Biochemical response of amphipods (Gammarid: Paramorea) in a sediment laboratory exposure from Ushuaia Bay, Beagle Channel

A coastal system (Ushuaia Bay, Argentina) impacted by anthropogenic activities was studied by the response of local amphipods (Parmorea sp., Gammaridae) to the exposure of coastal sediments in a laboratory assay. Four coastal areas with different loadings of contaminants and one considered as reference were studied. Organic matter, carbohydrates, proteins and heavy metals were measured in sediment samples. Organisms were exposed to sediments for seven days and catalase (CAT), glutathione S-transferase (GST), acetylcholinesterase (AChE) and lipid peroxidation (LPO) were measured afterward. Amphipods exhibited an activation of GST and inhibition of AChE in most impacted areas. Principal Component Analysis (PCA) was conducted in order to associate the biological responses with sediment metal concentration and its eutrophicated status. Levels of Cd and Cr were associated with the inhibition of AChE and with the enhancement of GST. CAT and LPO were enhanced in most areas, but no link was found with the contaminants studied by PCA, suggesting that other parameters present in sediments not included in the PCA affect the amphipods. The most impacted area corresponds to Nautical Club station, with a highly eutrophicated status and high content of metals, where amphipods after the exposure were affected in a biochemical level.     

Spatial Distribution of Antimony and Arsenic Levels in Manadas Creek, an Urban Tributary of the Rio Grande in Laredo, Texas

The Rio Grande and its tributaries represent a critical water source for both the human population and the ecological resources of the Rio Grande drainage basin. Manadas Creek, an urban tributary of the Rio Grande, is located in an industrialized area of Laredo, Texas, where warehouses, a major railroad, and a decommissioned antimony (Sb) smelter are located. Previous studies have found that the creek water is contaminated with heavy metals such as Sb and arsenic (As). However, data on the metal distribution in this creek are very limited. Herein, water and sediment core samples were collected from six sites along the creek in February, April, and May 2008. Samples were analyzed for dissolved and total metals in water, total metals in sediments, and available (soluble-exchangeable, surface adsorbed, and organically bound) fractions of metals associated with the sediments. Results show that concentrations of Sb in the water and sediment samples were significantly lower at the upstream control site compared to the two sites located near the decommissioned smelter. Decreasing levels of Sb were found at the sites located downstream. The As levels in the sediment remained constant at different depths, whereas Sb varied significantly. A high level, 420 mg/kg, of sediment Sb was found at the maximum sediment depth of 35.0 cm sampled. In addition, 65.7–76.9% Sb and 80.3–85.6% As were in their residual form, 15.0–22.5% Sb and 6.2–11.4% As were bound to organic matter, and the remaining As and Sb were in the soluble and surface adsorbed fractions. Pearson correlation analyses indicated that the distribution of Sb was only moderately correlated to iron and nickel in the sediment and its correlation with the sediment properties measured was insignificant. Cluster analyses only grouped the two Sb isotopes together for the sediments collected in May, indicating that sources other than natural occurrence were associated with Sb. The high level of sediment Sb observed indicates that the sediment bed of Manadas Creek was acting as a holding reservoir for Sb and a potential source for the Sb level in the stream water. Thus, the loss of the sediment Sb and the Sb level in the water column must be closely related to the mobility of the bed sediments and the fate of the sediment-associated Sb.     

Integrated sediment quality assessment in Paranaguá Estuarine System,Southern Brazil

Sediment quality from Paranaguá Estuarine System (PES), a highly important port and ecological zone, was evaluated by assessing three lines of evidence: (1) sediment physical–chemical characteristics; (2) sediment toxicity (elutriates, sediment–water interface, and whole sediment); and (3) benthic community structure. Results revealed a gradient of increasing degradation of sediments (i.e. higher concentrations of trace metals, higher toxicity, and impoverishment of benthic community structure) towards inner PES. Data integration by principal component analysis (PCA) showed positive correlation between some contaminants (mainly As, Cr, Ni, and Pb) and toxicity in samples collected from stations located in upper estuary and one station placed away from contamination sources. Benthic community structure seems to be affected by both pollution and natural fine characteristics of the sediments, which reinforces the importance of a weight-of-evidence approach to evaluate sediments of PES.     

