Sediment Chemical Concentrations Research Articles

Concentrations of Radioactive and Toxic Chemicals in Bottom Sediments of the Kara Sea

Concentrations of Radioactive and Toxic Chemicals in Bottom Sediments of the Kara Sea

Changes in aquatic microbial responses to C-substrates with stream water and sediment quality related to land use pressures

The degradation of aquatic ecosystems by multiply-acting stressors is a key threat requiring new approaches to identify impairment processes and restoration targets. Heterotrophic respiration of C-substrates can be an integrative indicator of how aquatic ecosystems respond to pollution. We utilised sixteen C-substrates (simple metabolites to dissolved organic matter (DOM)) to characterise substrate induced respiration (SIR) for sediments from sixteen NE Scotland streams covering a range of land use-related pollution pressures. Pollution explanatory variables were as assessed from GIS-derived land cover areas, dissolved water chemistry (N, P, base cations and trace elements) and sediment trace metals (by aqua-regia digest). Large inter-site variation in dissolved and sediment chemical concentrations was strongly significantly correlated with land cover: dissolved N, Ca, Mg, K, Na positively with agriculture and urban, negatively with semi-natural land areas; sediment As, Ba, Co, Zn with agriculture, Cu, Pb, Zn with urban areas. Simple linear regression modelling was used to explore the influences across land cover, dissolved and sediment chemistry with C-substrate responses, both individually and using principal components-derived SIR ‘fingerprints’. The data supported the hypothesis that pollution pressures altered water and sediment quality, in turn affecting sediment microbes and their respiration responses to a range of C-substrates, especially discriminating the DOM respiration. Since headwater DOM is a dominant pool of C driving ecosystem processes downstream then any loss of ability to utilise DOM should be further explored in terms of possible connections to pollution processes.

A comparison of Shoreline Cleanup Assessment Technique (SCAT) visual observations of oiling and measured soil and sediment chemical concentrations following the 2010 Deepwater Horizon accident.

Abstract This study examines the Deepwater Horizon SCAT results in comparison to measured chemical concentrations in shoreline sediments. Surface and subsurface oiling levels were grouped into oiling categories from Very Light to Heavy as per SCAT protocol. Discrete sediment and soil sample locations from the shoreline and immediate nearshore from 27 separate NRDA studies were separated into the SCAT oiling category zones. Measurements of chemical constituents associated with petroleum (i.e., PAH, saturated hydrocarbons, petroleum biomarkers) were used to evaluate the concentration and composition of petroleum present in samples. Hydrocarbon source interpretation (“fingerprinting”) was used to identify and exclude samples which were conclusively not DWH oil. Analysis of the chemical distributions in shoreline sediments shows that the oil character varied greatly in time and space, often over very small distances. Average PAH and alkane concentration data tend to agree with the SCAT designations, however, the concentration of petroleum chemicals in any individual sample could not be predicted by SCAT category alone. The results suggest limited predictive ability in specific locations; however, they are useful to estimate the average conditions within the landscape setting in the northern Gulf of Mexico and in the design of injury studies.

Influence of blooms of phytoplankton on concentrations of hydrophobic organic chemicals in sediments and snails in a hyper-eutrophic, freshwater lake

Blooms of phytoplankton, which are common in freshwater ecosystems, might not only affect quality of water but also influence biogeochemical processing of pollutants. Based on three years of field observations in sediments of Tai Lake, China, concentrations of organochlorine (OC) pesticides and polycyclic aromatic hydrocarbons (PAHs) in areas where blooms occurred were 2.4 and 3.4 times greater than concentrations in areas without blooms. Concentrations of octylphenol (OP), nonylphenol (NP) and bisphenol A (BPA) in areas where blooms did not occur were 3.8, 4.4 and 2.6 times greater than concentrations in areas where blooms did occur. To explain the differences, simultaneous, seasonally determinations of the water-sediment-phytoplankton-snails disequilibria were determined empirically. Greater sinking and lesser diffusion were shown to be probable drivers of the burial of δ-HCH, 4-ring and 5-ring PAHs in surface sediments of areas in which blooms occurred, being as much as 0.58, 38 and 45 g month−1. Large biodegradation and low burial was shown to be the probable reason of the inverse proportion of NP, OP and BPA in both water and sediment to biomass which might be due to the enhanced metabolic capacity of bacterial community associated with algae blooms. These phenomena further influence the persistent hydrophobic organic chemicals in the snail species (Bellamya quadrata) being greater in winter but lesser in summer, which is probably due to the positive relationship with the concentrations in sediment when snails were dormant and with the concentrations in water after dormancy. Thus, in Tai Lake, the fate and distribution of persistent and biodegradable contaminants in sediments and snails is influenced by blooms of phytoplankton, which should be included in models of environmental fates of contaminants.

