椒江口海域围填海强度及环境影响分析          下载免费PDF全文

钱健  陈立红  丰卫华  向芸芸  王志富 《海洋开发与管理》2018,35(9):62-66

文章对近10年来椒江口两岸主要的围填海工程进行了统计,利用基于围填海强度等级控制理念的围填海潜力评估方法,对椒江口海域的围填海强度及围填海潜力进行了定量评估,并对其造成的环境影响进行了分析。分析结果显示,椒江口海域虽然仍有一定的围填海潜力,但围填海压力较大,椒江口大规模的围填海工程对海岸带地形地貌、海域水文动力环境、滨海湿地生态系统、海洋水环境质量、海洋生物资源等均存在负面影响,为此提出了强化围填海管控、重视海岸带整治修复等建议,以期为椒江口的围填海管控和生态环境保护提供参考。  相似文献   

Degradation induces changes in the soil C:N:P stoichiometry of alpine steppe on the Tibetan Plateau     

ZHANG Zhen-chao  HOU Ge  LIU Miao  WEI Tian-xing  SUN Jian 《山地科学学报》2019,(10)

Due to the Tibetan Plateau's unique high altitude and low temperature climate conditions,the region's alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.  相似文献   

北京主城区伪基站时空规律分析     

汪伟  陶海燕  卓莉  李敏  李旭亮  汪珂丽  史清丽 《地球信息科学学报》2018,20(7):978-987

随着公众移动通信的快速发展,伪基站的泛滥不仅破坏正常电信秩序,危害公共安全,而且严重损害群众财产权益,侵犯公民个人隐私,已成为社会一大公害。如何从垃圾短信大数据中挖掘出伪基站活动的时空规律,寻找有效的防控方案,从源头上进行打击和治理成为管理部门和研究者共同关注的焦点。本文基于北京市垃圾短信数据,利用非负矩阵分解的方法分析伪基站的时空分布规律;并利用TF-IDF构建垃圾短信分类模型,对垃圾短信进行分类,结合土地利用数据,分析伪基站在发送不同类型垃圾短信时的时空分布规律。结果显示：北京市垃圾短信多分布于路网和中心城区;白天垃圾短信数量远远多于晚上;垃圾短信的分布随时间的推移沿着路网逐渐向内收缩;发送不同类型垃圾短信的伪基站的时空分布具有一定的差异;通过非负矩阵分解得到的结果,与垃圾短信分类后得到的结果有很好的匹配。研究表明,非负矩阵分解具有实现上的简便性、分解形式和分解结果上的可解释性等优点,可以有针对性的为有关部门建言打击伪基站的有效方案,对于伪基站违法行为的治理具有一定的意义。  相似文献   

南海风暴潮对风场和外围海水敏感性研究     

李健  刘清容  阮成卿  訚忠辉  冀承振 《海洋科学》2018,42(2):99-107

为探索来自西北太平洋台风风暴潮与南海局地生成台风风暴潮不同,本研究在假设两种台风气象条件相同情况下,研究随台风而来外围海水所形成增水对南海沿岸的影响。以0814"黑格比"强台风风暴潮为基础,使用ROMS(regional ocean modeling system)模式进行数值模拟并通过设计对比试验方法进行研究,研究发现在台风登陆时引起的增水最大,最大增水出现在台风路径右侧,其中在沿岸区域,外围海水形成增水约占总增水10%,且大约3 h后出现增水回震现象。同时,设计对比试验,研究来自西北太平洋台风风暴潮对台风路径、台风强度、台风移动速度和流入角等气象条件敏感性,并获得与前人一致的结果。  相似文献   

Hydrological management strategies for the control of algal blooms in regulated lowland rivers     

Jian Li  Wei Yin  Haiyan Jia  Xiaokang Xin 《水文研究》2021,35(6):e14171

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.  相似文献   

Stokes漂流对全球海表面温度模拟的影响     

肖林  史剑  蒋国荣  刘子龙  张成成 《海洋通报》2018,(1):55-87

Stokes漂流对海洋上混合层中的流场和温度场结构具有不可忽视的作用。本文基于WAVEWATCHⅢ海浪模式模拟的海浪要素计算得到Stokes漂流,将其引入SBPOM模式的动量方程中,从体积输运的角度研究Stokes漂流对全球海表面温度的影响。分析发现Stokes漂流与Stokes输运在全球呈现高纬度强于中低纬度的带状分布特征,且这种流动与输运对全球海表面温度具有降温作用,该降温作用的分布与全球Stokes输运强度相对应,高纬降温作用大于中低纬度,特别是南极绕极流海域平均降温明显大于其余海域,最大降温可达1.5℃,且全球月平均降温超过0.1℃。  相似文献   