Quality evaluation multiapproach of sediments in water bodies in Southern Italy

This study reports the toxicity of sediments from rivers and canals collected at two six-month intervals from 19 sampling points of the province of Naples in Southern Italy. The toxicity of the pore-water from sediments was determined with a battery composed of different freshwater microbiotests. The toxicity varied substantially from station to station, but none of the Toxkit tests was either the most or the least sensitive for all stations. Chemical analyses were accomplished on some heavy metals. Furthermore, the in situ biological communities of macroinvertebrates were assessed. Most of tested sediments were found to be very toxic for several if not all the microbiotests as well as the biological communities (EBI). Comparison between toxicological data and heavy metals revealed a positive correlation for zinc and copper. This study confirms that only an integrated approach is suitable for the evaluation of contaminated sediments and that single parameters are not always able to define a situation of environmental deterioration.     

Acute Toxicity Bioassay with the Amphipod, Grandidierella bonnieroides S. After Exposure to Sediments from an Urban Estuary (Macaé River Estuary, RJ, Brazil)

Acute toxicity to Grandidierella bonnieroides and physicochemical analysis were used for quality assessment of the sediment of the Macaé River urban estuary, located in the Brazilian coast where rapid socioeconomic growth has been induced by offshore oil and gas exploration at the Campos Basin. Sediment samples were collected during four events in four sampling sites of the estuary and also in a control site. Organism mortality after exposure to the estuarine sediments was, on average, 30 % a value higher than in the control site where it was 10 %. This result together with the physicochemical analysis suggests an initial toxicity condition of the sediments from this aquatic coastal environment.     

Acid Volatile Sulfides and Simultaneously Extracted Metals in a Metal-Polluted Area of Taihu Lake,China

There were similar distribution characteristics for acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) in surface sediments, and the concentrations of AVS and SEM decreased from the deposition area to the center of the bay (lake). The ratio of AVS to SEM was <1 in the surface sediments, indicating that heavy metals in surface sediments may be bioavailable. The concentration of AVS increased with sediment depth, followed by a decrease with large variation, while the concentration of SEM remained constant. By comparing the concentration of SEM with total metals, it was shown that extracted Cu and Ni decreased with sediment depth, indicating increasing association of Cu and Ni with sulfides in deeper sediment layers. The lower extracted ratios for Pb and Zn compared with sulfidic sediment illustrated that AVS should not have strong control on sediment Pb and Zn. The molar ratio of AVS and reactive iron showed that heavy metals were dynamic and active in sediments in this lake.     

Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary, South China

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and chemical partitioning in the sediment cores of the Pearl River Estuary (PRE) were studied. The concentrations of total metals, AVS, and SEM in the sediment cores were generally low in the river outlet area, increased along the seaward direction, and decreased again at the seaward boundary of the estuary. The amounts of AVS were generally greater in deeper sediments than in surface sediments. SEM/AVS was >1 in the surface sediments and in the river outlet cores. The ratio was <1 in the sediments down the profiles, suggesting that AVS might play a major role in binding heavy metals in the deep sediments of the PRE. The SEM may contain different chemical forms of trace metals in the sediments, depending on the metal reaction with 1M cold HCl in the AVS procedure compared with the results of the sequential chemical extraction. The SEM/AVS ratio prediction may overestimate trace metal availability even in the sediments with high AVS concentrations.     

