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1.
The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang
Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare
earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there
are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities
due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of
the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China
Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary
suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is
extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations
of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and
intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble
rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred.
In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang
estuarine surface waters. 相似文献
2.
《Marine Geology》2006,225(1-4):85-101
A flash flood that occurred in July 1996 in the Saguenay area (Québec, Canada), deposited a bed of cohesive sediments, average of 10–60 cm thick, over an area of 65 km2 of the deep fjord basin of the upper Saguenay Fjord. Because this turbidite covered contaminated sediments, the resuspension potential of surficial sediments is an important parameter in determining the efficiency of the 1996 layer as a natural capping layer. This is because contaminants that may have diffused through the 1996 layer may be resuspended. The resuspension potential of surficial sediments in Saguenay Fjord was investigated in situ over a 3-yr period at fifteen sites in the Baie des Ha! Ha! and the North Arm using a benthic flume, the Miniflume. In addition, geotechnical measurements, photographs of benthic sediments and recordings of benthic current velocities were also carried out. The measured critical velocities of sediment resuspension (uc) vary between 7 and 15 cm s− 1. The maximum bottom current speed recorded in the North Arm and in Baie des Ha! Ha! from May to August 2000 was 27 cm s− 1. Erosion depths were determined from Miniflume data combined with laboratory measurements carried out with an axial tomography scanner, which provided variation of sediment density at an interval of 0.13 mm. A general relationship between depth of erosion (ze, mm) and shear stress applied on the bed (τb, Pa) was determined. As Saguenay Fjord sediment characteristics vary greatly from one station to another, the potential for resuspension of surficial sediments shows the same trend. 相似文献
3.
S. Knox W. J. Langston M. Whitfield D. R. Turner M. I. Liddicoat 《Estuarine, Coastal and Shelf Science》1984,18(6):623-638
By combining field observations with a statistical approach and a simple but effective estuarine analogue, the main features of the cycling of arsenic in the Tamar estuary have been elucidated. As(III) and As(V) enrichment in the water column is due to a combination of localized inputs and effective recycling of sediment interstitial waters. The profiles of As(V) are similar to those of NH4+ and are dominated by an estuarine maximum resulting from an input from the sediments. As(III) profiles are correlated with those of dissolved manganese and exhibit both fresh water and estuarine maxima. As(III) appears to be effectively removed at the freshwater/brackish water interface by a combination of heterogenous oxidation, catalysed by hydrous manganese dioxide, and adsorption on to iron oxyhydroxide. The estuarine distribution of As(III) within the water column is consistent with the published rates of oxidation of As(III) to As(V) by both inorganic and microbiological processes. The reduction of As(V) to As(III) in the sediments is incomplete. On the basis of our observations a tentative estuarine arsenic cycle is presented. 相似文献
4.
Robert J. Diaz G. Randy Cutter Donald C. Rhoads 《Deep Sea Research Part II: Topical Studies in Oceanography》1994,41(4-6)
Even though the continental slope off Cape Hatteras has sediment accumulation rates on the order of 1 cm/year, large areas of soft sediment are intensively reworked by infaunal organisms. Primary sedimentary structures have been completely replaced with biogenic structures. Surface sedimentary structures are dominated by the bioturbational activities of a deep burrowing infauna (to at least 30 cm). The layer actively mixed by the benthos, as evidenced by sediment profile and X-ray images, is estimated to range from 5 to 20 cm, with the residence time for particles within the surface mixed layer ranging from about 4.5 to 18 years. The biological mixing parameter (G) ranges from 0.4 to 5.5, which indicates moderate to strong biological mixing relative to accumulation and strata formation. Bioturbation contributes to the dynamic forces affecting the surface sediments by decreasing compaction of sediment layers and dilating sediment fabrics by sediment mixing, and introducing large water-filled burrows and voids to subsurface sediments. The sediment profile images captured numerous subsurface feeding voids, and worms in the process of making deep burrows, many of which extended below the 5 to 10 cm average depth of the apparent color redoxpotential discontinuity layer. High rates of accumulation of organic-rich sediment lead to high standing stocks of benthos and intensive feeding/burrowing activity that result in organic rich stratagraphic sequences that are thoroughly mixed. Cape Hatteras is a apparent focusing point for the transport of shallow water sediments to the deep sea. Sediments across other areas of the continental slope just 100's of kilometers south of Cape Hatteras are not as thoroughly mixed or biologically active. 相似文献
5.
