An in situ toxicity identification evaluation method Part I: Laboratory validation

Identification of individual chemical groups is critical in evaluating sediment quality and fractionating these groups of chemicals in a mixture is important to determine the primary chemicals causing toxicity. The in situ toxicity identification evaluation (iTIE) is a novel method that was developed to fractionate chemicals in contaminated sediments and waters and assess toxicity organisms. The study objectives were to verify that the iTIE can help identify contaminant chemical classes and improve the toxicity assessment process; and compare the iTIE and U.S. Environmental Protection Agency's (U.S. EPA) toxicity identification evaluation (TIE) methods. The iTIE exposure chamber is powered by a portable air pump that suctions pore water, via a Venturi system, through selective sorption materials. After passing through the sorptive materials, the pore water passes into an exposure chamber containing Daphnia magna. The chemical sorption materials included Ambersorb 563 for nonpolar organic chemical adsorption, Chelex for metals chelation, and multiple zeolite types for ammonia adsorption. The laboratory studies were performed using water and sediments spiked with ammonia, cadmium, and fluoranthene. The laboratory validation of the iTIE approach showed that different classes of compounds readily could be separated via the resin treatments, resulting in significant differences in concentrations and thus exposures to in situ exposed organisms. Ammonia, cadmium, and fluoranthene were significantly removed by zeolite, Chelex, and Ambersorb, respectively. Although there was some cross-adsorption to the other nontarget resins, it was limited and allowed for treatment differences to be detected. Survival in the treatment resins exposed to the target compounds was as high as control survivals. A 24-h exposure period appeared optimal, allowing for replacement of initial culture water with pore waters, while longer exposures occasionally allowed for breakthrough of contaminants. The iTIE was more sensitive than the U.S. EPA TIE method, in that it detected toxicity more readily due to the greater loss of contaminant concentrations in the TIE manipulation process.     

Sequential toxicity identification evaluation (TIE) for characterizing toxicity of Venice Lagoon sediments: comparison of two different approaches

A toxicity identification evaluation phase-I (TIE-1) procedure was carried out on five pore water samples extracted from sediments of the Venice Lagoon previously investigated to assess both chemical contamination and toxic effects on the biota. Two different sequential TIE procedures were tested. A first sequence (TIE-1) provided for adding Na2S2O3, adding Na-EDTA, filtering, elution through a C18-SPE column and removing ammonia using the macroalgae Ulva rigida Agardh 1823, while a second procedure (TIE-2) was set up using U. rigida treatment for ammonia removal as first step, keeping unchanged the sequence of the other manipulations. Two different exposure time to the macroalgae were tested (3-h and 15-h). Sperm-cell toxicity test with the echinoid Paracentrotus lividus and embryotoxicity tests with the bivalves Mytilus galloprovincialis and Crassostrea gigas were performed on pore-water samples to assess the effect of the sequential treatments on the overall toxicity. The results confirmed that ammonia contribution to toxicity is strong in most of the samples and that metals, specially Cu, are of concern at least in three sites. The TIE-2 procedure provided more reliable results for the samples characterized by high ammonia contribution to the overall toxicity, whereas the results of TIE-1 and TIE-2 were equivalent for the samples where ammonia contribution was not prevailing. Chemical analyses and test results showed that a 3-h U. rigida exposure is suitable to remove ammonia toxicity minimizing potential metal up-take.     

Establishing cause-effect relationships in hydrocarbon-contaminated sediments using a sublethal response of the benthic marine alga, Entomoneis cf punctulata

