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1.
The pore water concentrations of dissolved silica in sediment cores from the continental slope offshore from Cape Hatteras, North Carolina, varied from 150 to almost 700 μ,M with depth in the top 40 cm of sediment. Sediment cores from 630 to 2010 m depth had very similar profiles of dissolved silica in their pore waters, even though these cores came from regions greatly different in slope, topography, sedimentation rate, and abundance of benthic macrofauna. Cores from 474 to 525 m were more variable, both with respect to pore water dissolved silica profiles, and with respect to sediment texture. Experiments indicate that both the rate of dissolution of silica and the saturation concentration decrease as sediment depth below the sediment-seawater interface increases. These data are consistent with depletion of a reactive silica phase in surface sediment, which may be radiolarian tests, or the alteration of biogenic silica to a less reactive form over time. Experimental results suggest that the pore water dissolved silica concentration in sediments below the top few centimeters may be higher than the sediments could now achieve. The flux of dissolved silica out of these sediments is estimated to be 15 μmoles cm−2 yr−1.  相似文献   

2.
Dissolution experiments in batch and flow-through reactors were combined with data on sediment composition and pore water silicic acid profiles to identify processes controlling the solubility of biogenic silica and the build-up of silicic acid in marine sediments. The variability of experimentally determined biogenic silica solubilities is due, in part, to variations in specific surface area and Al content of biosiliceous materials. Preferential dissolution of delicate skeletal structures and frustules with high surface areas leads to a progressive decrease of the specific surface area. This may cause a reduction of the solubility of deposited biosiliceous debris by 10–15%, relative to fresh planktonic assemblages. Dissolution of lithogenic (detrital) minerals in sediments releases dissolved aluminum to the pore waters. This aluminum becomes structurally incorporated into deposited biogenic silica, further decreasing its solubility. Compared to Al-free biogenic silica, the solubility of diatom frustules is lowered by as much as 25% when one out of every 70 Si atoms is substituted by an Al(III) ion.The build-up of silicic acid in pore waters of sediments with variable proportions of detrital matter and biogenic silica was simulated in batch experiments using kaolinite and basalt as model detrital constituents. The steady-state silicic acid concentrations measured in the experiments decreased with increasing detrital-to-opal ratios of the mixtures. This trend is similar to the observed inverse relationship between asymptotic pore water silicic acid concentrations and detrital-to-opal ratios in Southern Ocean sediments. Flow-through reactor experiments further showed that in detrital-rich sediments, precipitation of authigenic alumino-silicates may prevent the pore waters from reaching equilibrium with the dissolving biogenic silica. This agrees with data from Southern Ocean sediments where, at sites containing more than 30 wt.% detrital material, the pore waters remain undersaturated with respect to the experimentally determined in situ solubility of biogenic silica.The results of the study show that interactions between deposited biogenic silica and detrital material cause large variations in the asymptotic silicic acid concentration of marine sediments. The production of Al(III) by the dissolution of detrital minerals affects the build-up of silicic acid by reducing the apparent silica solubility and dissolution kinetics of biosiliceous materials, and by inducing precipitation of authigenic alumino-silicate minerals.  相似文献   

3.
Within the framework of the EU-funded BENGAL programme, the effects of seasonality on biogenic silica early diagenesis have been studied at the Porcupine Abyssal Plain (PAP), an abyssal locality located in the northeast Atlantic Ocean. Nine cruises were carried out between August 1996 and August 1998. Silicic acid (DSi) increased downward from 46.2 to 213 μM (mean of 27 profiles). Biogenic silica (BSi) decreased from ca. 2% near the sediment–water interface to <1% at depth. Benthic silicic acid fluxes as measured from benthic chambers were close to those estimated from non-linear DSi porewater gradients. Some 90% of the dissolution occurred within the top 5.5 cm of the sediment column, rather than at the sediment–water interface and the annual DSi efflux was close to 0.057 mol Si m−2 yr−1. Biogenic silica accumulation was close to 0.008 mol Si m−2 yr−1 and the annual opal delivery reconstructed from sedimentary fluxes, assuming steady state, was 0.065 mol Si m−2 yr−1. This is in good agreement with the mean annual opal flux determined from sediment trap samples, averaged over the last decade (0.062 mol Si m−2 yr−1). Thus ca. 12% of the opal flux delivered to the seafloor get preserved in the sediments. A simple comparison between the sedimentation rate and the dissolution rate in the uppermost 5.5 cm of the sediment column suggests that there should be no accumulation of opal in PAP sediments. However, by combining the BENGAL high sampling frequency with our experimental results on BSi dissolution, we conclude that non-steady state processes associated with the seasonal deposition of fresh biogenic particles may well play a fundamental role in the preservation of BSi in these sediments. This comes about though the way seasonal variability affects the quality of the biogenic matter reaching the seafloor. Hence it influences the intrinsic dissolution properties of the opal at the seafloor and also the part played by non-local mixing events by ensuring the rapid transport of BSi particles deep into the sediment to where saturation is reached.  相似文献   