Contaminated suspended sediments toxic to an Antarctic filter feeder: aqueous- and particulate-phase effects

Disturbances such as dredging, storms, and bioturbation result in the resuspension of sediments. This may affect sessile organisms that live on hard substrates directly above the sediment. Localized sediment contamination exists around many Antarctic research stations, often resulting in elevated contamination loads in marine sediments. To our knowledge, the potential impact of resuspended contaminated sediments on sessile fauna has not been considered, so in the present study, we assessed the sensitivity of Antarctic spirorbid polychaetes to aqueous metals and to metal-contaminated sediments that had been experimentally resuspended. Worms were first exposed to aqueous metals, both singly and in combination, over 10 d. Spirorbid mortality was tolerant to copper (median lethal concentration [LC50], 570 microg/L), zinc (LC50, > 4,910 microg/L), and lead (LC50, > 2,905 microg/L); however, spirorbid behavior responded to copper concentrations as low as 20 microg/L. When in combination, zinc significantly reduced mortality caused by copper. A novel technique was used to resuspend sediments spiked with four concentrations of three metals (up to 450 microg/g dry wt of copper, 525 micro/g dry wt of lead, and 2,035 microg/g dry wt of zinc). The response of spirorbids to unfiltered suspended sediment solutions and filtered solutions (aqueous metal exposure) was measured. Suspended sediments were toxic to filter-feeding spirorbids at concentrations approximating those found in contaminated Antarctica areas. Toxicity resulted both from aqueous metals and from metals associated with the suspended sediments, although suspended clean sediments had no impact. To our knowledge, the present study is the first to show that resuspension of contaminated sediments can be an important pathway for toxicity to Antarctic hard substrate organisms. Based on the present results, current sediment-quality guidelines used in the evaluation of Australian sediments may be applicable to Antarctic ecosystems.     

Monitoring of Nutrients, Pesticides, and Metals in Waters, Sediments, and Fish of a Wetland

Wetland areas are of extraordinary importance for the conservation of wildlife. The Aiguamolls de l’Empordà Natural Park, located in Girona (northeast Spain), is one of the few areas in Europe acting as a way station for migratory birds. The natural park is made up of a brackish water reserve and a fresh water reserve. Agriculture and tourism, which are concentrated especially around coastal population centers, are the main activities in this area and result in the release into the environment of nutrients, pesticides, and heavy metals. This article aims to investigate the presence of nutrients, selected pesticides (organochlorine compounds, permethrin and triazines) and metals (Cr, Cu, Cd, Ni and Pb) in water, sediments, and fish samples. In the case of water, seasonal variations in levels of contamination were also monitored. Comparison was made of the fresh and brackish water reserves and concentration factors for metals and pesticides in sediment were determined. We conclude that the most significant sources of contamination in the natural park are from the entry of pesticides and nutrients into surface waters and sediments as a result of the intensive farming activity of the surrounding areas. The pesticides with the greatest presence were found to be lindane, heptachlor epoxide, permethrin, and atrazine. Among the metals analyzed, Cu and Cr presented the highest concentrations in surface waters and sediments.     

Assessment of Metal Accumulation and Ecological Risk Around Rize Harbor, Turkey (Southeast Black Sea) Affected by Copper Ore Loading Operations by Using Different Sediment Indexes

The purpose of the study was to determine metal pollution and ecological risk in the sediments around Rize Harbor. Metal concentrations (Cu, Zn, Pb, Cd, As, Hg, Ni and Al), were determined in the sediments collected from 7 sites in November, 2010. Metal levels in the sediments were varied from 33.9 to 279.1 mg/kg for Cu, 82 to 383 mg/kg for Zn, 15.9 to 33 mg/kg for Pb, 4.9 to 12.3 mg/kg for As, 0.1 to 1.4 mg/kg for Cd, 0.01 to 0.07 mg/kg for Hg, 13.1 to 17.6 mg/kg for Ni, 1.5 % to 2.98 % for Al. Concentration of metals also was evaluated by enrichment factor, Sediment Quality Guideline (SQGs) of US EPA, and two sets of SQGs indices. A factor analysis was used to determine source of contamination. Two probable source types were identified as anthropogenic and crustal for metals, explaining 86.4 % of the total variance. Six sites were heavily polluted by Cu. Copper concentration in R1 station was found significant enrichment. Current concentration of copper would be expected to frequently be associated with the toxic effect on biota.     