A sublethal whole-sediment toxicity test that uses flow cytometry to measure inhibition of esterase activity in the marine microalga Entomoneis cf punctulata was applied to the assessment of hydrocarbon-contaminated sediments and toxicity identification and evaluation (TIE). Concentration-response relationships were developed, and a 20% effect concentration for total polycyclic aromatic hydrocarbons (PAHs) of 60 mg/kg normalized to 1% total organic carbon was calculated. Relationships between toxic effects and sediment organic carbon concentrations, organic carbon forms (e.g., black carbon), and sediment particle size indicated that further normalization of hydrocarbon concentrations to sediment particle size may improve concentration-response relationships. The algal toxicity test was applied as a rapid whole-sediment TIE procedure that involved the addition to sediment of powdered coconut charcoal (PCC), a hydrophobic, carbon-based material that strongly adsorbs PAHs and decreases the pore-water exposure pathway. Sediments with PCC concentrations of up to 15% (w/w) provided acceptable responses in control sediments. For six sediments with total PAH concentrations of 1,060, 4,060, 5,120, 9,150, 9,900, and 15,900 mg/kg, inhibition of E. cf punctulata esterase activity (% of control) was 75, 97, 94, 93, 100, and 97%, respectively. Following a 15% PCC amendment to these sediments, inhibition of esterase activity was 0, 1, 11, 69, 32, and 68%, respectively, indicating a decrease in toxicity in all sediments. Because the alga E. cf punctulata is exposed to toxicants via both pore water and overlying water, the reduction in toxicity achieved by 15% PCC additions can be related to the efficient removal of dissolved hydrocarbons released from sediment particles. The sediment-PCC manipulations coupled with algal whole-sediment toxicity tests provided an effective and rapid TIE method to determine whether hydrocarbon contaminants are responsible for toxicity in sediments.     

Comparison of techniques for the isolation of sediment pore water for toxicity testing

The objective of this study was to define an interstitial (pore) water isolation technique suitable for sediment toxicity testing and toxicity identification evaluation (TIE) research. Pore water was prepared from sediments collected at two fresh-water sites (Saginaw River, Keweenaw Waterway) using four or five different techniques, and the samples were compared with respect to toxicity to Ceriodaphnia dubia and several inorganic chemical parameters. Methods evaluated were: high speed (10,000×g) and low speed (2,500×g) centrifugation, syringe extraction, compression, and dialysis. Both high speed and low speed centrifugation resulted in adequate volumes of pore water for routine testing with relatively minimal effort, while the other three techniques were labor intensive and/or yielded small quantities of pore water. Filtration of samples either during preparation (syringe-extraction, compression) or subsequent to initial isolation (centrifuged samples) resulted in significant losses of toxicity, apparently due to the adsorption of contaminants onto the filter or particles retained by the filter. Low speed centrifugation generally resulted in much higher metal concentrations than the other four techniques. However, compared to samples prepared by high speed centrifugation or dialysis, a relatively high proportion of the metals in pore water isolated by low speed centrifugation were biologically unavailable, as inferred from the results of the toxicity tests. Based on these studies, as well as the work of others, we recommend that sediment pore water for toxicity testing and/or TIE analyses be prepared by centrifugation (preferably at 10,000×g) without subsequent filtration.     

Disturbances to metal partitioning during toxicity testing of iron(II)-rich estuarine pore waters and whole sediments

Metal partitioning is altered when suboxic estuarine sediments containing Fe(II)-rich pore waters are disturbed during collection, preparation, and toxicity testing. Experiments with model Fe(II)-rich pore waters demonstrated the rates at which adsorptive losses of Cd, Cu, Ni, Mn, Pb, and Zn occur upon exposure to air. Experiments with Zn-contaminated estuarine sediments demonstrated large and often unpredictable changes to metal partitioning during sediment storage, removal of organisms, and homogenization before testing. Small modifications to conditions, such as aeration of overlying waters, caused large changes to the metal partitioning. Disturbances caused by sediment collection required many weeks for reestablishment of equilibrium. Bioturbation by benthic organisms led to oxidation of pore-water Fe(II) and lower Zn fluxes because of the formation of Fe hydroxide precipitates that adsorb pore-water Zn. For five weeks after the addition of organisms to sediments, Zn fluxes increased slowly as the organisms established themselves in the sediments, indicating that the establishment of equilibrium was not rapid. The results are discussed in terms of the dynamic nature of suboxic, Fe(II)-rich estuarine sediments, how organisms perturb their environment, and the importance of understanding chemistry in toxicity testing with whole sediments or pore water. Recommendations are provided for the handling of sediments for toxicity testing.     

