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PubMed2005

Use of slow filtration columns to assess oxygen respiration, consumption of dissolved organic carbon, nitrogen transformations, and microbial parameters in hyporheic sediments.

Biogeochemical processes mediated by microorganisms in river sediments (hyporheic sediments) play a key role in river metabolism. Because biogeochemical reactions in the hyporheic zone are often limited to the top few decimetres of sediments below the water-sediment interface, slow filtration columns were used in the present study to quantify biogeochemical processes (uptakes of O2, DOC, and nitrate) and the associated microbial compartment (biomass, respiratory activity, and hydrolytic activity) at a centimetre scale in heterogeneous (gravel and sand) sediments. The results indicated that slow filtration columns recreated properly the aerobic-anaerobic gradient classically observed in the hyporheic zone. O2 and NO3- consumptions (256 +/- 13 microg of O2 per hour and 14.6 +/- 6.1 microg of N-NO3- per hour) measured in columns were in the range of values measured in different river sediments. Slow filtration columns also reproduced the high heterogeneity of the hyporheic zone with the presence of anaerobic pockets in sediments where denitrification and fermentation processes occurred. The respiratory and hydrolytic activities of bacteria were strongly linked with the O2 consumption in the experimental system, highlighting the dominance of aerobic processes in our river sediments. In comparison with these activities, the bacterial biomass (protein content) integrated both aerobic and anaerobic processes and could be used as a global microbial indicator in our system. Finally, slow filtration columns are an appropriate tool to quantify in situ rates of biogeochemical processes and to determine the relationship between the microbial compartment and the physico-chemical environment in coarse river sediments.

Bacteria, Aerobic↗

PubMed2002

Burrowing responses of the short-neck clam Ruditapes philippinarum to sediment contaminants.

The burrowing responses of a common tropical bivalve, the short-neck clam Ruditapes philippinarum, to cadmium (Cd)-spiked sediment, variations of sediment grain size and natural sediments collected from 15 locations in Hong Kong's inshore waters were investigated through a series of laboratory tests. Results showed that the burrowing response exhibited a negative relationship with an increase in Cd concentration in the spiked sediments. The level of Cd was also found to be directly proportional to the percent mortality of the clam. However, there was no significant difference (p > 0.05) in the time elapsed for the clam to burrow into sediments with different grain size composition. The elapsed time for 50% of the test clams to burrow into the sediment (ET50) over a period of 48 h was calculated for the sediment samples collected from the 15 locations. Results of ANOVA showed significant difference (p < 0.05) among the sediment samples. Tukey's multiple comparison test revealed two groups of sediments: group 1 containing 3 sediment samples collected from Victoria Harbour and group 2 containing 12 samples obtained from other coastal areas of Hong Kong. The ET50 value for group 1 sediments was found to be greater than 2,880 min whilst the ET50 for group 2 sediments had a mean of 173.9 min. Agglomerative classification of the sediment samples, based on metal content (As, Cd, Cr, Cu, Ni, Pb, Zn), also showed two similar groups, suggesting that the ET50 values were correlated with the metal level of the sediment samples. Group 1 sediments collected from Victoria Harbour had greater concentrations of Cd, Cr, Cu, Ni and Zn as compared to that in group 2. The present study demonstrated that high metal content in the sediment tends to inhibit the burrowing responses of the clam and that there is potential to develop the burrowing responses of R philippinarum as a sublethal sediment toxicity test.

Animals↗

PubMed2002

The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments.

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore.

Clostridium perfringens↗

PubMed2002

Bioconcentration of heavy metals in aquatic environments: the importance of bioavailability.

The importance of heavy metal bioavailability on the bioconcentration in aquatic biota is examined. To this purpose, mono- and multivariate statistical techniques are applied to develop correlations between heavy metal bioconcentration factor and sediment characteristics, that are expected to affect bioavailability, using a database of heavy metal concentrations in biota and sediment along with the available physicochemical characteristics. The statistical analysis shows that satisfactory correlations are obtained only when factors that affect bioavailability, such as metal oxides concentration and organic carbon content in the sediment, are taken into account.

Animals↗

PubMed2002

Temporal and spatial variations in kinetics of alkaline phosphatase in sediments of a shallow Chinese eutrophic lake (Lake Donghu).

