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PubMed1996

Differential Metabolism of Dimethylsulfoniopropionate and Acrylate in Saline and Brackish Intertidal Sediments

In anoxic Spartina alterniflora-dominated sediments along a naturally occuring salinity gradient (the Cooper River estuary, South Carolina, U.S.A.), dimethylsulfoniopropionate (DMSP) was metabolized to dimethyl sulfide (DMS) and acrylate by sediment microbes. The rate of DMSP degradation and acrylate mineralization by sediment microbes was similar at all sites along this 25-km transect. However, sediments amended with acrylate (or DMSP) showed significantly higher rates of N2 fixation (measured as acetylene reduction activity) (ARA) in the saline sediments downstream than brackish sediments. These results are consistent with the fact that acrylate stimulated the rates of both denitrification and CO2 production in the saline sediments at the mouth of the river more than tenfold over rates in brackish sediments. Enrichment experiments indicate that microbes capable of using DMSP or acrylate were not present in upstream sediments despite the fact that microbial biomass, percent organic matter, and both glucose-stimulated ARA and denitrification were highest upstream. It appears that acrylate utilizing, N2 fixing, and denitrifying populations are insignificant in the lower salinity sediments of the estuary. These results may reflect the availability of DMSP, which averaged 10.3 nmol g wet wt-1 of saline sediments and levels less than our detection limit (1 &mgr;M) in brackish sediments.

Journal Article↗
PubMed1998

Toxicity of Sediment Collected Upriver and Downriver of Major Cities Along the Lower Mississippi River

The Lower Mississippi River contributes significantly to the biodiversity and ecological stability of the alluvial valley, but agricultural, industrial, and municipal developments have historically impacted environmental quality of the river. Toxicity of sediment and sediment pore water was used to assess the current effects of major cities on sediment quality along the Lower Mississippi River. Composite sediment samples were collected from four sites upriver and four sites downriver of five major cities: Cairo, IL; Memphis, TN; Vicksburg, MS; Baton Rouge, LA; and New Orleans, LA. Acute toxicity was determined by exposing Hyalella azteca to solid-phase sediment for 10 days with two water renewals per day and to sediment pore water under static conditions for 96 h. After the initial tests, animals were exposed to ultraviolet light for 16 h. Sediments were analyzed for organics (organochlorine pesticides, PCBs, organophosphate insecticides, and PAHs) and metals (Cr, Cu, Pb, Mn, Ni, Zn). With the exception of upriver from Memphis, solid-phase sediments were not toxic to H. azteca. Pore water from sediments collected upriver of Memphis also showed slight toxicity. Exposure of H. azteca to ultraviolet light did not increase the toxicity of the sediment or pore-water samples, indicating a lack of toxicity from PAHs that are photoactivated by ultraviolet light. Chemical analyses did not reveal any contaminant levels of concern in the sediments. Based on toxicity testing and chemical analyses, quality of sediments collected from the Lower Mississippi was good, with the exception of sites sampled upriver of Memphis.

Journal Article↗
PubMed1998

Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments.

Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded.

Journal Article↗
PubMed1998

Recent Changes of Sediment Yield in the Upper Yangtze, China

/ Reservoir sedimentation is one of the many environmental problems associated with the Three Gorges Project in China. The rate and characteristics of sedimentation that directly affect the operating life of the reservoir are closely related to soil erosion and sediment transport dynamics in the upstream catchment and to the ability to manage the throughput of sediment-laden waters. The recent changes in sediment yield were examined using gauging data from 187 stations of varying sizes from less than 100 km2 to larger than 1,000,000 km2 in the Upper Yangtze basin between 1956 and 1987. Whereas many previous studies have concentrated on the trends in the main channel of the Yangtze, the distributed pattern of changes across the whole catchment is complex. Results from time series analysis indicate ten stations, mainly located in the Dadu and Wu tributaries (with a total incremental catchment area of 78,963 km2) have shown increasing trajectories of sediment yield, and six stations, located in the upper Jialing and Tuo tributaries (with a total incremental area of 27,816 km2) have experienced decreasing trajectories. By dividing the time series into three components, it is possible to map significant decadal changes in sediment yields that can be related to phases of deforestation and the construction of water conservancy projects. Most of the observed decreases in sediment yield are associated with large reservoir schemes on tributary rivers. The lack of evidence for increasing sediment input to the Three Gorges area masks a considerable variation in sediment conveyance and storage within the Upper Yangtze catchment.KEY WORDS: Sediment yield; Reservoir sedimentation; Three Gorges Project; Time series analysis; China

