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1.
Scanning electron microscopy and instrumental neutron activation analyses of filtered suspended matter from the Atlantic Ocean show that particulate aluminium (Alp) is a sensitive measure of bottom derived or resuspended material. The proportion of Alp in suspended particulate matter (SPM) increases slightly between surface and intermediate depths but shows large and steady increases in deep waters with approach to the bottom.

Fep/Alp andMnp/Alp ratios are always higher than the crustal ratios throughout the water column. We show that the processes which can explain such enrichments are different for particulate matter in surface waters (scavenging, incorporation in biogenic particles) than for resuspended material (precipitation from interstitial waters on surficial sediments).

Close to the Mid-Atlantic Ridge, the bottom suspended matter exhibits higher Fep/Alp andMnp/Alp ratios than in abyssal plains. A ridge crest source must be invoked to explain the striking enrichment of Mnp. This source could also explain the enrichment of Fep, although primarily because the resuspended flux is small in that region, one cannot exclude the contribution of particles from the mid-water column.  相似文献   


2.
湖泊水体中HCHs沉降通量及其与浮游植物间响应关系   总被引：1，自引：0，他引：1  
迟杰  王倩怡  马永民 《湖泊科学》2008,20(3):323-326
于2006年跨春夏秋三季对一封闭的小型湖泊水体中颗粒物的沉降通量和浮游植物生物量进行了采样调查,测定了沉降颗粒物中的TOC含量和六六六（HcHs）含量。结果表明,湖水中浮游植物在春末以及秋季密度较大,浮游植物密度、叶绿素含量和总悬浮颗粒物浓度总体变化趋势基本一致,说明水体总悬浮颗粒物浓度与浮游植物生物量密切相关;春季颗粒物沉降通量较大,且与总悬浮颗粒物浓度和叶绿素含量之间存在一定的滞后性,夏季和秋季颗粒物沉降通量保持在一个较低水平;HCHs的沉降通量呈现春季较大的现象,与颗粒TOC沉降通量变化趋势相一致,表明HCHs的沉降主要受颗粒TOC沉降通量的控制。  相似文献   

3.
The Fitzroy estuary (Queensland, Australia) receives large, but highly episodic, river flows from a catchment (144,000 km(2)) which has undergone major land clearing. Large quantities of suspended sediments, and particulate and dissolved organic carbon are delivered. At peak flows, delta(13)C (-21.7+/-0.8 per thousand) and C/N (14.8+/-1.3) of the suspended solids indicate that the particulate organic material entering the estuary is principally soil organic carbon. At the lower beginning flows the particulate organic matter comes from in-stream producers (delta(13)C=-26 per thousand). The DOC load is about 10 times the POC load. Using the inverse method, budgets for POC and DOC were constructed for high and low flows. Under high flows, only a small portion of the POC and DOC load is lost in the estuary. Under dry season (low flow) conditions the estuary is a sink for DOC, but remains a source of POC to the coastal waters.  相似文献   

4.
Wind-induced resuspension of particulate matter was investigated in a shallow coastal region off southwestern Australia, chosen for its isolation from the complexity of other confounding physical processes. The site had negligible river discharge, low nutrient concentrations and was largely devoid of tidal currents. Moorings were deployed in the micro-tidal waters to measure current speed, wave parameters, backscatter, subsurface irradiance and dissolved oxygen concentration. Two contrasting sites were chosen as representative of high and low wave-energy environments. Turbulent kinetic energy, recorded by the instruments, was dominated by the wind-wave signal. During wind events, at the most exposed site, bed shear stress exceeded the critical stress required to lift and resuspend sediments. At the most enclosed site, bed shear stresses only exceeded the critical stress required to suspend less dense material such as benthic fluff. Wind-waves were found to be the dominant mechanism driving the vertical redistribution of particulate matter. Low frequency storm events and high frequency (daily) sea breezes were found to differ significantly in their retention of particulate matter suspended in the water column. Long periods of calm generally followed the passage of a storm, allowing suspended particulate matter to settle out, while consecutive daily sea breezes were more effective in holding particulate matter in suspension. Linear correlations were found between the backscatter (a proxy for suspended particulate matter), light attenuation and dissolved oxygen concentration. Approximately half the variability in dissolved oxygen concentration could be attributed to the variability in light attenuation, with a decline in concentration during wind resuspension events. Variability in dissolved oxygen concentration was interpreted as a possible indicator of the moderation of pelagic phytoplankton productivity during wind events.  相似文献   

