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PubMed2006

Nickel speciation in the presence of different sources and fractions of dissolved organic matter.

This study evaluated nickel (Ni) speciation in the presence of different fractions (humic acid (HA), fulvic acid (FA)) and sources (natural sediment, Suwannee River, peat moss) of dissolved organic matter (DOM) at Ni concentrations toxicologically relevant to the freshwater amphipod, Hyalella azteca. The free Ni ion, Ni(2+), was measured in reconstituted water (with or without DOM) using a miniaturized ion-exchange technique (IET). Ni speciation from these experiments was compared to calculated results obtained from equilibrium modelling (WHAM, Model VI). While it is known that Ni will complex with DOM, it was found that under acutely toxic Ni exposure concentrations ([Ni(Total)]=5mg/L, or 85.1 microM) representative surface-water DOC concentrations ( approximately 10mg/L) played little or no role in Ni speciation. Conversely, at sublethal Ni exposure concentrations ([Ni(Total)]=0.2 and 0.5 microg/L, or 3.4 and 8.51 microM, respectively) DOM significantly affected Ni speciation with [Ni(2+)] decreasing with increasing concentration of DOM. It was found that for similar concentrations of DOC (same fraction, different sources), the measured Ni(2+) concentrations were reduced (relative to the control), but similar to one another. Conversely, at similar DOC concentrations, the HA fraction reduced Ni(2+) levels to a greater extent than the associated FA fraction. Overall, this study provides proof of principle that Suwannee River and peat humic substances are suitable analogues for natural sediment pore-water DOM when evaluating Ni bioavailability in freshwater.

Amphipoda↗
PubMed2005

Composition, sources, and potential toxicological significance of PAHs in the surface sediments of the Meiliang Bay, Taihu Lake, China.

Twenty-five surface sediment samples were collected from Meiliang Bay, Taihu Lake, China, in 2003. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs), identified as priority pollutants by the USEPA, were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). Total concentrations of the PAHs ranged from 1207 to 4754 ng/g dry weight. Sediment samples with the highest PAH concentrations were from the northern site of the bay, which is in proximity to the incoming PAH source; the PAH levels in the southern part were relatively low. The observed PAH levels were higher than those in river sediments in China but were lower than those found in sediments of urban areas and harbors. According to the observed molecular indices, PAHs originated largely from the high-temperature pyrolytic process, whereas the petrogenic process was more commonly responsible for PAH contamination in harbors. A good correlation existed between the benzo[a]pyrene level and the total PAH concentration (r=0.97), making benzo[a]pyrene a potential molecular marker for PAH pollution. According to the numerical effect-based sediment quality guideline (SQGs) of the United States, the levels of PAHs at most studied sites in Meiliang Bay, except some sites in the northern part of the bay, should not exert adverse biological effects. In the northern part of the bay, the PAH levels at sites 21 and 22 exceed the effects range low (ERL) and could thus cause acute biological impairments, in comparison with the sediment quality guidelines. The total PAH levels were expressed as the B[a]P toxicity equivalents (TEQs(carc)) and compared to the contaminated sediments from Guba Pechenga, Barents Sea, Russia.

China↗
PubMed2006

Presence of surfactants and their degradation intermediates in sediment cores and grabs from the Cadiz Bay area.

The occurrence and distribution of the major surfactants--LAS, AES, APEOs and AEOs--and their degradation intermediates--SPCs, AP and APECs--in a marine-estuarine environment at Spain are presented. Results show that their concentration in surface sediments is clearly correlated with their usage and the existence of wastewater discharges. The degradation processes appear to lead to the formation of SPCs in the case of LAS, and to the shortening of the average ethoxylated chain length in the case of NPEOs, AEOs and AES. Vertical profiles for AEOs and AES are reported for the first time and present the highest values nearest the surface, followed by a sharp decrease with depth for all surfactants, as well as the appearance of degradation intermediates in deeper sedimentary layers. Shorter LAS homologues and SPCs tend to be present in pore water while strongly non-polar intermediates like NP are firmly attached to the sediments.

Biodegradation, Environmental↗
PubMed2004

Potential sulfur metabolisms and associated bacteria within anoxic surface sediment from saline meromictic Lake Kaiike (Japan).

