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用^210Pb和^239Pu测定Saguenay湾的沉积速率 总被引：2，自引：0，他引：2
本文介绍了用＾２１０Ｐｂ和＾２３９Ｐｕ测定Ｓａｇｕｅｎａｙ湾沉积速率。在沉积物中过剩＾２１０Ｐｂ的比活度随着深度的增加呈指数衰减,但在柱状样８２－０７２的４５ｃｍ处和８２－１４７的６ｃｍ处,过剩＾２１０Ｐｂ的比活度发生突变。这可能与１９７１年发生的陆倾有关。用＾２１０Ｐｂ方法测得柱状样８２－０７２和８２－１４７的沉积速率分别为３．５０ｃｍ／ａ和０．４９ｃｍ／ａ,与用＾２３９Ｐｕ方法测得的沉积速率３ 相似文献
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本文介绍了用２１０Ｐｂ 和２３９Ｐｕ 测定Ｓａｇｕｅｎａｙ 湾的沉积速率。在沉积物中过剩２１０Ｐｂ 的比活度随着深度的增加呈指数衰减。但在柱状样８２－０７２ 的４５ｃｍ 处和８２－１４７ 的６ｃｍ 处,过剩２１０Ｐｂ 的比活度发生突变。这可能与１９７１ 年发生的陆倾有关。用２１０Ｐｂ 方法测得柱状样８２－０７２ 和８２－１４７ 的沉积速率分别为３．５０ｃｍ ／ａ 和０．４９ｃｍ ／ａ,与用２３９Ｐｕ 方法测得的沉积速率３．６０ｃｍ ／ａ和０．５０ｃｍ ／ａ 基本是一致的。 相似文献
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红树林潮滩沉积速率测量与研究 总被引：3，自引：0，他引：3
红树林捕沙促淤功能是红树林防浪护岸效益的主要表现之一。本文用标志桩法与（２１０）Ｐｂ同位素定年法测定红树林潮滩沉积速率。海南东寨港林市村岸段标志桩试验显示：红海榄Ｒｈｉｚｏｐｈｏｒａｓｔｙｌｏｓａ密林区普遍淤积，平均速率４．１ｍｍ·ａ（－１）；白滩与疏林区侵蚀，平均速率８．２ｍｍ·ａ（－１）。沉积速率随滩地高程增加或潮水浸淹频率的减小而减小。冬春淤积为主而夏季冲刷为主。区域性淤积速度受区域泥沙来源与海岸动态影响。在粤西廉江高桥镇凤地村岸段的（２１０）Ｐｈ测试显示，０—９０ｃｍ段沉积历时为１４５（１８４７—１９９２）ａ，平均沉积速率为６．２ｍｍ·ａ（－１）。其中０—４０ｃｍ段１９６６—１９９２年沉积速率１５．４ｍｍ·ａ（－１）最大，４０—５０ｃｍ段１９３０－１９６６年沉积速率２．８ｍｍ·ａ（－１）最小。 相似文献
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伯劳特中沉积物的沉积速率在０．１３－０．３３ｃｍ／ａ之间,平均值为０．２３ｃｍ／ａ。事故释入的＾２３９Ｐｕ在各个站位中的垂直分布在次表层都有一个最大值,这个值出现在５－７ｃｍ深睡。在最大值之前＾２３９Ｐｕ的比活度随深度的增加呈指数增加,最大值之后迅速下降到本底水平。 相似文献
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本文介绍了一种测定积物中＾２１０Ｐｂ的方法。沉积物中的＾２１０Ｐｂ用ＨＮＯ３和ＨＦ消化，然后＾２１０Ｐｏ在８５－９０℃下从０．５ｍｏｌＨＣＬ介质中自沉积在银片上；其全程放化回收率为８５．０±４．９×１０＾－２。 相似文献
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湄洲湾夏季的初级生产力 总被引：2，自引：3，他引：2
湄洲湾１９９２年夏季的叶绿素ａ，三磷酸腺苷，碳比积累速率，初级生产力的变化范围和均值分别为０．４５－４．７２，１．４９ｍｇ／ｍ＾３；０．１２－１．０７，０．３１μｇ／ｄｍ＾３；０．０６－０．５８，０．３４ｄ＾－１；０．０７－０．３４，０．２１ｍ／（ｍ＾２．ｄ）。叶绿素ａ与三磷酸腺苷之间。初级生产力与碳比积累速率之间均呈正相关关系。叶绿素ａ三磷本能腺苷的比值为４．８，湄洲湾夏季浮游植物的生长受氮不足 相似文献
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利用卫星遥感对同一地区重复成像的特点，采用从港湾不同时相的影像中提取不同潮位的水域面积的方法，建立潮位面积算式和采用分层求和的方法，建立沉 积参量算式。利用沉积参量算式和潮位面算式计算了海口港两个同时段的０ｍ以浅的沉积参量；１９６５－１９８４年时段沉积总量为４．５９×１０＾８ｍ＾３，沉积速率为２．４×１０＾５ｍ＾３／ａ；１９８４－１９９０年时段，沉积总量为－８．４×１０＾５ｍ＾３，沉积速率为－１． 相似文献
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台湾地区湖泊水库沉积速率初步探讨 总被引：3，自引：0，他引：3
对1989－1991年期间，在台湾地区采集的5个湖泊的沉积物岩芯和22个湖泊水库的表层沉积物，进行了沉积物超量210Pb活性的分析，以探讨其沉积速率。其中，小鬼湖沉积物岩芯取部分样品进行14C定年，以与210Pb所得结果比较。结果表明，数千年来，台湾高山湖泊、次高山湖泊的沉积速率相当稳定，除万里池外，大多介于0．06－0．16cm／a之间。火山湖的210Pb活性较一般湖泊高，这是由于火山湖当地安山岩及地下水释出较多的210Pb所致，但这并不意味其沉积速率慢。所以应用210Pb对火山湖沉积物定年时，须作特别修正。平地湖泊目前沉积速率，除了大埔水库高达6．42cm／a外，大多介于0．5—3、2cm／a之间，比高山湖泊的沉积速率高约10－20倍。另外，由水库淤沙资料显示1），历年平均沉积速率都比目前的沉积速率快数倍，其中以石门、白河、乌山头、阿公店4个水库的平均沉积速率较快。 相似文献
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A wide variety of sedimentary subenvironments are found within a 10-km stretch of James River including a flood dominated channel (Rocklanding Channel) and its bank (Rocklanding Shoal), a shoal with a water depth of 1 m separating two channels (Point of Shoals), an ebb-dominated channel (Burwell Bay Channel) and its bank (Burwell Bay Bank) and a tributary (Warwick River). The concentrations of Cs-137, Cu, Pb, Zn and organic carbon in the fine-grained sediments (i.e. < 63 μm) and the amount of fine-grained sediments in eight cores covering these subenvironments were determined. The sedimentation rates, estimated by Cs-137 geochronology, range from 0·4 to > 3 cm year?1. The sedimentation rates in the Burwell Bay region are two or more, times those in the Point of Shoals and in the Rocklanding Channel and