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1.
Resuspension of inorganic sediments in a very shallow Swedish lake is studied using settling sediment traps and measurements of suspended matter. Theoretical aspects of resuspension dynamics is discussed emphasizing special shallow lake aspects. Bottom shear stress distribution is computed for different wind conditions. 相似文献
2.
Estimation of the in-situ settling velocity of particles in lakes using a time series sediment trap 总被引:4,自引:0,他引:4
SUMMARY 1. We outline a simple method for estimating the in-situ settling velocity of particles in wind disturbed lakes. The total sedimentation rate (primary and secondary sedimentation) was measured during storm events in two lakes using a time series sediment trap.
2. The sediment trap had 12 sample bottles which were programmed to open for periods of 3–4 h, giving total deployment times ranging from 36 to 48 h.
3. Wave mixed layer theory was used to infer if and when sediment resuspension occurred and the first order rate equation was used to estimate the settling velocity of resuspended particles.
4. The settling velocity during three resuspension events in Lough Neagh and one in Lough Macnean were 34.3, 29.5, 24.1 and 77.3 m day−1 , respectively. These are similar to values obtained using recent in-situ video imaging in marine environments, but much larger than previous lake sediment trap studies. 相似文献
2. The sediment trap had 12 sample bottles which were programmed to open for periods of 3–4 h, giving total deployment times ranging from 36 to 48 h.
3. Wave mixed layer theory was used to infer if and when sediment resuspension occurred and the first order rate equation was used to estimate the settling velocity of resuspended particles.
4. The settling velocity during three resuspension events in Lough Neagh and one in Lough Macnean were 34.3, 29.5, 24.1 and 77.3 m day
3.
A. A. Koelmans 《Hydrobiologia》1997,364(1):15-29
This study describes the 1987–1992 time variationof the bulk chemical composition, levels of heavymetals, arsenic, nitrogen
and phosporous insuspended and settling solids in Lake Volkerak andLake Zoom (The Netherlands). Suspended and setlingsolids
were collected with continuous flowcentrifuges and sediment traps, respectively. Therelations between solids characteristics
and metalconcentrations in the particles were investigatedusing correlation and factor-analysis. Heavy metals,except manganese,
were associated with clay contentof the particles and with organic carbon which wasmainly determined by phytoplankton growth.
Manganesewas correlated with Org-C only. Clay and organicmatter with associated heavy metals showed negativetrends on all
locations, and a seasonality due toalgal biomass dilution. It is concluded that thetrophic state significantly affects trace
metalcycling. Sediment traps collect different types ofparticles than continuous flow centrifuges. Thetraps collect particles
with higher clay content,lower Org-C concentrations and higher Org-C/Nelemental ratios than the centrifuges.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The rates of the processes of bacterial sulfate reduction (SR) and total destruction of organic matter (Dtotal) were studied in the bottom sediments (BS) of 14 lakes in Lithuanian national and regional parks in the summers of 1998–2002. Anaerobic processes accounted for an average of 92% of Dtotal in the depressions of deep-water lakes; for the sediments of shallow lakes, high rates of oxygen uptake were noted. The SR rate in different lakes varied from 0.09 to 2.60 mg S2?/(dm3 day). At low sulfate concentrations (13.3–70.6 mg S-SO 4 2? /dm3), characteristic of the BS of freshwater ecosystems, the main factor that affected the SR rate in the BS of the lakes studied was the content of readily available organic matter; only in special cases, was it affected by a change in the sulfate ion concentration. In shallow lakes, temperature-dependent activation of sulfate-reducing bacteria and their inhibition by acidification of the environment were recorded. The contribution of SR to Dtotal was 0.2 to 11.0%. 相似文献
5.
