (56.2 g CaCO₃ m^?2 y^?1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future.  相似文献   

Depth of closure: New calculation method based on sediment data     

Luis Aragonés  Jose Ignacio Pagán  Isabel López  José C.Serra 《国际泥沙研究》2018,33(2):198-207

Obtaining depth of closure (DoC) in an accurate manner is a fundamental issue for coastal engineering, since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change (SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey (using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.  相似文献   

临汾地震台垂直摆倾斜观测资料阶变异常分析     

张红秀  罗振东  邰垣东  郭国祥 《地震地磁观测与研究》2018,39(4):154-157

对临汾地震台垂直摆倾斜观测资料中记录到的阶变型异常图像进行分析，对异常成因进行探讨，希望对观测数据异常判断、数据预处理及地震预测预报的应用研究，提供一定参考。  相似文献   

2016年射阳M_S 4.4地震前后重力场变化     

吴晓峰  宋浩  代宪鹏  孙君嵩  张辉 《地震地磁观测与研究》2018,40(1):96-101

利用江苏重力测网2014-2017年重力场观测资料，采用绝对重力控制与相对重力联测相结合的平差方法，获取2016年射阳M_S 4.4地震前后重力场变化图。根据射阳M_S 4.4地震前后射阳地区各测线重力段差变化特点，绘制重力场等值线并进行对比分析，结合相关机理，探讨重力场变化与该地震的内在联系。同震观测数据显示：射阳M_S 4.4地震发生在重力异常值高梯度带附近，发震时震中地区位于NS挤压正异常、EW张拉负异常状态，震后区域重力梯度变化量开始减小，是一种典型的重力异常调整现象。  相似文献   

从第三极到北极： 积雪变化研究进展   总被引：5，自引：5，他引：0  

刘一静  孙燕华  钟歆玥  王树发  肖雄新  马丽娟  苏航  赵文宇  张廷军 《冰川冻土》2020,42(1):140-156

在全球气候变化背景下， 第三极和北极地区积雪是地表最活跃的自然要素之一， 其动态变化对气候环境和人类生活产生重要影响。通过回顾第三极和北极积雪研究进展， 阐述了降雪、 积雪范围、 积雪日数、 积雪深度和雪水当量在第三极和北极地区的时空分布特征和变化趋势。结果表明： 近50年， 特别是进入21世纪以来， 第三极和北极地区降雪比率均呈下降趋势； 积雪范围、 积雪日数、 积雪深度、 雪水当量总体均呈减小趋势， 融雪首日有所提前。同时就积雪变化对生态系统与气候系统的影响进行了论述， 评估了积雪的反馈作用。通过总结第三极和北极积雪变化研究进展， 凝练研究中存在的不足和未来发展趋势， 为提升积雪对气候变化及经济社会发展影响的认识提供重要科学支撑。  相似文献   

Application of Glycerol Dialkyl Glycerol Tetraether Lipids in Paleoenvironment Reconstruction of Loess Deposits: A Review of Recent Progresses     

Shaohua Tian  Guoqiao Xiao  Huan Yang 《地球科学进展》2020,35(5):465-477

The Glycerol Dialkyl Glycerol Tetraethers (GDGTs) occur ubiquitously in a wide range of environments, such as loess, peat, lake, soil, and ocean, which vary compositionally in response to environmental changes, and provide a series of biomarker proxies for paleoenvironmental reconstruction. This paper introduced the structures and biological sources of GDGTs, and reviewed the recent progresses of the application of the GDGTs proxies in the paleoenvironmental reconstruction of loess deposits. The main progresses include: \mathrm{①} The GDGTs proxies have been widely used in reconstructing the climate changes in loess deposits, and have established the temperature changes of last 800 ka for the Chinese Loess Plateau; \mathrm{②}Temperature variations in Chinese Loess Plateau displayed significant correlation with the Northern Hemisphere insolation, which may be also regulated by the surface vegetation conditions; and \mathrm{③} In the Chinese Loess Plateau, the increase in monsoon precipitation during the last deglaciation significantly lagged behind the rise of temperature. However, problems still exist in the current studies. For instance, the GDGTs-based temperature is likely overestimated, probably reflecting the temperature of warm season, and relationships between GDGT indices and climate factors are still unclear. In the future, the development of new proxies and more accurate regional calibrations based on the separation of 6- methyl GDGTs are expected to provide more reliable paleoenvironmental information, and will provide essential evidence for the evolution of hydrothermal pattern and mechanisms behind climate changes in different regions.  相似文献   

Environmental change and the informal plastic recycling networks of Kolkata     

Nicolas Schlitz 《Singapore journal of tropical geography》2020,41(3):450-467

This article introduces plastic recycling networks in Kolkata, India, as a case to illustrate the contradictory entanglement of economic and environmental change in urban informal contexts of the Global South. In light of the prevailing environmental critique of informal plastic recycling in India, this article discusses plastic recyclers’ environmental impact and contribution as well as the potential to enhance the environmental and economic performance of their business. Network and chain approaches in the emerging field of Environmental Economic Geography are combined with the notion of social metabolism to conceptualize the entanglement of environmental and economic processes as well as socio-environmental inequalities entailed in recycling networks. The analysis reveals the impact that the heterogeneity and fluctuation of plastic waste supply has on the economic organization of recycling networks, giving rise to distinct forms of governance in its intermediate and down-stream segments. Such an integrated perspective also serves to explain why environmental upgrading is hard to achieve under prevailing circumstances by plastic recyclers in Kolkata. Based on an assessment of the social and political conditions of informality under which plastic recyclers operate, the adoption of common assumptions about ecological modernization imbuing parts of Environmental Economic Geography is called into question.  相似文献   

中国绿洲城市土地利用/覆盖变化研究进展          下载免费PDF全文

王一航  夏沛  刘志锋  卢文路  何春阳 《干旱区地理》2019,42(2):341-353

绿洲城市是干旱区人类生产和生活的集聚中心，也是人地关系最为敏感的区域之一。了解绿洲城市土地利用/覆盖变化的研究进展对于改善区域人地关系、促进绿洲城市可持续发展具有重要意义。利用系统综述方法，对研究我国绿洲城市土地利用/覆盖变化的相关文献进行梳理，在综述已有研究进展的基础上，探讨了已有研究存在的不足并对未来研究方向进行展望。绿洲城市土地利用/覆盖变化研究的相关文献数量和被引频次均呈增长趋势。已有研究主要在局地尺度上分析了绿洲城市土地利用/覆盖变化的过程、驱动机制和生态环境效应，关于绿洲城市可持续性和基于区域尺度的相关研究较少。因此，未来应在多个尺度上开展工作，综合研究绿洲城市土地利用/覆盖变化的过程、影响和可持续性。  相似文献