5.
The Odra river flood of 1997 was a rare hydrological as well as an interesting sedimentological event. At Hohenwutzen (Lower Odra River) we observed the suspended particulate matter transport and the temporal development of water and solidsπ pollution with heavy metals and As. While the suspended particulate matter concentration decreased the trace element concentrations increased during the flood by fractionation of particles and solution processes. Because of a successive flooding of differently contaminated sedimentary sources and polluted regions the contents of heavy metals developed irregularly. Their median particulate concentrations did not exceed the values of older samples taken under mean discharge conditions between 1989 and 1995. The dissolved amounts correspond to those of the Elbe river in 1990. During the flood the dissolved share of all analyzed total element contents increased. The total loads increased 4fold (Cr) to 17fold (Cd).  相似文献   

6.
Seasonal observations on the nature and concentration of suspended particulate matter (SPM) are presented for a cross-section of the English Channel, between the Isle of Wight (UK) and Cotentin peninsula (France) i.e. the western boundary of the eastern English Channel. The highest concentrations of suspended material are found adjacent to the English coastline, whereas the offshore waters are associated with low concentrations. Seasonal variations in the concentration and nature of suspended material are identified, with highest concentrations in winter. At this time, the suspended particles are characterised generally by peaked grain size spectra and an enrichment in coarse silt particles; in summer, the distributions are generally flat. The diatom communities found within the suspended matter indicate that material resuspended in the coastal zone and the estuarine environments is transported offshore. SPM fluxes (based upon the observed SPM concentrations and the output from a 2-D hydrodynamic model) from the western Channel through the Wight–Cotentin Section, ranged between 2 and 71×106 t a−1 with a mean of around 20×106 t a−1 over the period of the observations (1994–1995). These fluxes are comparable to the order of magnitude and mean value reported as output through the Dover Strait. Therefore, it is possible that the eastern English Channel may be characterised as an area of fine-grained sediment ‘bypass'. This interpretation is corroborated by: (a) the absence of fine-grained sediment deposits over the area; and (b) correlation between the potential resuspension time of the fine particles and the seabed sediment distribution.  相似文献   

7.
The composition and amount of colloidal and suspended participate matter transported during a small flood event in Magela Creek in tropical northern Australia was investigated. The flood studied constituted approximately 3 % of the total annual flow, most (90%) of which occurred between mid-January and mid-February of the study year. Three fractions were separated from water samples using a sequential method involving a continuous flow centrifuge to separate suspended particulate matter (SPM; nominally > 1 μm) followed by hollow fibre filtration, first using a 0.1 μm filter to separate course colloidal matter (CCM; nominal size 1–0.1 μm) and then a 0–015 μm filter to separate fine colloidal matter (FCM; nominal size 0.1–0.015 μm). The SPM was predominantly inorganic (organic matter 21 %), whereas the colloidal fractions were dominantly organic matter (CCM 60%; FCM 83%). Analysis of individual particles using electron microprobe and automated image analysis indicated that the mineral fractions in both the SPM and CCM were dominated by iron-enriched aluminosilicates (including kaolinite) (72–82%) and quartz (9–10%), indicative of a highly weathered and extensively laterized catchment. Surprisingly there was very little difference in the composition of the SPM or CCM fractions during the flood event studied, which may indicate either that sediment availability was restricted following the major run-off events in January and February, or that all the sediment sources within the catchment are geochemically similar. Approximately the same amounts of particulate (20 tonne), colloidal (21 tonne) and dissolved material (17 tonne) were transported during the 25 hour period of the main flood peak; over 90% of the colloidal matter was 0.1–1.0 μm in size. These data suggest that previous estimates of the amounts of particulate (and colloidal) matter transported by Magela Creek, which were based on suspended solids measurements, may have underestimated the particulate matter load by as much as 50%. It is possible that the relatively high proportion of colloidal matter is unique to Magela Creek because coagulation and aggregation of colloidal matter to particulate matter is slow due to the very low concentations of calcium and magnesium in these waters. However, if the result is more widespread, there are important implications for the global estimates of fluvially transported particulate and dissolved materials as many of the previous studies may have underestimated the particulate load and overestimated the dissolved load.  相似文献   