Monthly sediment and interstitial water samples were collected in a shallow Chinese freshwater lake (Lake Donghu) from three areas to determine if alkaline phosphatase activity (APA) plays an important role, in phosphorus cycling in sediment. The seasonal variability in the kinetics of APA and other relevant parameters were investigated from 1995-1996. The phosphatase hydrolyzable phosphorus (PHP) fluctuated seasonally in interstitial water, peaking in the spring. A synchronous pattern was observed in chlorophyll a contents in surface water in general. The orthophosphate (o-P) concentrations in the interstitial water increased during the spring. An expected negative relationship between PHP and Vmax of APA is not evident in interstitial water. The most striking feature of the two variables is their co-occurring, which can be explained in terms of an induction mechanism. It is argued that phosphatase activity mainly contributes to the driving force of o-P regeneration from PHP in interstitial water, supporting the development of phytoplankton biomass in spring. The Vmax values in sediment increased during the summer, in conjunction with lower Km values in interstitial water that suggest a higher affinity for the substrate. The accumulation of organic matter in the sediment could be traced back to the breakdown of the algal spring bloom, which may stimulate APA with higher kinetic efficiency, by a combination of the higher Vmax in sediments plus lower Km values in interstitial water, in summer. In summary, a focus on phosphatase and its substrate in annual scale may provide a useful framework for the development of novel P cycling, possible explanations for the absence of a clear relationship between PHP and APA were PHP released from the sediment which induced APA, and the presence of kinetically higher APA both in sediment and interstitial water which permitted summer mineralization of organic matter derived from the spring bloom to occur. The study highlighted the need for distinguishing functionally distinct extracellular enzymes between the sediment and interstitial water of lakes.

Alkaline Phosphatase↗

PubMed2001

The chemical and biogenotoxic characterization of organic xenobiotics in aquatic sediment materials 1. The application and comparison of chemically non-specific and biogenotoxic methods.

The aim of this work was to evaluate the Ames assay and mixed function oxidase (MFO)-Induct Test used in parallel with chemical group tests (ECD fingerprint and PAH estimation) for the characterization of the organic pollution of water sediment materials. Sediment materials were collected from "clean" and relatively heavily polluted locations in the Middle Adriatic Sea, and from some locations in continental Croatia polluted with wastewaters from different enterprises. Characterization of the organic extracts of the sediment materials investigated was performed chemically using UV spectrofluorometry for the determination polyaromatic hydrocarbons (PAH) and gas chromatography for the determination of volatile EC detector sensitive materials. Genotoxic analysis of the extracts was performed using the MFO-Induct Test and mutagenicity testing using the Standard Plate Incorporation Test as described by Maron and Ames with Salmonella typhimurium TA 98. Measurement of the BaPMO enzyme activity in the livers of carp treated i.p. with total extracts of the sediment investigated confirmed that the methanol extracts generally contained more inducing matter than the petroleum ether extracts. Ames assay showed that for all the samples following the elimination of the sulfur, there was an increase in the number of revertants in comparison to the control number, which indicates that the samples contained mutagenic substances. The larger doses of extracts generally demonstrated cytotoxicity, as evidenced by a reduced number of spontaneous revertants in the SalmonellalMicrosome Test. Investigation of the correlation of the chemical parameters with the biological parameter showed that the induction of BaPMO exhibited a statistically significant correlation with the level of the ECD fingerprint of the petroleum ether sediment extract.

Animals↗

PubMed2002

Effects of sample preparation on the measurement of organic carbon, hydrogen, nitrogen, sulfur, and oxygen concentrations in marine sediments.

The elemental composition of marine sediment provides useful information for the study of environmental processes including biogeochemical cycling and contaminant partitioning. It is common practice to acidify marine sediment samples to remove carbonate before measuring the concentrations of organic carbon (C). To date, however the effects of acidification on the concentrations of hydrogen (H), nitrogen (N), sulfur (S) and oxygen (O) in marine sediments have not been explicitly addressed. Acidification may contaminate or alter the sediment samples and create experimental artifacts affecting the validity of resulting H/C, C/N and O/C ratios. The objective of this study was to quantify how various preparation techniques affect the measured concentrations of C, H, N, S and O in marine sediments. Effects of four different pretreatments: unacidified (whole), acidification by HCl vapor, acidification by direct addition of HCl, and combustion were evaluated using five marine sediments and a standard reference material. The magnitude of carbonate loss between the vapor and direct acidification treatments was evaluated using stable C isotope analysis. Carbonates were most effectively removed by direct addition of HCl; and our results agree with findings of other studies which found direct addition of HCl to be the most accurate method for measuring organic C. However, the acid treatments elevated the apparent concentration of H and O; and in a few cases concentrations of N and S were significantly affected by acidification. In general, combustion significantly reduced all elemental concentrations compared to the whole sample. Based on these results, we recommend analysis of the untreated whole sediment for determining N, H, O, and S.