4.
Water samples from a Pacific Ocean basin have been analysed for a number of forms of chromium. Total Cr, almost entirely as dissolved Cr(VI), steadily increases with depth and correlates most closely with silica data. Mid-depth regeneration of Cr is suggested by a multiple regression equation which includes Cr(total), silica and phosphate data.The release of Cr and silica from bottom sediments is apparent as the continental margin is approached. Box model transport calculations suggest that a Cr flux from the sediments on the order of 100 nmol Cr m?2 day?1 could be balanced by horizontal and vertical eddy diffusion coefficients of 106 and 10 cm2 s?1, respectively, and by horizontal and vertical advection rates of 10?2 and 10?4 cm s?1, respectively.  相似文献   

5.
A new approach to predict biogenic particle fluxes to the seafloor is presented, which is based on diffusive oxygen uptake and, in particular, opal fluxes to the seafloor. For this purpose, we used a recently published empirical equation coupling benthic silica to oxygen fluxes, and showing a clear negative correlation between Si and O2 fluxes. Dissolution of biogenic silica mediated by aerobic microbial activity has been inferred at 24 sites along the African and South American continental margins. Based on the assumption that these findings hold essentially for the entire Southern Atlantic Ocean, we applied the silica to oxygen flux ratio to a basin-wide grid of diffusive oxygen uptake extracted from the literature. Assuming that the silica release across the sediment-water interface equals the particulate flux of biogenic opal to the seafloor, we estimated minimum opal rain rates. We combined these calculations with published relationships between aerobic organic carbon mineralization and dissolution rates of calcite above the hydrographical lysocline, thereby assessing the calcite rain rate and particulate organic carbon flux to the seafloor. The addition of the buried fraction completes our budget of biogenic particulate rain fluxes. The combination of such empirical equations provides a powerful and convenient tool which greatly facilitates future investigations of biogenic particle fluxes to the seafloor.  相似文献   

6.
Settling particles were collected at 1,460 m and 3,760 m depth in the Antarctic Ocean with sediment traps of time series type. The total deployment period of 40 days was divided into four terms of 10 days each. Seawater samples were collected both at deployment and retrieval of the traps at each site. During the 42 days the concentration of silicate in the surface water decreased by 32%, whereas those of nitrate and phosphate decreased by only 4–5%. The total particulate flux in the Antarctic Ocean is the largest among those hitherto observed in the world ocean. The time variation of the particulate flux at 1,460 m depth almost coincided with that at 3,760 m. The settling particles were comprised roughly of 80% biogenic silica, 15% organic matter and 5% other substances including sea salt. The clay fraction was only 0.05% at 1,460 m depth. The settling flux of biogenic silica agrees fairly well with the calculated rate of change in the concentration of silicate in the surface 100 m. Thus it is concluded that preferential propagation of diatoms reduces the concentration of silicate prior to other nutrients in the Antarctic Ocean.  相似文献   

