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PubMed2003

Sedimentation behaviour of sludge particles in a biogas tower reactor and the function of a hydrostatically pressurized sedimenter.

It was found that anaerobic sludge particles contain gas bubbles. Due to the compressibility of the bubbles, which are entrapped in the sludge agglomerates, a pressure-dependent sedimentation characteristic of the sludge particles was found and mathematically described. Enhanced hydrostatic pressure results in a considerable increase of the settling velocity of sludge particles. On this basis the concept of a hydrostatically pressurized sedimenter is presented and its performance analyzed. Due to the hydrostatical pressurization of the sedimenter the produced gas is kept in the liquid phase until the liquid phase is saturated. To avoid a degassing of the liquid which results in the undesired release of gas bubbles a maximum liquid dwell time in the sedimenter must not be exceeded.

Bacteria, Anaerobic↗
PubMed1979

Alkaline phosphatase assay for freshwater sediments: application to perturbed sediment systems.

The p-nitrophenyl phosphate hydrolysis-phosphatase assay was modified for use in freshwater sediment. Laboratory studies indicated that the recovery of purified alkaline phosphatase activity was 100% efficient in sterile freshwater sediments when optimized incubation and sonication conditions were used. Field studies of diverse freshwater sediments demonstrated the potential use of this assay for determining stream perturbation. Significant correlations between phosphatase and total viable cell counts, as well as adenosine triphosphate biomass, suggested that alkaline phosphatase activity has utility as an indicator of microbial population density and biomass in freshwater sediments.

Journal Article↗
PubMed1981

Comparison of formalin-ethyl ether sedimentation, formalin-ethyl acetate sedimentation, and zinc sulfate flotation techniques for detection of intestinal parasites.

Formalin-ethyl ether sedimentation, Formalin-ethyl acetate sedimentation, and zinc sulfate flotation techniques were compared using over 250 clinical parasitology specimens. Fifty positive specimens were identified, and a variety of parasites, including amoebae, flagellates, cestodes, nematodes, and trematodes, were encountered. The Formalin-ether and Formalin-ethyl acetate sedimentation procedures gave identical results for the detection of cysts, ova, and larvae, and these methods offered an advantage over the flotation procedure for the detection of selected ova. However, the zinc sulfate procedure was more effective for the detection of protozoan cysts, Hymenolepis nana, and hookworm eggs. The results indicate that the Formalin-ethyl acetate procedure provides a suitable alternative to the Formalin-ether method, and they demonstrate the value of using both flotation and sedimentation procedures in the analysis of fecal specimens for parasites.

Acetates↗
PubMed1978

Sedimentation of multicomponent viruses: evaluation of sedimentation coefficient ratios.

Ratios of the sedimentation coefficients for alfalfa mosaic virus components are shown to be independent of the virus concentration and the density of the solvent. Different numbers of components are observed in solvents of different density. This implies that in sedimentation velocity experiments an estimate of the number of components of a multicomponent virus should involve centrifugation in solvents of different density. For some viruses, estimates of the sedimentation coefficients of individual components can be obtained from the coefficient ratios observed in unfractionated solutions and the sedimentation coefficient of the most easily purified component.

Centrifugation, Density Gradient↗
PubMed2003

Remote-sensing reflectance of turbid sediment-dominated waters. Reduction of sediment type variations and changing illumination conditions effects by use of reflectance ratios.

Variations of sediment type (grain size and refractive index) and changing illumination conditions affect the reflectance signal of coastal waters and limit the accuracy of sediment-concentration estimations from remote-sensing measurements. These effects are analyzed from numerous in situ remote-sensing measurements carried out in the Gironde and Loire Estuaries and then reduced and partly eliminated when reflectance ratios between the near infrared and the visible are considered. These ratios showed high correlation with the sediment concentration. On the basis of the obtained relationships, performing correspondence functions were established that allow an accurate estimation of suspended sediments in the estuaries from Système Probatoire d'Observation de la Terre, Landsat, and Sea-Viewing Wide Field-of-View Sensor data, independently of the date of acquisition.

Journal Article↗
PubMedDate not supplied

Effects of pond water, sediment and sediment extract samples from New Hampshire, USA on early Xenopus development and metamorphosis: comparison to native species.