Integrated sediment quality assessment through biomarker responses and bioavailability measurements: Application in Tai Lake, China

A weight of evidence (WoE) framework has been applied to assess sediment quality of a typical freshwater lake, Tai Lake in China, where the sediments were contaminated by various chemicals but showed no acute lethality to the benthic invertebrate, Chironomus dilutus. A quantitative scoring method was employed to integrate three lines of evidence (LoE), including adverse effects in life cycle bioassays, biomarker responses, and bioavailability-based chemical analysis. Six biomarkers were determined in C. dilutus after the exposure to the sediments from Tai Lake and provided sensitive indication of sublethal effects at the molecular level. The biomarkers included cytochrome P450, glutathione S-transferase, carboxylesterase, acetylcholinesterase, catalase, and lipid peroxidation. The changes of the biomarkers were summarized for individual sampling sites by computing the integrated biomarker response (IBR) indices. Complementary information was also confirmed by the interrelationship of the LoEs. The IBR indices gained before pupation correlated well with the impairments of emergence of the midges, and altered acetylcholinesterase was corroborated by the detection of chlorpyrifos, an organophosphate pesticide. The relationship between bioavailable toxic units estimated by Tenax extractable concentrations of chemicals in sediment and the observed toxicity in the midges helped to identify the putative toxicity contributors to C. dilutus. Overall, the WoE method clearly distinguished the contaminated sites and ranked them by the level of contamination. Sediment-associated pesticides, particularly γ-hexachlorocyclohexane and chlorpyrifos, were the possible contributors to chronic toxicity to the midges.

The contribution of physical and chemical sediment characteristics to environmental risk from an irrigation scheme in South Africa

The physical and chemical characteristics of sediment from a South African irrigation scheme were used to determine the sediment stressors within the system and to determine whether or not stressors have the potential to contribute to pollutant risk within the system. The information generated also strengthens the database of sediment chemical concentrations in South Africa. The sediment condition at various sites along the Vaalharts Irrigation Scheme (VHIS) was assessed based on physical and chemical characteristics. Sediment samples were collected during three surveys from 2007 to 2009. Physical analysis included organic content and grain size determination. The chemical characteristics were analysed using sequential metal extractions and pesticide analysis. Sediment samples from the Harts River showed increasing organic content along the VHIS while some sediment deposition was evident. Chemical analysis indicated that no pesticide residues were present in the sediment. In general, the sediment metal concentrations indicated lower concentrations than measured at other sites in South Africa. The sequential extractions indicated that cadmium and manganese were contained mostly in the soluble phase resulting in a high to very high risk of metal pollution effects, as measured with the Risk Assessment Code (RAC). A medium risk was identified for cobalt and zinc concentrations. The high fractions of cadmium present in the soluble fraction indicated anthropogenic enrichment, potentially due to phosphate fertiliser which is used in agriculture. Sediment assessments are not routinely applied in South Africa resulting in very little reference or background data available for the area. The metal concentrations for the study area were generally lower than those for other studies in more polluted regions. A low risk for the majority of metals was identified using the RAC methodology with the exception of manganese and cadmium. The study also contributes to the available knowledge surrounding metal pollution in riverine sediments in South Africa.