7.
Sinking particles were collected using time-series sediment traps deployed at 350 and 20 mab at Site SB (34° 58.5’N, 139° 20.9’E, 1544 m depth) near the center of Sagami Bay, off Japan with high time resolutions of 5-8 days (March 1997 to August 1998) and 3-4.5 days (March 1998 to August 1998), respectively. The major components (CaCO3, OM, opal, and clay) of these sinking particles and surface bottom sediments were determined using a stepwise leaching method combined with gravimetry. Average total mass fluxes were 1480, 5560 and 3068 mg/m2/year at 350 mab, at 20 mab, and in the surface sediments, respectively, indicating an enhanced collection of sinking particles at 20 mab. Clay was the dominant component and biogenic components (opal+OM+CaCO3) were dominated mainly by opal and secondly by OM. On average, opal and CaCO3 contents decreased gradually as clay content increased with increasing depth from 350 mab-20 mab and in the surface sediments, indicating dissolution of opal and CaCO3 through sinking, rebound, resuspension or sedimentation processes. Thirteen total mass flux peaks at 17--40-day intervals were observed at 350 mab during the period from March 1997 to August 1998 except for winter, while eight peaks were observed at 20 mab for the period from March 1998 to August 1998. Two types of total mass peaks can be distinguished: one with a clear increase in biogenic flux (opal+OM+CaCO3) and little or no increase in clay flux and termed a bloom type (B-type), and the other with a clear increase in clay flux, little increase in biogenic flux and termed a resuspension type (R-type). Some R-type peaks, but not all, coincided with total mass flux peaks observed at the mouth of Tokyo Bay and suggested the possibility of the effect of particulate materials transported from Tokyo Bay to site SB. The enormously large peak observed at 20 mab in late May 1998 and that at 350 mab in early June 1998 were considered to be due to some physical perturbations from an earthquake swarm near site SB during the period from April to June 1998. The 17--40-day periodicity was associated clearly with the change in biogenic flux dominated by opal flux and is thought to reflect the periodicity of biological productivity dominated by diatoms in the euphotic zone of Sagami Bay.  相似文献   

8.
天然32Si是宇宙射线成因的，随着降水进入湖泊或海洋，被硅质生物摄取后最终存在于生物硅中。32Si来源单一，生产速率相对恒定，半衰期为150 a，可测年的时间尺度为100~1 000 a，是该时间尺度最合适的测年核素，填补了百年到千年时间尺度测年方法的空白。本文建立了海洋沉积物32Si的测量方法，主要步骤为:（1）样品前处理；（2）生物硅的分离与纯化；（3）生物硅样品中磷的分离与纯化；（4）32P的制样与β计数测量。全程通过硅钼蓝和磷钼蓝分光光度法监测实验过程硅和磷的损失情况，对南沙海域采集的沉积物岩心进行研究，得到南沙海域沉积物岩心32Si的平均活度为16.60 mBq/kg，范围值为8.39~33.34 mBq/kg；32Si在SiO2中的平均比活度为0.356 Bq/kg，32Si的核素丰度平均值为1.29×10-16（32Si/SiO2）；根据岩心32Si活度估算得深水区（水深1 335~1 537 m）和浅水区（121~141 m）岩心的沉积速率分别为0.106 cm/a、0.191 cm/a；根据32Si活度计算32Si的平均沉降通量为2.14×10-6 Bq/（cm2·a），与参考文献的结果较为吻合。  相似文献   

9.
Abstract. The importance of sponge spicules in the turnover of biogenic silica (BSi) in the detritic bottoms of the Eastern Ligurian Riviera was evaluated by studying sediment cores and the detrital matter collected by a trap over a one year period.
This study made evident that: i) Sponge spicules represent the main component of the BSi both in the sediments and in the trapped matter; ii) A correlation exists between the sponge biomass present on the overhanging cliff and the amount of sponge spicules found in the sediment below; iii) Inside the sediments, a superficial layer (10 cm deep) characterized by intensive silica dissolution processes can be observed; and iv) The amount of spicules collected using the trap is not constant throughout the year, but shows a characteristic trend with low values in spring and summer and high values in autumn and winter.  相似文献   

10.
Microbial mediation of benthic biogenic silica dissolution   总被引：1，自引：1，他引：0  
Pore water profiles from 24 stations in the South Atlantic (located in the Guinea, Angola, Cape, Guyana, and Argentine basins) show good correlations of oxygen and silicon, suggesting microbially mediated dissolution of biogenic silica. We used simple analytical transport and reaction models to show the tight coupling of the reconstructed process kinetics of aerobic respiration and silicon regeneration. A generic transport and reaction model successfully reproduced the majority of Si pore water profiles from aerobic respiration rates, confirming that the dissolution of biogenic silica (BSi) occurs proportionally to O2 consumption. Possibly limited to well-oxygenated sediments poor in BSi, benthic Si fluxes can be inferred from O2 uptake with satisfactory accuracy. Compared to aerobic respiration kinetics, the solubility of BSi emerged as a less influential parameter for silicon regeneration. Understanding the role of bacteria for silicon regeneration requires further investigations, some of which are outlined. The proposed aerobic respiration control of benthic silicon cycling is suitable for benthic–pelagic models. The empirical relation of BSi dissolution to aerobic respiration can be used for regionalization assessments and estimates of the silicon budget to increase the understanding of global primary and export production patterns.  相似文献   