Journal Article↗
PubMed2000

Bioavailability of sediment-bound Cd, Cr and Zn to the green mussel Perna viridis and the Manila clam Ruditapes philippinarum.

We assessed the degree to which Cd, Cr and Zn bound with sediment were assimilated by the green mussel Perna viridis and the Manila clam Ruditapes philippinarum. The influences of the metal concentration in the sediment, the presence of phytoplankton, and the oxidation condition of the sediment on metal assimilation were examined. No major difference was found for metal assimilation efficiency (AE) in sediment with different metal concentrations, except for Cd in the green mussels, in which the AE increased by 1.7x when the Cd concentration in sediment was elevated to 15x the natural background level. The higher assimilation of Cd with increasing Cd load in ingested sediment may be due to the higher desorption of Cd in the acidic gut of the bivalves. Both mussels and clams assimilated metals at a higher efficiency from the diatom diet (Thalassiosira pseudonana) than from inorganic sediment particles. The presence of algal particles had little influence on metal assimilation from ingested sediment, and conversely, the presence of sedimentary particles had little effect on metal assimilation from ingested diatom (except for Cd in the mussels). In the mussels, AEs were higher from oxic sediment than from anoxic sediment by 3.1x for Cd, 2.0x for Cr, and 1.4x for Zn, and in the clams AEs were higher from oxic sediment by 2.8x for Cd, 2.0x for Cr, and 2.0x for Zn. Our study suggested that metals associated with anoxic sediment can be potentially available to marine bivalves, and that metal AEs determined for a single diet were probably not affected by the presence of other food particles.

Journal Article↗
PubMed2001

Size-related shifts in the habitat associations of young-of-the-year winter flounder (Pseudopleuronectes americanus): field observations and laboratory experiments with sediments and prey.

Field surveys and laboratory studies were used to determine the role of substrata in habitat selection by young-of-the year winter flounder. A synoptic field survey of winter flounder and sediments in the Navesink River-Sandy Hook Bay estuarine system in New Jersey demonstrated that winter flounder distribution was related to sediment grain size. Analysis using a generalized additive model indicated that the probability of capturing 10-49 mm SL winter flounder was high on sediments with a mean grain diameter of </=0.5 mm, while fish 50-95 mm were least likely to be collected on fine sediments and most commonly on sediments with a grain-size near 1.0 mm. In the laboratory, sediment preferences and the burying ability of winter flounder (15-69 mm SL) were tested by exposing fish in 10-mm size groups to a choice of azoic sediments of different sediment grain sizes. Smaller individuals (<40 mm SL) preferred fine-grained sediments while larger individuals (>/=40 mm SL) preferred coarse-grained sediments. Burying ability increased with size and all flounders avoided sediments that prevented burial. Subsequent laboratory experiments revealed that the presence of live prey (Mya arenaria) can over-ride sediment choice by winter flounder (50-68 mm SL) indicating the complexity of interrelated factors in habitat choice.

Journal Article↗
PubMed2000

Supply and Removal of Sediment in a Landslide-Dominated Mountain Belt: Central Range, Taiwan.

A strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding. We reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern Central Range of Taiwan. Here, the magnitude-frequency distribution of landslides can be modeled by a robust power law, but this scale invariance is not mirrored in the sediment discharge at the mountain front. Instead, downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions. The rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment. Removal of landslide debris is a function of the transport capacity of the stream at the site of entry; thus, there is a dual supply and transport control on sediment loads in bedrock-floored streams. Over a monitoring period of >25 yr, the bulk of the sediment leaving the mountain belt was supplied by climate-triggered mass wasting. Peaks in water discharge were always closely followed by sediment load maxima, and the rapid decay of the latter indicates an effective removal of most supply. Where an important part of a catchment's sediment yield is derived from interfluves, sediment transport cannot simply be estimated from known water discharge time series, using a sediment rating curve, but requires instead a detailed knowledge of the spatial and temporal patterns of hillslope mass wasting and sediment transfer into the fluvial system.

Journal Article↗
PubMed1991

Ultrasonic interferometry: study of particle sedimentation in liquid.

An ultrasonic interferometry method was designed to study sedimentation of particles in liquid. The method, based on A mode echography, measures the amplitude of ultrasonic waves reflected (echo E1) by a fixed interface I1 called "solid plate-sediment" interface formed when particles are sedimenting on a solid plate. The amplitude of the echo depends both on mechanical properties of the three media (solid plate, sediment and suspension) on the thickness of the sediment and on the presence of a second mobile interface I2 called "sediment-suspension" interface. In the first phase of sedimentation when the second interface is very close to the first, two reflected waves interfere. Then, in the second phase of sedimentation when the sediment is thick enough, the amplitude of the echo E1 depends only on the sediment and solid plate properties. The first phase will give information on the sedimentation rate of particles (SR). We have compared SR of particles determined by this method with SR measured in a cylindrical tube of the same geometry as the ultrasonic measurement cell and with theoretical values of the sedimentation rate given by theoretical models.

Interferometry↗
PubMed2004

Transport and distribution of lindane and simazine in a riverine environment: measurements in bed sediments and modelling.

Aquatic sediments often remove hydrophobic contaminants from fresh waters. The subsequent distribution and concentration of contaminants in bed sediments determines their effect on benthic organisms and the risk of re-entry into the water and/or leaching to groundwater. This study examines the transport of simazine and lindane in aquatic bed sediments with the aim of understanding the processes that determine their depth distribution. Experiments in flume channels (water flow of 10 cm s(-1)) determined the persistence of the compounds in the absence of sediment with (a) de-ionised water and (b) a solution that had been in contact with river sediment. In further experiments with river bed sediments in light and dark conditions, measurements were made of the concentration of the compounds in the overlying water and the development of bacterial/algal biofilms and bioturbation activity. At the end of the experiments, concentrations in sediments and associated pore waters were determined in sections of the sediment at 1 mm resolution down to 5 mm and then at 10 mm resolution to 50 mm depth and these distributions analysed using a sorption-diffusion-degradation model. The fine resolution in the depth profile permitted the detection of a maximum in the concentration of the compounds in the pore water near the surface, whereas concentrations in the sediment increased to a maximum at the surface itself. Experimental distribution coefficients determined from the pore water and sediment concentrations indicated a gradient with depth that was partly explained by an increase in organic matter content and specific surface area of the solids near the interface. The modelling showed that degradation of lindane within the sediment was necessary to explain the concentration profiles, with the optimum agreement between the measured and theoretical profiles obtained with differential degradation in the oxic and anoxic zones. The compounds penetrated to a depth of 40-50 mm over a period of 42 days.

Adsorption↗
PubMed2006

Toxicity assessment of reference and natural freshwater sediments with the LuminoTox assay.