An updated Quantitative Water Air Sediment Interaction (QWASI) model for evaluating chemical fate and input parameter sensitivities in aquatic systems: Application to D5 (decamethylcyclopentasiloxane) and PCB-180 in two lakes

The QWASI fugacity mass balance model has been widely used since 1983 for both scientific and regulatory purposes to estimate the concentrations of organic chemicals in water and sediment, given an assumed rate of chemical emission, advective inflow in water or deposition from the atmosphere. It has become apparent that an updated version is required, especially to incorporate improved methods of obtaining input parameters such as partition coefficients. Accordingly, the model has been revised and it is now available in spreadsheet format. Changes to the model are described and the new version is applied to two chemicals, D5 (decamethylcyclopentasiloxane) and PCB-180, in two lakes, Lake Pepin (MN, USA) and Lake Ontario, showing the model’s capability of illustrating both the chemical to chemical differences and lake to lake differences. Since there are now increased regulatory demands for rigorous sensitivity and uncertainty analyses, these aspects are discussed and two approaches are illustrated. It is concluded that the new QWASI water quality model can be of value for both evaluative and simulation purposes, thus providing a tool for obtaining an improved understanding of chemical mass balances in lakes, as a contribution to the assessment of fate and exposure and as a step towards the assessment of risk.

From sediment to tissue and tissue to sediment: An evaluation of statistical bioaccumulation models

Biota-sediment accumulation factors (BSAFs) and biota-sediment accumulation regressions (BSARs) are statistical models that may be used to estimate tissue chemical concentrations from sediment chemical concentrations or vice versa. Biota-sediment accumulation factors and BSARs are used to fill tissue concentration data gaps, set sediment preliminary remediation goals (PRGs), and make projections about the effectiveness of potential sediment cleanup projects in reducing tissue chemical concentrations. We explored field-based, benthic invertebrate biota-sediment chemical concentration relationships using data from the US Environmental Protection Agency (USEPA) Mid-Continent Ecology Division (MED) BSAF database. Approximately two thirds of the 262 relationships investigated were very poor (r(2) < 0.3 or p-value ≥ 0.05); for some of the biota-sediment relationships that did have a significant nonzero slope (p-value < 0.05), lipid-normalized tissue concentrations tended to decrease as the colocated organic carbon (OC)-normalized sediment concentration increased. Biota-sediment relationships were further evaluated for 3 of the 262 datasets. Biota-sediment accumulation factors, linear regressions, model II regressions, illustrative sediment PRGs, and confidence intervals (CIs) were calculated for each of the three examples. These examples illustrate some basic but important statistical practices that should be followed before selecting a BSAR or BSAF or relying on these simple models of biota-sediment relationships to support consequential management decisions. These practices include the following: one should not assume that the relationship between chemical concentrations in tissue and sediment is necessarily linear, one should not assume the model intercept to be zero, and one should not place too much stock on models that are heavily influenced by one or a few high chemical concentration data points. People will continue to use statistical models of field-based biota-sediment chemical concentration relationships to support sediment investigations and remedial action decisions. However, it should not be assumed that the models will be reliable. In developing and applying BSAFs and BSARs, it is essential that best practices are followed and model limitations and uncertainties are understood, acknowledged, and quantified as much as possible.

Passive Equilibrium Sampler for in Situ Measurements of Freely Dissolved Concentrations of Hydrophobic Organic Chemicals in Sediments

In this study, an equilibrium passive sampling device is introduced that facilitates the in situ measurement of hydrophobic organic chemicals bioavailability in sediments in terms of freely dissolved concentrations. The new field sampler allows SPME fibers and silicone hollow fibers to be immersed and equilibrated in situ, whereas an automated liner exchanger (ALEX) facilitates the quantitative transfer of analytes to the GC without the use of extraction solvents. The sampler was developed for environmental monitoring as follows: (1) It is of very solid construction and can be reused practically ad infinitum. (2) Fibers with varying surface to volume ratios can be exposed in parallel in order to confirm that equilibrium was reached between sampler and sediment. (3) The equilibrium times allow a temporal resolution that is suited for monitoring of both long-term trends and seasonal effects. The automated thermal desorption reduced sample treatment to a minimum and ensured cost- and time-efficient measurements while minimizing potential error sources after the sampling. The sampler is applicable in a multitude of aquatic environments, especially where currents are low and sediments are muddy and well-mixed, e.g. by bioturbation. Examples for such environments are mud flats, harbor basins, river banks, and lakes.