Arsenic geochemistry in Chesapeake Bay: Dependence upon anthropogenic inputs and phytoplankton species composition 总被引：1，自引：0，他引：1
James G. Sanders 《Marine Chemistry》1985,17(4):329-340
Arsenic is not conservative in Chesapeake Bay. Inputs of man-derived arsenic, of the order of 100 kg d−1, cause substantial positive deviation from theoretical dilution. The chemical form of the arsenic varies both seasonally and along the axis of the bay. During winter, arsenic is present only as arsenate. During summer, substantial quantities of reduced and methylated forms are present in different areas, indicative of separate formation processes. Arsenite, present in low-salinity regions, may have been formed by chemical reduction in anoxic, subsurface waters and then mixed into the surface layer. Methylated arsenicals correlate highly with algal standing stocks. One particular form, methylarsonate, is highly correlated with the dominant algal genus, Chroomonas. As both arsenic reactivity and toxicity are altered by transformation of chemical form, the observed variations in arsenic speciation have considerable geochemical and ecological significance. 相似文献
6.
悬沙组分对再悬浮过程响应的初步研究——以长江口南槽口门为例 总被引：2，自引：1，他引：1
根据2011年5月31日至6月3日在长江口南槽口门附近海域投放三角架观测系统获取的沉积动力观测数据以及现场采集的水样和底质样品,进行底部边界层参数、悬沙粒度及悬沙组分分析,以探讨研究区近底部边界层特征和沉积物再悬浮过程。结果表明,研究区海域的悬沙以粉砂组分为主,潮周期内近底部流速与相应层位的悬沙浓度变化呈正相关,存在显著的再悬浮作用。分析发现,随着水体中悬沙砂组分的增加,再悬浮通量随之显著增加;砂组分减小,则再悬浮通量亦减小。因此,悬沙砂组分是对再悬浮过程响应的敏感组分,在一定程度上可指示和"示踪"再悬浮效应。 相似文献
7.
胶州湾中砷（Ⅴ）还原初步研究 总被引：2，自引：0，他引：2
研究胶州湾沉积物对砷（Ⅴ）的还原作用。结果表明：１．随泥水比增大，还原率升高，泥水比为且：１０００时，沉积物对砷（Ⅴ）的还原率为１６％；２．未煮沸的泥－水提取液还原率高于煮沸杀菌泥－水提取液。指示：沉积物有机质在微生物作用下，对砷（Ⅴ）有一定的还原作用。此外，根据胶州湾的调查结果及实验室藻类培养模拟实验结果，分析了胶州湾砷（Ⅲ）产生原因。指出：主要是由于藻类和沉积物、水体有机物的还原作用，两者的还原能力相当，但在不同季节所起的作用不同。 相似文献
8.