300 BC-1900 AD无定河流域城镇时空格局演变   总被引：2，自引：1，他引：1  

佟彪  党安荣  许剑 《地理学报》2019,74(8):1508-1524

通过分析和整理从战国中晚期（约300 BC）至清末（约1900 AD）无定河流域历代县级及以上城址的位置、兴废年代数据,结合行政区划沿革、经济社会发展、政权更迭等资料,分析流域城镇格局的时空演变过程。研究表明：① 受气候周期性波动影响,无定河流域城镇的兴起与衰废具有明显的周期性特征,城镇几何中心的移动轨迹具有明显的“西北—东南”向潮汐性运动特征;② 城址存续年限普遍较短,具有明显的阶段性特征,流域内曾存在过4个阶段性中心城镇,中心城镇移动的方向和过程与城镇几何中心的潮汐性移动过程趋势一致;③ 流域城镇空间格局可分为3种类型,即秦汉与隋唐时期的沿河流谷地分布,宋、明两代的沿边境线与长城分布,以及元、清两代集中于流域下游分布。流域城镇未来的发展布局应重视气候变化对城镇分布的长期影响,关注区域环境的脆弱性,合理安排城镇体系发展规模与布局。  相似文献   

杭州湾中部实测波浪特性分析   总被引：1，自引：0，他引：1  

杨斌  杨忠良  叶钦  张俊彪  施伟勇 《海洋工程》2018,36(3):96-103

利用杭州湾中部一年实测波浪资料,分析该地区的波参数统计变化特性,采用最小二乘法拟合得出相关参数之间的关系式,并统计分析了频谱特性。结果表明:杭州湾中部以小浪和轻浪为主,在各月分布较为均匀,年平均周期为2.97 s;最大一次波浪过程为冷空气影响所致,影响强度大于台风莫拉克;常浪向分布在东北至东南向,其中又以小浪出现较多,对应的波周期以2~4 s为主;强浪向主要分布在西北和东北方向,对应的波周期主要分布在3~5 s;多数特征波参数之间相关关系较好;由谱分析得知风浪占多数,且以单峰为主。研究结果可为相关工程和理论研究提供基础资料。  相似文献   

利用超快速精密星历约束的北斗卫星实时精密定轨     

范磊  施闯  李敏 《大地测量与地球动力学》2018,38(9):937-942

以广播星历为起算轨道的北斗卫星实时滤波精密定轨往往需要较长收敛时间，针对此，提出利用超快速精密星历约束的实时精密定轨方法。通过MGEX跟踪网全球分布的51个测站连续7 d的实测数据，利用平方根信息滤波对北斗卫星实时精密轨道进行确定，并以3 d解事后轨道作为参考，评估北斗卫星实时滤波轨道精度。结果表明，利用广播星历作起算轨道时，北斗实时滤波轨道平均需要经过15 h收敛才能达到稳定，而新方法在这段时间内轨道变化较为平稳，未出现明显的收敛现象，并且7 d时间内GEO卫星在切向、法向和径向上RMS分别优于2.5 m、20 cm和30 cm，IGSO和MEO卫星在3个方向上分别优于30 cm、15 cm和10 cm。
  相似文献   

On the electron density diagnostics of silicon <Emphasis Type="SmallCaps">viii</Emphasis> ion in solar transition region     

Jian He  Qingguo Zhang 《Astrophysics and Space Science》2018,363(9):194

The conditions for accurate electron density diagnostics in the solar transition region are discussed, and result shows that lines from Si?viii can provide an excellent tool for electron density diagnostics of the emitting plasma. For the Si?viii 1440.50 Å and 1445.75 Å lines, the principle of the electron density diagnostics is discussed for any intensity ratio. By the observed intensity ratio, the diagnostic results of the electron density for the quiet sun and the active region are calculated, and results indicate that in the quiet sun, the averaged electron density is \(\log (N_{e}) = 8.63\); while in the active region, the averaged density gets the maximum \(\log (N_{e}) = 8.86\) in the active region (B), and gets the minimum \(\log (N_{e}) = 8.38\) in the active region (E), where the electron density is in the unit of cm^?3. Finally, the relationship of intensity ratio and electron density is discussed, in the case of lower and higher electron density limits. This discussion is significant in the electron density diagnostics, which will be important for study on coronal heating and acceleration of solar wind.  相似文献