The behavior of heavy metals in tidal flat sediments during fresh water leaching

Many of the coastal tidal flats in China that were polluted with heavy metals are now being reclaimed for arable land. The safety of these soils for agriculture is of great concern. The present study investigated the sediment chemical properties, concentrations, and speciation of heavy metals at different levels of desalination during a controlled leaching experiment. After leaching with fresh water, the average reductions in the heavy metal species examined in 0–65 cm depth sediment were 32.1% for Pb, 26.2% for Cd, 14.0% for Zn, 13.8% for Cu, and 11.0% for Cr, while the Ni concentration in sediment did not change significantly. The amounts of Cd, Pb, Cr, Cu, and Zn bound to the reducible fraction, the amounts of Cd, Pb, and Zn bound to the exchangeable fraction, the amounts of Pb, Cr, Cu, and Zn associated with the carbonate fraction, and the Cu associated with the oxidizable fraction all decreased significantly. Complexation with salt anions, ion exchange between the cations and the metal ions, removal of SO 4 2 - , dissolution of carbonate, and the redox potential variations all contributed to the decreases in Pb, Cd, Zn, Cu, and Cr. These results suggest that leaching with fresh water can also remove a fraction of the heavy metal contamination when it diminishes sediment salinity.

Review of thin‐layer placement applications to enhance natural recovery of contaminated sediment

This article provides a review of thin-layer placement applications to enhance the natural recovery of contaminated sediment. Three principal case studies are presented in which thin-layer placement has been implemented as a component of enhanced monitored natural recovery (EMNR). EMNR is defined as the application of engineered means such as thin-layer placement or broadcasting of capping material to accelerate natural recovery processes in locations not appropriate for application of monitored natural recovery (MNR) alone. Case studies examine factors affecting the implementation of EMNR, including the impact of site conditions on stable and successful thin-layer placement of clean sediment or other capping material, as well as the challenges in development and implementation of monitoring plans that chart progress toward achieving remedy success. Pilot-scale or demonstration studies of thin-layer placement of clean sand or sediment are subsequently assessed to highlight a range of potentially successful strategies for placement and post-placement monitoring. The primary difference between the pilot-scale or demonstration sites and the 3 primary EMNR case studies is that monitoring at the demonstration sites has focused more explicitly on understanding mechanisms of material placement and/or chemical migration, rather than assessing longer-term or more comprehensive remedial action objectives (RAOs) such as reductions in human health or ecological risk. All sites discussed in this review appear to have demonstrated reductions in the surface sediment concentration of at least some chemicals of concern following thin-layer placement; however, the achievement of human and ecological risk reduction has been inconsistent or is still under evaluation. Effective monitoring as an integral component of EMNR continues to represent a challenge. For cap material stability, monitoring typically focuses on surface sediment chemistry and the persistence of the cap material, whereas monitoring of ecological recovery tends to be limited or difficult and is not always correlated with successful placement of the thin-layer, especially in the short term. Recontamination of the newly placed cap material has been a relatively common occurrence in many of the sites considered herein, and has led to exceedance of remedial targets. However, in no case did recontamination return surface sediment chemical concentrations to pre-placement levels. Where the placement of cap material is stable and there is no evidence of chemical migration through the cap, recontamination signals a need to update conceptual site models to better reflect sediment and contaminant transport processes in areas in which EMNR has been implemented.

PAH Bioavailability in Field Sediments: Comparing Different Methods for Predicting in Situ Bioaccumulation

In situ exposure concentrations of chemicals in sediments and their depending risks are determined by site-specific parameters (e.g., sediment organic carbon composition), controlling bioavailability. Over the years, several analytical methods have been developed to assess bioavailable concentrations or fractions. Some of these methods have been successful in the laboratory, but few attempts have been made to test their potential for predicting actual in situ bioavailability. In this study, solid-phase microextraction (SPME)-fibers and aquatic worms (Lumbriculus variegatus) were exposed in situ at three locations. In addition, laboratory-based methods, i.e., methods with which sampling of the bioavailable fraction/concentration took place in the laboratory, being SPME, polyoxymethylene solid-phase extraction (POM-SPE), hydroxypropyl-beta-yclodextrin-(HPCD), and 6 h-Tenax extraction were applied to sediments collected at the locations. Using equilibrium partitioning-based calculations, biotic PAH levels were calculated from the concentrations or fractions extracted by the used methods. In general, method-predicted concentrations were within a factor of 10 of those measured in field-exposed oligochaetes, with in situ SPME and laboratory-based POM-SPE yielding the best results. As a reference, the currently used generic risk assessment approach overpredicted biotic concentrations by a factor of 10-100, which corresponded to in situ SPME-derived sediment-water distribution coefficients and biota-to-sediment accumulation factors being up to 2 orders of magnitude higher and lower, respectively, than generic values. These observations advocate site-specific risk assessment for PAHs, for which potential tools were evaluated in this study.