To examine the source and preservation of organic matter in the shelf sediments of the East China Sea (ECS), we measured bulk
C/N and isotopes, organic biomarkers (n-alkanes and fatty acids) and compound-specific (fatty acids) stable carbon isotope ratios in three sediment cores collected
from two sites near the Changjiang Estuary and one in the ECS shelf. Contrasting chemical and isotopic compositions of organic
matter were observed between the estuarine and shelf sediments. The concentrations of total n-alkanes and fatty acids in the shelf surface sediments (0–2 cm) were 5–10 times higher than those in estuarine surface sediments
but they all decreased rapidly to comparable levels below the surface layer. The compositions of n-alkanes in the estuarine sediments were dominated by C26-C33 long-chain n-alkanes with a strong odd-to-even carbon number predominance. In contrast, the composition of n-alkanes in the shelf sediment was dominated by nC15 to nC22 compounds. Long-chain (>C20) fatty acids (terrestrial biomarkers) accounted for a significantly higher fraction in the estuarine sediments compared to
that in the shelf sediment, while short-chain (<C20) saturated and unsaturated fatty acids were more abundant in the shelf surface sediments than in the estuarine sediments.
Stable carbon isotopic ratios of individual fatty acids showed a general positive shift from estuarine to shelf sediments,
consistent with the variations in bulk δ
13CTOCTOC. These contrasts between the estuarine and shelf sediments indicate that terrestrial organic matter was mainly deposited
within the Changjiang Estuary and inner shelf of ECS. Post-depositional diagenetic processes in the surface sediments rapidly
altered the chemical compositions and control the preservation of organic matter in the region. 相似文献
9.
The Effect of Macrofauna on Porewater Profiles and Nutrient Fluxes in the Intertidal Zone of the Humber Estuary 总被引：3，自引：0，他引：3
R. J. G. Mortimer J. T. Davey M. D. Krom P. G. Watson P. E. Frickers R. J. Clifton 《Estuarine, Coastal and Shelf Science》1999,48(6):683
Macrofauna, nutrient fluxes, porewater chemistry and sediment characteristics were measured at six intertidal mudflat sites in the Humber Estuary, U.K., during the different seasons. Nereis diversicolor , Macoma balthica and Corophium volutator were found to be the dominant macrofauna. Salinity was the baseline control on macrofauna distribution but this was overprinted by periodic impoverishment due to sediment mobilization. High resolution gel probe porewater samplers provided direct evidence for the impact of burrows on porewater chemistry. The macrofauna modified nutrient fluxes during periods of mud flat stability. Nereis caused a decrease in silicate and phosphate effluxes but enhanced ammonia release and nitrate uptake. Macoma enhanced ammonia and nitrite release. The impact of Corophium was not possible to discern. The Humber is a large, highly dynamic macrotidal estuary in which sediment resuspension has a large impact on porewater profiles, nutrient fluxes and macrofaunal communities. Simple patterns and inter-relationships which are seen in small sheltered estuaries are not observed in the Humber. 相似文献
10.
11.
本文综合2000～2003年期间9个航次的研究结果,讨论了总溶解态无机砷（TDIAs,[TDIAs]=[As^5＋]＋[As^3＋]）和亚砷酸盐（As^3＋）在黄、东海的分布和季节性变化。调查海区覆盖了黄、东海不同水文和化学性质的区域,研究重点放在自长江口向东南琉球群岛沿伸的PN断面以讨论陆源输送的物质对中国陆架边缘海的影响。利用氢化物发生原子荧光光谱法（HG-AFS）分析砷的不同形态（TDIAs,As^3＋）。TDIAs受河流陆源输送的影响在近岸区域含量较高,并随着离岸距离的增加含量逐步下降。在东海陆架坡折带的近底层水中也存在TDIAs的高值中心,此区域具有低温、高盐、低悬浮颗粒物含量的特征,显示出入侵陆架的黑潮水是陆架区TDIAs另一个主要的源。TDIAs的季节性变化趋势受到长江冲淡水水量及黑潮入侵陆架强度的季节及年际变化共同影响。研究区域中As^3＋的分布特征与TDIAs相反,其含量、分布及季节性变化受到浮游植物活动的影响,表现出与叶绿索含量存在正相关关系。夏季东海陆架PN断面中As／P的化学计量比值约为2×10^3。黄、东海溶解态砷的含量与世界其它海区相近,表明其未受到明显人为活动的影响。 相似文献
12.