Potency and characterization of estrogen-receptor agonists in United Kingdom estuarine sediments

The activity of estrogen-receptor (ER) agonists in sediments collected from the United Kingdom (UK) estuaries was assessed using the in vitro recombinant yeast estrogen screen (YES assay). The YES assay was successfully used to determine the in vitro ER agonist potency of pore waters and solvent extracts of sediments collected from UK estuaries. Estrogen-receptor agonists were detected in 66% of the pore water samples and in 91% of the sediment solvent extracts tested. The pore waters tested had ER agonist potencies from less than 2 to 68 ng 17beta-estradiol (E2) L(-1), whereas sediment extracts had potencies from less than 0.2 to 13 microg E2 kg(-1). A toxicity identification evaluation approach using bioassay-directed fractionation was used in an attempt to identify the ER agonists in extracts of sediments collected from the Tyne and Tees estuaries (UK). Gas chromatography-mass spectrometry was used to provide lists of compounds in the fractions obtained that were evaluated for known ER agonist activity using published data and an ER quantitative structure-activity relationship model. Toxicity identification evaluation characterization failed to identify any ER agonists in pore water extracts; however, three compounds in sediment solvent extracts were identified as ER agonists. Nonylphenol, cinnarizine, and cholesta-4,6-dien-3-one were identified in the sample collected from the Tyne estuary. Important ER agonist substances that contaminate marine sediments remain unidentified. The present study as well as previous work on effluents point toward the involvement of natural products in the estrogenic burdens of marine sediments. Further work is required to establish the relative contribution of natural products and anthropogenic chemicals to current environmental impacts in the context of the Oslo and Paris Commission strategy to eliminate hazardous substances by 2020.     

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. Piperonyl butoxide addition

Piperonyl butoxide (PBO) is a synergist used in some pyrethroid and pyrethrin pesticide products and has been used in toxicity identification evaluations (TIEs) of water samples to indicate organophosphate or pyrethroid-related toxicity. Methods were developed and validated for use of PBO as a TIE tool in whole-sediment testing to help establish if pyrethroids are the cause of toxicity observed in field-collected sediments. Pyrethroid toxicity was increased slightly more than twofold in 10-d sediment toxicity tests with Hyalella azteca exposed to 25 microg/L of PBO in the overlying water. This concentration was found to be effective for sediment TIE use, but it is well below that used in previous water and pore-water TIEs with PBO. The effect of PBO on the toxicity of several nonpyrethroids also was tested. Toxicity of the organophosphate chlorpyrifos was reduced by PBO, and the compound had no effect on toxicity of cadmium, DDT, or fluoranthene. Mixtures of the pyrethroid bifenthrin and chlorpyrifos were tested to determine the ability of PBO addition to identify pyrethroid toxicity when organophosphates were present in a sample. The PBO-induced increase in pyrethroid toxicity was not seen when chlorpyrifos was present at or above equitoxic concentrations with the pyrethroid. In the vast majority of field samples, however, the presence of chlorpyrifos does not interfere with use of PBO to identify pyrethroid toxicity. Eleven field sediments or soils containing pyrethroids and/or chlorpyrifos were used to validate the method. Characterization of the causative agent as determined by PBO addition was consistent with confirmation by chemical analysis and comparison to known toxicity thresholds in 10 of the 11 sediments.     

Use of carboxylesterase activity to remove pyrethroid-associated toxicity to Ceriodaphnia dubia and Hyalella azteca in toxicity identification evaluations

Increases in the use and application of pyrethroid insecticides have resulted in concern regarding potential effects on aquatic ecosystems. Methods for the detection of pyrethroids in receiving waters are required to monitor environmental levels of these insecticides. One method employed for the identification of causes of toxicity in aquatic samples is the toxicity identification evaluation (TIE); however, current TIE protocols do not include specific methods for pyrethroid detection. Recent work identified carboxylesterase treatment as a useful method for removing/detecting pyrethroid-associated toxicity. The present study has extended this earlier work and examined the ability of carboxylesterase activity to remove permethrin- and bifenthrin-associated toxicity to Ceriodaphnia dubia and Hyalella azteca in a variety of matrices, including laboratory water, Sacramento River (CA, USA) water, and Salinas River (CA, USA) interstitial water. Esterase activity successfully removed 1,000 ng/L of permethrin-associated toxicity and 600 ng/L of bifenthrin-associated toxicity to C. dubia in Sacramento River water. In interstitial water, 200 ng/L of permethrin-associated toxicity and 60 ng/L of bifenthrin-associated toxicity to H. azteca were removed. The selectivity of the method was validated using heat-inactivated enzyme and bovine serum albumin, demonstrating that catalytically active esterase is required. Further studies showed that the enzyme is not significantly inhibited by metals. Matrix effects on esterase activity were examined with municipal effluent and seawater in addition to the matrices discussed above. Results confirmed that the esterase retains catalytic function in a diverse array of matrices, suggesting that this technique can be adapted to a variety of aquatic samples. These data demonstrate the utility of carboxylesterase treatment as a viable step to detect the presence of pyrethroids in receiving waters.     