Nonnutrient anthropogenic chemicals in seagrass ecosystems: Fate and effects

Impacts of human-related chemicals, either alone or in combination with other stressors, are important to understand to prevent and reverse continuing worldwide seagrass declines. This review summarizes reported concentrations of anthropogenic chemicals in grass bed-associated surface waters, sediments, and plant tissues and phytotoxic concentrations. Fate information in seagrass-rooted sediments and overlying water is most available for trace metals. Toxicity results in aqueous exposures are available for at least 13 species and a variety of trace metals, pesticides, and petrochemicals. In contrast, results for chemical mixtures and chemicals in sediment matrices are uncommon. Contaminant bioaccumulation information is available for at least 23 species. The effects of plant age, tissue type, and time of collection have been commonly reported but not biological significance of the chemical residues. Experimental conditions have varied considerably in seagrass contaminant research and interspecific differences in chemical residues and chemical tolerances are common, which limits generalizations and extrapolations among species and chemicals. The few reported risk assessments have been usually local and limited to a few single chemicals and species representative of the south Australian and Mediterranean floras. Media-specific information describing exposure concentrations, toxic effect levels, and critical body burdens of common near-shore contaminants is needed for most species to support integrated risk assessments at multiple geographical scales and to evaluate the ability of numerical effects-based criteria to protect these marine angiosperms at risk.

Effects of Hurricane Katrina on benthic macroinvertebrate communities along the northern Gulf of Mexico coast

The effects of Hurricane Katrina on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama, USA, were assessed in October, 2005, 2 months after the hurricane made landfall between New Orleans, LA and Biloxi, MS. Benthic macrofaunal samples, sediment chemical concentrations, and water quality measurements from 60 sites in Lake Pontchartrain and Mississippi Sound were compared with pre-hurricane conditions from 2000-2004. Post-hurricane benthic communities had significant reductions in numbers of taxa, H(') diversity, and abundance as well as shifts in composition and ranking of dominant taxa. These effects were not associated with changes in chemical contamination, organic enrichment of sediments, or hypoxia and were likely due to hurricane-related scouring and changes in salinity.

Avian ecological risk potential in an urbanized estuary: Lower Hackensack River, New Jersey, U.S.A.

As part of a comprehensive ecological risk assessment on a broad range of species, the potential for adverse effects in birds was evaluated at a chromate ore processing residue disposal site, Study Area 7, located at the confluence of the Lower Hackensack River, Passaic River, and Upper Newark Bay. Although detection of elevated concentrations of total chromium in sediment prompted the study, it was also necessary to consider potential risks related to other chemicals present in elevated concentrations due to widespread anthropogenic activities in Upper Newark Bay and its watershed. U.S. Army Corps of Engineers' TrophicTrace ® software was used to predict exposure to avian receptors using measured concentrations of chemicals in sediment, measured concentrations of chemicals in benthic invertebrates, and measured site physicochemical parameters. The TrophicTrace ® model was improved as part of the Study Area 7 ecological risk assessment to account for (1) incidental ingestion of sediment by dabbling and diving birds, (2) area use factors for spatial overlap of wide-ranging fish species and piscivorous birds, (3) spatially-explicit utilization of the site by birds with a variety of foraging strategies, and (4) temporal patterns of site utilization by migratory species. The ecological risk assessment demonstrated that chromium in sediment does not pose unacceptable hazards to avian receptors. Potentially unacceptable hazards were indicated for several organic chemicals (i.e., pesticides, polychlorinated biphenyls, and dioxins/furans), with hazard quotients highest for Upper Newark Bay reference conditions, reflecting potential widespread chemical impacts to the estuary. The modifications to TrophicTrace ® conducted for this assessment may be prudent and applicable for improving the accuracy and realism of other assessments involving avian receptors exposed to chemicals via contaminated sediment and transfer through the food web.

