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At least 991 records · Page 55Linked to original sources
PubMed2002

Sediments and sediment-derived soils in Illinois: pedological and agronomic assessment.

Dredging sediments from water bodies in Illinois is done to preserve reservoir capacity, maintain navigation and recreation channels, and restore habitats, but the fate of the sediments is an issue. In anticipation of a major sediment dredging operation in Lake Peoria in the Illinois River, a retrospective study of sediment placement operations was performed. Sediments previously dredged from reservoirs and placed in retaining ponds were sampled along with adjacent upland soils which served as references. Sediments from the Illinois River above Peoria were sampled from islands, river bottom, and adjacent floodplain. Dredged sediment retention ponds initially support wetland vegetation. After dewatering, the physical properties of sediments tend to become similar to upland soils and the retention basins are then able to support conventional agriculture. Sediment organic matter content was similar to local reference surface soils, and soil pH of the sediments was neutral or above. Sediment textures are dominated by silts and clays, with the Lake Peoria samples being most clayey. Calcium was the dominant cation in all the samples, and micronutrients measured were in adequate supply for plant growth. However, because the Illinois River watershed includes industrial inputs, river sediments contained elevated levels of some metals, but they were generally below levels of regulatory concern. Results indicated that properly handled dredge sediments could make high quality agricultural soils. In addition, sediment placement on poor soils could improve their productivity.

Agriculture↗
PubMed2002

Effects of phenanthrene on lemna minor in a sediment-water system and the impacts of UVB.

The objective of this study was to evaluate if the Lemna-bioassay is appropriate to test contaminated sediments. A mixture of sand was spiked with phenanthrene to investigate whether sediment-bound pollutants can affect the plants via direct contact of the roots or the underside of the leaves. After 24h of equilibration for sorption/desorption processes, the test was carried out in the sediment-water mixture, and another test was performed with the aqueous phase which was separated from the sediment. The growth inhibition of Lemna was nearly the same in both tests. Hence it follows that the toxicant is adsorbed from the aqueous phase via the underside of the leaves and sediment bound phenanthrene is not bioavailable. Polycyclic aromatic hydrocarbons are known to show photoinduced toxicity to plants in the presence of UV which is a result of photosensitization reactions in the plant and photomodification to more toxic and better soluble photoproducts. Photoinduced toxicity could be observed in the water phase during UVB treatment, whereas the presence of suspended sediment probably lowered the UV intensity, resulting in a lower growth inhibition.

Araceae↗
PubMed1999

Environmental factors affecting the occurrence of mycobacteria in brook sediments.

The occurrence of mycobacteria was studied in aerobic brook sediments from 39 drainage areas in Finland. The culturable counts of mycobacteria were related to climatic conditions, characteristics of the drainage area, chemical characteristics of the sediment and water, culturable counts of other heterotrophic bacteria, and microbial respiration rate in the sediment. The counts of mycobacteria varied from 1.1 x 10(2) to 1.5 x 10(4) cfu g-1 dry weight of sediment. They correlated positively with the proportion of the drainage area consisting of peatland, total content of C, content of Pb, microbial respiration rate in the sediment, and chemical oxygen demand of the water. The correlations of the mycobacterial counts with pH of sediment and alkalinity of water were negative. The results of the present sediment study and of the forest soil study published earlier strongly suggest that an increase in acidity increases the counts of mycobacteria and decreases the counts and activity of other heterotrophic bacteria. Mycobacterial counts were more than 100 times higher (per dry weight) in forest soils with pH 3.5-4.3 than in sediments with pH 4.5-6.3.

Climate↗
PubMed2005

The role of a salt marsh plant on trace metal bioavailability in sediments. Estimation by different chemical approaches.

