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At least 631 records · Page 35Linked to original sources
PubMed2004

Effects of shoreline discharge of iron mine tailings on a marine soft-bottom community in northern Chile.

This study evaluates the magnitude and extension of the impact produced by the discharge of inert allochthonous materials, including clays and particulate iron, on macrobenthic soft-bottom assemblages in the subtidal zone of a coastal bay in north-central Chile. An average of 118 Ton h(-1) of finely divided solids were discharged into the rocky intertidal zone of the bay for a period of over 16 years, producing continuous turbidity in the water column and sedimentation in the subtidal zone. Data obtained four months before cessation of the discharge showed that the macrofauna present at 20 and 50 m depth in the bay suffered an important decrease in abundance and species richness, low diversity/high dominance, and deep changes in community structure related to the discharge. The faunal assemblages present at 110 m depth did not show effects from the discharge, suggesting that the impact was limited to the inner part of the bay. The impoverished faunal aggregates at 20 and 50 m depth showed exclusive domination by the Lumbrineris bifilaris (polychaete)-Diastylis tongoyensis (cumacean) association, representing a simple trophic guild of deposit feeders. The complete absence of opportunistic species such as capitellid, spionid, and/or cirratulid polychaetes may be associated with the turbidity and sedimentation levels in the bay.

Aluminum Silicates↗
PubMed2004

Effects of algal turfs and sediment on coral settlement.

Successful settlement and recruitment of corals is critical to the resilience of coral reefs. Given that many degraded reefs are dominated by benthic algae, recovery of coral populations after bleaching and other disturbances requires successful settlement amidst benthic algae. Algal turfs often accumulate sediments, sediments are known to inhibit coral settlement, and reefs with high inputs of terrestrial sediments are often dominated by turfs. We investigated the impacts of two algal turf assemblages, and of sediment deposits, on settlement of the coral Acropora millepora (Ehrenberg). Adding sediment reduced coral settlement, but the effects of different algal turfs varied. In one case, algal turfs inhibited coral settlement, whereas the other turf only inhibited settlement when combined with sediments. These results provide the first direct, experimental evidence of effects of filamentous algal turfs on coral settlement, the variability in those effects, and the potential combined effects of algal turfs and trapped sediments.

Animals↗
PubMed2005

Butyltin compounds in a sediment core from the old Tilbury basin, London, UK.

Sections from a sediment core taken from the River Thames were analysed for butyltin species using gas chromatography with species-specific isotope dilution mass spectrometry. Results demonstrated that in most samples tributyltin concentrations of 20-60 ng/g accounted for <10% of the total butyltin species present, which is in agreement with data from other sediment samples which were historically contaminated with tributyltin. Vertical distribution of the organotin residues with depth throughout the core, with data on organochlorine compounds and heavy metals allowed for the construction of a consistent hypothesis on historical deposition of contaminated sediments. From this it was possible to infer that the concentrations of tributyltin in sediments deposited during the early 1960s were in the order of 400-600 microg/g by using degradation rate constants derived by other workers. Such values fall well within the range quoted for harbour sediments in the literature.

Environmental Monitoring↗
PubMed2006

Differences in SEM-AVS and ERM-ERL predictions of sediment impacts from metals in two US Virgin Islands marinas.

Two US Virgin Islands marinas were examined for potential metal impacts by comparing sediment chemistry data with two sediment quality guideline (SQG) values: the ratio of simultaneously extractable metals to acid volatile sulfides (SEM-AVS), and effects range-low and -mean (ERL-ERM) values. ERL-ERMs predicted the marina/boatyard complex (IBY: 2118 microg/g dry weight total metals, two exceeded ERMs) would have greater impacts than the marina with no boatyard (CBM: 231 microg/g dry weight total metals, no ERMs exceeded). The AVS-SEM method predicted IBY would have fewer effects due to high AVS-forming metal sulfide complexes, reducing trace metal bioavailability. These contradictory predictions demonstrate the importance of validating the results of either of these methods with other toxicity measures before making any management or regulatory decisions regarding boating and marina impacts. This is especially important in non-temperate areas where sediment quality guidelines have not been validated.