Anders Broberg Louise Malmgren Mats Jansson 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1995,4(4):285-294
In many Swedish lakes, the fallout of 137Cs from the Chernobyl accident in April 1986 has largely accumulated in the sediments. The availability and transfer of deposited 137Cs to biota is influenced by factors such as resuspension. The frequency of resuspension and the 137Cs-content of different fish species was studied in three shallow lakes in Uppland, central Sweden, and in one deeper lake in northern Sweden. Resuspension was measured by the use of sediment traps. Sedimentation rates measured from the traps in the shallower lakes were 5–10 times higher than normal for this type of lake, indicating that resuspension was an important factor. The decrease of the 137Cs-content in muscle tissue of pike, perch and roach was slow in each of the shallow lakes. 137Cs decreased by about 30% over a period of 2 years in the shallowest lake (maximum depth 4 m), whereas 137Cs decreased by 50% in the deeper lakes (maximum depth 10 m). The slower rates of decline of 137Cs in biota from the shallow lakes, are probably a function of sediment dynamics (mainly influenced by lake morphometry, wind direction and strength). They may be influenced, also, by bioavailability of resuspended sediment material. In the deepest northern lake, much of the 137Cs-containing material collected in the sediment traps originated from the catchment area. Resuspension was minimal, and the high activity of 137Cs in the sediment had no effect on content or decline of 137Cs in lake fish. 相似文献
6.
The objective of this project was to evaluate the changing composition and structure of the sediment-associated organic matter (OM) stored in the gravel bed of highly productive salmon-bearing streams and, determine if the OM changes affect the morphology and settling rates of the sediment. In July of 2001, a dozen infiltration gravel bags were buried in the channel bed of O'Ne-eil Creek in northern British Columbia (Canada) to collect fine sediment and the associated organic matter for chemical and morphological analysis. The bags were removed over a 10 week period which incorporated summer low flows, salmon spawning, salmon die-off and the onset of autumn low flow conditions. Our results indicate two visibly different structures in the organic matter film overlying the mineral material of the flocs. A web-like structure was noted during mid-spawn while a film-like covering was observed in pre-spawn and post-fish periods. The strength of the film-like covering is surmised to be associated with the larger gravel-stored floc sizes noted at these times. Chemical analysis of these biofilms indicated higher metal complexation properties during the spawning periods as opposed to before or after salmon were present. The changing OM contributions were associated with changes in floc size, density and settling rates. The physical disturbance to the gravels associated with spawning salmon was also correlated with altered characteristics of the gravel-stored flocs. 相似文献
7.
Petra Porcalov 《International Review of Hydrobiology》1990,75(3):273-279
The amount of settling phosphorus was measured in Římov Reservoir using sediment trap technique from April 1986 to April 1987. Sediment traps were placed at three depths near the dam of the reservoir and at the bottom along the reservoir. The highest amount of phosphorus in trapped material was found during the fall turnover in the epilimnion and near the bottom in both spring periods (1986,1997). During the growing season the changes in dry weight and total phosphorus in settling seston were related to changes of phytoplankton biomass in the trophogenic layer. The amount of trapped phosphorus was higher near the bottom than in the upper layers of the reservoir throughout the year. 相似文献
8.
Deepwater sediments and trophic conditions in Florida lakes 总被引:3,自引:2,他引:1
Sediment cores were taken from near maximum depth in 15 Florida lakes representing a wide range of trophic conditions. Chemical
analyses of surface sediments showed Al, Fe, and Ca to be the most abundant elements in all samples, and the ratio of Al to
Ca to be smaller for eutrophic lakes. Sediment organic matter increased with trophic state, as did the degree to which it
was enriched in nitrogen. Corresponding sediment C/N ratios decreased with increasing lake trophic state and showed significant
negative correlation with chlorophylla, total N, and total P in the water column. Concentrations of sedimentary chlorophyll derivatives showed some relation to
trophic state but differences in basin morphometry hinder its use as an inter-lake index of chlorophyll production. 相似文献
9.