GOAL, SCOPE AND BACKGROUND: The presence or absence of vegetation can condition sediment characteristics. The main aim of this work was to investigate the influence of the sea rush Juncus maritimus on metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) availability to organisms living on or in estuarine sediments, from Douro River (NW Portugal), by comparing the characteristics and chemical behaviour of rhizosediments (collected within the plant assemblage) and those of sediment (collected around the plant). In order to evaluate whether and how sediment characteristics condition the role of plants on metal availability, sandy and muddy sediments colonised by J. maritimus were studied in parallel. METHODS: Metal availability was estimated by enzymatic digestion with pepsin (ED), which may provide an estimate of metal availability to organisms living at estuarine sediments. Nevertheless, since no consensus exists yet on the most suitable methodologies to estimate metal bioavailability in sediments, two more conventional approaches, BCR sequential extraction (SE) and AVS/ SEM model, were also used, in parallel, and the information these approaches provided was compared with that provided by ED. Total-recoverable metal contents were determined by atomic absorption spectrophotometry after sediment digestion using a high-pressure microwave system. RESULTS AND DISCUSSION: Plants could concentrate metals around its roots and rhizomes. In addition, they were capable of oxidizing (release of oxygen by the roots) the anaerobic medium surrounding their roots in muddy sediment (reducing AVS). As sulphide oxidation renders metals (Cd, Cu, Ni, Pb and Zn) into more soluble forms, according to the AVS/SEM model, metals from muddy sites would be more available in rhizosediment than in sediment. The SE approach led to a similar conclusion. Nevertheless, the results provided by ED pointed at opposite conclusion, particularly for Cd and Zn, indicating less availability at rhizosediments than in the surrounding sediment. ED results were interpreted as a consequence of an enrichment of the rhizosediment in organic ligands exuded by the roots or liberated by dead plants. The effect of complexation of metals by organic compounds, which ED could not decompose/dissolve, seemed to overcome that caused by sediment oxidation. In general, a comparison of the informa tion about metal availability by ED, SE, AVS/SEM, showed that it did not always match and in few cases it was even contradictory. CONCLUSION AND OUTLOOK: Therefore, a thorough evaluation of the metal availability in sediments requires a combination of different chemical approaches, so as to take into consideration differences in ways of organism exposure (interstitial water and/or ingestion of sediment particles).

Bacteria, Anaerobic↗
PubMed2002

Vertical distribution and abundance of gymnamoebae (Rhizopoda) in bottom sediments of the brackish water Nivå Bay (Baltic Sea, The Sound).

The sandy sediments of Nivå Bay (Baltic Sea, The Sound, Denmark) are often covered with the mats of sulphur bacteria and are temporarily anoxic. The vertical distribution and abundance of naked amoebae species in three sediment cores from this bay were studied. Amoebae were most abundant and diverse in the upper 1 cm of sediment, and their number and diversity decreased with increasing depth into the sediment. Amoebae were recovered from both upper oxygenated and deep anoxic layers of sediments. The species composition and abundance of amoebae was very heterogeneous, even at spatial scales of several centimeters, suggesting the existence of microhabitats selectively occupied by particular species. All species found were recorded from aerobic cultures and some of these amoebae occur in both the aerobic and anaerobic layers of the sediment. Minimal possible number of amoebae in the sediments, estimated for the first time as areal abundance integrated for depth was: core 1 -597 cm(-2); core 2 -1,110 cm(-2); core 3 -1,430 cm(-2). These abundances are probably best regarded as "potential" abundances of amoebae hidden in the sediments, as the question of the ratio between active and resting amoebae remains open.

Amoebida↗
PubMed2004

Graphite electrodes as electron donors for anaerobic respiration.