Arsenic↗
PubMed2005

The impact of fine sediment accumulation on the survival of incubating salmon progeny: implications for sediment management.

This paper draws on results from a recent research programme on the impact of fine sediment transport through catchments to present a case for the development of new approaches to improving the quality of salmonid spawning and incubation habitats. To aid the development of these programmes, this paper summarises the mechanisms by which fine sediment accumulation influences the availability of oxygen (O2) to incubating salmon embryos. The results of the investigation indicate that incubation success is inhibited by: (i) the impact of fine sediment accumulation on gravel permeability and, subsequently, the rate of passage of oxygenated water through the incubation environment; (ii) reduced intragravel O2 concentrations that occur when O2 consuming material infiltrates spawning and incubation gravels; and (iii) the impact of fine particles (clay) on the exchange of O2 across the egg membrane. It is concluded that current granular measures of spawning and incubation habitat quality do not satisfactorily describe the complexity of factors influencing incubation success. Furthermore, an assessment of the trends in fine sediment infiltration indicates that only a small proportion of the total suspended sediment load infiltrates spawning and incubation gravels. This casts doubt over the ability of current catchment-based land use management strategies to adequately reduce fine sediment inputs.

Animals↗
PubMed2006

Isolation of mercury resistant bacteria and influence of abiotic factors on bioavailability of mercury -- a case study in Pulicat Lake North of Chennai, South East India.

Pulicat Lake sediments are often severely polluted with mercury compounds and other toxic heavy metals. Several mercury-resistant bacteria were isolated and identified from the sediments and all the isolates exhibited broad spectrum resistance (both organic and inorganic mercuric compounds). Mercury volatilization showed that four of the isolated Bacillus cereus strains were able to reduce water soluble ionic form of mercury into volatile form via the well known enzymatic reduction. The effect of increasing concentration of mercuric chloride and phenyl mercuric acetate in the growth of this mercury reducing strain was also determined. To study the native physico-chemical parameters, which influence the bioavailability of mercury to bacteria in Pulicat Lake ecosystem, a total of 60 water and 30 sediment samples were collected and analyzed for pH, temperature, dissolved oxygen, salinity, nitrate, nitrite, silicate, phosphate, organic matter and organic carbon. Increased levels of phosphate, nitrite, nitrate, silicate, organic matter and organic carbon during the post monsoon reduce the bioavailability of mercury by forming complexes which may increase the concentration of mercury in the sediments during post monsoon.

Drug Resistance, Bacterial↗
PubMed2006

Biogenic phosphorus in oligotrophic mountain lake sediments: differences in composition measured with NMR spectroscopy.

Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using 31P-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using 31P-NMR spectroscopy for quantification of sediment P forms.

Fertilizers↗
PubMed2003

Turbidity regimes over fringing coral reefs near a mining site at Lihir Island, Papua New Guinea.

An extensive sediment transport survey took place at Lihir Island (Papua New Guinea), where mining operations involve disposal of waste rocks and soil in nearshore waters. To investigate the potential impact of these practices over neighbouring fringing reefs, turbidity and sediment accumulation were measured continuously for extended periods. Turbidity records provided a map of observed impact zones based on turbidity thresholds. The main zoning features were (a) that an extreme turbidity gradient persists between the inner harbour (turbidity levels of 100-1000 mg l(-1)) and the adjacent reefs (turbidity levels in the order of 10 mg l(-1)), and (b) that observed zones conform with pre-operations impact predictions. Accumulation measurements unveiled no significant sediment accumulation over fringing coral reefs. This study contributes to the understanding of the potential impact of sediment discharge to nearshore waters.

Animals↗
PubMed2002

Pyrene bioavailability; effect of sediment-chemical contact time on routes of uptake in an oligochaete worm.

