Nutrient gradients from the eutrophic Changjiang (Yangtze River) Estuary to the oligotrophic Kuroshio waters and re-evaluation of budgets for the East China Sea Shelf   总被引：22，自引：1，他引：22  

J. Zhang  S.M. Liu  J.L. Ren  Y. Wu  G.L. Zhang 《Progress in Oceanography》2007,74(4):449-478

Eutrophication has become an overwhelming phenomenon in the coastal environment off the Changjiang (Yangtze River) Estuary, illustrated by an increase in nutrient concentration, frequent red-tide events and hypoxia in near-bottom waters, while the open East China Sea Shelf and Kuroshio waters remain oligotrophic. Observations made in the Changjiang Estuary and the East China Sea in 1999–2003 cover a broad range of hydrographic and chemical properties. The concentration gradients of nutrients across the shelf indicate that high levels from land-sources are constrained to the coastal and inner-shelf region by the complex circulation regime. In surface waters, nutrient species gradually decrease from eutrophic coastal to oligotrophic open shelf waters, depending on the hydrographic stages of the Changjiang, although biological uptake and regeneration in the upper water column can produce patchy character of nutrient distribution. Taiwan Current Warm Water and Kuroshio Surface Water are devoid of nutrients. Remineralization of nutrient species takes place in the near-bottom waters in the inner-shelf following extensive bacterial demand for organic matter. Hence the burial efficiency is low with regard to the biogenic species, either allochthonous or autochthonous, or both. The Kuroshio Sub-surface Waters are rich in nutrients, and their incursion into the East China Sea can be tracked by salinity and temperature, reaching within water depth of 50–100 m at mid-shelf. Relative to shelf waters, the Kuroshio intrusion is characterized by high and DIP/DOP ratios. In the water column, the ratio of DIP/DOP to is higher than the Redfield P/N value, suggesting rapid regeneration of phosphorus relative to nitrogen in the East China Sea. The results of a box-model suggest that the East China Sea Shelf do likely not export substantial amounts of dissolved biogenic elements to the open Northwest Pacific Ocean.  相似文献   

胶州湾现代沉积速率和沉积通量研究   总被引：19，自引：0，他引：19  

李凤业  宋金明  李学刚  汪亚平  齐君 《海洋地质与第四纪地质》2003,23(4):29-33

对胶州湾沉积岩心J39、J37和J94进行了210Pb的测定,绘制了岩心中210Pb的垂直分布图,岩心J37和J94的210Pb呈两段分布模式,岩心J39的210Pb呈三段分布模式。胶州湾西北部大沽河口外海域近百年来沉积速率为0 768cm/a,沉积通量为0 7716g/(cm2·a)。胶州湾中部沉积速率为0 64cm/a,沉积通量为0 65g/(cm2·a)。胶州湾口外J94站沉积速率为0 54cm/a,沉积通量为0 81g/(cm2·a)。结果表明,胶州湾海域210Pb活度与悬浮体含量密切相关,悬浮体含量高的区域,210Pb活度高;反之,悬浮体含量低的区域,210Pb活度低。根据210Pb的垂直分布、活度和沉积速率及悬浮体含量,结合历史资料,对胶州湾近百年来的沉积环境和物质扩散进行了探讨。  相似文献   