It has been demonstrated previously that Geobacter species can transfer electrons directly to electrodes. In order to determine whether electrodes could serve as electron donors for microbial respiration, enrichment cultures were established from a sediment inoculum with a potentiostat-poised graphite electrode as the sole electron donor and nitrate as the electron acceptor. Nitrate was reduced to nitrite with the consumption of electrical current. The stoichiometry of electron and nitrate consumption and nitrite accumulation were consistent with the electrode serving as the sole electron donor for nitrate reduction. Analysis of 16 rRNA gene sequences demonstrated that the electrodes supplied with current were specifically enriched in microorganisms with sequences most closely related to the sequences of known Geobacter species. A pure culture of Geobacter metallireducens was shown to reduce nitrate to nitrite with the electrode as the sole electron donor with the expected stoichiometry of electron consumption. Cells attached to the electrode appeared to be responsible for the nitrate reduction. Attached cells of Geobacter sulfurreducens reduced fumarate to succinate with the electrode as an electron donor. These results demonstrate for the first time that electrodes may serve as a direct electron donor for anaerobic respiration. This finding has implications for the harvesting of electricity from anaerobic sediments and the bioremediation of oxidized contaminants.

Anaerobiosis↗
PubMed1999

Phylogenetic affiliation and quantification of psychrophilic sulfate-reducing isolates in marine Arctic sediments.

Thirteen psychrophilic sulfate-reducing isolates from two permanently cold fjords of the Arctic island Spitsbergen (Hornsund and Storfjord) were phylogenetically analyzed. They all belonged to the delta subclass of Proteobacteria and were widely distributed within this group, indicating that psychrophily is a polyphyletic property. A new 16S rRNA-directed oligonucleotide probe was designed against the largest coherent cluster of these isolates. The new probe, as well as a set of available probes, was applied in rRNA slot blot hybridization to investigate the composition of the sulfate-reducing bacterial community in the sediments. rRNA related to the new cluster of incompletely oxidizing, psychrophilic isolates made up 1.4 to 20.9% of eubacterial rRNA at Storfjord and 0.6 to 3. 5% of eubacterial rRNA at Hornsund. This group was the second-most-abundant group of sulfate reducers at these sites. Denaturing gradient gel electrophoresis and hybridization analysis showed bands identical to those produced by our isolates. The data indicate that the psychrophilic isolates are quantitatively important in Svalbard sediments.

Arctic Regions↗
PubMed2004

Effects of exposure to a combination of zinc- and lead-spiked sediments on mouthpart development and growth in Chironomus tentans.

Exposures to either zinc or lead in contaminated sediments have been shown to induce characteristic deformities in larval chironomids. This study examined the effects of exposure to lead and zinc in combination on Chironomus tentans larvae. Proportions of mouthpart deformities in populations of larvae reared in sediments containing nominal combinations of lead and zinc were tested for additive, synergistic, and antagonistic interactions using logistic regression. Metal body burdens, body size measurements, and survival were used to evaluate toxicity and developmental impacts. Results demonstrate zinc and lead mixtures produce fewer deformities than the individual metal, so their interaction may be characterized as antagonistic. However, exposure to the metal mixtures also caused delayed development and failure to hatch. The apparent decline in deformities may be an artifact of higher mortalities or developmental effects. This research provides better understanding of some of the problems and considerations for use of chironomid population deformity proportions in bioassessments for sediment metal contamination.

Animals↗
PubMed2004

Effects of the pesticides captan, deltamethrin, isoproturon, and pirimicarb on the microbial community of a freshwater sediment.

In three microcosm experiments, we exposed microbial communities of a natural sediment to environmentally relevant concentrations of the fungicide captan, the herbicide isoproturon, and the insecticides deltamethrin and pirimicarb. Exposure concentrations were estimated negligible concentrations (NCs), maximum permissible concentrations (MPCs), and 100 times MPC (100MPC). Experimental endpoints were microbial community respiration and biomass, bacterial activity, and denitrification. All four pesticides inhibited bacterial activity by 20 to 24% at MPC, which corresponded to concentrations in the range of microg/kg dry-weight sediment. Treatments with deltamethrin and isoproturon showed inhibiting effects on bacterial activity at NC exposures. Surprisingly, for captan, deltamethrin, and isoproturon, this inhibiting effect was not observed at 100MPC treatments. Microbial biomass was negatively effected in MPC treatments with deltamethrin and in NC treatments with isoproturon. The tested pesticides did not affect community respiration and denitrification rates. These results show that exposure to the tested pesticides may induce toxic responses in sediment microbial communities at concentrations that are predicted to be environmentally safe.