We examined the possibility of adapting the LuminoTox, a recently-commercialized bioanalytical testing procedure initially developed for aqueous samples, to assess the toxic potential of sediments. This portable fluorescent biosensor uses photosynthetic enzyme complexes (PECs) to rapidly measure photosynthetic efficiency. LuminoTox testing of 14 CRM (Certified Reference Material) sediments was first undertaken with (1) a "solid phase assay" (Lum-SPA) in which PECs are in intimate contact with sediment slurries for a 15 min exposure period and (2) an elutriate assay (Lum-ELU) in which PECs are exposed for 15 min to sediment water elutriates. CRM sediment toxicity data were then compared with those generated with the Microtox Solid Phase Assay (Mic-SPA). A significant correlation (P < 0.05) was shown to exist between Lum-SPA and Mic-SPA, indicating that both tests display a similar toxicity response pattern for CRM sediments having differing contaminant profiles. The sediment elutriate Lum-ELU assay displayed toxicity responses (i.e. measurable IC20s) for eight of the 14 CRM sediments, suggesting that it is capable of determining the presence of sediment contaminants that are readily soluble in an aqueous elutriate. Lum-SPA and Mic-SPA bioassays were further conducted on 12 natural freshwater sediments and their toxicity responses were more weakly, yet significantly, correlated. Finally, Lum-SPA testing undertaken with increasing mixtures of kaolin clay confirmed that its toxicity responses, in a manner similar to those reported for the Mic-SPA assay, are also subject to the influence of grain size. While further studies will be required to more fully understand the relationship between Lum-SPA assay responses and the physicochemical makeup of sediments (e.g., grain size, combined presence of natural and anthropogenic contaminants), these preliminary results suggest that LuminoTox testing could be a useful screen to assess the toxic potential of solid media.

Aliivibrio fischeri↗
PubMed2002

Ecological benefits of contaminated sediment remediation.

Contaminated sediment has been identified as a source of ecological impacts in marine and freshwater systems throughout the world, and the importance of the contaminated sediment management issue continues to increase in all industrialized countries. In many areas, dredging or removal of sediments contaminated with nutrients, metals, oxygen-demanding substances, and persistent toxic organic chemicals has been employed as a form of environmental remediation. In most situations, however, the documentation of the sediment problem has not been quantitatively coupled to ecological impairments. In addition, the lack of long-term, postactivity research and monitoring for most projects has impeded a better understanding of the ecological significance of sediment contamination. Establishing quantitatively the ecological significance of sediment-associated contamination in any area is a difficult time- and resource-consuming exercise. It is, however, absolutely essential that it be done. Such documentation will likely be used as the justification for remedial and rehabilitative action(s) and also as the rationale for proposing when intervention is necessary in one place but not another. Bounding the degree of ecological impact (at least semiquantitatively) provides for realistic expectations for improvement if sediment remediation is to be pursued. It should also provide essential information on linkages that could be used in rehabilitating other ecosystem components such as fish or wildlife habitat. The lack of information coupling contaminated sediment to specific ecological impairments has, in many instances, precluded a clear estimate of how much sediment requires action to be taken, why, and what improvements can be expected to existing impairment(s) over time. Also, it has likely resulted in either a delay in remedial action or abandonment of the option altogether. A clear understanding of ecological links not only provides adequate justification for a cleanup program but also represents a principal consideration in the adoption of nonintervention, alternative strategies. In developing this understanding, it is important to know not only the existing degree of ecological impairment associated with sediment contaminants but also the circumstances under which those relationships and impacts might change (i.e., contaminants become more available and more detrimental). Because contaminated sediment remediation often costs millions of dollars per area, adequate assessment, prediction, and monitoring of recovery would seem obvious. However, experience has shown that this is not always the case, particularly for prediction and monitoring of ecological recovery. This scenario would never happen in the business world and should not occur in the environmental management field.

Animals↗
PubMed2006

Evaluation of extraction approaches linked to ELISA and HPLC for analyses of microcystin-LR, -RR and -YR in freshwater sediments with different organic material contents.