11.
A.E. Aksu 《Marine Geology》1983,53(4):331-348
Calcium-carbonate dissolution has been studied in several grab samples and piston cores from Baffin Bay and Davis Strait ranging in water depth from 200 to 2300 m. The intensity of dissolution was determined from examining: (1) the ratio of arenaceous to calcareous benthonic foraminifera; (2) the ratio of benthonic to planktonic foraminifera; (3) the relationships between the dissolution-susceptible and dissolution-resistant foraminifera; (4) the degree of foraminiferal test fragmentation; and (5) the relationships between plankton tows and the fauna in the surface sediments. All core tops and grab samples from Baffin Bay surface sediments below 600–900 m water depth demonstrated intense dissolution of calcium carbonate. Sediments below 900 m were biogenic carbonate free, indicating 100% foraminiferal loss due to dissolution. Possible causes of substantial undersaturation in calcium carbonate of Baffin Bay Bottom Water are very low temperatures, and higher concentrations of carbon dioxide. All cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1, 3, 5, 7 and 9. Similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom-water masses during these periods. The preservation state of biogenic carbonate debris in glacial isotope stages 2, 4, 6, 8 and 10 is similar to the assemblage found in the water at present.  相似文献   

12.
Natural marine sediments can release dissolved silica to silica-poor seawater and can remove silica from seawater enriched with dissolved silica. These are fast reactions, with sufficient reaction occurring within the first 48 hours to indicate clearly the direction of the reaction. The relative importance of these two processes varies with the ratio of clays to biogenic silica in the sediment. Both the release and the uptake reactions approach the interstitial water concentration of dissolved silica as an end point, which suggests that these reactions may influence this concentration. No change in sediment reactivity with respect to silica uptake or release reactions was observed with increasing depth in core for the three sediment cores investigated; this indicates that uptake sites are not saturated, and silica is available for dissolution for a long time after deposition.  相似文献   

13.
南海南部表层沉积物中生物硅的分布及其环境意义   总被引：1，自引：0，他引：1  
对南海南部25个表层沉积样进行了生物硅的测定分析,试图揭示南海南部表层沉积生物硅的分布及其对现代海洋环境的指示意义,以便为古海洋学研究提供进一步的科学依据。研究发现,表层沉积物中生物硅含量与其所处水深呈显著正相关关系,相关系数达到0.782。陆架浅水区表层沉积物中生物硅含量非常低,不能反映表层水体中硅质生物生产力情况,这可能与沉积类型和陆源物质输入影响有关。深水区表层沉积物中生物硅的含量分布表明,其不仅能反映表层水体中硅质生物的古生产力水平,而且还能指示上升流的强弱,从而进一步证实了利用沉积物中生物硅含量来追踪上升流发育和变化的有效性与可信度。研究结果还显示,在研究区域中北部表层沉积生物硅中放射虫和海绵骨针较硅藻占有更大的比重,这可能是由于硅藻易被溶解并易被其他生物体摄食的缘故。在有上升流发育的海域,放射虫、硅藻和海绵骨针基本上表现出较高的丰度,这与高的生物硅含量相一致。  相似文献   

14.
This report presents major and minor element profiles for interstitial waters recovered from the oxygen-minimum zone of the Gulf of California. The major elements and nutrients show concentration-depth profiles typical for anoxic, laminated sediments, with sulfate-reduction occurring close to the sediment-water interface, accompanied by increases in alkalinity and ammonia. Barium is solubilized near the sediment-water interface, but decreases below 10 cm depth, showing concentrations consistent with barite solubility. The dissolved concentrations of Mn, Fe, and Al are higher in the upper part of the sedimentary column; Mn and Fe due to reduction of oxides and Al probably because of dissolution of siliceous material. In contrast, dissolved Mo, V, and Cr show concentrations increasing with depth. The strong correlation of the concentrations of Mo, V and Cr with “yellow substance” absorbance reflect the importance of dissolved organic matter for the mobility of these elements during early diagenesis.  相似文献   