Bacteria↗
PubMed2005

Light as a confounding factor for toxicity assessment of complex contaminated sediments.

Polycyclic aromatic hydrocarbons (PAHs) are contaminants often found in sediments. Their relevant contribution to toxic effects induced by environmental samples has been demonstrated using effect-directed analysis (EDA). Toxicity of PAHs previously has been reported to depend on light conditions. The aim of this study was to analyze the influence of simulated sunlight, in comparison to standard algal growth light, on the toxicity of samples, in which PAHs were identified as major toxicants using EDA. Additionally, toxicity of identified toxicants and mixtures of these compounds were assessed. It can be shown that the samples, the PAH compounds, and the created mixtures exhibit photoenhanced toxicity. The combined effects of the mixtures can be predicted using the model of concentration addition. This is surprising because different modes of action have been reported to contribute to phototoxicity of the identified toxicants. For the confirmation step in EDA, the toxicity assessment under simulated sunlight reveals that less of the samples' toxicity can be explained by the identified compounds, compared to the assessment conducted under standard growth light. Finally, the relevance of light conditions in the toxicity assessment is demonstrated for eight out of 13 transect samples of sediment extracts from river Elbe, Germany.

Confounding Factors, Epidemiologic↗
PubMedDate not supplied

Fate and toxicity of endosulfan in Namoi River water and bottom sediment.

Endosulfan (6,7,8,9,10,10,-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) sorption (standardized to 1% total organic carbon and dry weight) was significantly (P < 0.05) more concentrated on the large (>63 microm) particle fraction compared with smaller size fractions (<5 microm and 5-24 microm) of bottom sediments from the Namoi River, Australia. Following completion of the particle size fractionation (6 to 12 wk) and a sediment toxicity assessment (2 wk), the sediments showed large decreases in concentrations of alpha-endosulfan that coincided with an increase in endosulfan sulfate concentrations and minimal changes in beta-endosulfan concentrations. In the Namoi River, similar patterns were observed in the composition of total endosulfan in monthly measurements of bottom sediments and in passive samplers placed in the water column following runoff from cotton (Gossypium hirsutum L.) fields. The toxicity of endosulfan sulfate in river water indicated by the nymphs of the epibenthic mayfly Jappa kutera, was more persistent than the alpha- and beta-endosulfan parent isomers due to its longer half-life. This suggests that endosulfan sulfate would contribute most to previously observed changes in population densities of aquatic biota. Measured concentrations of total endosulfan in river water of up to 4 microg L(-1) following storm runoff, exceed the range of the 96-h median lethal concentration (LC50) values in river water for both alpha-endosulfan (LC50 = 0.7 microg L(-1); 95% confidence interval [CI] = 0.5 to 1.1) and endosulfan sulfate (LC50 = 1.2 microg L(-1); 95% CI = 0.4 to 3.3). In contrast, the 10-d LC50 value for total endosulfan in the sediment toxicity test (LC50 = 162 microg kg(-1); 95% CI = 120 to 218 microg kg(-1)) was more than threefold higher than the highest measured concentration of total endosulfan in field samples of bottom sediment (48 microg kg(-1)). This suggests that pulse exposures of endosulfan in the water column following storm runoff may be more acutely toxic to riverine biota than in contaminated bottom sediment.

Animals↗
PubMedDate not supplied

Microcosm studies on anaerobic phosphate flux and mineralization of lake sediment organic carbon.