东海深部地层时深转换关系的分段优化拟合          下载免费PDF全文

陶天生  李春峰  李珂迪  姚泽伟 《海洋学研究》2020,38(3):65-75

在将钻井垂直地震剖面(VSP)数据的时深拟合公式应用于深部地层的时深转换时,拟合深度与计算的层速度常常不够准确。本文首先利用多项式和幂函数给出了东海陆架盆地中部某凹陷41口钻井VSP数据的时深拟合公式,并用双程旅行时(TWT)最深达8 s的三维地震速度体数据与多道地震剖面对拟合公式在深部地层的适用性进行分析。在TWT为8 s时,速度体数据表明41口钻井位置的平均深度为18 140 m,平均层速度为6 208 m/s,二次多项式的平均拟合深度较之偏高9.2%,计算的层速度偏高36.2%,幂函数则分别偏低28.9%与35.6%,拟合效果都不理想。对此,本文采用通过识别VSP数据的增速拐点并对增速拐点前的VSP数据进行二次多项式拟合,对增速拐点后的VSP数据进行幂函数拟合的分段拟合模型,将TWT为8 s时的平均拟合深度和层速度的误差降到3.3%与4.7%。地震剖面显示研究区莫霍面深度约为TWT=11 s,分段拟合模型在TWT=11 s的平均拟合深度为27 516 m,层速度为7 334 m/s,更接近前人研究成果,表明该模型能显著提高深部地层时深转换的精度。  相似文献   

舟山群岛峡道潮滩动力沉积特性   总被引：14，自引：3，他引：11  

蒋国俊  陈吉余  姚炎明 《海洋学报》1998,20(2):139-147

潮滩研究是现代河口海岸学研究中一直受到重视的重要方面,自德国学者Hantzschel[1].  相似文献   

Characteristics of river discharge and its indirect effect on the tidal bore in the Qiantang River,China     

Cunhong Pan  Qiushun Wang  Dongzi Pan  Chengfei Hu 《国际泥沙研究》2023,38(2):253-264

Based on field data of river discharge, tide, tidal bore, and riverbed topography, the characteristics of river discharge, the effect of river discharge on riverbed erosion and sedimentation, and the feedback effect of riverbed erosion and sedimentation on the tide and tidal bore in the Qiantang River are analyzed. The results show that the inter-annual and seasonal variation of river discharge in the Qiantang River is noticeable, while the seasonal distribution of river discharge tends to be un...  相似文献   

Diagenetic signatures in the deltaic and fluvial-estuarine Messinian sandstone reservoirs in the Nile Delta as a tool for high-resolution stratigraphic correlations     

《国际泥沙研究》2023,38(5):754-768

The current study utilizes a range of diagenetic fingerprints to differentiate between sandstone facies deposited in the Nile Delta before and during the Messinian salinity crisis (MSC), which is normally a challenging task considering the complex bio- and lithostratigraphic subdivisions of Messinian rock units. Subaerial exposure of the pre-MSC (Qawasim deltaic sandstone), during drawdown of the Mediterranean Sea at the time of the MSC, triggered pervasive dissolution of unstable rock fragments, kaolinization of feldspar, and meteoric dolomitization of carbonate. This was followed by mesogenetic calcite cementation and kaolinite transformation into dickite in deeply buried Qawasim sandstone. Comparatively, the Abu Madi estuarine facies, deposited during transgression after drawdown related to the MSC, is characterized by eogenetic iron (Fe)-calcite, glauconite, and pyrite (averages of 14.5%, 6%, and 2%, respectively). This facies transition is marked by abundance of mature glauconite (with potassium oxide (K₂O) at about 8%) whose content abates upward from the transgression surface. Moreover, the compositional variability of the Abu Madi sandstone gave rise to multiple diagenetic trajectories that resulted in chlorite formation presumably following smectite and kaolinite. Listed diagenetic variations in the studied Messinian sandstone resulted from a complex interplay between rocks’ compositional, depositional, and burial attributes, ultimately serving as a basis for high-resolution stratigraphic correlation in continental and marginal marine settings with poor biostratigraphic controls.  相似文献   

云南洱海现代沉积研究   总被引：1，自引：1，他引：0  

D.Eism  孙顺才  X.Song  E.Thomasse 《湖泊科学》2000,12(1):25-37

洱海是位于云南省境内较大的但相对较浅的断陷湖泊（水深小于２０ｍ）。根据１９９０－１９９３年对该湖现代沉积的研究,结果表明,湖泊沉积物主要是来自西部相对高２０００ｍ以上的山地,东部为低矮石灰岩山地,物源较少,南北两条入湖河流亦是重要的物源供应区。湖区沉积物主要是由粉砂质粘土组成,来自山地的粗碎屑物质则大量的堆积于此地,三角洲、扇三角洲及滨湖地带,沉积速度在过去１３０００年中平均为０．２ｃｍａ＾－１,  相似文献   

