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At least 1,063 records · Page 59Linked to original sources

PubMed2001

Erosion investigation and sediment quality measurements for a comprehensive risk assessment of contaminated aquatic sediments.

In this paper, an assessment strategy is introduced which allows one to evaluate the ecological hazard of contaminated sediments in connection with the risk of in-stream erosion. Special techniques for sediment sampling, non-intrusive density profiling, and depth related measurement of erosion are presented, which, in combination with ecological aspects, lead to a comprehensive risk assessment of fluvial sediments. The strategy was applied to a lock-regulated reach of the River Neckar in Germany. The spatial pattern of contamination in the river reservoir was found to be remarkably heterogeneous. At some sites, very high heavy metal concentrations were detected at the sediment surface. A sudden increase in contamination with depth at other sites could be attributed to an erosional unconformity. The critical shear stress of erosion for old contaminated sediments is higher than for recently deposited material. Nevertheless, during major flood events, bottom shear stress in the river exceeds the critical shear stresses of erosion of all sediments. Accordingly, there is a substantial risk that old contaminated sediment can be mobilised from the reservoir and transported downstream.

Conservation of Natural Resources↗

PubMed2002

Quality of dredged material in the river Seine basin (France). II. Micropollutants.

Dredging rivers is needed to ensure safe navigable waters, rivers and waterways. To anticipate the management of dredged materials in the case of the river Seine basin, the quality of the sediments in the river is checked every 3 years before dredging operations. The river Seine Basin is heavily submitted to pollution pressure from nearby industrial activities and urban expansion of Paris and its region. Here, the micropollutant content of the sediment sampled in 1996, 1999 and 2000 before dredging is discussed compared to regulatory standards. The results indicate that most of the sediment samples from the river Seine basin are lightly to moderately contaminated with organic and inorganic micropollutants (heavy metals, PAH, PCB), which makes the management after dredging easier. This pollution is strongly correlated with the organic matter content and to the fine fraction (<50 microm) of the sediment. These results can lead to other management options than the ones already used in the river Seine basin: (1) dumping of lightly to moderately polluted sediments in quarries; and (2) physical treatment (sieving, hydrocycloning) of contaminated sediments issued from 'hot spots'.

Conservation of Natural Resources↗

PubMed1999

Sedimentary fluxes of 90Sr, 137Cs, 239,240Pu and 210Pb in the East Sea (Sea of Japan).

Sediment cores collected from the deep basins of the East Sea (Sea of Japan) provide an ongoing and historical record of artificial radionuclides contamination into one of the most highly publicized radioactive waste dumping areas in the world ocean. The depth distributions of 90Sr, 137Cs and 239,240Pu in sediment cores were investigated with the aid of 210Pb-derived sediment accumulation and mixing rates in the deep basins of the East Sea (Sea of Japan). Five box core samples were collected from the northern Yamato Ridge, Korea Plateau, Ulleung and Japan Basins below 1000-m depth. Sediment inventories of 137Cs and 239,240Pu are inversely correlated with water depth and linearly correlated with sediment accumulation rates. The inventories of these nuclides are linearly correlated with the accumulation rates of organic carbon in sediments. The 238Pu/239,240Pu activity ratios in sediments are 0.036 +/- 0.009 suggesting that most of the Pu to the study area is derived from the global fallout. The activity ratios of 239,240Pu/137Cs, and 90Sr/137Cs in bottom sediments are much lower than those of global fallout due to the differences of particle affinity and biological uptake of these nuclides. Sediment inventories of 90Sr and 137Cs constitute < 4% of the anticipated inventories from the global fallout, while those of 239,240Pu constitute 30-150% of the anticipated inventories from the global fallout. The residence time of the dissolved 239,240Pu in the study area is estimated to be 200-400 years based on the sediment inventory and/or sediment accumulation rate, and water column inventory.

Cesium↗

PubMed2001

Microbial community assessment in oil-impacted salt marsh sediment microcosms by traditional and nucleic acid-based indices.

The effect of oil amendment in salt marsh sediment microcosms was examined by most probable number (MPN), DNA-hybridization with domain-specific oligonucleotide probes and whole community 16S rDNA-hybridizations. Gas chromatography (GC/MS) analysis of oil residues in sediments from microcosms after 3 months of operation showed that the quantity of petroleum hydrocarbons was lower in microcosms amended with oil compared to microcosms amended with oil+plant detritus. Bacterial numbers (total-MPN) increased in all experimental microcosms (amended with plant detritus, oil, and oil+plant detritus). In comparison to the intact sediment, the proportions of oil-degrading bacteria increased >100-fold in the oil amended microcosm and >10-fold in the plant detritus and the oil+plant detritus amended microcosms. DNA-hybridizations with Bacteria, Archaea and Eukarya oligonucleotide probes indicated few changes in the petroleum contaminated sediment community profile. In contrast, rDNA-hybridizations indicated that the bacterial community profile of the oil-impacted sediments, after 1 month of exposure, was significantly different from the control sediment.