Bioavailability of sediment-sorbed compounds may vary with increasing contact time. This may result in the dietary uptake route becoming more significant as conditions in the gut flora aid the extraction of contaminants, which have migrated into sites within the sediment particle. Such mechanisms may have important implications on risk assessments performed on substances released into the environment. A series of experiments were carried out using sediment spiked with 14C-labelled pyrene, a polycyclic aromatic hydrocarbon. The sediment was left at room temperature over a period of 220 days. Periodically (at 0, 1, 14, 28, 70, 220 days) the sediment was used to perform a bioaccumulation study using the freshwater oligochaete Lumbriculus variegatus. A novel methodology using feeding and (decapitated) non-feeding worms, allowed differentiation between uptake via ingestion and simple sorption. Results showed that there was a decline in bioavailability with time and that this was a 3 stage process. A rapid initial decline was observed over the first day when a 40% decrease was measured, an intermediate period were levels remained stable (day 14 to day 70) and an ultimate decrease in pyrene activity in worm tissue of 70% after 220 days. Over this period the chemical extractability of pyrene also decreased by 50%, as the chemical migrated deeper into unavailable sites within the sediment matrix. Normalising bioavailability to the chemically extractable fraction of pyrene within the sediment provided an overall decrease in bioavailability of 58%. The importance of the dietary route of uptake for pyrene varied during the sediment aging process, reflecting the changes in the physico-chemical interactions between the pyrene, sediment and pore water.

Absorption↗
PubMed2000

Sorption-desorption behaviour of 2,4-dichlorophenol by marine sediments.

Batch kinetic and isotherm experiments were conducted to determine the sorption-desorption behavior of 2,4-dichlorophenol from seawater solutions by marine sediments containing various amounts of organic carbon (from 1.02% to 12.72% dry weight). The results indicated linear type isotherms for sorption and desorption in all marine sediments studied. The observed difference in linear sorption coefficients between sorption and desorption was indicative of sorption hysteresis. The kinetic experiments showed that equilibrium was established in less than 20 h. The study is significant with respect to sediment remediation in contaminated harbors and coastal areas.

Adsorption↗
PubMed1999

Mobilization of heavy metals from Le An River sediment.

The release of sediment-bound heavy metals can have a significant influence on river water quality. Generally speaking, variations of pH and oxygen are among the most important chemical factors that affect the mobility of sediment-bound metals. Recent research has indicated that sulfide, measured as acid-volatile sulfide (AVS), is an important partitioning component of heavy metals. We determined the metal release potential of sediments from the Le An River which receives drainage from a major copper mining operation. We found that the in-situ Cu, Pb, Zn, Cd and As concentrations of the Le An River sediments below the mine are much higher than are the global background values, but that Ni was not elevated. There is potential for mobilization of bound metals to the overlying water, the order of metal release ratio in terms of pH dependencies is Zn > Cu > Cd approximately Pb. Sulfide is not a major binding component for metals in Le An River sediment. It is more likely that the iron and manganese oxides are the most important metal binding components in the sediments of the Le An River.

China↗
PubMed1999

Underwater gamma surveys of Mururoa and Fangataufa lagoons.

Underwater gamma-ray spectrometry is an effective alternative or complement to traditional sampling and laboratory analyses for applications such as contamination assessment in emergency situations, long-term monitoring of radioactive releases or investigation of sunken radioactive objects. This technique was recently used in a seabed contamination study undertaken at the South Pacific nuclear weapons test sites of the Mururoa and Fangataufa atolls in order to guide and focus sediment core sampling in the areas with highest gamma-emitting radionuclide levels. 60Co inventories estimated on the basis of the underwater gamma-ray spectrometry survey were in good agreement with results previously obtained by traditional sediment sampling and laboratory analysis.

Geologic Sediments↗
PubMed1999

The IAEA worldwide intercomparison exercises (1990-1997): determination of trace elements in marine sediments and biological samples.