黄河三角洲海底土波致再悬浮研究 总被引：1，自引：1，他引：0
在现代黄河三角洲采集土样,制备室内水槽试验的底床,施加波浪作用,观测波致悬沙含量的变化规律,分析不同波高、作用时间对单位面积底床再悬浮量的影响,及波浪停止作用后悬浮泥沙的静水沉降规律。研究发现,在水深一定条件下底床再悬浮量呈现随波高增大而增大的特性,两者线性拟合的相关性很好;在一定波高的波浪连续作用下,约5 000~6 000个波周期底床再悬浮过程完成;在波浪作用初始阶段底层悬沙含量与中上层的相差很大,悬沙含量垂线结构呈斜线型,稳定阶段的悬沙浓度垂向结构呈准直线型,底层与表层含沙量比值为0.98~1.25,整个水层含量分布均匀;静水沉降过程中当悬沙含量大于1 g/dm3,悬沙含量(SSC)呈现出随时间指数衰减的规律,悬沙浓度与沉降通量呈线性关系。研究结果对认识黄河水下三角洲泥沙运移规律具有一定的科学意义。 相似文献
13.
Several important mechanisms for storm-induced entrainment of estuarine cohesive sediments are analyzed using field measurements collected in a moderately energetic estuary, central Long Island Sound, U.S.A. The sediment concentration and hydrographic data were obtained by an array of sensors mounted at 1 m above the bottom. The bottom sediment in the study site composed mostly of silt and silty sand. The study showed that the bottom shear stress, computed using a wave-current interaction model, increased significantly during the episodic wind events. A large resuspension event was triggered by a frontal passage when strong wind-driven currents augmented the tidal currents. The timing of storm waves with respect to the tidal phase also was a critical factor. Based on the changes of suspended sediment concentration, the bottom appeared to respond to the shear stress in two phases: the tidal resuspension and the storm-induced erosion. During each tidal cycle, entrainment was associated with resuspension of high water content, loosely consolidated material. During episodic events, a thin layer of more consolidated bed below the sediment-water interface was eroded by the enhanced bottom stress. 相似文献
14.
Don Maurer Richard T Keck Jeff C Tinsman Wayne A Leathem 《Marine environmental research》1982,6(1):49-68
The survival of benthic invertebrates from dredging and disposal activities is a major environmental concern in such projects. The purpose of the research described in this paper was to determine the ability of benthos (polychaetes, Scoloplos fragilis and Nereis succinea) to migrate vertically in natural and exotic sediments and to determine the survival of benthos when exposed to particular amounts of simulated dredged material.Mortalities generally increased with increased sediment depth, exotic sediment and burial time. Temperature also affected vertical migration and mortalities. These experiments, together with other experiments conducted by us and other workers, indicate that polychaetes in particular, and benthos in general, can survive dredging and disposal projects. Under certain conditions several major taxa (polychaetes, molluscs, crustaceans) can be expected to successfully recolonise disposal sites by vertical migration. 相似文献
15.
海底沉积物再悬浮及其分布取决于海洋水动力、沉积物类型与床面形态之间复杂的相互作用,准确地理解和确定沉积物再悬浮过程对于沉积物输运的研究具有重要的意义。本文在祥云湾海洋牧场典型海域开展现场原位观测,获取研究区波浪、海流及悬浮沉积物浓度数据;分析了波、流作用下海底边界层悬浮沉积物垂向分布特征,并探究了海洋水动力和床面形态对悬浮沉积物垂向分布的影响。结果表明,研究区波流之间的相互作用不显著,沉积物再悬浮受控于风暴浪作用,风暴浪作用下底床切应力可以达到沉积物临界切应力的10～15倍,沉积物的再悬浮滞后于风暴浪作用2～3 h。在波浪荷载微小的情况下,悬浮沉积物垂向分布呈现"I"型,波浪荷载下,悬浮沉积物垂向分布呈现幂指函数分布,表现为"L"型;床面形态随波、流作用而演化,影响沉积物的再悬浮过程,u_(?w)/u_(?c)=1.00可作为波浪和海流起主导控制作用的床面形态的判别依据,纯波浪荷载作用下的u_(?w)/u_(?c)显著高于波浪主控作用下,但二者之间的界线随着波浪荷载的增加而升高。 相似文献
16.