Carbon↗

PubMed2000

Sediment-air equilibrium partitioning of semi-volatile hydrophobic organic compounds part 2. Saturated vapor pressures, and the effects of sediment moisture content and temperature on the partitioning of polyaromatic hydrocarbons.

A gas saturation methodology was used to determine the sediment/air partition coefficient (K(SA)) for phenanthrene and dibenzofuran on a local sediment from the Campus Lake, Baton Rouge. The effects of sediment moisture content, air relative humidity and temperature on K(SA) for phenanthrene were ascertained. The saturated vapor pressures of the compounds were also measured. The sediment moisture content had a striking effect on K(SA); increasing sediment moisture content decreased K(SA). Temperature also had a dramatic effect on K(SA). The variation with temperature was used to evaluate the heats of adsorption on both 'dry' (< 0.8% by mass of water) and 'wet' (> 6% by mass of water) sediments. The heat of adsorption for phenanthrene normalized to unit molecular surface area indicated for the physically adsorbed organic compound was seven times smaller than that for a water molecule. The experimental value of K(SA) was used to test a proposed theoretical model. A good agreement was observed for both phenanthrene and dibenzofuran. The model can be extended to other compounds and sediment types for prediction of air emissions from exposed sediment and dredged materials.

Air Pollutants↗

PubMed2003

Modelling hydrodynamics and sediment flux within a macrotidal estuary: problems and solutions.

A model of estuarine circulation and sediment transport is described. The model uses a 2-D longitudinal and vertical grid to predict the distribution of tidal elevation, current velocity, density and sediment concentration. It has been developed for relatively narrow estuaries that have a large tidal range and potentially high river flow. The advantage over simple 1-D and depth-averaging 2-D models is that it can give reasonable representation of both gravitational circulation and the vertical distribution of suspended sediment concentrations, thereby providing better estimates of the bottom stress and sediment flux, particularly in the deep channel. The model has been developed as a management tool to provide some of the advantages of a full 3-D model, but with smaller development and running costs. It can be used to predict concentrations of contaminants in estuaries that have a significant load of suspended cohesive sediment, and can differentiate between dissolved contaminants and those that are attached to suspended sediments. It is a potentially useful tool for predicting the distribution of relatively short-lived contaminants that are affected by sediment concentration, such as bacteria and some radionuclides.

Bacteria↗

PubMed2002

Heavy metals in organisms and sediments from Turkish Coast of the Black Sea, 1997-1998.

During the period 1997-1998, macroalgae, sea snail, mussel, fish and sediment samples were collected at different stations of the Turkish Black Sea coast in order to establish the concentration of selected heavy metals. Heavy metals analyzed were Cd, Co, Cr, Ni, Zn, Fe, Mn, Pb and Cu. The results showed that the Turkish Black Sea coast is facing heavy metal pollution. The metal concentrations in macroalgae, sea snail, mussel and sediment samples are very high. However, Cd, Pb and Cu concentrations in anchovy fish decreased, while Co, Fe, Zn, Cr, Mn and Ni contents had changed when compared previous data. The metal levels in macroalgae did not follow the same pattern as concentrations in sediments at the same station. On the other hand, concentrations of Cd, Co, Cr, Zn, Fe, Mn and Cu in sea snail, mussel and fish samples were related to sediment data in the examined stations.

Animals↗

PubMed2001

Relationships between sea-bed radionuclide activities and some sedimentological variables.

Natural radionuclides (232Th, 226Ra, 40K) and 137Cs, coming from atmospheric radioactive fallout, have been measured in sea-bed sediments of the Bay of Cádiz (South Western Spain). In this report, multivariate analysis methods have been employed to study the relationships between the activities of the radionuclides and some sedimentological variables like granulometric facies, organic content and apparent density. The correlation functions found show that it is possible to determine, with a satisfactory degree of approximation, the granulometric facies of the sediments using only radiometric information.

Geologic Sediments↗

PubMed2001

Cadmium accumulation in the freshwater isopod Asellus racovitzai: the relative importance of solute and particulate sources at trace concentrations.

