Preliminary comparison of sediment extraction procedures and exchange solvents for hydrophobic compounds based on inhibition of bioluminescence

Two procedures for extracting hydrophobic contaminants from sediment samples collected from various sites in Florida were compared. The sediments, which varied in nature and degree of chemical contamination, were extracted with dichloromethane by shaking (24 h) and sonication (15 min). The dichloromethane extracts obtained were solvent exchanged into either methanol or dimethyl sulfoxide (DMSO). The efficiency of each procedure was evaluated based on the response of Photobacterium phosphoreum in the Microtox assay to the solvent extracts. The 24-h shaking procedure produced significantly higher toxicity than the 15-min sonication procedure for 8 of the 10 sediment samples tested. Comparisons of methanol and DMSO as exchange solvents revealed that there was generally no significant difference between these solvents in terms of toxicity.     

Comparisons between microscale and whole-sediment assays for freshwater sediment toxicity assessment

The use of several microscale assays for evaluating freshwater sediment toxicity was investigated to develop a representative and cost-effective test battery. The bioassays evaluated (18 assays total) included microscale assays performed on solid-phase, pore water, and organic extracts as well as conventional standardized whole-sediment assays with Chironomus riparius and Hyalella azteca on 10 sediment samples collected in the St. Lawrence/Great Lakes system. Selected sediment physical and chemical characteristics were also conducted to aid in the interpretation of results. Benthic invertebrate assays such as C. riparius and H. azteca endpoints were found to correlate well to contaminant levels. Microscale assays such as ATP (adenosine triphosphate) measurement of sediment microbial biomass gave promising results to predict whole-sediment toxicity to benthic invertebrates. Most assays on pore water did not adequately represent whole-sediment toxicity, whereas organic extracts appeared to be more representative, alleviating some potential confounding factors such as interference due to toxicity caused by ammonia. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13 : 93–110, 1998     

Direct sediment toxicity testing procedure using sediment-chromotest kit

A semiquantitative direct sediment toxicity testing procedure using the Sediment-Chromotest was developed. This procedure has advantages over many other toxicity bioassays. It is simple, quick, and reliable, and does not require special instrumentation. The direct sediment toxicity testing procedure involves the use of serial dilutions of solid phase suspensions mixed with stressed bacteria (Escherichia coli) and a cocktail containing the specific inducer for the chromogenic enzyme and other essential factors. The assay is based on the ability of toxicants to inhibit the de novo synthesis of an inducible enzyme, beta-galactosidase. The amount of de novo synthesized enzyme is determined by a colorimetric reaction. This new procedure measures the presence of bioavailable toxicants in sediments, suspended sediments, soils, and other solid wastes directly without extraction and concentration. © by John Wiley & Sons, Inc.     

Sediment Toxicity in the St. Lucie River Watershed and Everglades Agricultural Area

DDD, DDE and ametryn were the most frequently detected pesticides in sediment in the St. Lucie River Watershed (SLR) and Everglades Agricultural Area (EAA). Concentrations of organochlorine compounds typically exceeded NOAA (SQuiRTs) TELs for freshwater sediment. Microtox BSPT EC50s from sediments in the SLR and EAA were lower than other sediment samples and reference controls. Single-species 10-day toxicity tests with Hyalella azteca and Chironomus tentans and whole sediment sample exposures from the SLR and EAA showed no effects on survival or growth of both species. However, in 28-day tests with H. azteca, survival was reduced at two sites compared to a reference control and a third sampling site. There were no correlations between contaminant concentrations, EC50s and toxicity test results.     

Biochemical and genotoxic effects in the vicinity of a pulp mill discharge

Sediment and water samples were taken from five sites in Thunder Bay, one upstream (control) and four downstream locations from a bleached kraft pulp mill. Biochemical effects were examined by estimating the carbohydrate content and enzymatic activities of alkaline phosphatase, cellulase, and dehydrogenase in the sediment. Genotoxicity and toxicity of sediment and water were assessed by the SOS Chromotest, although liver microsomal samples were not used to screen for progenotoxic substances. Sediment and water samples were also analyzed for resin and fatty acids, which indicate the degree of effluent contamination. Significant differences in enzyme activity and carbohydrate content were found between sites. Genotoxic values were obtained for downstream water samples for most of the sampling months, however, the sediment only showed genotoxic activity in the July and October samples. The study showed that there are substances causing genotoxic and biochemical effects in the Kaministiquia River, Ontario. © 1994 by John Wiley & Sons, Inc..     