Assessment of supercritical fluid extraction use in whole sediment toxicity identification evaluations

Supercritical fluid extraction (SFE) with pure CO(2) was assessed as a confirmatory tool in phase III of whole sediment toxicity identification evaluations (TIEs). The SFE procedure was assessed on two reference sediments and three contaminated sediments by using a combination of toxicological and chemical measurements to quantify effectiveness. Sediment toxicity pre- and post-SFE treatment was quantified with a marine amphipod (Ampelisca abdita) and mysid (Americamysis bahia), and nonionic organic contaminants (NOCs) polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured in sediments, overlying waters, and interstitial waters. In general, use of SFE with the reference sediments was successful, with survival averaging 91% in post-SFE treatments. Substantial toxicity reductions and contaminant removal from sediments and water samples generated from extracted sediments of up to 99% in two of the contaminated sediments demonstrated SFE effectiveness. Furthermore, toxicological responses for these SFE-treated sediments showed comparable results to those from the same sediments treated with the powdered coconut charcoal addition manipulation. These data demonstrated the utility of SFE in phase III of a whole sediment TIE. Conversely, in one of the contaminated sediments, the SFE treatments had no effect on sediment toxicity, whereas sediment concentrations of PCBs and PAHs were reduced. We propose that, for some sediments, the SFE treatment may result in the release of otherwise nonbioavailable cationic metals that subsequently cause toxicity to test organisms. Overall, SFE treatment was found to be effective for reducing the toxicity and concentrations of NOCs in some contaminated sediments. However, these studies suggest that SFE treatment may enhance toxicity with some sediments, indicating that care must be taken when applying SFE and interpreting the results.     

Toxicity Identification Evaluation of Lake Orta (Northern Italy) Sediments Using the Microtox System

Pore waters extracted by centrifugation from Lake Orta (Northern Italy) sediments were studied with a modified Toxicity Identification Evaluation (TIE) procedure using the Microtox bacterial luminescence toxicity test system. The most toxic pore water samples were from stations near a rayon factory, known as a source of copper and ammonium discharges. The TIE manipulations used were filtration, EDTA chelation, and C18 solid-phase resin adsorption. The most effective treatments to remove toxicity were the EDTA and C18, indicating that both metals and nonpolar organic compounds contribute to the observed toxicity.     

Causes of water toxicity to Hyalella azteca in the New River, California, USA

The New River (CA, USA) was created in 1905 to 1907 when the Colorado River washed out diversionary works and flowed into the Salton Basin, creating the Salton Sea. Approximately 70% of the river's current flow is agricultural wastewater from the Imperial Valley. The river is contaminated with pesticides, industrial organic chemicals, metals, nutrients, bacteria, and silt. Monitoring for the State of California Surface Water Ambient Monitoring Program has indicated persistent water column toxicity to the epibenthic amphipod Hyalella azteca. Four toxicity identification evaluations (TIEs), along with chemical analyses, were performed, and the results indicated multiple and varying causes of toxicity. The first two TIEs characterized the causes of toxicity as a combination of metals and organics, but only the second sample contained enough total copper to contribute to toxicity. The third TIE used an emerging method for characterizing and identifying toxicity caused by pyrethroid pesticides. This TIE characterized organics as the cause of toxicity, and a carboxylesterase enzyme treatment further identified the cause of toxicity as pyrethroids. The final TIE used the enzyme and Phase II procedures to identify cypermethrin as the cause of toxicity. The TIE results demonstrate the evolving causes of toxicity in the New River and should assist regulators with implementing the total maximum daily load process for pesticides, particularly pyrethroids. Further research will determine if pyrethroids and other New River contaminants are having an impact on the Salton Sea.     