Lake sediment has long been recognized as an important source of nutrients such as phosphorus. To gain a better understanding of phosphorus flux at the sediment-water interface, it is crucial to investigate the sediment porewater. There is also growing concern and interest in identifying whether organic-rich sediment is an important source of greenhouse gases such as CO(2) and CH(4). In the present study, we took sediment samples from West Lake, a shallow hypereutrophic lake in Hangzhou, Zhejiang Province, China and incubated subsamples under anaerobic conditions at 25 degrees C for 182 d using a specially designed microcosm that permits repeated extraction of sediment porewater and sampling of headspace gases. Anaerobic phosphate fluxes and mineralization of sediment organic carbon were measured. Average diffusive flux of soluble phosphorus was 0.81 mg P m(-2) d(-1) during the initial 18 d of incubation. Decomposition of sediment organic C followed zero-order reaction kinetics and methane accounted for about 50% of the mineralization products. The results suggest that organic-rich sediments can be important sources of P and methane under anaerobic conditions. Laboratory studies simulating field conditions and field studies are necessary to determine the contribution of sediment as a source of P and greenhouse gases.

Carbon↗
PubMed2006

Phosphorus sorption by sediments in a southeastern coastal plain in-stream wetland.

A close relationship has been reported between sediment organic C (SedOC) content and its P sorption capacity (P(max)) and total P (TP) concentration. Phosphorus sorbed to organically complexed cations is a proposed explanation for this relationship. The objectives of this study were (i) to determine relationships between in-stream wetland SedOC content and both the sediment's P(max) and TP concentrations, and (ii) to ascertain the role of both organically complexed and oxalate-extractable cations on the sediment P(max) and TP values. The sediment's oxalate-extractable Fe (Fe(ox)) and Al (Al(ox)) contents were determined using acidified ammonium oxalate, while sodium pyrophosphate was used to extract organically complexed cations (Al(pryo), Ca(pyro), Fe(pyro), Mg(pyro), and Mn(pyro)). Both the sediment's P(max) and TP contents were strongly correlated with its SedOC concentration (r(2) > 0.90, P < 0.001). Only the Al(ox) contents were significantly correlated with TP and P(max), suggesting that amorphous Al forms have an important role in P sorption. All five pyrophosphate-extracted cations were significantly correlated with SedOC contents. Regression analyses showed that the Al(pyro) accounted for 88% of the variation in sediment P(max) values, whereas a combination of Al(pyro) and Ca(pyro) accounted for 98% of the variation in sediment TP concentrations. Additionally, Al and Ca chelated by SedOC compounds also have an important role in P binding and indicate that a linkage exists between the wetlands SedOC and P(max) content and its ability to accumulate TP. This study identified that two different mechanisms have significant roles in regulating P sorption by sediments in a southeastern Coastal Plain in-stream wetland.

Adsorption↗
PubMed2006

Trace metal levels in sediments deposited in urban stormwater management facilities.

Characteristics of solids recovered from stormwater best management practice (BMP) facilities, including stormwater ponds, constructed wetlands, an infiltration basin, a biofilter, a stormwater treatment clarifier, and three-chamber oil and grit separators were described with respect to their metal chemistry. The reported trace metal concentrations in BMP sediments were assessed against the Ontario Sediment Quality Guidelines. Between 80 to 100% of all samples were marginally-to-intermediately polluted by Cd, Cr, Cu, Fe, Pb, Mn, Ni and Zn. Severe pollution of sediments was noted for Cr (122 microg/g), Cu (151 and 196 microg/g), Mn (1,259 and 1,433 microg/g), and Zn (1,116 microg/g), at several facilities studied, and even higher levels of metals were reported in the literature for certain oil and grit separators. With respect to individual BMPs, the severe pollution was found in sediments from oil and grit separators (for Cd, Cr, Cu, Pb and Zn), the stormwater clarifier sludge (Cu, Mn and Zn), a biofilter (Cu and Mn), an industrial area stormwater pond (Cu only), and a commercial/residential pond (Cr only). Finally, the chemical pollution of pond sediment triggered toxicity testing at some of the facilities studied, and sediment toxicity was confirmed at several sites.