Simple two-step sediment extraction procedure for use in genotoxicity and toxicity bioassays

Three simple sediment extraction procedures, using Milli-Q water, DMSO, and methanol, were applied to 16 sediment samples collected from the Thames River, Ontario, Canada. The three extracts were tested for the presence of toxicity and genotoxicity using the Microtox,® Toxi-Chromotest,® and Mutatox® (with and without S9) procedures. Results of the study indicated that the Mutatox genotoxicity screening test was an extremely sensitive procedure responding to chemicals in all three types of extracts. Methanol was found to be more efficient than DMSO in extracting toxic and genotoxic chemicals from these sediments. Procedural details and results are discussed.     

The effects of elutriates from PAH and heavy metal polluted sediments on Crassostrea gigas (Thunberg) embryogenesis,larval growth and bio-accumulation by the larvae of pollutants from sedimentary origin

The release, bio-availability and toxicity of contaminants, when sediments are resuspended have been examined, studying concurrently their effects on the embryogenesis and on the larval growth of the Crassostrea gigas larvae and their bio-accumulation in those organisms. Three characteristic sediments have been selected (one contaminated by PAHs, a second by heavy metals and the last by the both pollutants). The organisms were directly exposed to elutriates obtained from each sediment or fed on algae (Isochrysis galbana) contaminated with the same elutriates. The elutriates used in this study show contamination levels similar to those observed in some polluted coastal and estuary environments. The larval growth test has appeared to be more sensitive that the embryotoxicity test. The biological effects and the contaminant bio-accumulation were more pronounced when larvae were directly exposed to different elutriates. In the case of PAHs, the contamination of algae was sufficient to lead to effect on the larval growth of the Crassostrea gigas. In all cases, a fraction of contaminants adsorbed on suspended particles was bio-available and accumulated by the larvae. This study has shown that resuspending polluted sediments constitutes a threat to pelagic organisms and than the C. gigas larval growth may be proposed as a test to protect the most sensitive areas.     

Sediment quality triad assessment survey of the Galveston Bay,Texas system

To characterize the quality of sediments at key sites in the Galveston Bay Estuary, sediment samples were collected concurrently for chemical and physical analyses, toxicity testing and an assessment of benthic community structure. Significant toxicity, as determined by the sea urchin (Arbacia punetulata) pore water embryological development assay, was observed at 12 of the 24 sites investigated in this study. No toxicity was observed at any of the sites with the amphipod (Grandidierella japonica) solid-phase test. There were a number of sites with elevated levels of trace metals and petroleum hydrocarbons. The chemistry, toxicity and benthic data were ranked by station and a scaled rank sum was calculated to facilitate comparisons among the stations. Five sites exhibited strong evidence of contaminant-induced degradation, while 15 stations showed no evidence of contaminant-induced degradation. At eight additional sites the sediment quality triad (SQT) data indicated that unmeasured chemicals or conditions were stressing the system. Contaminant impacts could be reduced or eliminated by alternative regulatory and management practices, including the restriction of produced water discharges into coastal estuaries and the use of dredge material disposal practices that minimize the reintroduction of sediment-associated contaminants to the bays.     

Genotoxicity of marine sediments in the fish hepatoma cell line PLHC-1 as assessed by the Comet assay

The main goal of this study was to test the usefulness of the Comet assay in the PLHC-1 hepatoma fish cell line as a tool for detecting the presence of genotoxic compounds in contaminated marine sediments. The system has been tested using both model chemicals (benzo[a]pyrene (B[a]P) and ethyl methanesulfonate (EMS)) and extracts of sediment samples obtained with solvent dichloromethane/methanol. For all of the analysed sediment extracts as well as for the model chemicals a concentration dependent genotoxic effect was observed. The sediment with the highest observed genotoxic potential was additionally extracted using various solvents in order to test which class of compounds, according to their polarity, is most responsible for the observed genotoxic effect. Non-polar solvents (cyclohexane and dichloromethane) yielded stronger genotoxic effect but the highest level of DNA damage was determined after exposure to sediment extract obtained with the solvent mixture dichloromethane/methanol which extracts a wide range of contaminants. Our results indicate that the PLHC-1 cell line is a suitable in vitro model in sediment genotoxicity assessment and encourage the use of fish cell lines as versatile tools in ecogenotoxicology.     