Desorption and Bioavailability of Spiked Pentabromo Diphenyl Ether and Tetrachlorodibenzo(p)dioxin in Contaminated Sediments

The relationship between desorption kinetics and bioavailability of sediment-associated 2,2',4,4,5' pentabromo diphenyl ether [(14)C] (BDE-99) and 2,3,7,8 tetrachlorodibenzo(p)dioxin [(3)H] (TCDD) was examined in the contaminated sediments. The desorption kinetics were measured in a sediment-water suspension using Tenax extraction, and bioaccumulation was examined by exposing Lumbriculus variegatus (Oligochaeta) to BDE-99 and TCDD spiked sediment in a 14-day kinetic study. Both chemicals had a high affinity to the finest particle size fraction (<20 microm) and the large, very slowly desorbing fraction (58-75%). The biota-sediment accumulation factors ranged between 1.9 and 4.4 for BDE-99 and between 1.4 and 2.8 for TCDD. The chemical outflux from the rapidly desorbing fraction and influx into organisms shows the connection between desorption and bioavailability. Despite this, normalization to the rapidly desorbing fraction was unable to reduce differences in bioavailability estimates between the chemicals. Thus, it is evident that chemical extraction in the mixed system (Tenax tubes) does not fully describe the bioavailable fraction that worms face in stagnant sediments in a similar way for all chemicals. However, when all desorbing domains were included in the calculation, the difference between the chemicals disappears. Desorbing fractions were also able to reduce variability in the biota-sediment accumulation factors between the tested sediments when organic carbon-based sediment chemical concentrations were modified by the desorbing fractions.

Contaminant chemistry and toxicity of sediments in Sydney Harbour, Australia: spatial extent and chemistry–toxicity relationships

The spatial distribution of chemical contamination and toxicity of surficial sediments in Sydney Harbour, Australia, was investigated in a 3-tiered, hierarchical approach. An initial chemical investigation throughout the entire estuary (Stage 1) indicated wide ranges and different spatial patterns in sediment chemical concentrations. Sediment quality guidelines (SQGs) were used as a preliminary estimate of possible toxicity in Stage 2 of the investigation. Assessment of chemical mixtures indicated that sediments in a small part (~2%) of the harbour had the highest probability of being toxic (~75%), whereas sediment in almost 25% of the port was estimated to have an inter- mediate (~50%) probability of being toxic. The SQG assessment in Stage 2 enabled careful stratifica- tion of the harbour into areas with different toxicity risks, reducing cost and time commitments in the final tier of assessment. The spatial survey carried out in Stage 3 involved concurrent chemical and ecotoxicological analyses. In this final stage, the degree of response in tests of amphipod survival in whole sediment samples, as well as in tests of microbial metabolism (Microtox©) and sea urchin egg fertilisation and embryo development in pore waters, generally increased with increasing chemical concentrations. However, amphipod response was lower than predicted due to relatively low sensi- tivity of the indigenous amphipod Corophium colo. Areas initially predicted, using SQGs, to be most at risk were highly toxic in the combined chemistry-toxicity investigation, while sediment from areas with the lowest predicted risk were least toxic, but still toxic in at least one ecotoxicological test. The results demonstrate that the empirical approach used for this study, which was originally developed in North America, produced plausible outcomes elsewhere and that observed toxicity, based on SQGs, matched predictions using different species but similar methodologies.