15.
对南海南部25个表层沉积样进行了生物硅的测定分析，试图揭示南海南部表层沉积生物硅的分布及其对现代海洋环境的指示意义，以便为古海洋学研究提供进一步的科学依据。研究发现，表层沉积物中生物硅含量与其所处水深呈显著正相关关系，相关系数达到0．782。陆架浅水区表层沉积物中生物硅含量非常低，不能反映表层水体中硅质生物生产力情况，这可能与沉积类型和陆源物质输入影响有关。深水区表层沉积物中生物硅的含量分布表明，其不仅能反映出表层水体中硅质生物的古生产力水平，而且还能指示上升流的强弱，从而进一步证实了利用沉积物中生物硅含量来追踪上升流发育和变化的有效性与可信度。研究结果还显示，在研究区域中北部表层沉积生物硅中放射虫和海绵骨针较硅藻占有更大的比重，这可能是由于硅藻易被溶解并易被其他生物体摄食的缘故。在有上升流发育的海域，放射虫、硅藻和海绵骨针基本上均表现出较高的丰度，这与高的生物硅含量相一致。  相似文献   

16.
The diatom species composition of settling biogenic silica particles collected in sediment traps was compared with the underlying sediment to determine the preservation of the various diatom species and to investigate the potential of biogenic silica as an indicator for changes in paleo-upwelling intensity. During the Netherlands Indian Ocean Programme (NIOP), settling particles were collected at two sampling sites off Somalia (NW Indian Ocean) for 9 months, from June 1992 to February 1993. One sediment trap array was deployed on the Somali slope directly below one of the main upwelling gyres, and a second array, meant as a reference site to reflect pelagic sedimentation, was moored in the Somali Basin away from direct coastal upwelling influence. At both sites diatoms represented over 90% of the total opal microorganisms. On the Somali slope, total annual diatom flux was 12.6×109 valves m−2, 76% of which was collected during the 112 d of the southwest monsoon, with peak fluxes in October, the end of the upwelling season. In the Somali Basin, the total annual flux was lower, 4.8×109 valves m−2, and only 39% was collected during the SW monsoon period (98 d). At both sampling sites, a distinct seasonal diatom species succession of ‘pre-upwellers’, ‘upwellers’ and ‘oceanic species’ was apparent. Although only a small part of the diatom assemblage escaped dissolution at the sediment–water interface, two species, Thalassionema nitzschioides and Chaetoceros resting spores, were preserved in the sediment, indicating that they are resistant to dissolution at the sediment–water interface. Eighty one percent of the deposition of Thalassionema nitzschioides and 78% of the deposition of Chaetoceros occurred during the upwelling period. Since these two species are the dominant component of the diatom assemblage in the sediments, and thus determine the biogenic silica content, we conclude that this preserved biogenic silica reflects the upwelling in the surface layer of the water column. On the Somali Margin, variations in biogenic silica flux as inferred from sedimentary records can therefore be used as an indicator for changes in paleo-upwelling intensity.  相似文献   

17.
Problems with biogenic silica measurement in marginal seas   总被引：5，自引：0，他引：5  
Surface sediment samples from the Bohai, Yellow Sea, and the Pacific were used to assess biogenic silica (BSi) content and to study uncertainties in BSi measurements. The contents of BSi in the Bohai and Yellow Sea are all less than 1%. The dissolution of BSi in sediments from the Bohai and Yellow Sea is very important to maintain high levels of silicate in the water column. The non-biogenic silica from clay minerals has an obvious effect on BSi of sediment samples in the Bohai and Yellow Sea with low BSi and high clay minerals. The solid to solution ratio was found to have a great influence on BSi measurement, which can induce uncertainties up to 75%. The effect of loss by sorption and centrifugation is negligible. Interlaboratory comparison of techniques for BSi measurement by the wet alkaline extraction technique of Mortlock and Froelich [Deep-Sea Res. 36 (1989) 1415-1426] with clay correction was suggested to give no significant differences. However, differences in sediment compositions and reagent to sample ratio may limit the application of the wet alkaline extraction method.  相似文献   