Evidence of genotoxic substances in the Niagara river watershed

The SOS chromotest was used to detect genotoxicity of sediment samples from seven locations in the Welland River, Ontario, Canada, in December 1986 and April 1987. DMSO extracts of sediment samples from one location situated directly below the discharge pipe of a polyvinyl chloride plant showed a statistically significant (p < 0.01) genotoxic effect. It was concluded that genotoxic contaminants were associated with vinyl chloride contaminated sediments from this location. At a distance of 5 m downstream of the polyvinyl chloride plant's discharge, the mean SOS induction factor was 2.05, while 100 m further downstream the SOS induction factor had dropped to 1.54. The Ames test was used to detect genotoxicity of samples that gave positive responses in the SOS chromotest. The results of the Ames test were negative. This may suggest that the SOS chromotest is more sensitive than the Ames test for testing genotoxicity in these types of samples.     

The shifts of sediment microbial community phylogenetic and functional structures during chromium (VI) reduction

The Lanzhou reach of the Yellow River, located at the upstream of Lanzhou, has been contaminated by heavy metals and polycyclic aromatic hydrocarbons over a long-time. We hypothesized that indigenous microbial communities would remediate those contaminants and some unique populations could play an important role in this process. In this study, we investigated the sediment microbial community structure and function from the Lanzhou reach. Sediment samples were collected from two nearby sites (site A and site B) in the Lanzhou reach along the Yellow River. Sediment geochemical property data showed that site A sediment samples contained significantly (p?<?0.05) higher heavy metals than site B, such as chromium (Cr), manganese (Mn), and copper (Cu). Both site A and B samples were incubated with or without hexavalent chromium (Cr (VI)) for 30 days in the laboratory, and Cr (VI) reduction was only observed in site A sediment samples. After incubation, MiSeq sequencing of 16S rRNA gene amplicons revealed that the phylogenetic composition and structure of microbial communities changed in both samples, and especially Proteobacteria, as the most abundant phylum increased from 45.1?% to 68.2?% in site A, and 50.1?% to 71.3?% in site B, respectively. Some unique OTUs and populations affiliated with Geobacter, Clostridium, Desulfosporosinus and Desulfosporosinus might be involved in Cr (VI) reduction in site A. Furthermore, GeoChip 4.0 (a comprehensive functional gene array) data showed that genes involved in carbon and nitrogen cycling and metal resistance significantly (p?<?0.05) increased in site A sediment samples. All the results indicated that indigenous sediment microbial communities might be able to remediate contaminants like Cr (VI), and this information provides possible strategies for future bioremediation of the Lanzhou reach.     

Using an Integrated Approach to Assess the Sediment Quality of an Mediterranean Lagoon,the Bizerte Lagoon (Tunisia)

The present study investigates the quality of surface sediments from the Bizerte lagoon (North Tunisia) using an integrated approach including chemical contaminant analysis, bioassays and sediment quality guidelines (SQGs). Sediment samples were collected at 9 sites and analyzed for eight heavy metals (Hg, Cd, Cr, Cu, Pb, Zn, Ni, Fe and Mn). PAHs, PCBs, OCPs were measured previously in the same sediment samples. Our results indicated that the highest concentrations of metals were found near urban areas due to the municipial and industrial wastewater discharges. Sediment pollution assessment was carried out using geoaccumulation index and enrichment factor, which indicate a widespread pollution by Cd, Pb, Ni and Zn in the studied sediments. For bioassays, aqueous and organic extracts were used to assess toxicity and genotoxicity in sediments by using Microtox^® and SOS Chromotest, respectively. Toxicity levels were compared to metallic and organic pollutants contents. Our results highlight differences in the pattern of responses between the different assays and show no correlation with all the studied contaminants, emphasizing the influence of other contaminants not analyzed in the present study. Based on SQGs, the results of toxicity assessment indicated that adverse effects caused by Ni and Zn would be expected frequently. Nickel was found to have the highest predicted acute toxicity, followed by Zn, Pb, Cd, Cu and Cr. There was no significant relationship between sediment toxicity calculated from heavy metal concentrations (SQG approach) and those measured with bioassays. These findings support the use of integrated approachs for evaluating the environmental risks of sediments.     