The effects of light and of added electron donors and sulfur compounds on sulfur metabolisms in the microbial mat dilutions from the saline meromictic Lake Kaiike were investigated. Sulfide concentrations in the mat dilution without any electron donor gradually increased by approximately 0.6-1 mM in the dark. Additions of lactate, acetate, H(2)/CO(2), propionate and iso-butylate stimulated sulfide production, whereas benzoate did not, indicating the limitation of sulfate reduction by available electron donor concentrations. More sulfide was produced, without a decrease of sulfate, in an elemental sulfur-amended dilution than in a non-amended control. In contrast, the addition of a high concentration of sulfide slowed down sulfide production. After enrichment under various conditions, microbial communities in the dilutions were characterized by a denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene and sequencing. As a result, microorganisms affiliated with mesophilic sulfate-reducing bacteria group within the Deltaproteobacteria and the Epsilonproteobacteria were mainly enriched by the addition of electrons used in this study, suggesting that these microorganisms might play an important role in sulfur metabolisms within the surficial sediment of Lake Kaiike.

DNA, Bacterial↗
PubMedDate not supplied

Exposure of grass shrimp to sediments receiving highway runoff: Effects on reproduction and DNA.

A grass shrimp bioassay was carried out on sediments from three estuarine stations which were different distances from a highway storm drain. Total polycyclic aromatic hydrocarbon (PAH) concentrations were 29, 1.5 and 0.1 microg/g sediment at stations A (next to drain), B (100 m from drain) and C (500 m from drain), respectively. Lower embryo production and embryo hatching rates and a higher level of DNA strand breaks (comet assay) were observed in grass shrimp exposed to stations A and B sediments. There appeared to be an association between reproduction abnormalities and increased DNA strand breaks as a result of grass shrimp exposure to estuarine sediments receiving highway runoff.

Animals↗
PubMed2005

Variability of Mediterranean coralligenous assemblages subject to local variation in sediment deposition.

This study tested whether the development of coralligenous assemblages on horizontal and vertical surfaces differed between localities of high and low sediment deposition. The development and structure of these assemblages varied in predictable ways according to the level of sediment deposition. These differences were largely independent of the orientation of substratum. Turfs were more extensive in areas of high sediment deposition while erect and encrusting algae were most extensive in areas of low sediment deposition. Encrusting invertebrates characterised vertical surfaces and were most extensive in areas of high sediment deposition. These results are consistent with studies from other temperate regions of the globe, suggesting that effects of sedimentation on temperate coasts are substantial and widespread.

Animals↗
PubMedDate not supplied

Dynamics and influencing factors of heterotrophic bacterial utilization of acetate in constructed wetlands treating woodwaste leachate.

14C-acetate was used as a tracer of substrates for heterotrophic bacteria to investigate the dynamics and influencing factors of bacterial activity in surface flow wetlands treating woodwaste leachate. Epiphytic assimilation and mineralization of acetate increased considerably over three weeks of microbial colonization. No significant longitudinal variation in acetate uptake was found. The temporal variation of bacterial activity was neither correlated to water temperature nor acetic acid concentration. Mineralization percentage varied significantly with acetate uptake rate. Acetate uptake rates of bacterioplankton (408+/-258 microg L(-1) h(-1)), epiphyton (67.7+/-41.7 mg m(-2) h(-1)) and sedimentary bacteria (26.7+/-25.6 microg g(-1) h(-1)) were influenced by the concentrations of organic substrates and inorganic nutrients. Sedimentary bacteria contributed to the majority (55-73%) of the total heterotrophic acetate uptake, while epiphytic bacteria played only a minor role (1-3%). The acetate mineralization percentage of sediment (16%) was much lower than that of water (55%) and epiphyton (64%). Addition of ammonium nitrate fertilizer increased acetate uptake rates significantly, especially for sediment. No remarkable changes in mineralization percentage and the relative importance of water, sediment and epiphyton were found due to fertilization.

Acetates↗
PubMed2002

Determination of polycyclic aromatic hydrocarbons and polycylic aromatic sulfur heterocycles by high-performance liquid chromatography with fluorescence and atmospheric pressure chemical ionization mass spectrometry detection in seawater and sediment samples.

Two methods for determining 10 polycyclic aromatic compounds were developed. Both methods were based on high-performance liquid chromatography (HPLC), but one method used fluorescence detection, while the other used atmospheric pressure chemical ionization mass spectrometry (APCI-MS). For water analysis, solid-phase extraction (SPE) was on-line coupled to the separation system. Using a styrene-divinylbenzene copolymer (PLRP-s) as sorbent in the SPE and adding 20% of acetonitrile to the water sample before its preconcentration, recoveries were above 70% for most of the compounds. For the fluorescence method, all compounds were detected and six of them could be quantified at concentrations higher than 0.02 microg 1(-1). For the MS detection method, only seven of the compounds were detected and six were quantified at concentrations higher than 0.06 microg 1(-1). To analyse sediment samples, an extraction with dichloromethane was used and, due to the complexity of the matrix, a standard addition calibration was carried out. Seawater and sediment samples taken from the Tarragona fishing port and marina on the coast of Catalonia (Spain) were analysed, and five compounds (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene) were quantified in the sediment samples.