In an effort to assess potential ecological hazards to amphibian species in selected regions within New Hampshire, the traditional Frog Embryo Teratogenesis Assay-Xenopus (FETAX), a 14-/21 day tail resorption thyroid disruption assay and >30 day limb development tests were conducted with representative surface water and sediment samples. Two separate sets of samples collected from five sites were evaluated. The primary objectives of the study were to determine if samples were capable of inducing early embryo-larval maldevelopment, to determine if maldevelopment included limb defects, to determine if thyroxine co-administration altered the rates of limb malformation and to evaluate the impact of the samples on growth rates, developmental progress and metamorphic climax. Results from these studies suggested that pond water and sediment extract samples, but not whole sediment samples, from B2, FW, LP and W ponds were capable of inducing abnormal early embryo-larval development. In addition, water samples from B2 and W ponds induced significant abnormal hindlimb development. Some abnormal forelimb development was noted in the tail resorption studies, but not to the same extent as the hindlimbs. Each of the water samples induced appreciable developmental delay, including the paired reference site B1, which could be reversed by the addition of exogenous thyroxine.

Animals↗
PubMed2005

Organic pollutants in sediment cores of NE-Germany: comparison of the marine Arkona Basin with freshwater sediments.

During a contamination survey in NE-Germany sediment cores were sampled at 5 locations with freeze-coring devices and conventional box-coring systems. In total more than 40 samples were analysed for several organic compounds (136 PCDD/F, 33 PCB, 39 PAH, 10 DDX, 4 HCH, 4 CB), sedimentological parameters (TOC,TC,TIC,LOI), some total trace metals (Pb,Cd,Cr,Cu,Zn) and dated by measurement of the (210)Pb and (137)Cs activity. The deepest segment of the cores from the Arkona Basin and the freshwater lakes were dated back to the end of the 19th century. A comparison of marine versus freshwater data is presented. The contamination levels of Arkona Basin were often lower than anthropogenically influenced freshwater sediments and more similar to a freshwater sediment core only influenced by deposition, with an additional Oder River inflow. Differences in patterns and contamination levels are discussed.

Environmental Monitoring↗
PubMed2001

Polycyclic aromatic hydrocarbon 13C/12C ratio measurement in petroleum and marine sediments application to standard reference materials and a sediment suspected of contamination from the Erika oil spill.

This paper describes a simple and rapid sample preparation procedure allowing to measure the stable carbon isotopic composition of polycyclic aromatic hydrocarbons (PAHs) in petroleum and in sediments. The aromatic fraction is first purified and isolated on alumina and silica micro-columns. A high-performance liquid chromatography fractionation allows one then to isolate each aromatic family in order to limit coelutions between PAHs. Moreover, this purification step reduces the importance of the unresolved complex mixture which otherwise contribute to the GC-isotope ratio MS background signal. The application of this analytical procedure has allowed one to determined PAH isotopic composition in a reference material crude oil (SRM 1582) and a marine sediment (SRM 1944) with good reproducibility as uncertainties between three independent assays performed were lower than 0.5 per thousand. This analytical procedure has then been successfully applied to confirm the contamination of a sediment by the petroleum product spilled by the Erika tanker after its wreck on 12 December 1999 close to the Atlantic Coast of France.

Atlantic Ocean↗
PubMed2001

Influence of sediment and pore-water composition on nitrite accumulation in a nitrate-perfused freshwater sediment.

Anaerobic nitrate consumption was accompanied by the accumulation of nitrite in the range of 3-52 micromoll(-1) in laboratory sediment cores continuously perfused with nitrate from below. Highest interstitial nitrite concentrations were observed in organically poor sediment cores with a low extractable protein content. Supplemented with an additional source of fixed nitrogen (ammonium), the nitrate-perfused sediments exhibited considerably lower nitrite concentrations than the respective control treatments. The simultaneous addition of ammonium and chloramphenicol, however, resulted in high nitrite concentrations. This suggests that in the absence of chloramphenicol an ammonium-fuelled bacterial protein de novo synthesis prevented the accumulation of nitrite in the course of anaerobic nitrate consumption. Additional DOC (glucose, methanol) generally increased the anaerobic nitrate consumption rate and the interstitial nitrite concentrations. The different scales of these increases were probably related to the degradability of the respective DOC compound and to the taxonomic composition of the microbial community evolving under different feeding regimes.

