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以江苏弶港潮滩为典型研究区,基于2007—2012年在潮滩及条子泥匡围工程实施期间采集的9条潮滩断面高程数据,建立潮滩剖面形态的二次函数统计模型,并结合同步采集的表层沉积物粒度数据,对围垦影响下的潮滩剖面演化机制进行了探讨。结果表明,受围垦工程影响较小的北部潮间带上部的淤积强度要大于潮间带中下部淤积强度,潮滩剖面呈上凹型;正在实施的围垦工程加剧了垦区内潮滩的淤积,尤其在下部呈现高强度淤积而造成垦区内潮滩剖面的上凸趋势减缓,剖面曲率减小。此外,由于垦区内逐渐失去潮汐水动力作用,与附近非垦区类似潮滩带相比,垦区内滩面沉积物呈细化趋势。围垦工程在潮间带中下部筑堤坝,对涨潮水体有阻滞作用,使得外海带来的细颗粒沉积物在围堤外侧快速堆积,造成原潮间带下部快速淤高,形成垦区外向海侧微下凹的潮滩剖面形态。 相似文献
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对江苏沿岸2006年1月4日-2007年1月31日28个站位的水位数据使用潮位统计和经验正交函数(EOF)方法进行分析和比较.统计分析得到了各站位的平均潮差、最大潮差、平均潮周期、平均高潮相位差数据.经验正交函数分析结果显示,第1模态与平均潮差吻合较好,包含了水位数据73.7%的信息.前2个模态均为主要半日分潮的信息,为潮汐按相位正交分离的结果;第3模态显示了径流输入变化引起的海面变化信息;之后的数个模态还包含了水位扰动的信息.研究表明,经验正交函数应用于潮汐分析的效果良好,可作为潮汐分析的有效工具,且在扰动检测方面有一定潜力. 相似文献
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根据南黄海辐射沙脊群定点站位的流速和浊度数据,利用通量分解方法,分析了潮汐水道的悬沙输运特征和输运机制。结果表明,辐射沙脊群海域潮汐水道中潮流为往复流,悬沙浓度较高,属于强潮流控制的悬沙浓度相对较高的陆架浅海环境;悬沙输运主要受欧拉余流和潮汐捕捉效应控制,再悬浮的沉积物通过平流作用进行输运。其中,陈家坞槽和西洋水道的悬沙输运以潮汐捕捉效应占优,沉积物向潮汐水道外输运,处于冲刷状态;苦水洋水道以欧拉余流输运为主,水道内的再悬浮的沉积物在强潮流作用下向陆输运,主要堆积在蒋家沙和西洋西侧岸滩等浅滩和潮间带上。由此可见,在陆源物质供应减少背景下,南黄海辐射沙脊群内部的物质充当了新的物源,短期内能够维持近岸潮滩和沙脊的持续增长。 相似文献
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In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer (BBL). Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath (under the lowest tidal level), a tripod system was installed with AWAC (Acoustic Wave And Current), ADCP (Acoustic Doppler Current Profilers), OBS-3A (Optical Backscatter Point Sensor), ADV (Acoustic Doppler Velocimeters), etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt: 1) The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2) The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension. 相似文献
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鸭绿江河口及近岸地区沉积物中重金属分布的影响因素分析 总被引:15,自引:1,他引:14
对鸭绿江河口不同地区沉积物中重金属分布特征和埋藏通量的垂向变化进行了分析;探讨了其独特的动力环境等因素对重金属分布的影响;评价了鸭绿江河口地区重金属污染状况及潜在生态风险程度.结果显示,自1920年代到2000年以来,除了Cu的含量和埋藏通量逐年减小之外,Cr、Ni、Zn、Cd、Pb、As和Hg的浓度和埋藏通量具有逐渐增加的趋势;鸭绿江河口地区重金属总体污染程度为重到严重,其中西水道沉积物的重金属总体污染程度和总潜在生态风险程度均最高,重金属污染已经对鸭绿江河口地区的生态环境构成了严重的危害;粒度控制效应不是鸭绿江河口地区重金属分布的最主要影响因素;Cu和其他几种重金属有着不同的来源;最大浑浊带独特的动力机制是造成中水道重金属(除Cu外)的高值分布区和最大浑浊带内的高悬沙浓度分布区相对应的最主要原因. 相似文献
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Knowledge of the sediment flux derived from different sources is critical for interpreting the sedimentary records associated with large river sedimentary systems. For the Changjiang River system, previous studies hardly focused on the sediment load from the adjacent Zhoushan Archipelago(ZA). Based on four prediction models, aiming to improve the understanding of the sediment load from the ZA during the Holocene, we show that the predicted sediment flux of the ZA ranges from ~0.7 to 26.5 Mt·yr~(-1), with an average value of 10.7 Mt·yr~(-1), and the islands with a relatively large area or high relief contribute greatly to the total flux. This sediment load is an order of magnitude lower than that of the Changjiang River, but it is similar to those of the local small rivers. Located in the core area of the southward dispersal path of the Changjiang River plume, the ZA also influences the sediment transport into Hangzhou Bay and over the Zhejiang-Fujian coastal seas. On the Holocene temporal scale, e.g., for the period from 6 ka BP to 2 ka BP, the sediments discharged from the ZA had a considerable effect on the shelf sedimentary system. This study provides evidence for an important role an archipelago can play in terms of sediment supply and transport in coastal and inner continental shelf regions. 相似文献