A stable isotope tracer technique was used to evaluate the relative importance of particulates and water as respective sources of cadmium (Cd) uptake in the freshwater isopod Asellus racovitzai (Isopoda, Crustacea). 113Cd(NO3)2 was applied to the sediment at a nominal concentration of 20.0 ng g-1, and 114Cd(NO3)2 was added to the overlying water (nominal concentration of 4.4 ng g-1), in the same test systems. Asellids added were either free-ranging on the sediment surface, where they were exposed to both particulate and water sources of Cd, or were enclosed in dialysis 'tubes', 10 cm above the sediment surface, and were therefore exposed to Cd in water only. By analysis of both isotopes, uptake vectors could be determined simultaneously. After 7 days of exposure, average 114Cd concentrations in 'free' asellids were 15.6 +/- 2.0 micrograms/g, compared with 10.4 +/- 1.8 micrograms/g in 'tube'-held asellids (P < 0.05), i.e. at least 60% of accumulated 114Cd was from water. Furthermore, water-spiked 114Cd was accumulated in asellids to tissue concentrations that were more than four-times greater than sediment-spiked 113Cd. When the sediment organic content was increased (20% peat moss), total Cd concentrations in both overlying water and asellids were significantly lower (P < 0.01), compared with the mineral sediment treatments, and Cd accumulation in tube and free asellids was similar. This study shows that water is an important vector of Cd accumulation in A. racovitzai, and factors that lower Cd concentrations in solution (such as increased organic content of sediment), decrease Cd bioaccumulation.

Animals↗

PubMed2001

Factors controlling the bioaccumulation of mercury and methylmercury by the estuarine amphipod Leptocheirus plumulosus.

The bioaccumulation of inorganic mercury (HgI) and monomethylmercury (MMHg) by benthic organisms and subsequent trophic transfer couples the benthic and pelagic realms of aquatic systems and provides a mechanism for transfer of sedimentary contaminants to aquatic food chains. Experiments were performed to investigate the bioavailability and bioaccumulation of particle-associated HgI and MMHg by the estuarine amphipod Leptocheirus plumulosus to further understand the controls on bioaccumulation by benthic organisms. HgI and MMHg are particle reactive and have a strong affinity for organic matter, a potential food source for amphipods. Microcosm laboratory experiments were performed to determine the effects of organic matter on Hg bioaccumulation and to determine the major route of Hg uptake (i.e. sediment ingestion, uptake from water/porewater, or uptake from 'food'). Amphipods living in organic-rich sediment spiked with Hg accumulated less Hg than those living in sediments with a lower organic matter content. Feeding had a significant impact on the amount of HgI and MMHg accumulated. Similarly, amphipods living in water with little organic matter accumulated more Hg than those living in water with a greater percentage of organic matter. MMHg was more readily available for uptake than HgI. Experimental results, coupled with results from a bioaccumulation model, suggest that accumulation of HgI and MMHg from sediment cannot be accurately predicted based solely on the total Hg, or even the MMHg, concentration of the sediment, and sediment-based bioaccumulation factors. All routes of exposure need to be considered in determining the accumulation of HgI and MMHg from sediment to benthic invertebrates.

Animals↗

PubMed2003

Temporal-spatial trends in heavy metal contents in sediment-derived soils along the Sea Scheldt river (Belgium).

The aim of this study was to survey the alluvial plains of the Sea Scheldt river in Belgium for the presence of old sediment-derived soils, and to appraise the heavy metal contamination at these sites. Historically, sediments of periodical dredging operations have been disposed in the alluvial plain without concern for the potential presence of contaminants. Up to 96% of the areas that were affected by sediment disposal (ca. 120 ha) was found to be polluted by at least one of the metals Cd, Cr, Zn or Pb. Concentrations of Cd, Cr and Zn were, in 10% of the cases, higher than 14, 1400 and 2200 mg/kg DM, respectively. Based on the Flemish decree on soil sanitation, Cu and Ni concentrations were of less environmental concern on any site. The pollution in the Sea Scheldt alluvial plain nevertheless is lower than for the Upper Scheldt alluvial plain. The sediment-derived soils in the most upstream part near Ghent were used for disposal of sediments from dredging operations elsewhere. Metal concentrations were explored and both spatial and temporal trend were analysed. The pollution levels encountered warrant caution as most of the soils affected by historical dredged sediment disposal are currently in use for pasture.

Belgium↗

PubMed2003

Phytoremediation prospects of willow stands on contaminated sediment: a field trial.