Anaerobiosis↗
PubMed2002

Determination of areal sedimentation rates in rivers by using plate sediment trap measurements and flow velocity-settling flux relationship.

Not much is known about sedimentation of organic particles in rivers. Plate sediment traps deployed in fast flowing River Spree and in a slowly flowing side arm yielded trapping rates between 0.7 and 52gDW m(-2) d(-1). A linear regression between flow velocity and trapping rates was used to extrapolate from point measurements to areal average trapping rates, which were 11 gDW m(-2) d(-1) in the side arm and 1.4 gDW m(-2) d(-1) in the free flowing river section. These rates are typical for the River Spree, but different from other rivers. The plate trap measurements provide the basic variables for the sedimentation rate sed = C x W*s(1-V/V(crit,sed)), i.e. concentration of particles (C), sinking velocity (Ws) flow velocity (V), and a threshold velocity (V(crit,sed)).

Chemical Phenomena↗
PubMed2003

Bioavailability of sediment-associated PCDD/Fs and PCDEs: relative importance of contaminant and sediment characteristics and biological factors.

Factors that determine accumulation of sediment-associated polychlorinated dibenzo-p-dioxins and furans and polychlorinated diphenyl ethers into semipermeable membrane devices (SPMDs) and benthic oligochaete worms (Lumbriculus variegatus) were examined. These factors included both physical-chemical and structural characteristics of the contaminants (water solubility, lipophilicity, dipole moment, molecular size, and conformation) and sediment characteristics (organic carbon content, particle size, aromaticity, and polarity of organic carbon). The results of partial least squares regression analysis indicated that lipophilicity alone is not a sufficient predictor for contaminant bioaccumulation potential, even though it is a significant contributor. It was shown that contaminant molecular size and conformation (specifically planarity/nonplanarity) as well as sediment characteristics also have a significant role. The studied factors contributed up to 63-88% of the variation in accumulation data for SPMDs and 50-65% for oligochaetes. Comparison of (bio)accumulation factors (BAF28d for oligochaetes and AF28d for SPMDs) revealed that accumulation of contaminants in oligochaetes is largely influenced by biological factors (e.g., feeding habits), while the physical-chemical nature of the process is emphasized for SPMDs.

Animals↗
PubMed2001

Distribution of chlorinated organic pollutants in harbor sediments of Livorno (Italy): a multivariate approach to evaluate dredging sediments.

Dredging is a very important procedure for harbor management. In Italy the guidelines for the offshore dumping of dredged materials are issued by the Ministry of Environment. They described a few steps of dredging activities, such as the sampling strategy, but do not deal with limits or guide-values for the chemical, physical and biological composition of the resulting sediments. The quality of dredged materials is mainly dependent on the presence of inorganic and organic pollutants. In particular, polychlorinated biphenyls (PCBs) and organo-chlorinated pesticides are seen as a high priority in marine environment by international organizations because of their persistence, toxicity and bioaccumulation capacity. In this article the presence of some PCBs and organo-chlorinated pesticides in sediment samples collected from the harbor of Livorno (Northern Tyrrhenian Sea) was investigated. The concentration of HCHs, Aldrin, Chlordanes, DDEs, DDTs, and PCBs in 12 representative sites ranged between <1 microg kg(-1) and 95, 19, 32, 35, 107, and 111 microg kg(-1), respectively. The application of univariate and multivariate statistical techniques, such as linear regression analysis and principal component analysis, to the experimental data showed a different distribution of PCBs in the two sediment layers. On the contrary, the vertical distribution of the other investigated pollutants was more homogeneous and affected by random variability. The multivariate approach was an important tool to establish more rational criteria for the management of dredged materials.

Conservation of Natural Resources↗
PubMed1976

Comparison of the Wintrobe erythrocyte sedimentation rate with the zeta sedimentation ratio.

Erythrocyte sedimentation rate (ESR) determinations performed by the Wintrobe method were correlated with a newer, rapid method, the zeta sedimentation ratio (ZSR), in 189 adult patients. Good correlation between the two methods was achieved over a wide range of values, with a correlation coefficient of 0.88 in female and 0.92 in male subjects. The precision of each method was evaluated by performing ten replicate determinations for 11 patients. The average variance for the ZSR was 2.91%, compared with 7.04% for the Wintrobe ESR; a difference significant at p < 0.01. Good correlation with standard methods, speed of performance and superior precision make the ZSR an attractive alternate procedure for the determination of the sedimentation rate.