8.
Based on three continuous in situ underwater light field measurement under different wind waves conditions in Longgan Lake, Meiliang Bay of Taihu Lake in July 2003 and littoral zone near TLLER in July 2004, respectively, the effects of sediment resuspension caused by wind waves on PAR diffuse attenuation, absorption coefficients and euphotic depths are analyzed. In Longgan Lake, PAR diffuse attenuation coefficients during small, middle and large wind waves were 1.74, 2.02 and 2.45 m?1, respectively, and the corresponding PAR spectral diffuse attenuations ranged from 0.98 to 2.97, 1.34 to 3.95 and 1.80 to 5.40 m?1, respectively. In Meiliang Bay, PAR diffuse attenuation coefficients were 2.63, 3.72, 4.37 m?1 during small, middle and large wind waves. PAR diffuse attenuation coefficients increased by 41% and 66% from small to middle, large wind waves, respectively. Absorption coefficients integrated over the range of PAR of CDOM, phytoplankton were 0.26, 0.28 m?1; 0.76, 0.49 m?1, respectively during middle and large wind waves. Absorption coefficients integrated over the range of PAR of non-algal particulate matter and total suspended particulate matter increased from 0.94 to 1.73 m?1, and from 1.70 to 2.22 m?1, respectively during middle and large wind waves. Relative contributions of absorption coefficients of non-algal particulate matter to total absorption coefficient integrated over the range of PAR were 44.14%, 65.05%, respectively, during middle and large wind waves. PAR euphotic depths decreased by 0.40, 0.19, 0.20 m from middle to large wind waves in Longganhu Lake, Meliang Bay and littoral zone near TLLER. Significant correlations were found between transparency, PAR diffuse attenuation coefficients, euphotic depths and total suspended particulate matter, wind velocity, wave height. Most significant correlations were found between transparency, PAR diffuse attenuation coefficients, euphotic depths and inorganic suspended particulate matter but low correlations for chlorophyll a, dissolved organic carbon. Increase of total suspended particulate matter, especially inorganic suspended particulate matter caused by wind waves was the dominant factor affecting underwater light field in shallow lakes in the middle and lower reaches of the Yangtze River based on observations at three stations.  相似文献   

9.
After having estimated the patterns of flow to the ocean and found some seasonal and tidal differences, mainly with regard to the relative importance of dissolved and particulate fractions, mercury partitioning at the interface between a contaminated lagoon and the Atlantic Ocean was investigated during four tidal cycles in contrasting season and tidal regimes. Mercury was found to be located predominantely in the particulate fraction throughout the year, contributing to its retention within the system. Seasonal conditions, variations in marine and fluvial signals and processes affecting bed sediment resuspension influenced the character and concentration of suspended particulate matter in the water column. Variation in the nature, levels and partitioning of organic carbon in the particulate fraction affected levels of particulate mercury as well as mercury partitioning. These results highlight the dominant role of suspended particulate matter in the distribution of anthropogenic mercury and reinforce the importance of competitive behavior related to organic carbon in mercury scavenging.  相似文献   

10.
Determinations of dissolved reactive and total dissolved mercury, particulate and sedimentary mercury, dissolved organic carbon (DOC), particulate organic carbon (POC) and suspended particulate matter (SPM) have been made in the estuary of river Douro, in northern Portugal. The estuary was stratified by salinity along most of its length, it had low concentrations of SPM, typically <20 mg dm(-3), and concentrations of DOC in the range <1.0-1.8 mg dm(-3). The surface waters had a maximum dissolved concentration of reactive mercury of about 10 ng dm(-3), whereas for the more saline bottom waters it was about 65 ng dm(-3). The surface waters had maximum concentrations of total suspended particulate mercury of approximately 7 microg g(-1) and the bottom waters were always <1 microg g(-1). Concentrations of mercury in sediments was low and in the range from 0.06 to 0.18 microg g(-1). The transport of mercury in surface waters was mainly associated with organic-rich particulate matter, while in bottom waters the dissolved phase transport of mercury is more important. Lower particulate organic matter, formation of chlorocomplexes in more saline waters and eventually the presence of colloids appear to explain the difference of mercury partitioning in Douro estuarine waters.  相似文献   