Trace Metals Bioavailability Approach in Intertidal Estuarine Sediments and Bioaccumulation in Associated Nereidid Polychaetes

Polychaetes that inhabit the sediments of estuaries are important prey to many species all around the world. Laeonereis acuta is a deposit feeder living in estuaries along the Atlantic coast of South America. Ragworms accumulate metals from the sediment, and represent a means of entry of sediment contaminants into the trophic network. The concentrations of Zn, Pb, Cu, Cr and Cd were determined in polychaetes and sediments (total and extractable) from six estuarine beaches of Río de la Plata. The associations between total and extractable concentrations in sediment and accumulated concentrations in L. acuta were analyzed. Sediments extracted by weak acid digestion appear to be a good proxy model of bioavailable metal fractions in the sediment. The association between metals in sediment and polychaetes denotes the role of L. acuta as an important link in metal trophic transfer from sediments to potential fish and bird predators of the worm.     

Bioaccumulation of Heavy Metals in Mollusca Species and Assessment of Potential Risks to Human Health

Along the Alexandria coast of the Egyptian Mediterranean Sea, five edible species of bivalve molluscs and one gastropoda species (Mactra coralline, Ruditapes decussates, Paphia undulate, Venerupis rhomboids, Crista pectinata and Coralliophila meyendorffi) were analyzed for content of metals (Cadmium, Chromium, Lead, Cobalt and Nickel) in the muscle and in the sediments where they live. The potential health risks of metals to humans via consumption of seafood were assessed by estimated daily intake and target hazard quotient. Significant positive correlations (p < 0.05) were obtained between tissue concentrations for all pairs of metals, with the exception of Cadmium. Significant positive correlations were also obtained for the concentrations of Cd and Ni in tissues of all studied species relative to their concentrations in surface sediments. However, correlations between tissue and sediment concentrations for Chromium, Lead and Cobalt were negative. Ruditapes decussates and C. meyendorffi had the highest values for the summed target hazard quotient and may pose a potential risk to local inhabitants through their consumption in the diet. The potential risk would arise from exposure to high tissue concentrations of Cd and Pb, which exceeded published guidelines for safety of seafood products in some cases. Chromium contributed a considerable fraction of the total target hazard quotient for all metals combined, but did not exceed the published guidelines. Cobalt and Ni did not contribute greatly overall to the target hazard quotient, except in the case of Ni in V. rhomboids.     

Effects of Contaminants in Dredge Material from the Lower Savannah River

Contaminants entering aquatic systems from agricultural, industrial, and municipal activities are generally sequestered in bottom sediments. The environmental significance of contaminants associated with sediments dredged from Savannah Harbor, Georgia, USA, are unknown. To evaluate potential effects of contaminants in river sediments and sediments dredged and stored in upland disposal areas on fish and wildlife species, solid-phase sediment and sediment pore water from Front River, Back River, an unnamed Tidal Creek on Back River, and Middle River of the distributary system of the lower Savannah River were tested for toxicity using the freshwater amphipod Hyalella azteca. In addition, bioaccumulation of metals from sediments collected from two dredge-disposal areas was determined using the freshwater oligochaete Lumbriculus variegatus. Livers from green-winged teals (Anas crecca) and lesser yellowlegs (Tringa flavipes) foraging in the dredge-spoil areas and raccoons (Procyon lotor) from the dredge-disposal/river area and an upland site were collected for metal analyses. Survival of H. azteca was not reduced in solid-phase sediment exposures, but was reduced in pore water from several locations receiving drainage from dredge-disposal areas. Basic water chemistry (ammonia, alkalinity, salinity) was responsible for the reduced survival at several sites, but PAHs, metals, and other unidentified factors were responsible at other sites. Metal residues in sediments from the Tidal Creek and Middle River reflected drainage or seepage from adjacent dredge-disposal areas, which could potentially reduce habitat quality in these areas. Trace metals increased in L. variegatus exposed in the laboratory to dredge-disposal sediments; As, Cu, Hg, Se, and Zn bioaccumulated to concentrations higher than those in the sediments. Certain metals (Cd, Hg, Mo, Se) were higher in livers of birds and raccoons than those in dredge-spoil sediments suggesting bioavailability. Cadmium, Cr, Hg, Pb, and Se in livers from raccoons collected near the river and dredge-disposal areas were significantly higher than those of raccoons from the upland control site. Evidence of bioaccumulation from laboratory and field evaluations and concentrations in sediments from dredge-disposal areas and river channels demonstrated that some metals in the dredge-disposal areas are mobile and biologically available. Drainage from dredge-disposal areas may be impacting habitat quality in the river, and fish and wildlife that feed and nest in the disposal areas on the lower Savannah River may be at risk from metal contamination. Received: 21 October 1998/Accepted: 9 February 1999     