Shoal, reflecting the weaker currents in the Burwell Bay region. These sedimentation rates agree well with those obtained independently by measuring changes in the bathymetry of this area between 1873 and 1943. The concentrations of Cs-137, Cu, Pb, Zn and organic carbon in surface sediments vary by a factor of two to three. The concentrations are higher in the Burwell Bay region, probably as a result of the higher rates of accumulation of recently formed sediments in these subenvironments. The inventories of fine-grained sediments and of Cs-137, Cu, Pb, Zn and organic carbon accumulated since 1954 are also up to an order of magnitude higher in the Burwell Bay region. Although the concentrations of fine-grained sediments in three cores obtained in this region are similar, the inventories still vary by a factor of two to three. The inventories of Cs-137, Cu, Pb, Zn, organic carbon and fine-grained sediments correlate well with each other indicating that Cs-137 can be a useful tracer for studying the fate of these metals and organic carbon in estuarine environments. The inhomogeneity of the concentrations and inventories of the different elements along a 10-km segment of a river suggests that a closely-spaced sampling programme is essential for characterizing the sedimentary provinces within an estuary. The concentrations of Cs-137, metals and organic carbon in the coarse-grained sediments (i.e. > 63 μm) are considerably lower than those in fine-grained sediments. Thus, the contribution of coarse-grained sediments to the total inventory of these elements is small. 相似文献
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To relate the textural characteristics of the bottom sediments of a tidal inlet to hydrodynamics, 45 sediment samples from the Tauranga Entrance to Tauranga Harbour were analysed for textural parameters, and tidal currents and waves were monitored. Tidal currents dominate sediment transport processes near the Tauranga Entrance although swell waves are significant on the ebb tidal delta, and wind waves may influence intertidal sediments within the harbour. The bulk of the sediment is probably derived from marine sand from the Bay of Plenty continental shelf, but tidal currents and waves have changed its textural character. In areas of swift tidal currents, particularly in the inlet channel itself, sediment is coarser, more poorly sorted, and more coarsely skewed than that in areas of slower currents. 相似文献
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Larry G. Ward 《Geo-Marine Letters》1985,5(1):71-75
Resuspension of bottom sediments by waves and tidal currents was investigated in three characteristic environments of middle
Chesapeake Bay (shallow platform, deep platform, and main channel). In the shallow near shore platform wind waves frequently
resuspended significant amounts of sediment, some of which was transported offshore. In both the shallow and adjacent deep
platform regions, tidal currents were too weak (<20 cm cm/sec) to resuspend bottom sediments. In the main channel, peak current
velocities were substantially stronger (40 cm/sec), but were still not competent to erode the bottom. The stability of the
bottom in this area is related to the activities of the benthic organisms which are influenced by seasonal anoxia.