A large-scale categorization of sites in San Francisco Bay, USA, based on the sediment quality triad, toxicity identification evaluations, and gradient studies

Sediment quality was assessed in San Francisco Bay, California, USA, using a two-tiered approach in which 111 sites were initially screened for sediment toxicity. Sites exhibiting toxicity were then resampled and analyzed for chemical contamination, recurrent toxicity, and, in some cases, benthic community impacts. Resulting data were compared with newly derived threshold values for each of the metrics in a triad-based weight-of-evidence evaluation. Sediment toxicity test results were compared with tolerance limits derived from reference site data, benthic community data were compared with threshold values for a relative benthic index based on the presence and abundance of pollution-tolerant and -sensitive taxa, and concentrations of chemicals and chemical mixtures were compared with sediment quality guideline-based thresholds. A total of 57 sites exceeded threshold values for at least one metric, and each site was categorized based on triad inferences. Nine sites were found to exhibit recurrent sediment toxicity associated with elevated contaminant concentrations, conditions that met program criteria for regulatory attention. Benthic community impacts were also observed at three of these sites, providing triad evidence of pollution-induced degradation. Multi- and univariate correlations indicated that chemical mixtures, heavy metals, chlordanes, and other organic compounds were associated with measured biological impacts in the Bay. Toxicity identification evaluations indicated that metals were responsible for pore-water toxicity to sea urchin larvae at two sites. Gradient studies indicated that the toxicity tests and benthic community metrics employed in the study predictably tracked concentrations of chemical mixtures in Bay sediments.     

Ecotoxicologic impacts of agricultural drain water in the Salinas River, California, USA

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California (USA). Large areas of this watershed are cultivated year-round in row crops, and previous laboratory studies have demonstrated that acute toxicity of agricultural drain water to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. We investigated chemical contamination and toxicity in waters and sediments in the river downstream of an agricultural drain water input. Ecological impacts of drain water were investigated by using bioassessments of macroinvertebrate community structure. Toxicity identification evaluations were used to characterize chemicals responsible for toxicity. Salinas River water downstream of the agricultural drain was acutely toxic to the cladoceran Ceriodaphnia dubia, and toxicity to C. dubia was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to the amphipod Hyalella azteca, a resident invertebrate. Toxicity identification evaluations (TIEs) conducted on sediment pore water suggested that toxicity to amphipods was due in part to OP pesticides; concentrations of chlorpyrifos in pore water sometimes exceeded the 10-d mean lethal concentration (LC50) for H. azteca. Potentiation of toxicity with addition of the metabolic inhibitor piperonyl butoxide suggested that sediment toxicity also was due to other non-metabolically activated compounds. Macroinvertebrate community structure was highly impacted downstream of the agricultural drain input, and a number of macroinvertebrate community metrics were negatively correlated with combined TUs of chlorpyrifos and diazinon, as well as turbidity associated with the drain water. Some macroinvertebrate metrics were also correlated with bank vegetation cover. This study suggests that pesticide pollution is the likely cause of ecological damage in the Salinas River, and this factor may interact with other stressors associated with agricultural drain water to impact the macroinvertebrate community in the system.     

Determining stressor presence in streams receiving urban and agricultural runoff: development of a benthic in situ toxicity identification evaluation method