Bacteria↗

PubMed2001

Lead and zinc in sediments and biota from Maarmorilik, West Greenland: an assessment of the environmental impact of mining wastes on an Arctic fjord system.

Lead and zinc levels in sediments and biota from the fjord system surrounding the lead/zinc mine at Maarmorilik, West Greenland, were investigated to evaluate the impact of waste rock and marine-deposited tailings on the marine biota. Concentrations of metal in the sediment were up to 8,922 +/- 622 microg g(-1) (dry wt.) for lead and 19,351+/- 476 microg g(-1) (dry wt.) for zinc. Levels of lead and zinc were also elevated in a suite of monitor organisms. The feeding modes of the organisms were used to explain the sources of metals to the organisms. After closure of the mine, the concentrations of metals in the upper centimetres of the sediments decreased, and a decreased impact of metals on the brown alga Fucus distichus was observed. However, the metals in the sediments still affect the marine biota in the area.

Animals↗

PubMed2001

Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea.

The residues of oragnochlorine pesticides (OCPs) in 62 sediments from Kyeonggi Bay and nearby areas in the west coast of Korea were determined. The concentrations of chlordanes (CHLs) and DDTs showed a distinctive gradient of contamination between inner and outer sites of Incheon North Harbor (INH), whereas hexachlorocyclohexanes (HCHs) were uniformly distributed at most sites studied. The distribution of CHLs and DDTs was strongly correlated with total organic carbon contents in sediments while HCH residue levels were independent. Relationship between contaminant's concentration and environmental factors was analyzed by principal component analysis. Distribution patterns of T-CHLs, T-DDTs, and TOC were similar while those of T-HCHs, mud content, and grain size were similar. The notable contamination by CHLs and DDTs was found in INH where these levels were one or two orders of magnitude higher than other sites. The dominant OCPs in sediments were beta-HCH among HCH compounds, trans-chlordane among CHL compounds, and p,p'-DDD among DDT compounds. The higher concentrations and compositional pattern of OCPs in INH sediments indicate that INH is in the vicinity of the source.

Carbon↗

PubMed2003

An automated overlying water-renewal system for sediment toxicity studies.

An automated water-renewal toxicity test system is described for exposing benthic invertebrates to whole sediments. The system will intermittently deliver laboratory or on-site water for overlying water replacement in sediment exposures. A range of cycle rates can be used to produce different volume additions of overlying water per day to exposure chambers. The system can be used with six different treatments and eight replicates per treatment producing 48 exposure chambers. Three formulated sediments with variable organic carbon (1.5%, 7.5%) and sand (14%, 63%) content were prepared to test the system exposing amphipods, Hyalella azteca and midges, Chironomus tentans in 10 day whole sediment tests. Intermittent water flow was used with a 90 min cycle time to create two volume additions of laboratory water per 24 h in exposure chambers (180 ml sediment, 320 ml water). Overlying water quality conditions, and survival and growth of both species were consistent and within acceptable limits for the testing requirements of the U.S. EPA guidelines for sediments with freshwater invertebrates.

Animals↗

PubMed1995

Preservation of cell structures in permafrost: a model for exobiology.

The present report is the first contribution toward a comprehensive fine-structural study of microbial cells from permafrost. Prokaryotes with a variety of cell wall types demonstrate high stability of cell structure after long-term cryopreservation in frozen soils and sediments of the Arctic. The surface capsular layers that were a salient feature of the cells both in situ and on nutrient media may be an adaptation to low temperature. To the extent that permafrost regions on Earth approximate Martian conditions, preservation of cell structure there can serve as the basis for predictions about preservation in Martian permafrost sediments.

Arctic Regions↗

PubMed2000

Isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) as a tool to discriminate between differently contaminated small river systems.

Isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) were exposed to native waters and acetone sediment extracts of Krähenbach and Körsch, two small rivers in south-west Germany with different levels of chemical contamination, and were investigated by means of electron microscopic and enzyme biochemical techniques to evaluate sublethal cytotoxic effects. Between both rivers as well as between free water phase and sediment, significant differences in the toxic burden could be detected. Results document that dilutions of Krähenbach and Körsch surface water and sediment extracts induce time- and dose-dependent morphological and biochemical changes. Especially in water and sediments of the river Körsch, strong contamination could be observed. After exposure to samples from the Körsch, both morphological and biochemical responses of isolated hepatocytes were more prominent than following exposure to samples of Krähenbach, thus reflecting the different chemical burden of the two river systems. Cytopathological effects also included deformation of nuclear envelopes and increase of heterochromatin, heterogeneity of mitochondria, vesiculation of cisternae of the rough endoplasmic reticulum, as well as proliferation of the smooth endoplasmic reticulum. Moreover, peroxisomal and lysosomal proliferation could be correlated to a stimulation of the corresponding marker enzymes, catalase and acid phosphatase. In both rivers, activities of lactate dehydrogenase and alanine aminotransferase as markers of cytosolic glycolysis and protein metabolism were increased indicating a general stimulation of cellular metabolism. Cytological changes in isolated hepatocytes thus not only serve to discriminate between different levels of contamination of water, but may also help to differentiate between pollution levels of sediments.

Acid Phosphatase↗

PubMed2000

Analysis of alkylphenol ethoxylate metabolites in the aquatic environment using liquid chromatography-electrospray mass spectrometry.

A quantitative method is described for the analysis of the metabolites of alkylphenol ethoxylate (APEO) surfactants in estuarine water and sediment samples using reversed-phase high-performance liquid chromatography with electrospray mass spectrometry detection. Nonyl- and octylphenols, nonyl- and octylphenol mono-, di-, and triethoxylates, halogenated nonylphenols, and nonylphenol ethoxycarboxylates were concentrated from water samples using a C18 solid-phase extraction procedure. A novel, continuous-flow, high-temperature, sonicated extraction system was developed to isolate APEO metabolites from sediment samples. Quantitative LC-MS was performed in the negative ion mode for nonylphenols, octylphenols, and halogenated nonylphenols and in the positive ion mode for nonyl- and octylphenol ethoxylates using selected ion monitoring with isotopically labeled surrogate standards. Recoveries for sediment and water analyses ranged between 78 and 94%, and detection limits for APEO metabolites were between 1 and 20 pg injected on column. This is a significant improvement over previously reported methods. Suppression of analyte response was encountered in the presence of matrix components in sediment samples, but this effect was eliminated by careful selection of surrogate and internal standards. Individual APEO metabolite concentrations of 1-320 ng/L and 5-2000 ng/g are reported for water and sediment samples, respectively, from Jamaica Bay, NY.

Biotransformation↗

PubMed2004

Combination of LC/TOF-MS and LC/Ion trap MS/MS for the identification of diphenhydramine in sediment samples.

Diphenhydramine (Benadryl) is a popular over-the-counter antihistaminic medication used for the treatment of allergies. After consumption, excretion, and subsequent discharge from wastewater treatment plants, it is possible that diphenhydramine will be found in environmental sediments due to its hydrophobicity (log P = 3.27). This work describes a methodology for the first unequivocal determination of diphenhydramine bound to environmental sediments. The drug is removed from the sediments by accelerated solvent extraction and then analyzed by liquid chromatography with a time-of-flight mass spectrometer and an ion trap mass spectrometer. This combination of techniques provided unequivocal identification and confirmation of diphenhydramine in two sediment samples. The accurate mass measurements of the protonated molecules were m/z 256.1703 and 256.1696 compared to the calculated mass of m/z 256.1701, resulting in errors of 0.8 and 2.3 ppm. This mass accuracy was sufficient to verify the elemental composition of diphenhydramine in each sample. Furthermore, accurate mass measurements of the primary fragment ion were obtained. This work is the first application of time-of-flight mass spectrometry for the identification of diphenhydramine and shows the accumulation of an over-the-counter medication in aquatic sediments at five different locations.

Anti-Allergic Agents↗

PubMed2001

Multivariate analysis of U.K. salt marsh sediment contaminant data with reference to the significance of PCB contamination.