The anthropogenic stable lead content of the sediments of eight softwater Precambrian lakes in southern Ontario was measured at 34–92 sites per lake. Whole-lake anthropogenic lead burdens varied between only 610 and 770 mg m–2. There was no relationship between lead burden and either water replenishment time of the lake (TW) or the ratio of watershed area to lake area (Ad/A0), which varied by factors of 4 and 12 respectively. These results can be explained if a) the lead deposition in this region is uniform, and b) the only significant input of lead to the lakes is via deposition from the atmosphere directly on the lakes' surfaces. Therefore spatial differences in anthropogenic lead within a lake represent the redistribution or focusing pattern of the sediments. 相似文献
10.
Bottom dynamics in lakes 总被引:4,自引:4,他引:0
A proper understanding of the bottom dynamic conditions (erosion, transportation, accumulation) in lakes is essential in most
sedimentological contexts. Fine cohesive materials generally dominate the open water areas, whereas coarser deposits (sand,
gravel) dominate shallow regions where erosion and transportation of fine materials prevail. At present, there is no physical
model available which describes the linkage between the energy content of the water-mass and the capacity for sediment entrainment
in open water areas. Water-mass energy depends on, e.g. wind direction, duration, velocity, fetch, and the presence of a thermocline.
Entrainment depends on, e.g. density, compaction, water and organic content of the sediments and the number and type of bottom
fauna.
Four different methods are used to determine bottom dynamics, two aresite typical and two arelake typical.Site andlake typical methods each include one method based on collected field data and one based on theoretical data. One method, the
cone apparatus, is presented for the first time. It consists of two cones, one of which has a narrow angle and the other a
wide angle, which are zero adjusted at the sediment surface before being released to penetrate the sediments. The differential
cone penetration, refered to as the penetration ratio, is used to indicate the degree of surficial sediment compaction. This
simple, inexpensive instrument provides quantitative data on physical sediment characteristics which may be related to bottom
dynamic conditions. 相似文献
11.
Sedimentation in the Gouet reservoir (France), measured for 2 years at 8 stations, was maximal during summer, when river inputs
were minimal. Physical and chemical conditions in the deposits indicate that the endogenous part of sedimentation was about
70% and resulted from significant diatom production. The high sedimentation rate on the bottom was favoured by the funnel
morphology of the reservoir, the chronic lack of oxygen in the water column, and the repeated copper sulfate treatment. The
former river meanders of the reservoir were the preferential deposit sites. 相似文献
12.
Inorganic and organic nutrients are continuously transported to lake bottoms by sedimentation. By various biological, physical, chemical and mechanical processes quantities of certain nutrients can be brought back to the free water again. This cycling between the sediments and water may occur according to various schemes dependent on lake type and bottom conditions. Lake morphology, temperature regimes, trophic level and sediment type can all strongly influence the size of nutrient pools and rates of turnover.The various activities of bacteria, benthic algae, macrophytes, benthic invertebrates and fish, in conjunction with influences of temperature, pH-values, Eh-values, water content, organic matter and elemental sediment composition, lead to the extremely complex nature of nutrient cycling. Three essential components of aquatic ecosystems are discussed, namely carbon, nitrogen and phosphorus.The objective of this paper is to illustrate in condensed form the heterogeneous nature of nutrient cycling processes. In addition, the importance of sediments in understanding nutrient cycling is discussed from a water management perspective. 相似文献
13.
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15.
The distribution of zinc in Lake Vanajavesi and Lake Mallasvesi, South Finland, was determined on the basis of water and sediment
studies. Lake Vanajavesi is one of the most polluted of large inland lakes, in Finland. The zinc load comes mainly from industrial
sources. Lake Mallasvesi, situated near Vanajavesi, is in almost natural condition. The water samples were taken by a Ruttner
sampler. In collecting sediment samples, a freezing technique was used. The results of zinc analyses indicate that, during
several winters, zinc has spread with waste water to different parts of L. Vanaja against the main course of flow. A close
correlation between sedimentation of zinc and waste discharge from a textile factory was found in the present study. 相似文献
16.