Ecotoxicity of Sediments Contaminated by the Oil Spill Associated with the Tanker “Prestige” Using Juveniles of the Fish Sparus aurata

In November 2002, the oil spill from the tanker Prestige in the Galician Coast caused an ecological catastrophe in Spain. The adverse effects associated with the contaminants bound to sediments were tested using juveniles of the fish Sparus aurata (seabream). The approach evaluates sediment quality by using an integrated assessment including chemical and ecotoxicological data. Sediment samples were physicochemically characterized, and the concentration of contaminants (polycyclic aromatic hydrocarbons—(PAHs) and metals) was measured. Different biomarkers of exposure (metallothioneins and ethoxyresorufin O-deethylase activity (EROD)) and biomarkers of effect (histopathology) were analyzed along the time. A multivariate analysis approach was used to correlate concentration of contaminants and sublethal effects measured in individuals of fish. Results show that increasing concentrations of PAHs in sediments were related to increased EROD activities and histopathological lesions. This is the first evidence showing adverse effects associated with petroleum contamination of PAHs in sediments after this spill, and it demonstrates the utility of the sublethal toxicity tests for monitoring the impact of petroleum spills.     

The present environmental scenario of the Nador Lagoon (Morocco)

In this paper, we present a multivariate approach (waters, sediments, microfauna) concerning the environmental state of the Nador Lagoon (NE Morocco). The normal water quality parameters (salinity, pH, nutrients) of the dominant marine flows are altered by local fecal water effluents, urban discharges, sewages derived from a water treatment station, and residues originated in a slaughterhouse. The geochemical analyses carried out in surficial sediment samples show very high concentrations of all metals studied near an old iron mine and moderate contents between Nador and its treatment station. Ostracods are good bioindicators of these environmental impacts, with the presence of a highly brackish assemblage in the quieter, more confined areas or the appearance of opportunistic species under hypoxic conditions. In addition, these microcrustaceans are absent in polluted bottom sediments or areas with high hydrodynamic gradients, whereas they decrease in both density and diversity if the subaerial exposure increases.     

Toxicity of sediments and pore water from Brunswick Estuary,Georgia

A chlor-alkali plant in Brunswick, Georgia, USA, discharged >2 kg mercury/d into a tributary of the Turtle River-Brunswick Estuary from 1966 to 1971. Mercury concentrations in sediments collected in 1989 along the tributary near the chlor-alkali plant ranged from 1 to 27 μg/g (dry weight), with the highest concentrations found in surface (0–8 cm) sediments of subtidal zones in the vicinity of the discharge site. Toxicity screening in 1990 using Microtox^® bioassays on pore water extracted on site from sediments collected at six stations distributed along the tributary indicated that pore water was highly toxic near the plant discharge. Ten-day toxicity tests on pore water from subsequent sediment samples collected near the plant discharge confirmed high toxicity to Hyalella azteca, and feeding activity was significantly reduced in whole-sediment tests. In addition to mercury in the sediments, other metals (chromium, lead, and zinc) exceeded 50 μg/g, and polychlorobiphenyl (PCB) concentrations ranged from 67 to 95 μg/g. On a molar basis, acid-volatile sulfide concentrations (20–45 μmol/g) in the sediments exceeded the metal concentrations. Because acid-volatile sulfides bind with cationic metals and form metal sulfides, which are generally not bioavailable, toxicities shown by these sediments were attributed to the high concentrations of PCBs and possibly methylmercury.     