11.
Based on three continuous in situ underwater light field measurement under different wind waves conditions in Longgan Lake, Meiliang Bay of Taihu Lake in July 2003 and littoral zone near TLLER in July 2004, respectively, the effects of sediment resuspension caused by wind waves on PAR diffuse attenuation, absorption coefficients and euphotic depths are analyzed. In Longgan Lake, PAR diffuse attenuation coefficients during small, middle and large wind waves were 1.74, 2.02 and 2.45 m-1, respectively, and the corresponding PAR spectral diffuse attenuations ranged from 0.98 to 2.97, 1.34 to 3.95 and 1.80 to 5.40 m-1, respectively. In Meiliang Bay, PAR diffuse attenuation coefficients were 2.63, 3.72, 4.37 m-1 during small, middle and large wind waves. PAR diffuse attenuation coefficients increased by 41% and 66% from small to middle, large wind waves, respectively. Absorption coefficients integrated over the range of PAR of CDOM, phytoplankton were 0.26, 0.28 m-1; 0.76, 0.49 m-1, respectively during middle and large wind waves. Absorption coefficients integrated over the range of PAR of non-algal particulate matter and total suspended particulate matter increased from 0.94 to 1.73 m-1, and from 1.70 to 2.22 m-1, respectively during middle and large wind waves. Relative contributions of absorption coefficients of non-algal particulate matter to total absorption coefficient integrated over the range of PAR were 44.14%, 65.05%, respectively, during middle and large wind waves. PAR euphotic depths decreased by 0.40, 0.19, 0.20 m from middle to large wind waves in Longganhu Lake, Meliang Bay and littoral zone near TLLER. Significant correlations were found between transparency, PAR diffuse attenuation coefficients, euphotic depths and total suspended paniculate matter, wind velocity, wave height. Most significant correlations were found between transparency, PAR diffuse attenuation coefficients, euphotic depths and inorganic suspended paniculate matter but low correlations for chlorophyll a, dissolved organic carbon. Increase of total suspended paniculate matter, especially inorganic suspended paniculate matter caused by wind waves was the dominant factor affecting underwater light field in shallow lakes in the middle and lower reaches of the Yangtze River based on observations at three stations.  相似文献   

12.
Concentrations of Cd, Cr, Cu, Ni and Pb were determined in filtered water, suspended particulate matter, and bottom sediments from a 2000 km section of the Ob and Irtysh Rivers. Dissolved Cd, Cr, Cu and Ni concentrations are similar to, or higher than, results from other Russian Arctic and large world river-estuaries. Concentrations of Cd, Cr, Cu, Ni and Pb in suspended particulate matter are generally comparable to results from other Russian Arctic and large world rivers and estuaries. Comparison of trace metal ratios in crustal material and suspended particulate matter and bottom sediment suggests that the source of Cr, Cu and Ni is continental weathering. Particulate Cd and Pb are elevated relative to their crustal abundance, suggesting a source of these metals to the Ob-Irtysh in addition to continental weathering.  相似文献   

13.
Specific features of the concentration dynamics of biogenic substances, organic C, and phytoplankton in the lower reaches of the Selenga and its delta branch are identified. The quantitative and qualitative changes in these components are demonstrated for the conditions of extremely low water abundance. High correlation was shown to exist between variations of the concentrations of nitrate N, mineral P, and phytoplankton biomass.  相似文献   

14.
水下光照分布是影响水生态系统的重要因素,研究光合有效辐射衰减特征对于沉水植物恢复具有一定的指导意义.根据沉水植物生物量资料,将东太湖划分为沉水植物茂盛区、沉水植物稀疏区和无植物区3种区域.基于2019年夏季原位水下光场资料,探讨了东太湖光衰减特性和光照衰减因子的空间差异以及不同区域内的主导衰减因子,分析了东太湖的稳态阶段和富营养化水平,并阐述了真光层深度与透明度的关系,以期为东太湖沉水植物恢复和保护提供相关资料.结果表明:东太湖不同区域光衰减特性差异显著,光合有效辐射衰减系数(k d(PAR))在0.73~11.80 m^-1之间变化,真光层深度范围为0.39~6.31 m.不同区域的无机悬浮物和有机悬浮物浓度存在显著性差异,稀疏区叶绿素a浓度显著高于茂盛区,而与无植物区没有显著差异,有色可溶性有机物(CDOM)吸收系数在3种区域无显著性差异.k d(PAR)与无机、有机悬浮物的线性拟合效果较好,而与叶绿素a、CDOM拟合较差.水体吸收和散射作用是茂盛区光衰减的主要原因,无植物区域主导衰减因子仅有无机悬浮物,稀疏区由叶绿素a和无机悬浮物共同主导,是生态修复需要重点关注的区域,有机悬浮物和CDOM对东太湖光照衰减没有太大影响.东太湖目前正处于从草型稳态向藻型稳态过渡的阶段,整个湖泊属于富营养水平,真光层深度大约为透明度的2.7倍.  相似文献   

