An evaluation of metal bioaccessibility in estuarine sediments using the commercially available protein, bovine serum albumin   总被引：2，自引：0，他引：2  

Judit Kalman  Andrew Turner   《Marine Chemistry》2007,107(4):486-497

The bioaccessibility of metals (Al, Ca, Fe, Mn, Ag, Cd, Co, Cu, Ni, Pb, Sn, Zn) in oxic estuarine sediments has been evaluated using solutions of a commercially available protein (bovine serum albumin; BSA) that mimic the chemical conditions encountered in the gut environment of many deposit-feeding organisms. Over a 20 h incubation period with 5 g L^− 1 BSA, metal mobilisation was generally biphasic in that a relatively short period of rapid release was succeeded by more gradual release or approach to equilibrium, although in some cases metal readsorption was evident during the time-courses. Availability to BSA, defined as metal released after 20 h relative to metal extracted by boiling aqua regia, was greatest for Cd, Ni, Ca and Zn and lowest for Fe and Mn, and correlated well with, but was an order of magnitude lower than, metal digested by acidified hydrogen peroxide. Time-courses conducted in the absence of the protein revealed that significant quantities of Ca and Mn were water-soluble, reflecting the partial dissolution of carbonates and hydrous Mn oxides, respectively. Additional experiments indicated a net increase in metal release with increasing BSA concentration and, with the exception of Ca and Mn, a substantial increase in metal mobilisation after sediment organic matter had been digested by peroxidation. These observations suggest that, apart from Ca and Mn, metal release proceeds via complexation with component amino acids of the protein, denudation of organic host phases, and exposure of inorganic, metal-bearing minerals. Accordingly, the bioaccessibility of a metal is predicted to be dependent on its (i) affinity for proteinaceous ligands, (ii) association with components of digestible sediment organic matter, and (iii) degree of binding at relatively weak sites on sediment phases that are exposed or modified by the action of proteins and other chemical constituents of the gut environment.  相似文献   

长江口拦门沙地区的泥沙运动规律   总被引：12，自引：0，他引：12  

潘定安  孙介民 《海洋与湖沼》1996,27(3):279-286

依据１９８８年７月和１２月水文观测资料，通过流，盐，沙的综合分析，认识到长江口拦门沙地区的泥沙运动有与河口其他地区不同的特点，泥沙输移在水平面上和垂直面上存在着多种循环，潮流和盐水截留大量泥沙积聚的拦门沙地区，河口在盐淡水交锋地带，除了涨，落急时段外，发现在转流时期泥沙也可能产生再悬浮，从而形成一个潮周期中出现３次或４次再悬浮的特殊规律。  相似文献   

Comparative tolerance of two estuarine annelids to fluoranthene under normoxic and moderately hypoxic conditions     

Weinstein JE  Sanger DM 《Marine environmental research》2003,56(5):637-648

The tolerance of the oligochaete Monopylephorus rubroniveus and the polychaete Streblospio benedicti to sediment-associated fluoranthene was characterized under normoxic (>80% dissolved oxygen saturation) and moderately hypoxic ( approximately 50% dissolved oxygen saturation) conditions. Under both conditions, M. rubroniveus was highly tolerant of fluoranthene. Streblospio benedicti was considerably less tolerant of fluoranthene compared with M. rubroniveus. In addition, S. benedicti was less tolerant to fluoranthene under moderately hypoxic conditions, although no differences in sensitivity between the two oxygen conditions were observed based upon median lethal tissue residues. Bioaccumulation factors were higher for S. benedicti exposed to moderate hypoxia, suggesting that behavioral adaptations to compensate for the lower dissolved oxygen increased its bioaccumulation of fluoranthene. The results of the present laboratory study demonstrate that (1). changes in annelid tolerance to fluoranthene under varying oxygen conditions is a species-dependent phenomenon and (2). the differential tolerance of these two annelids to these combined stressors is consistent with their relative abundances in the field.  相似文献   

The dimensions of sand ripples in full-scale oscillatory flows   总被引：1，自引：0，他引：1  

T. O'Donoghue  J.S. Doucette  J.J. van der Werf  J.S. Ribberink 《Coastal Engineering》2006,53(12):997-1012

New large-scale experiments have been carried out in two oscillatory flow tunnels to study ripple regime sand suspension and net sand transport processes in full-scale oscillatory flows. The paper focuses on ripple dimensions and the new data are combined with existing data to make a large dataset of ripple heights and lengths for flows with field-scale amplitudes and periods. A feature of the new experiments is a focus on the effect of flow irregularity. The combined dataset is analysed to examine the range of hydraulic conditions under which oscillatory flow ripples occur, to examine the effects of flow irregularity and ripple three-dimensionality on ripple dimensions and to test and improve existing methods for predicting ripple dimensions.The following are the main conclusions. (1) The highest velocities in a flow time-series play an important role in determining the type of bedform occurring in oscillatory flow. Bedform regime is well characterised by mobility number based on maximum velocity in the case of regular flow and based on the mean of the highest one tenth peak velocities in the case of irregular flow. (2) For field-scale flows, sand size is the primary factor determining whether equilibrium ripples will be 2D or 3D. 2D ripples occur when the sand D₅₀ ≥ 0.30 mm and 3D ripples occur when D₅₀ ≤ 0.22 mm (except when the flow orbital diameter is low). (3) Ripple type (2D or 3D) is the same for regular and irregular flows and ripple dimensions produced by equivalent regular and irregular flows follow a similar functional dependence on mobility number, with mobility number based on maximum velocity in the case of regular flow and based on the mean of the highest one tenth velocities in the case of irregular flow. For much of the ripple regime, ripple dimensions have weak dependency on mobility number and ripple dimensions are similar for regular and irregular flows with the same flow orbital amplitude. However, differences in ripples produced by equivalent regular and irregular flows become significant at the high mobility end of the ripple regime. (4) Ripple dimensions predicted using the Wiberg and Harris formulae are in poor agreement with measured ripple dimensions from the large-scale experiments. Predictions based on the Mogridge et al. and the Nielsen formulae show better overall agreement with the data but also show systematic differences in cases of 3D ripples and ripples generated by irregular flows. (5) Based on the combined large-scale data, modifications to the Nielsen ripple dimension equations are proposed for the heights and lengths of 2D ripples. The same equations apply to regular and irregular flows, but with mobility number appropriately defined. 3D ripples are generally smaller than 2D ripples and estimates of 3D ripple height and length may be obtained by applying multipliers of 0.55 and 0.73 respectively to the 2D formulae. The proposed modified Nielsen formulae provide an improved fit to the large-scale data, accounting for flow irregularity and ripple three-dimensionality.  相似文献   