The impact of resuspension on sediment mercury dynamics, and methylmercury production and fate: A mesocosm study 总被引：5，自引：0，他引：5
Eun-Hee Kim Robert P. Mason Elka T. Porter Heather L. Soulen 《Marine Chemistry》2006,102(3-4):300-315
The objective of this study was to investigate the effects of resuspension on the fate and bioaccumulation of mercury (THg) and methylmercury (MeHg) in shallow estuarine environments, using mesocosms. Two 4-week experiments were conducted in July (Experiment 1) and October (Experiment 2) of 2001 with Baltimore Harbor sediments. Hard clams, Mercenaria mercenaria, were introduced into sediments for Experiment 2. Tidal resuspension (4 h on and 2 h off cycles) was simulated, with 3 replicate tanks for each treatment—resuspension (R) and non-resuspension (NR). Sediment cores were collected during the experiments for THg, MeHg, organic content and AVS analyses, and for the determination of methylation/demethylation using Hg stable isotopes (199Hg(II) and CH3199Hg(II)). Zooplankton samples were collected once a week while clams were taken before and after Experiment 2 for THg and MeHg analyses. Our results suggest that the interplay between Hg methylation and MeHg degradation determines the overall MeHg pool in sediments. Sediment resuspension does not appear to directly impact the Hg transformations but can lead to changes in the association to Hg binding phases, influencing Hg methylation. The bioaccumulation results indicate that sediment resuspension can play an important role in transferring sediment MeHg into organisms. 相似文献
17.
Contribution of benthic and epiphytic diatoms to clam and oyster production in the Akkeshi-ko estuary 总被引：1，自引：0，他引：1
The species composition and dynamics of phytoplankton in the water column and its contribution to clam, Ruditapes philippinarum, and oyster, Crassostrea gigas, production were studied in the Akkeshi-ko estuary, eastern part of Hokkaido, Japan. A total 128 taxa of diatoms were identified,
with 103 and 102 species occurring on the surface sediments and in the water column, respectively. Amphora sp., Bacillaria paradoxa var paxilifer, Cocconeis scutellum, Navicula sp., Nitzschia sigma, Paralia sulcata, Rhoicosphenia curvata, Synedra ulna and Thalassiosira sp. were most common and dominant in all stations in both water column and surface sediment. Benthic diatoms were most dominant
in both water column and surface sediment. The species composition of epiphytes was, in part, similar to diatom assemblage
of the water column and also to that of the surface sediment. The benthic and pelagic ratio in the diatom assemblage of the
water column was very high. Benthic diatoms were able to resuspend into water column by turbulence stimulated by wind. Chlorophyll
a concentration in the water column increased as wind speed increased. Seventy and 67% of the gut contents oysters consisted
of benthic diatoms in 2003 and 2004 and also 78 and 87% of clams in 2003 and 2004, respectively. The availability of benthic
and epiphytic diatom assemblages contributes significantly to food resources for clam and oyster mariculture due to resuspension
by disturbance in the Akkeshi-ko estuary. 相似文献
18.