University of Maryland Center for Environmental and Estuarine Studies (CEES) Contribution No. 1572. 相似文献
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Sediment cores from the harbour and the coastal zone of Mytilene, island of Lesvos, Greece, were used to study the metal contamination caused by the discharge of untreated urban effluents into the sea. In the harbour. the upper layers were highly enriched in Cd, Cu, Pb and Zn, while no metal enrichment was recorded in the cores from the wider coastal zone. The metal data were normalized to Li (conservative element) to compensate for the natural textural and mineralogical variability. It was found that only the upper 18 cm of the core collected from the harbour of Mytilene could be reported as metal contaminated. Also, through the normalization procedure, it was found that the surface layers of coastal sediments assumed 'clean' were enriched in Pb, probably as a result of atmospheric transportation of the metal from the nearby town. 相似文献
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杭州湾南岸潮滩的~(210)Pb分布及其沉积学意义 总被引：1，自引：0，他引：1
杭州湾南岸潮滩的~(210)Pb垂向分布具有随深度波动的特征。湖滩颗粒物在吸附模拟系统中的~(210)Pb分配系数,主要受颗粒物含量的影响。本文从潮滩沉积~(210)Pb初始比度在低于平衡点一侧波动的机理,以及被沉积间断所分隔的有效封闭段的存在出发,提出选择常态沉积层的高~(210)Pb比度窗口,建立以CIC模式估计潮滩沉积速率的方法。 相似文献
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The narrow shelf along the coast of central Vietnam is seasonally supplied by large amounts of sediment from the adjacent
mountainous hinterland following monsoonal precipitation. This study examines the fate of these sediments, and their accumulation
rates along two transects across the shelf, based on analyses of radionuclides (210Pb, 137Cs), sediment texture and structure, as well as carbonate content. The inner shelf is covered by sands, and probably serves
as bypass zone for fine sediments transported offshore. Sediment characteristics suggest that the transport to the mid and
outer shelf is related to flood events. Averaged over the last century, the 210Pb-based mud mass accumulation rates on the mid and outer shelf vary between 0.25 g cm −2 and 0.56 g cm −2 year −1 (corresponding to linear sediment accumulation rates of 0.20–0.47 cm year −1). Along with high excess 210Pb inventories, these high accumulation rates suggest a significant sediment depocentre on the mid shelf. The 210Pb-derived sediment accumulation rates were found to be several times higher than 14C-derived rates previously reported for the Holocene, at the same location on the outer shelf. This is probably due to the
incompleteness of the Holocene record, and an overestimation of the modern rate. Another explanation would be increased erosion
within the rivers’ drainage basins, due to 20th century deforestation. This hypothesis is supported by the difference between
recent (less sand, more lithic grains in the sand fraction) and older sediments. In terms of modern sedimentation processes
and rates, the central Vietnam shelf, although being a part of a narrow passive continental margin, is similar to active flood-dominated
continental margins. 相似文献
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Changes in the transport and sedimentation of suspended particulate matter (SPM) after deepening of the navigation channel of the Elbe Estuary in 1999 were studied. Long-term series of the grain size composition of sediments and sedimentation rates in the main stream and its branches (Nebenelben) were compared with changes in flow velocities and tidal water levels. In addition, water quality parameters like biological oxygen demand (BOD7), dissolved oxygen and particulate organic carbon (POC) were analysed to determine changes in the origin and fate of the SPM. In the main stream, deepening produced no significant changes of the flow velocities. However, there was a decrease of the mean tidal low water level between 5.7 and 8.1 cm at the upper end of the estuary. These small changes in hydrology had the effect that fine-grained suspended matter derived from freshwater run-off accumulated in the surface water of the freshwater region in the estuary and remained within this region until all degradable organic matter was consumed. Accumulation of the fine-grained SPM produced an increase of the <63 μm fraction in the sediments of the Hamburg harbour by about 20% and in the SPM along the freshwater longitudinal profile up to about 120%. Coupled to this the mean BOD7 increased between May and August by 38%. Enhanced oxygen deficiencies thus occurred after 1999, with concentrations of below 6 mg O2 L−1 over a length of about 100 km along the freshwater longitudinal profile of the Elbe Estuary. In the shallow water regions present in the branches of the main stream, deepening of the navigation channel was followed by a 25% decrease in the flow velocities during low tide. This was coupled to an increase of the sedimentation rates which produced a rise of the sediment level between 0.7 and 1.5 m until 2004 and a permanent loss in the capacity of the branches for re-aeration of the open water. The results indicate that in tidal systems SPM might be more sensitive for monitoring changes in the transport regime than hydrological parameters. 相似文献