Establishing fast growing willow stands on land disposed contaminated dredged sediment can result in the revaluation of this material and opens possibilities for phytoremediation. A field trial was designed to assess the impact of planting a willow stand (Salix viminalis L. 'Orm') on the dissipation of organic contaminants (mineral oil and PAHs) in dredged sediment. In addition, the accumulation of heavy metals (Cd, Cu, Pb and Zn) in the biomass was determined. After 1.5 years, a significant decrease of 57% in the mineral oil concentration in the sediment planted with willow was observed. Degradation of mineral oil in sediment which was left fallow, was only 15%. The mineral oil degradation under willow was most pronounced (79%) in the root zone of the stand. In the sediment which was left fallow there was a significant reduction of the total PAH content by 32% compared with a 23% reduction in the planted sediment. The moderate and selective metal uptake, measured in this study, limits the prospects for phytoextraction of metals from dredged sediment.

Biodegradation, Environmental↗

PubMed2000

Genotoxic potential of marine sediments from the North Sea.

The alkaline comet assay is a method for detecting DNA strand breaks and alkali labile sites in individual cells. An in vitro system was used to investigate the genotoxic potential of complex mixtures such as organic extracts of marine sediments. DNA damage was induced in leukocytes isolated from carp (Cyprius carpio) by exposure to organic sediment extracts from the North Sea or hydrogen peroxide as positive control, respectively. The minimum concentration for significant effects ranged from 1 to 40 mg sediment dry weight per milliliter assay volume. The sensitivity of the method was enhanced by using the DNA repair inhibitor, 1-beta-D-arabinofuranosylcytosine (ara C). From the results, it can be suggested that total organic carbon (TOC) as well as the different compositions of contaminants present in the sediment extracts may contribute to the genotoxic effects observed. The comet assay can be applied successfully as an in vitro bioassay for investigations on genotoxicity of marine sediment extracts.

Animals↗

PubMed2002

Potential remobilization of 137Cs, 60Co, 90Tc, and 90Sr from contaminated Mayak sediments in river and estuary environments.

Following 50 years of nuclear production at Mayak PA, sediments in storage reservoirs are significantly contaminated. Dam failure or flooding could potentially transport large amounts of sediments, via rivers, to the Ob estuary and Kara Sea. The objectives of this work were to investigate fresh and seawater remobilization of 137Cs, 50Co, 99Tc, and 90Sr from contaminated Reservoir 10 sediments. Sediments were extracted sequentially using synthetic Techa freshwater, seawater, and chemical reagents with increasing dissolution powers. 137Cs and 90Sr freshwater distribution coefficients (apparent Kd) agreed quite well with published values; values for 99Tc were higher and values for 60Co were lower than expected. In seawater, mean apparent Kd values decreased by 94, 77, 48, and 73% (137Cs, 60Co, 99Tc, and 90Sr, respectively), indicating increased radionuclide mobility. Remobilization in seawater was 5, 15, 1, and 23% of total activities (i.e., releases of 165, 11, 0.3, and 170 kBq kg(-1) d.w.) for 137Cs, 60Co, 99Tc, and 90Sr, respectively. 137Cs and 99Tc were strongly bound to sediments (60% and 80%, respectively). 60Co and 90Sr were more mobile (70% reversibly bound). In conclusion, Mayak Reservoir sediments could potentially contaminate the Ob estuary due to remobilization of sediment-held radionuclides upon contact with seawater.

Environmental Monitoring↗

PubMed2002

Considerations for capping metal-contaminated sediments in dynamic estuarine environments.

The effects of tides, bioturbating organisms, and periods of anoxia on metal fluxes from contaminated harbor sediments in a shallow tidal estuarine bay were studied, together with capping technology options for the containment of metal contaminants. Zinc fluxes from the sediments were high, ranging from 10 to 89 mg of Zn m(-2) day(-1). In the absence of capping, experiments in corer-reactors showed that simulated tidal processes increased zinc fluxes 5-fold. Fluxes were also greater in the presence of sediment-dwelling organisms. If organisms were removed, and recolonizing organisms later added, their bioturbation activities initially lowered zinc fluxes, but fluxes gradually reached steady state at the higher levels seen previously. Capping materials physically isolate contaminated sediments, provide a binding substrate for metals released from the sediment and importantly create an anoxic environment below the cap, which stimulates the formation of insoluble metal sulfides. Clean sediment (5 mm) was the most effective capping material in reducing zinc fluxes. Zeolite/sand mixtures (10 mm) also greatly reduced these fluxes, but significant breakthrough of zinc occurred after 2 weeks. Sand (20 mm) was not effective. The presence of organisms disturbed capping materials and increased zinc fluxes. Installed capping materials should have depths of >30 cm to minimize organisms burrowing to contaminated sediments beneath.

Environmental Pollution↗