Ingemar Renberg 《Hydrobiologia》1986,140(1):93-95
Several lakes in northern Sweden have laminated sediments, of which many are interpreted as varved (annually laminated). In one of these lakes, a core of the recent sediment has been sampled annually since 1979 (except 1984). These cores verify that one varve, comprising of a thick summer layer (often colour-banded) and a thin winter layer, is formed each year. The cores also show, that, other than compaction, no change in visual appearance of the individual varves takes place after they have been overlain by new varves. 相似文献
17.
Recent work on the settling, diffusion, entrainment, and deposition of fine-grained sediments in fresh water is reviewed and
synthesized. Particular attention is given to the dependence of these processes on sediment properties such as particle size.
The application of this knowledge to the analysis and numerical modeling of sediment transport is also discussed. Much of
the work is concerned with the Great Lakes and, more specifically, with the Western Basin of Lake Erie. 相似文献
18.
T. Wiederholm 《Hydrobiologia》1984,109(3):243-249
The occurrence of deformed mouth parts in recent and subfossil material of mostly Chironomus, Micropsectra and Tanytarsus increased from less than 1 % of the larvae at unpolluted sites or time periods to figures in the range of approx. 5–25% at strongly polluted sites. Deformities occurred in species that are widely separate in taxonomic position and way of living. Several heavy metals are suspected causative agents. Deformities in various mouth parts are illustrated by SEM photographs. 相似文献
19.
Lead-210 dating of sediments compared with accumulation rates estimated by natural markers and measured with sediment traps 总被引:5,自引:3,他引:2
Methods to provide accurate accumulation rates for lake models are discussed. Cores were taken in 1979 in two basins of Lake Lucerne, Switzerland, and accumulation rates were calculated by using Pb-210 dating and by a natural landslide marker of 1795 in one basin (Weggis). In the other basin (Horw Bay) the sediment accumulation rates based on the lead method were compared with yearly sedimentation rates measured by sediment traps in 1969/70. At the Weggis station, the core dating yielded sediment accumulation rates of about 400 g dry wt. m–2 y–1 with the lead method, averaged over a sediment depth of 4–20 cm; accumulation was about 700 g dry wt. m–2 y–1 with the marker method, averaged over 0–33 cm. In Horw Bay, the trap method yielded about 1300 g dry wt. M–2 y–1 compared with 400–1000 g dry wt. m–2 y–1 obtained with the lead method and related to various depth intervals. The characteristic sources of error of the three methods as well as several hypotheses for these discrepancies are discussed. 相似文献
20.
Deposition,resuspension, and decomposition of particulate organic matter in the sediments of Lake Itasca,Minnesota, USA 总被引:7,自引:2,他引:5
Sediment traps were used to investigate the settling, resuspension, and decomposition of particulate organic matter in Lake Itasca, MN (USA). Traps were deployed in the epilimnion and hypolimnion of the deepest basin during June, 1988, sampled twice during stratified conditions (August, September) and once after the lake had mixed (October). The downward flux of particulate material increased from summer to fall. The net sedimentation of organic matter ranged from 0.6 to 2.3 g m–2 d–1 at 4 m and increased to 2.1 to 3.2 g m–2 d–1 two meters above the bottom sediment indicating that resuspended sediment was at least 33% of the settling mass during all periods. The C:N ratios of captured particles (6.8–9.5) were between the ratios of plankton (5.8 to 6.8) and the sediments (9.9 to 10.2) but smaller than the ratios of terrestrial organic materials (13.5 to 222). The monosaccharide compositions of the entrapped particles were similar to plankton samples and different from the distinct composition of the sediments. Capture of rebound particles similar to the primary flux and not decomposition may have been responsible for this similarity. Total monosaccharide concentrations were lower in the sediments than in entrapped particles. Individual sugars exhibited different patterns of accumulation in the sediments. Glucose was lowest in sediments when the relative concentrations were compared to those in source materials and entrapped particles. In contrast, sediments had the highest rhamnose and fucose concentrations. Bacterial biomass could only account for small portions of these sugars in the sediment. The distinct monosaccharide composition of resuspended sediments was not strongly recorded in materials captured by the sediment traps even after the lake had mixed. 相似文献