18.
分析了南海62个表层沉积物样品中生源(有机质、碳酸钙和蛋白石)和非生源(岩源物质)组分的含量变化和分布特征,并以沉积学分区为基础,结合5个沉积物捕获器站位,将南海划分为N、C-NE、SW和S 4个区域,对比分析了各区表层沉积物和水柱中沉降颗粒物中各组分含量、沉积通量分布特征和变化,探讨了表层沉积物的输出生产力、沉降颗粒物的初级生产力及真光层下100 m输出生产力三者之间的对应关系.结果显示:南海4个海域表层沉积物中各组分平均含量多数低于沉降颗粒物中的平均含量,而碳酸钙、岩源物质的沉积通量却多数高于沉降颗粒物中的沉积通量,分析得出表层沉积物中各组分平均含量和沉积通量不仅受水柱中各组分输出量影响,还受到陆源物质输入、溶解作用和上层水体营养盐影响.南海表层沉积物中生源组分沉积通量大小对应其输出生产力的大小.但是,由于陆源有机质、生源颗粒侧向漂移的影响,表层沉积物的输出生产力大小分布并不完全对应沉降颗粒物的初级生产力大小分布,尽管南海真光层下100 m输出生产力与沉降颗粒物的初级生产力比值与世界大洋"f"比平均值基本一致,但是,明显低于表层沉积物的输出生产力大小,只有在沉降颗粒物的初级生产力较高区域,真光层下100 m输出生产力大小才最接近表层沉积物的输出生产力大小.  相似文献   

19.
A 43 cm long E271 sediment core collected near the East Pacific Rise(EPR) at 13°N were studied to investigate the origin of smectite for understanding better the geochemical behavior of hydrothermal material after deposition.E271 sediments are typical metalliferous sediments. After removal of organic matter, carbonate, biogenic opal,and Fe-Mn oxide by a series of chemical procedures, clay minerals(2 μm) were investigated by X-ray diffraction,chemical analysis and Si isotope analysis. Due to the influence of seafloor hydrothermal activity and close to continent, the sources of clay minerals are complex. Illite, chlorite and kaolinite are suggested to be transported from either North or Central America by rivers or winds, but smectite is authigenic. It is enriched in iron, and its contents are highest in clay minerals. Data show that smectite is most likely formed by the reaction of hydrothermal Fe-oxyhydroxide with silica and seawater in metalliferous sediments. The Si that participates in this reaction may be derived from siliceous microfossils(diatoms or radiolarians), hydrothermal fluids, or detrital mineral phases. And their δ30 Si values are higher than those of authigenic smectites, which implies that a Si isotope fractionation occurs during the formation because of the selective absorption of light Si isotopes onto Feoxyhydroxides. Sm/Fe mass ratios(a proxy for overall REE/Fe ratio) in E271 clay minerals are lower than those in metalliferous sediments, as well as distal hydrothermal plume particles and terrigenous clay minerals. This result suggests that some REE are lost during the smectite formation, perhaps because their large ionic radii of REE scavenged by Fe-oxyhydroxides preclude substitution in either tetrahedral or octahedral lattice sites of this mineral structure, which decreases the value of metalliferous sediments as a potential resource for REE.  相似文献   

20.
Understanding biogenic silica (bSi) dissolution kinetics in margin environments is important in assessing the global silicon cycle, a cycle closely linked to the global carbon cycle. This understanding is also essential to answer the question of whether bSi content in marine sediment is a valid indicator of productivity in the overlying surface ocean. In this study, plankton tow, sediment trap, and sediment samples were collected at sites in three Southern California borderland basins. Batch dissolution experiments with plankton tow and sediment trap materials (conducted in the laboratory at 22 °C) showed linear dissolution kinetics, from which mean dissolution rate constants of 0.05 d? 1 for plankton tow samples and 0.07 d? 1 for sediment trap samples could be calculated. The dissolution rate constants for both types of samples showed seasonal variability but not the same seasonal patterns. Faster dissolution was observed with sediment trap samples collected at 800 m than at 550 m. With sediment multi-core samples, non-linear dissolution kinetics was observed, which complicates the direct comparison of dissolution rates. Nonetheless, dissolution appeared to be slower for the sediments samples than for samples collected from the water column and to decrease with depth in the sediments. Rate constants for surface sediment (0–0.5 cm) were at least 3–5 times less, and sediments at depths > 2 cm had rate constants at least 6–13 times less than those for material sinking to the sediment surface at these sites. Dissolution experiments conducted with Santa Barbara Basin surface sediment samples amended with dissolved aluminum (Al) and San Pedro Basin trap samples amended with enriched detrital materials (obtained by leaching bSi from sediment samples) suggested that dissolution was inhibited by Al and that the sediments from the different basins varied in the extent of Al release.  相似文献   

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