Short-term shoreline changes due to cross-shore structures: a one-line numerical model     

I. O. Leont'yev   《Coastal Engineering》1997,31(1-4)

The proposed numerical model simulates the short-term temporal changes in shoreline position due to a structure interrupting the longshore sediment flux. The impacts of both the groin-type construction and underwater trench of arbitrary orientation relative to the shore are discussed. In order to estimate the sediment mass trapped by the structure, a submodel of the longshore sediment transport induced by a random wave field is developed. The contribution of the surface roller in momentum balance as well as in sediment suspension is included. The shoreline changes are computed from the equation deduced from the mass conservation. The perturbations in the longshore sediment discharge caused by a structure are assumed to concentrate within some boundary area of which the spatial scale is proportional to the structure's length until the latter is exceeded by the width of the sediment flux. It is shown in particular that the total effect of a long trench (channel) and a pier in its nearshore part results in general shoreline recession except for the vicinity of a pier. The model is tested against the laboratory data of Baidei et al. (1994) and applied to the Baidara Bay coast (Kara Sea) where a pipeline would be designed.  相似文献   

渤海湾及其附近海域沉积物中Cu,Pb,Zn,Cd环境背景值的研究   总被引：10，自引：1，他引：10  

李淑媛  郝静 《海洋与湖沼》1992,23(1):39-48

根据渤海湾及其毗邻河口区10柱岩芯样细颗粒（＜0．063mm）（GF 1983－1985年采集）中重金属含量特点，结合^216Pb年代学编年资料，用未受人类影响沉积层中元素含量，藉统计学方法获得渤海湾岩芯样中Cu，Pb，Zn，Cd的分布类型，并根据各区重金属的含量水平，用t检验法获得了渤海湾Cu，Pb，Zn，Cd的环境背景值。  相似文献   

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin     

Chandralata Raghukumar  G. Sheelu  P. A. Loka Bharathi  Shanta Nair  C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.  相似文献   

沉积物镁铝含量比及其古气候意义   总被引：3，自引：2，他引：3  

张士三  陈承惠 《台湾海峡》1993,12(3):266-271

沉积物的镁铝含量比——m 值(m=100×MgO/Al_2O_3)与沉积水介质的盐度、pH 水温关系密切。当水温处在冰点以下时,沉积物的m 值随水温降低而增大。当水温处在冰点以上时,水介质的盐度、pH 和水温的增加,都有利于m 值增大。由于气候条件能直接或间接地影响沉积水介质的特征,因此,沉积物的m 值对古气候的变化具有一定的判别功能。通过对中国元古宙以来沉积物m 值的分析,发现古气候的热冷变化有1200Ma 的周期,其中还有次一级的热冷气候波动。第四纪的气候是处在热气候期后期的一个冷的气候波动阶段。  相似文献   

山东荣成湾月湖口门落潮干道的推移质输运   总被引：6，自引：2，他引：6  

薛允传  高抒  贾建军 《海洋与湖沼》2002,33(4):356-363

改进了Gao等 ( 1 994)方法 ,并用以计算潮汐汊道口门落潮干道的垂线平均流速。利用月湖潮汐汊道系统冬、夏季各一个月的潮位资料 ,计算落潮干道的潮流流速和推移质输运率。结果表明 ,流速的计算值和实测值呈良好的相关性 ,落潮干道内落潮流的输沙能力高于涨潮流输沙能力  相似文献   

辽宁东五家子金矿矿脉含矿性评价标志研究   总被引：2，自引：1，他引：1       下载免费PDF全文

朴寿成  师磊  杨明亮  王宝岩 《地质找矿论丛》2008,23(3):204-208

辽宁东五家子金矿的矿脉由蚀变岩和石英脉透镜体构成,可采矿体均为硫化物石英脉型.工业矿脉中,石英为烟灰色,发育他形、半自形的细粒黄铁矿等硫化物,有较大规模的矿体.矿化脉中,石英为乳白色,发育粗粒、自形的浅色黄铁矿,无可采矿体.在工业矿脉、次要矿脉、矿化脉的蚀变岩和石英脉样品中,Au,Hg与其他元素的相关性有明显区别.用石英脉样品的As-Ni-Ba图解和蚀变岩样品的Au-Ag-Ba图解预测,矿区外围的西沟1号脉和西沟3号脉属于工业矿脉.  相似文献