Canada↗
PubMed1998

The inhibition of Clostridium botulinum type C by other bacteria in wetland sediments.

Bacteria with inhibitory activity against Clostridium botulinum type C were isolated from 32% of sediment samples (n = 1600) collected from 10 marshes in a northern California wetland over a 12 mo period. Aerobic and anaerobic bacteria with inhibitory activity were isolated from 12% and 23% of the samples, respectively. Bacteria with inhibitory activity were isolated from all 10 study sites and throughout the year. This study demonstrates that bacteria with inhibitory activity against C. botulinum type C occur naturally in wetland sediments.

Analysis of Variance↗
PubMed2002

The benefits and risks of using river sediment for Vietnamese agriculture: a case study of the Nhieu Loc canal in Ho Chi Minh City.

This study was conducted to assess the potential of river sediment for amendment of agricultural land with respect to heavy metal mobilization. The mobility and concentration of bioavailable heavy metal containing in the sediment were evaluated with the use of DTPA (diethylenetriamine pentaacetic acid) extraction techniques. Sum of metals in exchangeable and carbonate fractions obtained from sequential extraction scheme was used to evaluate the potential plant available. Four land blocks of size (1 m x 5.8 m) were prepared for cabbage field experiment and applied with different loading rates of sediment (approximately 28 and 42 ton/ha or equivalent to 100 kgN/ha and 150 kgN/ha). In parallel test, land blocks treated with fertilizer at similar nitrogen loading rates were also conducted for comparisons. Pure soil plot was used as a control system. Results show that both plant available and total heavy metal concentration were found higher in those plots treated with higher loading rates of sediment (42 ton/ha). The concentrations of heavy metals (Cu,Zn,Pb) in soil were decreased with time after crop harvesting and the residues remain in the soil were well below those of the UK, USA and Germany standards. Simple linear regression was used to show the correlation between the DTPA extractable metals and the plant metals fractions (root and shoot) resulting from fertilizer and sediment applications in the amended soils. In most cases, plant available metal concentrations showed positively correlated with plant metal uptake concentrations (R2 = 0.01-0.95, n = 3). Concentration of metals in the cabbage tissue detected: Zn at 131.53+/-10.43 mg kg(-1) DM, Cu at 20.84+/-1.62 mg kg(-1) DM, Pb at 0.09+/-0.01 mg kg(-1) DM, Cd at 0.21+/-0.09 mg kg(-1) DM and Ni at 0.44+/-0.05 mg kg(-1) DM. None of these metals concentration exceeded the tolerable limits of plant. One-way analysis of variance (ANOVA) was applied to find out the effect of different soil amendments on cabbage yield in term of fresh and dry weights. The sequence of crop yields in this field studies for amended soils is chemical fertilizer > sediment > control soil.

Agriculture↗
PubMed2002

Evaluation of reduced sediment volume toxicity test procedures using the marine amphipod Ampelisca abdita.

During the past 20 years, the role of sediment toxicity tests has expanded from testing of primarily dredged material to risk assessment, decontamination technologies, large-scale regional sediment-quality assessments, and toxicity identification evaluations. Sediment toxicity tests are needed that can provide reliable data using less sediment and smaller test chambers, thus utilizing resources more efficiently. We compared survival results from 10-d standard marine amphipod tests at 20 degrees C using 200 ml of sediment to reduced-volume tests containing 20 or 50 ml of sediment and found no significant differences. Similar survival also was observed in tests conducted for 7-d at 23 degrees C versus the standard 10-d exposure at 20 degrees C. However, amphipod sensitivity was significantly less in reduced-volume tests conducted for only 4- or 7-d at 20 degrees C. The 10-d sediment toxicity tests using 50 ml of sediment provided comparable results to the standard protocol, whereas time for sampling, preparing, and sieving sediments for a test was substantially reduced.

Amphipoda↗