The efficiencies of conventional extraction techniques and analytical methods (HPLC-DAD and ELISA) were investigated for analyses of microcystins (MCs) in sediments. Our results showed several limitations. First, the extraction efficiency strongly depends on the extraction solvent, and extraction with 5% acetic acid in 0.2% trifluoroacetic acid (TFA)-methanol was confirmed as being the most appropriate for three different sediments (recovery: 33.1-44.9% of total MCs according to HPLC analyses). Second, the recovery of MCs was affected by the type of sediment but did not clearly correlate with the content of organic carbon. These results suggest that the sorption of MCs onto inorganic materials such as clay minerals is probably a more important process than interactions of the MCs with organic sediment matter. Third, the structure of the MCs is another crucial factor that affects the sorption of MCs and their recovery from sediments. Hydrophilic MC-RR gave much lower recoveries (20.0-38.8%) than MC-YR (44.1-59.5%) or MC-LR (55.3-77.8%) from three different types of spiked sediments. Recovery results analysed with HPLC-DAD correlated well with ELISA analyses. Further, extraction with 5% acetic acid in 0.2% TFA-methanol was used for analyses of MCs in 34 natural sediment samples collected from Brno reservoir (Czech Republic) from April to October 2005. Concentrations of MCs in sediments ranged from 0.003 to 0.380 microg/g sediment d.m. (ELISA results) or 0.016-0.474 microg/g d.m. (HPLC results). These values are equivalent to 0.63-96.47 microg/L of sediment (ELISA) or 4.67-108.68 microg/L (HPLC), respectively. Concentrations of sediment MCs showed both temporal and spatial variability, with the highest MC contents observed in the spring (April and May) and the lowest concentrations in July and August. Our results demonstrate the suitability of the methods described here for studying the occurrence, fate and ecological role of MCs in the aquatic environment.

Chromatography, High Pressure Liquid↗
PubMed2006

Microbial diversity in sediments of saline Qinghai Lake, China: linking geochemical controls to microbial ecology.

Saline lakes at high altitudes represent an important and extreme microbial ecosystem, yet little is known about microbial diversity in such environments. The objective of this study was to examine the change of microbial diversity from the bottom of the lake to sediments of 40 cm in depth in a core from Qinghai Lake. The lake is saline (12.5 g/L salinity) and alkaline (pH 9.4) and is located on the Qinghai-Tibetan Plateau at an altitude of 3196 m above sea level. Pore water chemistry of the core revealed low concentrations of sulfate and iron (<1 mM), but high concentrations of acetate (40-70 mM) and dissolved organic carbon (1596-5443 mg/L). Total organic carbon and total nitrogen contents in the sediments were approximately 2 and <0.5%, respectively. Acridine orange direct count data indicated that cell numbers decreased from 4 x 10(9) cells/g at the water-sediment interface to 6 x 10(7) cells/g wet sediment at the 40-cm depth. This change in biomass was positively correlated with acetate concentration in pore water. Phospholipid fatty acid (PLFA) community structure analyses determined decrease in the proportion of the Proteobacteria and increase in the Firmicutes with increased depth. Characterization of small subunit (SSU) rRNA genes amplified from the sediments indicated a shift in the bacterial community with depth. Whereas the alpha-, beta-, and gamma-Proteobacteria and the Cytophaga/Flavobacterium/Bacteroides (CFB) were dominant at the water-sediment interface, low G + C gram-positive bacteria (a subgroup of Firmicutes) became the predominant group in the anoxic sediments. Both PLFA and the sequence data showed similar trend. The Proteobacteria, CFB, and gram-positive bacteria are present in other saline lakes, but the presence of Actinobacteria and Acidobacteria/Holophaga in significant proportions in the Qinghai Lake sediments appears to be unique. The archaeal diversity was much lower, and clone sequences could be grouped in the Euryarchaeota and Crenarchaeota domains. The archaeal clones were not related to any known cultures but to sequences previously found in methane-rich sediments. Acetate-utilizing methanogens were isolated from sediment incubations, and alpha- and gamma-proteobacterial isolates were obtained from a water sample from the lake-bottom (23 m). Our data collectively showed that the observed diversity and shift in the community structure with depth was correlated with geochemical parameters (the redox state and availability of electron acceptor and donor). Heterotrophic methanogenesis is possibly adominant metabolic process in the Qinghai Lake sediments. These results reinforce the importance of geochemical controls on microbial ecology in saline and alkaline lake environments.

Acridine Orange↗
PubMed2006

Environmental effects of dredging on sediment nutrients, carbon and granulometry in a tropical estuary.