Four major worldwide intercomparison exercises for the determination of trace elements in various environmental matrices were completed by the IAEA Marine Environment Laboratory since 1990: SD-M-2/TM, deep sea marine sediment; IAEA-350, tuna fish homogenate; IAEA-356, contaminated coastal sediment and IAEA-140, sea plant (Fucus sp.). These intercomparison exercises aim at enabling individual laboratories to monitor their performance. The results of these exercises allowed us to make an overall evaluation of the quality of data provided for environmental assessment and to identify the trends of analytical performance in the determination of trace elements over the years. The number of participants in each exercise varied between 68 and 130, and permits statistical evaluation of the performance for a number of elements. For each intercomparison exercise, the performance of the participant laboratories was assessed by comparing reported results with established reference values calculating 'Z-scores'. The results show that for each sample matrix, the values reported by some laboratories were far from satisfactory in the earlier exercises, in particular for Cd, Cr and Pb. Nevertheless, over time, a general improvement of performance can clearly be seen for all elements. Moreover, there was a noticeable increase in the number of laboratories with good performance in the two most recent exercises, observed both for biological and for sediment matrices. However, the determination of trace elements such as Cd, Cr, Pb and Hg in low level environmental samples still remains a major challenge to the analysts. For this reason and in order to assess the current performance of laboratories for low environmental levels of contaminants, the future intercomparison exercises will concentrate on low level sediment and fish samples.

Animals↗
PubMedDate not supplied

Immune response of greenback flounder Rhombosolea tapirina after exposure to contaminated marine sediment and diet.

Non-specific immune response of greenback flounder, Rhombosolea tapirina, exposed to contaminated marine sediments was examined. Reference sediments from Port Sorell and contaminated sediments from Deceitful Cove, Tasmania, Australia were investigated. Hatchery-reared flounder were exposed to reference sediment, contaminated sediment or contaminated sediment and diet for 6 weeks. Phagocytic capacity and lysozyme response in flounder were examined on cessation of exposure trial. Significant differences were found in phagocytic capacity and lysozyme response between treatments. Exposure to contaminated sediment, irrespective of diet or benthic disturbance elicited inhibition of phagocytic efficiency in flounder. Disturbance of contaminated sediment stimulated lysozyme activity. The immune response in flounder indicates potential immunotoxicity of sediment from Deceitful Cove.

Animals↗
PubMed2002

Routes of TBT uptake in the clam Ruditapes decussatus. I. Water and sediments as vectors of TBT uptake.

This study assesses the relative importance of water and sediments as vectors of TBT uptake in the sediment-dwelling suspension feeder, Ruditapes decussatus. Accumulation of TBT was determined in R. decussatus exposed for 60 days to moderately high but environmentally realistic levels of TBT in water (100 ng Snl(-1)) and sediments (0.8 microg Sn g(-1) dw), separately or in combination, using constant-flow systems. The results indicate that this species accumulates TBT predominantly from water. Although some accumulation from sediments does occur, the processing of large amounts of water needed to sustain the filter-feeding habits of this species is a prime determinant of TBT uptake. The route of exposures reflected in tissue distributions of TBT in R. decussatus. However, gills are the most important site for accumulation of TBT from water, irrespective of whether contaminated sediments are present or not.

Animals↗
PubMed2001

Geochemistry of natural and anthropogenic metals in the coastal sediments of the island of Lesvos, Aegean Sea.

The geochemistry of metals in the harbor and coastal zone of the town of Mytilene (island of Lesvos, Aegean Sea, Greece) was studied after normalization of the metal data to a conservative element. In the study area, Li was proven to be better suited than Al for such normalization and it was able to describe successfully the natural metal variability of the coastal sediments. Metal contamination (Cd, Cu, Pb, Zn) was recorded in the harbor sediments, while no pollution signs were detected in the wider coastal zone or the sediments of the ancient harbor, at the northern part of the town. The geochemical normalization of metal data to Li is a method that can detect the degree of metal contamination taking into consideration the natural metal variability in the sediments of a study area.

Chemical Phenomena↗