15.
The iodine content of marine suspended matter obtained from thirteen stations in the Atlantic between 75°N and 55°S has been measured. The concentration of particulate iodine is high in the surface, up to 127 ng/kg of seawater being observed. Below the euphotic zone, it drops sharply to 1–2 ng/kg. The iodine-containing particles are probably biogenic. A simple box-model calculation shows that only 3% of the particulate iodine produced in the surface water may reach the deep sea and that the residence time of these particles in the surface water is about 0.1 year.  相似文献   

16.
The retention of particulate matter of the Odra River in flooded areas was estimated by determining suspended particulate matter (SPM) elimination and particle-bound nutrient retention in a polder area of the Lower Odra Valley national park. Water and suspended matter samples collected before, during, and after the 1997 summer flood at the inlet and the outlet of the investigated polder (Polder A/B close to Schwedt) offer the opportunity to balance the matter retention inside the floodplain. The maximum level of retained SPM (more than 80%) was calculated for the record flood of summer 1997, while in ordinary winter floods retention differs between 33% and 70%. Basic properties of the flowing particles like settling velocity, density, loss on ignition etc. change on their way through the polder area. In the investigated Polder A/B a retention of at least 50% of particle-bound phosphorus which was independent of the incoming suspended matter load from the Odra River was observed. The retention of particle-bound nitrogen and carbon varied seasonally to different extents. The presented balance demonstrates that particle-bound nutrient retention in polders is an important factor in the self-purification process of the river system. Some additional effort was done to study changes of plankton composition: during a joint field experiment in spring 1998, the authors determined biological parameters (abundance and biomass of phytoplankton and zooplankton) of water samples at polder inflow and outflow points.  相似文献   

17.
Previous studies have shown how biogenic silica particles undergo conversion to aluminosilicate phases in large tropical deltaic systems, thus affecting the world ocean budget of major seawater cations. This study tackles the important question of the silica budget in the coastal zone of the Mississippi River Delta, providing evidence for the role of biogenic silica diagenesis in this subtropical system from direct examination of individual diatom particles, sediment leachates and pore-water composition. The estimated reactive silica stored in the study area (5990 km2) is based on operational leaches that account for altered biogenic silica particles and other authigenic aluminosilicate phases in addition to fresh biogenic silica. Early diagenesis of silica in the delta front occurs mainly where more siliceous material is deposited. An inner-shelf area, where hypoxic conditions are found, significantly contributes to the formation of authigenic products of Si alteration. Data suggest that the limiting factor of silica alteration processes is the availability of detrital phases such as Al and Fe. The estimated total reactive silica accumulation in the study area is 1.45×1010 mol Si year−1, representing ∼2.2% of the long-term bulk sediment accumulation. On the basis of a conservative appraisal, the authigenic mineral components account for ∼40% of the long-term reactive silica storage. This study shows that non-tropical deltaic systems are significantly more important sinks of silica than previously thought and that, where conditions are favourable, a consistent portion of reactive silica not leaving the shelf is stored within the delta in the form of authigenic components.  相似文献   

18.
The concentrations of particulate and dissolved organic matter and mineral nutrients in the Lena River and its major tributaries are analyzed. The concentrations of these components are shown to be nonuniform and feature wide variations under the effect of matter input by major tributaries. The total fluxes of matter increase downstream the river in agreement with increasing water runoff. The effect of delta in matter accumulation is considered. The organic matter in the Lena was found to be represented mostly by soil terrigenous material.  相似文献   

19.
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20.
Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail.In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4–11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by cross-checking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR50 and pIRIR160) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR160 dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of ∼3 Gy ka−1). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ∼6 ka between 9.65 and 5.50 m in core H1 and ∼2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR160 signals suggest less light exposure of the core top sediments and of those from the transition layer between ∼6 ka to ∼2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.  相似文献   

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