Atmospheric Pressure↗
PubMed2001

Sources and geochemical constraints of polycyclic aromatic hydrocarbons (PAHs) in sediments and mussels of two Northern Irish Sea-loughs.

Polycyclic aromatic hydrocarbons (PAHs) were sampled from 30 sediment and 8 mussel (Mytilus edulis) stations in two Northern Irish Sea-toughs. Analysis was performed by gas chromatography coupled to mass spectrometry (GC-MS). Sedimentary organic carbon, % silt/clay and mean grain size were analysed in order to assess the role of geochemistry on PAH distribution. With the exception of two sites in Larne Lough representing localized regions of high contamination, sum(PAHs) in sediments ranged between 83 and 2300 ng g(-1). Regression analysis indicated that particle size and organic C were dominant factors in controlling the distribution of PAHs throughout the sediments. Sources of PAHs in both sea-loughs were dominated by pyrogenic inputs suggesting that diffuse sources such as atmospheric deposition may be a major source to both water bodies. The sum of PAHs in mussels ranged between 95 and 184 ng g(-1). Variations in concentrations may be explained by differences in the condition between mussel populations. Mussels in both sea-loughs exhibit similar metabolic activities towards the PAH compounds which were predominantly bioaccumulated from sediments.

Animals↗
PubMed2003

Bacteria and organic matter dynamics during a bioremediation treatment of organic-rich harbour sediments.

We studied the dynamics of bacteria and organic matter in the Ancient Port of Genoa (Italy) during a bioremediation treatment of sediment (during summer-autumn 1998) in an area characterised by continuous sewage discharge. A strong increase in total benthic bacterial density (TBN) was recorded at the end of the study, from 14 x 10(8) to 58-172 x 10(8) cell g(-1) in different parts of the treated area. The TBN increase was linked to organic matter depletion, from more than 40 to less than 20 mg x g(-1). In order to highlight the main ecological mechanisms involved in bioremediation, a laboratory experiment based on both water and sediment from the basin studied was carried out. We observed an increase in TBN during the first 20 days and a decrease in sediment organic matter (up to about 20%). Increases of organic matter (about 2-fold) and TBN (from 21 to 33 x 10(9) cell l(-1)) occurred in the overlying water, suggesting a strong association between the sediments and water column processes. Hydrolytic activities, which double in the sediment and increase up to a 300-fold in the water, are consistent with the decrease in sediment organic matter and with the water fraction dynamics.

Bacteria↗
PubMed2002

Chemical and bacterial changes during laboratory conditioning of formulated and natural sediments.

Within the framework of toxicity testing using formulated sediment, a conditioning treatment prior to toxic contamination has been examined. This preliminary step enables the bacterial colonisation of the sediment, the initiation of organic matter degradation, and the establishment of stable biological and physico-chemical conditions. The treatment involved in keeping the formulated sediment under water in conditions similar to that chosen for toxicity tests. The behaviour of a formulated sediment was compared with a natural sediment. The monitoring of physico-chemical and biological parameters of sediment and water column was carried out over a 30-day incubation in two laboratories. The parameters of pH and redox, dissolved organic carbon (DOC), NH4 and NO2, total organic carbon (TOC) were measured. The bacterial community was characterised by the determination of bacterial density, in total bacteria number or colony forming units (CFU), several exoenzymatic activities (P-glucosidase, xylosidase, leucine-amino-peptidase phosphatase and sulfatase activities), and three gas productions (CO2, N2O and CH4). The same experiment was carried out with a natural sediment. A 10- to 15-day conditioning allowed a physico-chemical stabilisation and corresponded to kinetic changes in hydrolysis activities. As compared to data of the natural sediment, the biological activity of the formulated sediment showed a different dynamic with lower activity levels. For both sediments, an important decrease of activities levels was observed after 15 days because of a substrate limitation. The work showed that a preliminary conditioning treatment of a formulated sediment provides the stabilisation of parameters that can affect toxicant bioavailability. Additional research is needed to determine the real influence of conditioning on the bioavailability of contaminants. The possible advisability of organic matter input, to maintain the sediment bacterial activity, has to be studied.

Bacteria↗
PubMed2000

Leaching, runoff and speciation of arsenic in a laboratory mesocosm.