This monitoring study encompassed a period prior to dredging, during dredging and post dredging between July 1999 to June 2000 in Ponggol estuary located along the northeastern coast of Singapore. Mean concentrations of sediment nutrients in mg x Kg(-1) (+/- standard error of means) prior to dredging, during dredging and post dredging were 9.75 +/- 4.24, 8.18 +/- 4.29 and 11.46 +/- 4.74 for ammonium, 0.08 +/- 0.05, 0.06 +/- 0.02 and 0.09 +/- 0.01 for nitrite, 0.04 +/- 0.04, 0.11 +/- 0.17 and 0.25 +/- 0.30 for nitrate, 4.83 +/- 3.48, 0.77 +/- 0.48 and 8.33 +/- 9.73 for phosphate respectively. Pre dredge, dredge and post dredge levels of total carbon (TC) were 18.5 +/- 3.7, 20.2 +/- 3.5 and 34.6 +/- 12.0, of total organic carbon (TOC) were 10.5 +/- 2.9, 19.5 +/- 3.6 and 34.6 +/- 12.0 and of total inorganic carbon (TIC) were 7.9 +/- 1.0, 0.7 +/- 0.4 and non detectable in the sediments, respectively. Both, sediment nutrients and carbon registered lower concentrations with onset of dredging, with the exception of nitrate and TOC. A shift in sedimentary carbon from inorganic carbon to organic carbon was also observed with the onset of the dredging activities when the organically enriched historically contaminated layer was exposed. Sediment granulometry showed that the sediments in the estuary were predominantly silt and clay prior to dredging, which changed to sand with onset of dredging. Silt load in the sediments was highest post-dredge. Sediment nutrients and sediment organic carbon were observed to associate with the finer fractions (silt and clay) of sediments. Finer fractions of sediments get resuspended during a dredging event and are dispersed spatially as the result of tides and water movements. Prior to this study, the potential for nutrient release and sediment granulometry due to dredging have been suggested, but there have been few studies of it, especially in the tropics. The baseline information gathered from this study could be used to work out effective management strategies to protect similar tropical ecosystems elsewhere, should there be no other alternative to dredging.

Carbon↗
PubMed2006

Metals associated with suspended sediments in lakes Erie and Ontario, 2000-2002.

Sediment traps were deployed in the three major basins of Lake Erie, and the central (Mississauga) basin of Lake Ontario, and refurbished seasonally over the period 2000-2002. In Lake Ontario, sediment down-flux rates and corresponding contaminant down-flux rates were highest in winter during periods of unstratified thermal conditions, and generally increased with depth due to the influence of resuspended bottom sediments during all sampling periods. Lake Ontario suspended sediments exhibited the highest concentrations of metals; concentrations of mercury and lead frequently exceeded guideline values for bottom sediments. Contaminant levels in Lake Ontario suspended sediments were similar to concentrations in bottom sediments in the same area. There was a spatial trend toward higher suspended sediment metals concentrations from the eastern basin to the western basin of Lake Erie, which is similar to the trend in bottom sediment contamination. In the eastern basin of Lake Erie, which is the deepest area of the lake, there was no trend in down-flux rate with depth in 2001; however, down-flux rates increased with depth in 2002. Suspended sediments in the western basin of Lake Erie were determined to be largely resuspended bottom sediments; all western basin samples collected in the study exceeded the guideline value for mercury (0.486 microg/g).

Environmental Monitoring↗
PubMed1987

Clinical utility of erythrocyte sedimentation rate and plasma protein analysis in the elderly.

The utilization and interpretation of the erythrocyte sedimentation rate in the elderly have been surrounded by controversy and confusion. To improve the understanding of the erythrocyte sedimentation rate and its determinants in the aged, a defined population of 111 ambulatory, retirement-home residents underwent thorough clinical and laboratory evaluation. Westergren erythrocyte sedimentation rate, Wintrobe erythrocyte sedimentation rate, and plasma viscosity measurements were all significantly correlated with one another as well as with plasma proteins, particularly fibrinogen and globulins. Age per se had no influence on the erythrocyte sedimentation rate in the study population. On the basis of standard upper limits of normal for younger populations, the Wintrobe sedimentation rate was most commonly abnormal and plasma viscosity least commonly abnormal. The "normal" upper limit of 20 mm/hour for Westergren sedimentation rate was also the optimal limit of normal by receiver operating characteristic analysis of the study population. Although the sensitivity of the Westergren sedimentation rate for the presence of an inflammatory condition or monoclonal gammopathy was only 0.55, the specificity was 0.96, and the positive predictive value of an elevated erythrocyte sedimentation rate being associated with a clinical disorder was 0.93. The enhanced clinical utility of the erythrocyte sedimentation rate in this population compared with other elderly populations may be due to a low prevalence of anemia and hypoalbuminemia. In such populations, the erythrocyte sedimentation rate may remain a useful clinical test, regardless of patient age.