Concentrations of Metals Associated with Mining Waste in Sediments, Biofilm, Benthic Macroinvertebrates, and Fish from the Coeur d'Alene River Basin, Idaho

Arsenic, Cd, Cu, Pb, Hg, and Zn were measured in sediments, biofilm, benthic macroinvertebrates, and fish from the Coeur d'Alene (CDA) River to characterize the pathway of metals transfer between these components. Metals enter the CDA Basin via tributaries where mining activities have occurred. In general, the ranking of food-web components from the greatest to smallest concentrations of metals was as follows: biofilm (the layer of abiotic and biotic material on rock surfaces) and sediments > invertebrates > whole fish. Elevated Pb was documented in invertebrates, and elevated Cd and Zn were documented in sediment and biofilm approximately 80 km downstream to the Spokane River. The accumulation of metals in invertebrates was dependent on functional feeding group and shredders-scrapers that feed on biofilm accumulated the largest concentrations of metals. Although the absolute concentrations of metals were the largest in biofilm and sediments, the metals have accumulated in fish approximately 50 km downstream from Kellogg, near the town of Harrison. While metals do not biomagnify between trophic levels, the metals in the CDA Basin are bioavailable and do biotransfer. Trout less than 100 mm long feed exclusively on small invertebrates, and small invertebrates accumulate greater concentrations of metals than large invertebrates. Therefore, early-lifestage fish may be exposed to a larger dose of metals than adults. Received: 3 April 1997/Accepted: 8 September 1997     

Biomarkers of exposure and effects of environmental contaminants on swallows nesting along the Rio Grande, Texas, USA

We collected adult cave swallows (Petrochelidon fulva) and cliff swallows (P. pyrrhonota) during the breeding seasons in 1999 and 2000 from eight locations along the Rio Grande from Brownsville to El Paso (unless otherwise specified, all locations are Texas, USA) and an out-of-basin reference location. Body mass, spleen mass, hepatosomatic index (HSI), gonadosomatic index (GSI), thyroxine (T4) in plasma, DNA damage measured as the half-peak coefficient of variation of DNA content (HPCV) in blood cells, as well as acetylcholinesterase and butyrylcholinesterase in brain were compared with concentrations of organochlorines, metals, and metalloids in carcasses to determine potential effects of contaminants on swallows during the breeding season. Concentrations of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) were significantly greater in swallows from El Paso than in those from most locations, except for Pharr and Llano Grande. All swallows from these three locations had p,p'-DDE concentrations of 3 microg/g wet weight or greater. Swallows from El Paso either had or shared the highest concentrations of p,p'-DDE, polychlorinated biphenyls, and 13 inorganic elements. Swallows from El Paso exhibited greater spleen mass and HPCV values as well as lower T4 values compared with those from other locations. Thyroxine was a potential biomarker of contaminant exposure in swallows of the Rio Grande, because it was negatively correlated with p,p'-DDE and Se. Spleen mass was positively correlated with selenium and HSI and negatively correlated with body mass, GSI, Mn, and Ni. Overall, the present study suggests that insectivorous birds living in areas of high agricultural and industrial activity along the Rio Grande bioaccumulate environmental contaminants. These contaminants, particularly p,p'-DDE, may be among multiple factors that impact endocrine and hematopoietic function in Rio Grande swallows.     