A data set acquired to establish an inventory of pollutants in salt marsh sediments has been evaluated using two numerical techniques, principal component analysis and discriminant analysis. Results indicate that sites proximate to the River Thames exhibit a greater degree of contamination, and numerical analysis supports the hypothesis that the river has been the major source of contaminants to the region. The presence of the contaminants within salt marsh sediments may be of concern due to changes in flood defense techniques. The use of managed realignment, where the line of flood defense is moved back to higher ground which requires only a low, minimal cost, sea-wall protected by newly created salt marsh from former farmland, is not free from problems of historical pollution. Mature salt marsh, laid down during previous decades, may be eroded and reworked within the new coastal geomorphology created by breaching existing seawalls and what were previously considered to be sinks of pollutants may have become sources. However, evaluation of the sediment burden of PCB within the salt marshes of the U.K. Essex coast indicates that they are not likely to be a major source of pollutants should sediments be remobilized during managed realignment programs.

Conservation of Natural Resources↗

PubMed2001

Cerro Negro bitumen degradation by a consortium of marine benthic microorganisms.

Cerro Negro bitumen, separated from an Orimulsion sample, was incubated for up to 120 days with sediments collected at a petroleum-impacted site in Tampa Bay, Florida. Biodegradation conditions were optimized by increasing bitumen surface area, continuous agitation on a shaker apparatus, use of a complete growth medium, and maintenance at 37 degrees C. Aerobic degradation conditions were promoted by maintaining sediment contact with the laboratory atmosphere. Bitumen recovered in solvent extracts when compared to autoclaved controls decreased by up to 40% during the first 56 days. There was no detectable change after this. Molasses addition and use of a culture enriched from the sediments did not change the extent or rate of decrease in bitumen recovery. Chemical fractionation of bitumen control and degraded bitumen showed that aromatic and aliphatic fractions were depleted by approximately equals 50%. Accumulation of polars was observed; however, the apparent increase was relatively small when compared to the mass loss of the other fractions. Selected biomarker ratios were not affected by incubation indicating their utility for fingerprinting the source bitumen in environmental samples. PAH distribution in the aromatic fraction favored the higher alkyl-homologues with the relative degree of alkylation increasing as the mass of bitumen recovered decreased with degradation. The study showed that up to 40% of the bitumen was bioaccessible and that bioremediation may be a treatment option for sediments contaminated with bitumen by an Orimulsion spill.

Aerobiosis↗

PubMed2003

Degradation of PCBs in a marine sediment treated with ionizing and UV radiation.

Radiolytic (electron beam) and photolytic (ultraviolet, UV) dechlorination of polychlorinated biphenyls (PCBs) in a marine sediment are described. Samples of a PCB-laden marine sediment, Standard Reference Material (SRM) 1944, NewYork/New Jersey Waterway Sediment, have been mixed with aqueous alcohol solutions and irradiated with an electron beam or photolyzed. Additives, such as alcohol, enhance the radiolytic yield and PCB dechlorination. In the electron beam irradiated samples, the concentrations of 29 PCB congeners decrease with irradiation dose. At the highest dose (500 kGy), the total concentration of PCBs is decreased by 83%. Photolysis leads to little dechlorination, but photolysis with added triethylamine leads to dechlorination (about 60%). It is likely that photolysis under optimal conditions (other additives, exposure time) may be as effective as electron beam radiolysis for the dechlorination of PCBs in sediment.

Electrons↗

PubMed2003

Sources and variations of mercury in tuna.

While the bulk of human exposure to mercury is through the consumption of marine fish, most of what we know about mercury methylation and bioaccumulation is from studies of freshwaters. We know little of where and how mercury is methylated in the open oceans, and there is currently a debate whether methylmercury concentrations in marine fish have increased along with global anthropogenic mercury emissions. Measurements of mercury concentrations in Yellowfin tuna caught off Hawaii in 1998 show no increase compared to measurements of the same species caught in the same area in 1971. On the basis of the known increase in the global emissions of mercury over the past century and of a simple model of mercury biogeochemistry in the Equatorial and Subtropical Pacific ocean, we calculate that the methylmercury concentration in these surface waters should have increased between 9 and 26% over this 27 years span if methylation occurred in the mixed layer or in the thermocline. Such an increase is statistically inconsistent with the constant mercury concentrations measured in tuna. We conclude tentatively that mercury methylation in the oceans occurs in deep waters or in sediments.

Animals↗

PubMed2004

Addition of carbon sorbents to reduce PCB and PAH bioavailability in marine sediments: physicochemical tests.