Age Factors↗
PubMed2004

Processes controlling metal transport and retention as metal-contaminated groundwaters efflux through estuarine sediments.

Factors affecting the transport and retention of Cd, Cr, Cu, Ni, Pb and Zn in acidic groundwaters as they pass through estuarine sediments were investigated using column experiments. Acidic groundwaters caused the rapid dissolution of iron sulfide (AVS) and other iron and manganese phases from sediments that are important for metal binding and buffering. Metal breakthrough to overlying water occurred in the order of Ni>Zn>Cd>>Cu>>Cr/Pb. Metal transport increased as the sediment permeability increased, reflecting the low resistance to flow caused by larger sand-sized particles and the decreased abundance of metal adsorption sites on these materials. Metal mobility increased as the groundwater pH decreased, as flow rate or metal concentrations increased, and as the exposure duration increased. Groundwater Cr and Pb were promptly attenuated by the sediments, the mobility of Cu was low and decreased rapidly as sediment pH increased above 4.5, while Cd, Ni and Zn were the most easily transported to the surface sediments and released to the overlying waters. For groundwaters of pH 3, metal migration velocities through sandy sediments were generally 0.5-2% (Cr, Pb), 1-6% (Cu) and 4-13% (Cd, Ni, Zn) of the total groundwater velocity (9-700 m/yr). The oxidative precipitation of Fe(II) and Mn(II) in the groundwaters did not affect metal mobility through the sediments. The results indicated that the efflux of acidic and metal-contaminated groundwater through estuarine sediments would affect organisms resident in sandy sediments more greatly than organisms resident in fine-grained, silty, sediments.

Animals↗
PubMed2004

Metal partitioning in river sediments measured by sequential extraction and biomimetic approaches.

We quantified the concentrations and distributions of metals (Cd, Cr, Cu, Ni, Pb, and Zn) in the sediments of Tuen Mun River, Hong Kong. The potential bioavailability of metals was assessed with a biomimetic extraction method using the sipunculan gut juices. The sediments were characterized by relatively high concentrations of trace metals. Field collected sediments were highly anoxic and the ratio of simultaneously extractable metal (sigmaSEM) to acid volatile sulfide (AVS) was much less than one in these sediments. The majority (>67%) of Cd, Pb, and Zn were bound to AVS, thus their concentrations in the sediment porewater were low. In contrast, Ni was little bound to AVS due to its lower ratios of SEM-Ni to total Ni concentrations. For Cu, relatively high concentrations in the sediment porewater was found, and total organic carbon, AVS and other resistant sulfide phase were the controlling factors for sedimentary Cu partitioning. Net metal adsorption from gut juices to anoxic sediments was observed in metal extraction experiments, suggesting that AVS determined the bioaccumulation and potential bioavailability of most metals in these sediments. Extraction of metals from the oxidized sediments by the gut juices was mainly attributed to metal redistribution from AVS to other geochemical phases. The gut juices were the most effective solvent or extractant than the simple electrolyte solution [I (NaNO(3)) = 0.01 M] and the natural overlying water. Cd was more easily extracted from the oxidized sediments than Zn that tended to have a stronger binding affinity with Fe-Mn oxide, clay and organic matter. The application of partial removal techniques in metal extraction experiments further demonstrated the differential controls of various sediment geochemical phases in affecting metal bioavailability, with the order of TOC > Fe-Mn oxides > carbonate.

Animals↗