Determining toxicity in streams during storm-water runoff can be highly problematic because of the fluctuating exposures of a multitude of stressors and the difficulty of linking these dynamic exposures with biological effects. An underlying problem with assessing storm-water quality is determining if toxicity exists and then which contaminant is causing the toxicity. The goal of this research is to provide an alternative to standard toxicity testing methods by incorporating an in situ toxicity identification evaluation (TIE) approach. A benthic in situ TIE bioassay (BiTIE) was developed for separating key chemical classes of stressors in streams during both low- and high-flow events to help discern between point and nonpoint sources of pollution. This BiTIE method allows for chemical class fractionation through the use of resins, and these resins are relatively specific for removing nonpolar organics (Dowex Optipore), ammonia (zeolite), and polywool (control). Three indigenous aquatic insects, a mayfly (Isonychia spp.), a caddisfly (Hydropsyche spp.), and a water beetle (Psephenus herricki), were placed in BiTIE chambers that were filled with natural substrates. Acute 96-h exposures were conducted at Honey Creek, New Carlisle, Ohio, USA (reference site), and Little Beavercreek, Beavercreek, Ohio, USA (impaired site). At both sites, significant (p < 0.025) stressor responses were observed using multiple species with polywool or no resin (control) treatments exhibiting < 80% survival and resin treatments with >80% survival. The BiTIE method showed stressor-response relationships in both runoff and base flow events during 96-h exposures. The method appears useful for discerning stressors with indigenous species in situ.     

Ecological impacts of lead mining on Ozark streams: toxicity of sediment and pore water

We studied the toxicity of sediments downstream of lead-zinc mining areas in southeast Missouri, using chronic sediment toxicity tests with the amphipod, Hyalella azteca, and pore-water toxicity tests with the daphnid, Ceriodaphnia dubia. Tests conducted in 2002 documented reduced survival of amphipods in stream sediments collected near mining areas and reduced survival and reproduction of daphnids in most pore waters tested. Additional amphipod tests conducted in 2004 documented significant toxic effects of sediments from three streams downstream of mining areas: Strother Creek, West Fork Black River, and Bee Fork. Greatest toxicity occurred in sediments from a 6-km reach of upper Strother Creek, but significant toxic effects occurred in sediments collected at least 14 km downstream of mining in all three watersheds. Toxic effects were significantly correlated with metal concentrations (nickel, zinc, cadmium, and lead) in sediments and pore waters and were generally consistent with predictions of metal toxicity risks based on sediment quality guidelines, although ammonia and manganese may also have contributed to toxicity at a few sites. Responses of amphipods in sediment toxicity tests were significantly correlated with characteristics of benthic invertebrate communities in study streams. These results indicate that toxicity of metals associated with sediments contributes to adverse ecological effects in streams draining the Viburnum Trend mining district.     

Use of powdered coconut charcoal as a toxicity identification and evaluation manipulation for organic toxicants in marine sediments

We report on a procedure using powdered coconut charcoal to sequester organic contaminants and reduce toxicity in sediments as part of a series of toxicity identification and evaluation (TIE) methods. Powdered coconut charcoal (PCC) was effective in reducing the toxicity of endosulfan-spiked sediments by 100%. Powdered coconut charcoal also was effective in removing almost 100% of the toxicity from two field sediments contaminated with polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). Powdered coconut charcoal did not change the toxicity of ammonia or metal-spiked sediments; however, there was some quantitative reduction in the concentrations of free metals (element specific) in metal-spiked sediments. Powdered coconut charcoal is an effective, relatively specific method to sequester and remove toxicity from sediments contaminated with organic contaminants.     

Marine sediment toxicity identification evaluation methods for the anionic metals arsenic and chromium

Marine sediments accumulate a variety of contaminants and, in some cases, demonstrate toxicity because of this contamination. Toxicity identification evaluation (TIE) methods provide tools for identifying the toxic chemicals causing sediment toxicity. Currently, whole-sediment TIE methods are not available for anionic metals like arsenic and chromium. In the present paper, we describe two new anion-exchange resins used in the development of whole-sediment TIE methods for arsenic and chromium. Resins were shown to reduce whole-sediment toxicity and overlying water concentrations of the anionic metals. Sediment toxicity, expressed as the median lethal concentration, was reduced by a factor of two to a factor of nearly six between amended sediment treatments containing resin and those without resin. Aqueous concentrations of arsenic and chromium in the toxicity exposures decreased to less than the detection limits or to concentrations much lower than those measured in treatments without resin. Interference studies indicated that the anion-exchange resins had no significant effect on concentrations of the representative pesticide endosulfan and minimal effects on concentrations of ammonia. However, the anion-exchange resins did significantly reduce the concentrations of a selection of cationic metals (Cd, Cu, Ni, Pb, and Zn). These data demonstrate the utility of anion-exchange resins for determining the contribution of arsenic and chromium to whole-sediment toxicity. The present results also indicate the importance of using TIE methods in a formal TIE structure to ensure that results are not misinterpreted. These methods should be useful in the performance of marine whole-sediment TIEs.     