The addition of activated carbon as particulate sorbent to the biologically active layer of contaminated sediment is proposed as an in-situ treatment method to reduce the chemical and biological availability of hydrophobic organic contaminants (HOCs) such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). We report results from physicochemical experiments that assess this concept. PCB- and PAH-contaminated sediment from Hunters Point Naval Shipyard, San Francisco Bay, CA, was contacted with coke and activated carbon for periods of 1 and 6 months. Sediment treated with 3.4 wt % activated carbon showed 92% and 84% reductions in aqueous equilibrium PCB and PAH concentrations, 77% and 83% reductions in PCB and PAH uptake by semipermeable membrane devices (SPMD), respectively, and reductions in PCB flux to overlying water in quiescent systems up to 89%. Adding coke to contaminated sediment did not significantly decrease aqueous equilibrium PCB concentrations nor PCB or PAH availability in SPMD measurements. Coke decreased PAH aqueous equilibrium concentrations by 38-64% depending on coke dose and particle size. The greater effectiveness of activated carbon as compared to coke is attributed to its much greater specific surface area and a pore structure favorable for binding contaminants. The results from the physicochemical tests suggest that adding activated carbon to contaminated field sediment reduces HOC availability to the aqueous phase. The benefit is manifested relatively quickly under optimum contact conditions and improves in effectiveness with contact time from 1 to 6 months. Activated carbon application is a potentially attractive method for in-situ, nonremoval treatment of marine sediment contaminated with HOCs.

Adsorption↗

PubMed2005

PCBs and OCPs in sediment cores from the Lower St. Lawrence Estuary, Canada: evidence of fluvial inputs and time lag in delivery to coring sites.

Three sediment cores were collected along the longitudinal axis of the Laurentian Trough in the Lower St. Lawrence Estuary (LSLE) and an additional one at the junction of the Estuary and the Gulf of St. Lawrence. After core-slicing, each sediment layer was analyzed for polychlorinated biphenyls (PCBs) and some organochlorine pesticides (OCPs) including p,p'-dichlorodiphenyltrichloroethane (DDT) and its metabolites, hexachlorobenzene (HCB) and Mirex. 210Pb activity was also measured in these sediments, which allowed us to confirm that these cores were too much affected by the overall impact of surface mixing to be dated. Nevertheless, POP sedimentary profiles in cores from the LSLE upstream stations showed well-defined subsurface peak concentrations. Apparently, the peak inputs of POPs to these sediment cores had occurred after the years of maximum sales and production of these chemicals in North America, suggesting a time lag in the delivery of POPs to the LSLE sediments. Concentrations of POPs in the LSLE surface sediments as well as POP inventories in sediment cores decreased in the seaward direction, confirming that the head of the LSLE acts as a sink for sediments and associated constituents. Surface concentrations of sigmaPCBs, sigmaDDTs, and HCB in the most upstream core were on average similar to those reported in two fluvial lakes of the St. Lawrence River but were between 12 and 39 times lower than those from Lake Ontario. For Mirex, the surface concentration in that core was 5 and 130 times lower than the average values found in the fluvial lakes and Lake Ontario, respectively. Differences between Lake Ontario sediment cores and the most upstream core from the LSLE were much smaller on the basis of POP inventories than surface concentrations of POPs, but were still important. The total burdens of POPs in LSLE sediments below the 200 m isobath were 8704 kg for sigmaPCBs, 1825 kg for sigmaDDTs, 319 kg for HCB, and 27.5 kg for Mirex. These values represent between 1% and 10% of the total burdens of these POPs in Lake Ontario sediments. The estimated contribution of POPs by direct atmospheric deposition into the water column area of the LSLE represented at most 30% of the total sediment burdens of POPs in the LSLE, illustrating the importance of fluvial inputs.

Canada↗

PubMed2005

Storm disturbance of sediment contaminants at a hot-spot in the Baltic Sea assessed by 234Th radionuclide tracer profiles.

Fly ash sludges from an abandoned metal smelter were dumped into the shallow inner part of the Mecklenburg Bay until 1971, representing the most severe heavy metal contamination hot-spot along the German coast. Half of the dumped Zn (455 t) and Pb (173 t) inventory was found to be spread from the originally 0.5 km2 hot-spot site to a now 360 km2 affected adjacent area. Wave-driven resuspension during gale events produced large pulses of contaminated sediments from this hot-spot due to the only 23 m water depth. Instantaneous sediment mixing down to 10 cm occurs during such a wave event as evidenced by activity profiles of the short-lived radionuclide 234Th in sediment cores. According to these estimated sediment exchange fluxes in the transport bottom area, each wave event may have mobilized Zn and Pb pulses on the order of several hundreds of kilograms from the dump site, sufficient to build up a plume in sediments of the outer bay area. With each centimeter (approximately 5 yr) of additional natural sediment capping, however, the amount of metal remobilization would decrease by about 50%.

Environmental Monitoring↗