Adult↗
PubMed2006

Sea-level, topographical and sediment supply controls on Holocene sediment composition in the Humber Estuary, UK.

To increase our understanding of the relative control of antecedent topography, sediment supply and sea-level change on grain size and organic content in the Humber Estuary, the composition of its Holocene fill over space and time has been evaluated. A model based-upon bed-by-bed description of over 3,500 bore holes was sub-horizontally 'sliced' to analyse the composition of sediments in different parts of the estuary across the entire fill, as well as solely within estuary marginal sequences. Results demonstrate that different physio-graphic parts of the estuary are characterized by distinctive vertical sediment profiles that reflect the relative control of antecedent topography as well as sea-level upon them. The results raise questions about the processes controlling sand and gravel abundance in marginal sequences, where the estuary is physio-graphically most constrained. This semi-quantitative evaluation, the first of its kind on an estuarine fill, provides a technique for interpreting the relative importance of controls on an estuarine system, but highlights the need for improved modelling of estuarine channel form and dynamics over centurial to millennial time-scales.

Computer Simulation↗
PubMed2001

Length of sedimentation reaction in undiluted blood (erythrocyte sedimentation rate): variations with sex and age and reference limits.

Although the length of sedimentation reaction in blood (LSRB) (commonly, but improperly called erythrocyte sedimentation rate, ESR) has long been used in clinical laboratories because it is simple and low-cost, its sensitivity and specificity are unsatisfactory. Usually, the values are reported using the Westergren method with sodium citrate-anticoagulated specimens. We used a new procedure, the TEST1, which measures the length of sedimentation reaction in undiluted K3EDTA anticoagulated blood samples following ICSH (International Committee for Standardization in Haematology) recommendations. Samples obtained from 840 reference individuals (430 females and 410 males, mean age 44 and 46.5 years respectively, range 1 to 90 years) were utilised to estimate the reference limits. The subjects, classified by sex, were subdivided into four statistically different age groups to determine the reference limits (2.5th and 97.5th percentiles). Sex difference was statistically significant in two age groups, from 14 to 50 (p < 0.0001) and from 50 to 70 years (p < 0.01). We did not observe significant sex difference within the age bracket from 1 to 14 years and from 70 to 90 years. In both sexes LSRB values increased with age, in significant correlation with fibrinogen concentration (p < 0.0001), and became significantly higher in subjects older than 70 compared to all the younger subjects (p<0.01 in females and p < 0.02 in males). Thus, we defined adequate reference ranges in elderly.

Adolescent↗
PubMed1971

Pressure-induced dissociation of sedimenting ribosomes: effect on sedimentation patterns.

Anomalous sedimentation patterns arise when free ribosomes from sea urchin eggs are centrifuged at high speeds. Pressure-induced dissociation of the ribosomes during sedimentation can explain the peculiar behavior; the assumption of such dissociation also yields estimates of the equilibrium constant (as a function of KCl concentration) and the change in molecular volume (500 +/- 100 ml/mol) in the reaction: subunits right arrow over left arrow ribosome. Such dissociation during centrifugation may explain many experiments in which apparent reduced sedimentation coefficients for ribosomes, and increased coefficients for the subunits, have been ascribed to conformational changes.

Animals↗
PubMed1990

Hydrocarbon mineralization in sediments and plasmid incidence in sediment bacteria from the campeche bank.

Rates of degradation of radiolabeled hydrocarbons and incidence of bacterial plasmid DNA were investigated in sediment samples collected from the Campeche Bank, Gulf of Mexico, site of an offshore oil field containing several petroleum platforms. Overall rates of mineralization of [C]hexadecane and [C]phenanthrene measured for sediments were negligible; <1% of the substrate was converted to CO(2) in all cases. Low mineralization rates are ascribed to nutrient limitations and to lack of adaptation by microbial communities to hydrocarbon contaminants. Plasmid frequency data for sediment bacteria similarly showed no correlation with proximity to the oil field, but, instead, showed correlation with water column depth at each sampling site. Significant differences between sites were observed for proportion of isolates carrying single or multiple plasmids and mean number of plasmids per isolate, each of which increased as a function of depth.

Journal Article↗