Sediment toxicity identification evaluation (TIE) studies at marine sites suspected of ordnance contamination

A sediment quality assessment survey and subsequent toxicity identification evaluation (TIE) study was conducted at several sites in Puget Sound, Washington. The sites were previously suspected of contamination with ordnance compounds. The initial survey employed sea urchin porewater toxicity tests to locate the most toxic stations. Sediments from the most toxic stations were selected for comprehensive chemical analyses. Based on the combined information from the toxicity and chemical data, three adjacent stations in Ostrich Bay were selected for the TIE study. The results of the phase I TIE suggested that organics and metals were primarily responsible for the observed toxicity in the sea urchin fertilization test. In addition to these contaminants, ammonia was also contributing to the toxicity for the sea urchin embryological development test. The phase II TIE study isolated the majority of the toxicity in the fraction containing nonpolar organics with high log K _ow, but chemical analyses failed to identify a compound present at a concentration high enough to be responsible for the observed toxicity. The data suggest that some organic or organometallic contaminant(s) that were not included in the comprehensive suite of chemical analyses caused the observed toxicological responses. Received: 12 December 2000/Accepted: 11 May 2001     

An evaluation of logistic regression models for predicting amphipod toxicity from sediment chemistry

An empirical screening level approach was developed to assess the probability of toxicity to benthic organisms associated with contaminated sediment exposure. The study was based on simple logistic regression models (LRMs) of matching sediment chemistry and toxicity data retrieved from a large database of field-collected sediment samples contaminated with multiple chemicals. Three decisions were made to simplify the application of LRMs to sediment samples contaminated with multiple chemicals. First, percent mortality information associated with each sediment sample was condensed into a dichotomous response (i.e., toxic or nontoxic). Second, each LRM assumed that toxicity was attributable to a single contaminant. Third, individual contaminants present at low concentrations were excluded from toxic sediment samples. Based on an analysis of the National Sediment Inventory database, the LRM approach classified 55% of nontoxic sediments as toxic (i.e., false-positives). Because this approach has been used to assess the probability of benthic toxicity as reported by the U.S. Environmental Protection Agency (U.S. EPA), the resultant estimates of potential toxicity convey a misleading impression of the increased hazard that sediments pose to the health of aquatic organisms at many sites in the United States. This could result in important resources needlessly being diverted from truly contaminated sites to evaluate and possibly remediate sediments at uncontaminated sites.     

Development of toxicity identification evaluation procedures for pyrethroid detection using esterase activity

Recent agrochemical usage patterns suggest that the use of organophosphate (OP) pesticides will decrease, resulting in a concomitant increase in pyrethroid usage. Pyrethroids are known for their potential toxicity to aquatic invertebrates and many fish species. Current toxicity identification evaluation (TIE) techniques are able to detect OPs, but have not been optimized for pyrethroids. Organophosphate identification methods depend upon the use of piperonyl butoxide (PBO) to identify OP-induced toxicity. However, the use of PBO in TIE assays will be confounded by the co-occurrence of OPs and pyrethroids in receiving waters. It is necessary, therefore, to develop new TIE procedures for pyrethroids. This study evaluated the use of a pyrethroid-specific antibody, PBO, and carboxylesterase activity to identify pyrethroid toxicity in aquatic toxicity testing with Ceriodaphnia dubia. The antibody caused significant mortality to the C. dubia. Piperonyl butoxide synergized pyrethroid-associated toxicity, but this effect may be difficult to interpret in the presence of OPs and pyrethroids. Carboxylesterase activity removed pyrethroid-associated toxicity in a dose-dependent manner and did not compromise OP toxicity, suggesting that carboxylesterase treatment will not interfere with TIE OP detection methods. These results indicate that the addition of carboxylesterase to TIE procedures can be used to detect pyrethroids in aquatic samples.