不同超声强度下微囊藻群体沉降及其上浮过程对光照和温度的响应     

谭啸  孙玉童  段志鹏  曾庆飞  郑雪莹  刘倩倩 《湖泊科学》2017,29(5):1168-1176

以太湖微囊藻群体为研究对象,研究低频超声作用下,4种超声强度和不同处理时间对微囊藻群体的抑制效应,试图得出最优超声参数,同时探讨超声处理后的微囊藻群体对光照和温度的响应.结果表明,当超声强度为0.0353 W/cm~3、处理时间为60 s时,藻细胞沉降量高达80%,且此时藻细胞浓度和叶绿素a浓度均保持不变,表明超声未破碎藻细胞,细胞内含物不会泄漏污染水质,因此作为最优超声参数.随后,对超声处理后的微囊藻群体在不同光照和温度条件下进行恢复培养,结果表明光照和温度均能影响微囊藻群体的浮力恢复,但光照的影响更明显,当光照度为2000 lx时,藻细胞在培养120 h后漂浮率恢复至对照组水平.超声后的藻细胞在较低温度(≤20℃)下漂浮率无显著变化,而在较高温度(25℃)下,培养72 h后漂浮率迅速升高,至120 h能恢复至对照组水平的80%左右.因此,野外超声控藻应选择低光强、低温的时段,采用间歇式多次处理,抑制微囊藻群体上浮,使其彻底沉降.  相似文献   

Study on the assessment of the comprehensive benefits of the utilization of sediment resources in reservoir areas     

Jingmin Hou  Yuanjian Wang 《国际泥沙研究》2017,32(3)

The utilization of sediment in reservoirs as resources is an efficient way to reduce reservoir sedi-mentation and turn disadvantage into benefit. Based on economic, social and ecological functions of sediment resources, this paper puts forward a two-layer, three-dimensional evaluation index system. It also establishes six direct and indirect indicators with their formulas to calculate the comprehensive benefits of sediment utilization in the Xixiayuan reservoir of the Yellow River with a volume of 2000 m3. The results show that social benefits would be more prominent, with the ecological benefits coming second. This demonstrates that the indirect public value of utilizing the sediment resources in the Yellow River Basin can be far greater than its direct economic value.  相似文献   

Influences of retrogressive erosion of reservoir on sedimentation of its downstream river channel——A case study on Sanmenxia Reservoir and the Lower Yellow River     

Jianguo Chen  Wenhao Zhou  Shanshan Han  Gaohu Sun 《国际泥沙研究》2017,32(3)

Retrogressive erosion, a widespread phenomenon of sediment transport in reservoirs, often impacts on both the reservoir capacity and the sedimentation in the downstream river channel. Based on field data from the Sanmenxia Reservoir and the Lower Yellow River over the past decades, three courses of ret-rogressive erosion with distinctive features were analyzed. The results indicate that retrogressive erosion, especially caused by rapid reduction in the water level till the reservoir is empty, often results in the serious siltation of the lower Yellow River and threatens the safety of the flood control in the Lower Yellow River. Unreasonable operation of the reservoir and incoming hyperconcentrated floods accom-panied by retrogressive erosion also aggravate the siltation of the main channel of the river. However, a reasonable operation mode of the reservoir so named"storing the clear (low sediment concentration) water in the non–flood season, and sluicing the muddy(high sediment concentration) water in the flood season" was found, which might mitigate the deposition in both the reservoir and the Lower Yellow River. This operation mode provides important experience for the design and operation of large reser-voirs in other large rivers carrying huge amounts of sediment.  相似文献