Katharine R. Hendry Michael P. Meredith Christopher I. Measures Damien S. Carson Rosalind E.M. Rickaby 《Estuarine, Coastal and Shelf Science》2010
The use of dissolved Al as a tracer for oceanic water masses and atmospheric dust deposition of biologically important elements, such as iron, requires the quantitative assessment of its sources and sinks in seawater. Here, we address the relative importance of oceanic versus atmospheric inputs of Al, and the relationship with nutrient cycling, in a region of high biological productivity in coastal Antarctica. We investigate the concentrations of dissolved Al in seawater, sea ice, meteoric water and sediments collected from northern Marguerite Bay, off the West Antarctic Peninsula, from 2005 to 2006. Dissolved Al concentrations at 15 m water depth varied between 2 and 27 nM, showing a peak between two phytoplankton blooms. We find that, in this coastal setting, upwelling and incorporation of waters from below the surface mixed layer are responsible for this peak in dissolved Al as well as renewal of nutrients. This means that changes in the intensity and frequency of upwelling events may result in changes in biological production and carbon uptake. The waters below the mixed layer are most likely enriched in Al as a result of sea ice formation, either causing the injection of Al-rich brines or the resuspension of sediments and entrainment of pore fluids by brine cascades. Glacial, snow and sea ice melt contribute secondarily to the supply of Al to surface waters. Total particulate Al ranges from 93 to 2057 mg/g, and increases with meteoric water input towards the end of the summer, indicating glacial runoff is an important source of particulate Al. The (Al/Si)opal of sediment core top material is considerably higher than water column opal collected by sediment traps, indicative of a diagenetic overprint and incorporation of Al at the sediment–water interface. Opal that remains buried in the sediment could represent a significant sink of Al from seawater. 相似文献
19.
黄河水下三角洲位于半封闭的渤海内部,海底沉积物中重金属Cu污染严重,且该区域多发风暴潮,引起沉积物再悬浮甚至液化,导致沉积物中重金属Cu重新释放进入海水中。本研究以黄河口粉质土作为底床,采用室内波浪水槽试验模拟重金属Cu在不同水动力条件下,通过静态扩散、底床未液化状态下再悬浮以及底床液化状态下再悬浮3种方式进入上覆水体的释放过程。结果表明:上覆水体中重金属Cu的浓度分布与悬浮泥沙浓度分布密切相关,呈现出一致的变化规律;沉积物液化会明显促进重金属Cu向上覆水体中释放,底床液化再悬浮阶段上覆水体中溶解态Cu的浓度为静态扩散阶段的18倍,为底床非液化再悬浮阶段的11倍;此外,底床液化会导致沉积物中重金属Cu向深处扩散,扩散深度约为沉积物液化深度的一半。 相似文献
20.
A. Maher W. S. Douglas D. Yang F. Jafari V. R. Schaefer 《Marine Georesources & Geotechnology》2013,31(3-4):221-235
A preliminary study was conducted to determine the potential for cement deep soil mixing (CDSM) technology as a method for in-situ solidification of contaminated river and estuarine sediments. The study was conducted in Newark Bay, near the mouth of the Passaic River, New Jersey. The primary objective of the study was to evaluate the viability of CDSM for the in-situ S/S with a focus on: 1) determining the correct mix of the cement slurry, which provides rapid stabilization of the sediment matrix, 2) potential resuspension of solids during CSDM operations, 3) the effects of high organic content on the solidification process, and 4) the feasibility of using conventional dredging/extraction methods once the sediments have been stabilized and allowed to cure. The results of the study show CDSM slurry mixtures, as low as 7% in cement content, result in significant solidification and strength gain of in-situ sediments under ambient conditions. In sediments with very high organic contents (> 20%), the slurry mix would need to be adjusted to account for retardation effects of organics on cement hydration. Sediment resuspension during application was shown to be minimal at a distance of as little as 75 feet from the mixing head. Strength gains were considerable, effectively consolidating the sediment particles in a secure matrix, but not so high as to preclude extraction of solidified sediments with conventional dredging equipment. Dredged solidified sediment exhibited characteristics of a stiff glacial clay, and as such was easier to handle and transport than untreated dredged sediments. This technique has high potential to be used as an interim remedial measure prior to either extraction and decontamination/disposal or proper capping. 相似文献