A comparison of techniques used to extract solid samples prior to acute toxicity analysis using the microtox test

To date, there has been no widely accepted or standardized procedure for preparing leachates of solid samples for acute toxicity bioassays such as Microtox. Leaching procedures reported in the literature were evaluated for use with nonspecific environmental sample submissions. Using toxic environmental samples, two experiments were conducted to compare the effect that varying selected parameters would have on the effectiveness of the leaching procedure in removing toxicants from a solid sample matrix. Parameters that were varied included the type of toxicant, aqueous solvent system used to leach the sample, ratio of solid:liquid, type of mixing action, length of extraction time, and method of removing suspended solids from the leachate. Results from these experiments demonstrated that unacceptable variations of measured toxicity of a solid sample occurs with simple modifications of the method. The most dramatic shifts in 15 min EC₅₀ values were observed between vacuum filtering (EC₅₀ mean = 55.8%) and centrifuging (EC₅₀ mean = 22.3%) samples to clarify leachates. This and other significant interactions, between sample contaminant and aqueous system, suggest that no standard procedure will give readily interpretable results for different types of contamination. Investigators should carefully consider the application of the assay (e.g., the detection of toxicants using a sensitive method, or modeling the leaching of toxicants under specific environmental conditions) before selecting a leaching procedure. © 1996 by John Wiley & Sons, Inc.     

Polycyclic aromatic hydrocarbons in surface sediments of the Jialu River

The Jialu River, an important branch of the Huaihe River in China, was seriously polluted because of rapid economic growth and urbanization. In order to evaluate the potential for serious environmental consequences as a result of anthropogenic contamination, the distribution of polycyclic aromatic hydrocarbons (PAHs) has been investigated in surface sediment samples collected in connection with field surveys of 19 sites along the Jialu River. The total concentration of the 16 USEPA priority PAHs ranged from 466.0 to 2605.6 ng/g dry weight with a mean concentration of 1363.2 ng/g. Sediment samples with the highest PAH concentrations were from the upper reaches of the river, where Zhengzhou City is located; the PAH levels in the middle and lower reaches were relatively low. According to the observed molecular indices, PAHs originated largely from the high-temperature pyrolytic process. According to the numerical effect-based sediment quality guidelines (SQGs) of the United States, the levels of PAHs in the Jialu River should not exert adverse biological effects. The total benzo[a]pyrene toxicity equivalent (TEQ) values calculated for samples varied from 50.4 to 312.8 ng/g dry weight with an average of 167.4 ng/g. The relationships between PAHs and environmental factors, including chemical properties of sediments, water quality, aquatic organisms, hydrological conditions, and anthropogenic activities, are also discussed. PAHs exerted a potential negative impact on the benthos. Settlement percentage, population density and industrial GDP per capita had a significant influence on the distribution of PAHs.     

Toxicokinetic approach for the assessment of endocrine disruption effects of contaminated dredged material using female <Emphasis Type="Italic">Carcinus maenas</Emphasis>

Ecotoxicological effects associated with contaminants present in dredged material from three Spanish ports, Ría of Huelva (SW, Spain), La Coruña (NW, Spain) and Bay of Cádiz (SW, Spain) were determined using a marine biotest based on endocrine disruption effects (vitellogenesis process alteration). Intermoult female Carcinus maenas were exposed in the laboratory to sediments from the Spanish ports per replicate during 21 days. Crab haemolymph samples were taken for vitellogenin/vitellin (VTG) analysis on days 0, 7, 14 and 21. Furthermore, chemical analysis was performed in the stations to determine the degree and nature of sediment contamination (Cr, Ni, Cu, Zn, Cd, Pb, Hg, As, PAHs and PCBs). A significant induction (P < 0.05) in vitellogenin/vitellin concentration was observed over time in individuals exposed to sediment samples containing significant concentrations of PAHs, PCBs, Hg, Pb and Zn. The toxicokinetic approach, proposed in this study related to the use of this biomarker in C. maenas, proved to be a powerful and sensitive tool to evaluate toxicity effects associated with contaminants present in dredged material. Moreover the integration of the results obtained through multivariate analysis approach (MAA) allowed the identification contaminants bound to sediments associated with adverse effects, validating the use of this marine biotest in a regulatory framework.     

Biotoxicity of tributyltin acrylate polymers

The biotoxicity of 3 tributyltin monomers, their homopolymers, and 8 copolymers of tributyltin α-chloroacrylate (TCA) against 2 microorganisms (Pseudomonas aeruginosa, Sarcina lutea) and the larvae Artemia salina (Naupli II) is reported. Biotoxicity of the TCA monomer was found to be lower than that of the tributyltin acrylate (TBTAA) monomer. However, the toxicity of homopolymers of TCA was higher than that of TBTAA. The toxicity of copolymers increased with an increase in tributyltin content in the polymer. The biotoxicity could not be correlated with the chemical structure of the polymer.     