Leaching and runoff of arsenic (As) from the contaminated soil of an old wood impregnation plant, and fate in a recipient freshwater ecosystem, was studied in soil-water-sediment mesocosms in laboratory (0.9 m3; total water volume 200 l). During the 4-month experiment total leaching and discharge of As from regularly irrigated soil was approximately 40 mg, i.e. approximately 0.6% of total initial As content in the soil. Of the total As load, 7.5% remained in the water; 44% settled down to the shallow (water depth 5-30 cm) sediment zone; and 48.5% to the deeper (water depth 80 cm) sediment zone. The different arsenic species; arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA), were analysed from irrigation and discharge water; mesocosm pool water; and sediment pore water using ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). The total amounts of arsenic in soil, water and sediment were determined by ICP-MS. Arsenic was leached out from the soil as As(V). In mesocosm water As(V) was the predominant dissolved species, but DMAA and particle bound species, were also detected. In shallow sediment, As(V) was the most abundant species together with some DMAA, whereas in deep sediment As(III) was the dominant species.

Arsenic↗
PubMed1999

Mercury in contaminated coastal environments; a case study: the Gulf of Trieste.

Some general facts, uncertainties and gaps in current knowledge of Hg cycling in coastal and oceanic environments are given. As a case study the Gulf of Trieste is chosen. The Gulf is subject to substantial Hg pollution, originating from the Soca river, that drains the cinnabar deposits of the world's second largest Hg mining area, Idrija, Slovenia. The Gulf belongs to one of the most polluted areas in the Mediterranean. Apart from Hg problems, the Gulf is also a subject to industrial and sewage pollution. Due to deteriorating water quality in the Gulf there is a great concern that Hg can be remobilized from sediments to the water column as well as enhance methylation rates which may consequently increase already elevated Hg levels in aquatic organisms. The paper presents data from a recent study which aims to assess the extent of contamination of the Gulf of Trieste after the closure of the Hg mine. Mercury and methylmercury were measured in various environmental compartments (estuarine and marine waters, sediments, and organisms) during the period 1995-1997. Data obtained show that even 10 years after closure of the Hg mine, Hg concentrations in river sediments and water are still very high and did not show the expected decrease of Hg in the Gulf of Trieste. A provisional annual mercury mass balance was established for the Gulf of Trieste showing that the major source of inorganic mercury is still the River Soca (Isonzo) while the major source of methylmercury is the bottom sediment of the Gulf.

Geologic Sediments↗
PubMed2001

Sediment-associated tri-n-butyltin chloride and its effects on osmoregulation of freshwater-adapted 0-group European flounder, Platichthys flesus (L.).

The disruption of osmoregulatory processes was examined in European flounders exposed to environmental concentrations (150 ng TBTCl g(-1) dry weight sediment) of sediment-associated tri-n-butyltin chloride (TBTCl), by using radiotracers to measure changes in hydromineral fluxes and water balance. The water permeabilities of TBTCl-exposed fish varied during the course of the experiment and were significantly lower than those of the corresponding controls that did not change significantly with time. It was found that the maximum decrease in water permeability of TBTCl-exposed fish occurred after 14 days; thereafter there was an increase towards control values. However, there was a differential reduction of the diffusional (P(d)) and osmotic (P(os)) permeability coefficients, where the former decreased more rapidly than the latter, reflecting the reduction of diffusional membrane permeability and the increasing importance of osmotic permeability. In fish exposed to TBTCl sodium efflux and drinking rates were significantly increased but Na(+)/K(+)-ATPase activities and urine production rates were not affected. The effects of TBTCl exposure are also manifested at the level of the whole organism by a reduction in the increase of the body length of exposed fish, when compared to controls. It was concluded that tributyltin-n-chloride in sediments is capable of significantly disrupting the osmoregulatory functions of a benthic estuarine fish, at concentrations found in the sediments of Southampton Water and the River Itchen.

Animals↗
PubMed2002

Measurement of movement patterns of Caenorhabditis elegans (Nematoda) with the Multispecies Freshwater Biomonitor (MFB)--a potential new method to study a behavioral toxicity parameter of nematodes in sediments.

The nematode Caenorhabditis elegans receives increasing attention in sediment ecotoxicology and new toxicity tests with sensitive test parameters are under development. In this study, the motility of C. elegans could be measured for the first time online in sediment, using the Multispecies Freshwater Biomonitor. Whereas single nematodes could not be recorded, groups of 10 nematodes gave typical locomotive signals in different media (water, agar, sediment) with comparable precision and accuracy. The results of this study encourage to develop a new rapid online whole-sediment toxicity test with behaviour as sensitive test parameter.

Animals↗
PubMed1995

Dissolution and reduction of magnetite by bacteria.

Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

Electron Transport↗