Laboratory Toxicity and Benthic Invertebrate Field Colonization of Upper Columbia River Sediments: Finding Adverse Effects Using Multiple Lines of Evidence

From 1930 to 1995, the Upper Columbia River (UCR) of northeast Washington State received approximately 12 million metric tons of smelter slag and associated effluents from a large smelter facility located in Trail, British Columbia, approximately 10 km north of the United States-Canadian border. Studies conducted during the past two decades have demonstrated the presence of toxic concentrations of heavy metals in slag-based sandy sediments, including cadmium, copper, zinc, and lead in the UCR area as well as the downstream reservoir portion of Lake Roosevelt. We conducted standardized whole-sediment toxicity tests with the amphipod Hyalella azteca (28-day) and the midge Chironomus dilutus (10-day) on 11 samples, including both UCR and study-specific reference sediments. Metal concentrations in sediments were modeled for potential toxicity using three approaches: (1) probable effects quotients (PEQs) based on total recoverable metals (TRMs) and simultaneously extracted metals (SEMs); (2) SEMs corrected for acid-volatile sulfides (AVS; i.e., ∑SEM - AVS); and (3) ∑SEM - AVS normalized to the fractional organic carbon (f(oc)) (i.e., ∑SEM - AVS/f(oc)). The most highly metal-contaminated sample (∑PEQ(TRM) = 132; ∑PEQ(SEM) = 54; ∑SEM - AVS = 323; and ∑SEM - AVS/(foc) = 64,600 umol/g) from the UCR was dominated by weathered slag sediment particles and resulted in 80% mortality and 94% decrease in biomass of amphipods; in addition, this sample significantly decreased growth of midge by 10%. The traditional ∑AVS - SEM, uncorrected for organic carbon, was the most accurate approach for estimating the effects of metals in the UCR. Treatment of the toxic slag sediment with 20% Resinex SIR-300 metal-chelating resin significantly decreased the toxicity of the sample. Samples ∑SEM - AVS > 244 was not toxic to amphipods or midge in laboratory testing, indicating that this value may be an approximate threshold for effects in the UCR. In situ benthic invertebrate colonization studies in an experimental pond (8-week duration) indicated that two of the most metal-contaminated UCR sediments (dominated by high levels of sand-sized slag particles) exhibited decreased invertebrate colonization compared with sand-based reference sediments. Field-exposed SIR-300 resin samples also exhibited decreased invertebrate colonization numbers compared with reference materials, which may indicate behavioral avoidance of this material under field conditions. Multiple lines of evidence (analytical chemistry, laboratory toxicity, and field colonization results), along with findings from previous studies, indicate that high metal concentrations associated with slag-enriched sediments in the UCR are likely to adversely impact the growth and survival of native benthic invertebrate communities. Additional laboratory toxicity testing, refinement of the applications of sediment benchmarks for metal toxicity, and in situ benthic invertebrate studies will assist in better defining the spatial extent, temporal variations, and ecological impacts of metal-contaminated sediments in the UCR system.     

Changes in the geochemistry and ecotoxicity of a Zn and Cd contaminated dredged sediment over time after land disposal

The management of dredged sediments is of environmental concern worldwide since they may be overloaded with myriads of pollutants. For inland waters’ sediments, disposal on land is a common practice. For the long-term risks assessment of such a management, a better understanding of the fate of pollutants over time and an assessment of possible associated biological consequences are needed. Here, we studied the geochemical distribution of Fe, Mn, Zn and Cd in sediment dredged from the Scarpe canal (Nord-Pas-de-Calais Region, France). Analyses were carried out immediately after dredging and 12, 18 and 24 months after disposal in field conditions. In parallel, ecotoxicity of sediment leachates was assessed using standardized bioassays. The results reflected an initial oxidation of sulphides (first year) followed by changes explained by a reversible binding of metals to organic matter in winter and to Fe oxihydroxides in summer. The water-leachable fraction represented less than 2% of the total metal and its ecotoxicity was higher for deposited sediments than for the fresh one. After first year of disposal, sediment ecotoxicity remained stable. A long-term natural attenuation of metals within disposed sediment seemed unlikely since their speciation seemed to fluctuate seasonally without any time trend over years.