Sediment‐contact and survival of fingernail clams: Implications for conducting short‐term laboratory tests

Porewater toxicity tests have been used as indicators of whole sediment toxicity. However, many species commonly tested in porewater predominately reside in the water column and otherwise have little to no direct contact with sediment and associated porewater. We assessed the feasibility of porewater toxicity tests with fingernail clams Musculium transversum, a benthic macroinvertebrate that inhabits soft bottom sediments and feeds by filtering surface and porewater. Fingernail clams were exposed to water or sediment in a 96 h laboratory test with a 5×2 factorial experimental design. The five treatments included sediments from four sites in the Mississippi River and one sediment‐free control (well water). In all treatments, clams were exposed to the sediments or water either directly (no enclosure) or indirectly (enclosure, suspended above the sediment surface). There were three replicates for each of the ten treatment combinations. Overall, survival of fingernail clams did not vary among the five treatments (p=0.36). In treatments without enclosures, survival of clams in the sediment‐free control was not significantly different (p=0.34) from the sediment‐containing treatments. Survival of clams in the sediment‐free control averaged 85%—suggesting that direct sediment contact is not necessary for survival in short‐term tests. In contrast, survival of clams in the sediment‐containing treatments differed significantly (p=0.03) between exposures with (mean, 77%) and without (mean, 89%) enclosures. Thus, fingernail clams may provide an alternative species for evaluating benthic macroinvertebrates in short‐term laboratory porewater tests. However, more information on their physiological requirements and the development of sublethal endpoints is recommended before their use in tests of longer duration. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 23–27, 2000     

Hazard assessment of inorganics,individually and in mixtures,to two endangered fish in the San Juan River,New Mexico

Acute toxicity tests were conducted for 96 h with larval Colorado squawfish (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) in a reconstituted water quality simulating the San Juan River near Shiprock, New Mexico, to determine biological effect concentrations. Tests were conducted with arsenate, copper, selenate, selenite, zinc, and five mixtures of seven to nine inorganics simulating environmental mixtures reported for sites along the San Juan River (Ojo Amarillo Canyon, Gallegos Canyon, Hogback East Drain, Mancos River, and McElmo Creek). Razorback suckers were significantly more sensitive to arsenate, selenate, selenite, Hogback East Drain mixture, and Ojo Amarillo Canyon mixture than were Colorado squawfish. For both species, the Gallegos Canyon mixture had synergistic toxicity, the Mancos River and McElmo Creek mixtures had additive toxicity, and the Ojo Amarillo Canyon mixture had antagonistic toxicity. The Hogback East Drain mixture had additive toxicity to Colorado squawfish, but synergistic toxicity to razorback suckers. The major toxic component in the five mixtures was copper. Comparison of biological effect concentrations (i.e., 96-h LC₅₀) with environmental water concentrations from the San Juan River resulted in a ratio of <100, which revealed a high potential hazard for copper and all five environmental mixtures. The high hazard ratios suggest inorganic contaminants could adversely affect larval Colorado squawfish and razorback suckers in the San Juan River at sites receiving elevated inorganics such as from nonpoint discharges and irrigation return flows. ©1997 by John Wiley & Sons, Inc. Environ Toxicol Water Qual 12 : 195–209, 1997     

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

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

Effect of Extended Storage Time on the Toxicity of Sediment-Associated Cadmium on Midge Larvae (Chironomus tentans)

The effect of the duration of spiked sediment storage on cadmium toxicity was studied. Sediment samples were spiked with cadmium to obtain concentrations of 0.6,16.0, 29.0 and 53.0 g Cd per g sediment (dry weight). The spiked sediment was then stored in sealed plastic containers at 4°C in the dark. Sediment bioassays, using Chironomus tentans, were conducted immediately and at periodic intervals for up to 4 months. Though the levels of cadmium in the bulk sediment samples from different stored periods were not significantly different, different toxicity levels to C. tentans were observed. The toxicity was significantly different between subsequent storage times. There was a significant decrease in the bioaccumulation factor (BAF) values with extended storage times, indicating a reduction in the bioavailability of cadmium. This study suggests that the storage of spiked sediment used in sediment toxicity study can influence the results.