Comparison of methods for evaluating acute and chronic toxicity in marine sediments

Sublethal test methods are being used with increasing frequency to measure sediment toxicity, but little is known about the relative sensitivity of these tests compared to the more commonly used acute tests. The present study was conducted to compare the sensitivity of several acute and sublethal methods and to investigate their correlations with sediment chemistry and benthic community condition. Six sublethal methods (amphipod: Leptocheirus plumulosus survival, growth, and reproduction; polychaete: Neanthes arenaceodentata survival and growth; benthic copepod: Amphiascus tenuiremis life cycle; seed clam: Mercenaria mercenaria growth; oyster: Crassostrea virginica lysosome destabilization; and sediment-water interface testing with mussel embryos, Mytilus galloprovincialis) and two acute methods (amphipod survival with Eohaustorius estuarius and L. plumulosus) were used to test split sediment samples from stations in California. The test with Amphiascus proved to be the most sensitive sublethal test and the most sensitive overall, identifying 90% of the stations as toxic. The Leptocheirus 10-d test was the most sensitive of the acute tests, identifying 60% of the stations as toxic. In general, the sublethal tests were not more sensitive to sediments than the acute tests, with the sublethal tests finding an average of 35% of the stations to be toxic while the acute found 44%. Of the sublethal tests, only the Amphiascus endpoints and Neanthes growth significantly (p <or= 0.05) correlated with sediment chemical concentrations. Poor correspondence occurred between the toxicity endpoints and the indicators of benthic community condition. Differences in test characteristics such as mode of exposure, species-specific contaminant sensitivity, changes in contaminant bioavailability, and influence of noncontaminant stressors on the benthos may have been responsible for variation in response among the tests and low correspondence with benthic community condition. The influence of these factors cannot be easily predicted, underscoring the need to use multiple toxicity methods, in combination with other lines of evidence, to provide an accurate and confident assessment of sediment toxicity.

Environmental Consequences of Water Pumped from Greater New Orleans Following Hurricane Katrina: Chemical, Toxicological, and Infaunal Analysis

The U.S. Army Engineer Research and Development Center Environmental Laboratory, Vicksburg, MS, conducted a study to determine the extent to which Hurricane Katrina floodwaters in the New Orleans, Louisiana area may have had impacts on wildlife habitat and other biological resources in surrounding areas. These studies were conducted as part of the Interagency Performance Evaluation Taskforce, an investigation of environmental impacts originating from the failure of the hurricane protection system during Hurricane Katrina. This paper presents data regarding the effects of pumped floodwaters on sediment chemistry, toxicity, and benthic invertebrate assemblages near pumping stations that discharged floodwaters into marshes near Chalmette and Violet, Louisiana. Chemical contamination of sediments was observed and varied among sample locations (e.g., outfall locations, wastewater treatment plant, canals, and wetlands); however, trends in the chemistry data were not always consistent with bioassay results. A comparison of the sediment chemistry data from this study with three other studies reporting concentrations of chemicals in sediments within the city of New Orleans suggested that sediments and associated contaminants present within the levees were not pumped into the marsh in appreciable quantities.

Calculation and Uses of Mean Sediment Quality Guideline Quotients: A Critical Review

Fine-grained sediments contaminated with complex mixtures of organic and inorganic chemical contaminants can be toxic in laboratory tests and/or cause adverse impacts to resident benthic communities. Effects-based, sediment quality guidelines (SQGs) have been developed over the past 20 years to aid in the interpretation of the relationships between chemical contamination and measures of adverse biological effects. Mean sediment quality guideline quotients (mSQGQ) can be calculated by dividing the concentrations of chemicals in sediments by their respective SQGs and calculating the mean of the quotients for the individual chemicals. The resulting index provides a method of accounting for both the presence and the concentrations of multiple chemicals in sediments relative to their effects-based guidelines. Analyses of considerable amounts of data demonstrated that both the incidence and magnitude of toxicity in laboratory tests and the incidence of impairment to benthic communities increases incrementally with increasing mSQGQs. Such concentration/response relationships provide a basis for estimating toxicological risks to sediment-dwelling organisms associated with exposure to contaminated sediments with a known degree of accuracy. This sediment quality assessment tool has been used in numerous surveys and studies since 1994. Nevertheless, mean SQGQs have some important limitations and underlying assumptions that should be understood by sediment quality assessors. This paper provides an overview of the derivation methods and some of the principal advantages, assumptions, and limitations in the use of this sediment assessmenttool. Ideally, mean SQGQs should be included with other measures including results of toxicity tests and benthic community surveys to provide a weight of evidence when assessing the relative quality of contaminated sediments.