The use of sediment toxicity identification evaluation methods to evaluate clean up targets in an urban estuary

A review of peeper passive sampling approaches to measure the availability of inorganics in sediment porewater

Sediment porewater dialysis passive samplers, also known as "peepers," are inert containers with a small volume of water (usually 1-100 mL) capped with a semi-permeable membrane. When exposed to sediment over a period of days to weeks, chemicals (typically inorganics) in sediment porewater diffuse through the membrane into the water. Subsequent analysis of chemicals in the peeper water sample can provide a value that represents the concentrations of freely-dissolved chemicals in sediment, a useful measurement for understanding fate and risk. Despite more than 45 years of peeper uses in peer-reviewed research, there are no standardized methods available, which limits the application of peepers for more routine regulatory-driven decision making at sediment sites. In hopes of taking a step towards standardizing peeper methods for measuring inorganics in sediment porewater, over 85 research documents on peepers were reviewed to identify example applications, key methodological aspects, and potential uncertainties. The review found that peepers could be improved by optimizing volume and membrane geometry to decrease the necessary deployment time, decrease detection limits, and provide sufficient sample volumes needed for commercial analytical laboratories using standardized analytical methods. Several methodological uncertainties related to the potential impact of oxygen presence in peeper water prior to deployment and oxygen accumulation in peepers after retrieval from sediment were noted, especially for redox-sensitive metals. Additional areas that need further development include establishing the impact of deionized water in peeper cells when used in marine sediment and use of pre-equilibration sampling methods with reverse tracers allowing shorter deployment periods. Overall, it is expected that highlighting these technical aspects and research needs will encourage work to address critical methodological challenges, aiding in the standardization of peeper methods for measuring porewater concentrations at contaminated regulatory-driven sediment sites.

Review of DDT, DDE, DDD, DDMU and DDMS Toxicity Data for Organisms Used in Estuarine and Marine Sediment Toxicity Tests

The open literature was searched for laboratory toxicity data for marine/estuarine organisms exposed to dichlorodiphenyltrichloroethane (DDT) and its degradation products of dichlorodiphenyldichloroethylene (DDE), dichlorodiphenyldichloroethane (DDD), dichlorodiphenylchloroethylene (DDMU), and dichlorodiphenylchloroethane (DDMS). The goal of the review was to determine water-column toxicity values that could be used for porewater-based assessment of sediment toxicity. Data for individual compounds (and isomers thereof) in this group were very limited; most available data were for mixtures of multiple compounds, some defined and others undefined. Further, the majority of relevant studies involved exposure to spiked or field-contaminated sediment (rather than waterborne exposure), which requires inferring concentration in porewater from bulk sediment. Comparing data on the basis of effect concentrations for water or inferred concentration in sediment pore water, the lower reported effect concentrations were in the range of 0.05 to 0.1 µg/L, generally in studies of longer duration and/or evaluating sub-lethal effects. Because field exposures are generally to mixtures of these compounds in varied proportions, additional data on chemical-specific toxicity would aid in pore-water based toxicity assessment for marine/estuarine sediments contaminated with DDT-related chemicals.

Spiking organic chemicals onto sediments for ecotoxicological analyses: an overview of methods and procedures

Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects of known concentrations of toxicants, interactions of the toxicants with sediment and biota, and uptake kinetics. Since spiking of the sediment may be performed by using different strategies, a plethora of procedures was proposed in the literature for spiking organic chemicals onto sediments to perform ecotoxicological analyses. In this paper, we reviewed the scientific literature intending to characterise the kind of substrates that were used for spiking (i.e. artificial or field-collected sediment), how the substrates were handled before spiking and amended with the organic chemical, how the spiked sediment was mixed to allow the homogenisation of the chemical on the substrate and finally how long the spiked sediment was allowed to equilibrate before testing. What emerged from this review is that the choice of the test species, the testing procedures and the physicochemical properties of the organic contaminant are the primary driving factors affecting the selection of substrate type, sediment handling procedures, solvent carrier and mixing method. Finally, we provide recommendations concerning storage and characterization of the substrate, equilibrium times and verification of both equilibration and homogeneity.

Microscale Toxicity Identification Evaluation (TIE) for interstitial water of estuarine sediments affected by multiple sources of pollution

Estuaries in the world are affected by different contamination sources related to urbanisation and port/industrial activities. Identifying the substances responsible for the environmental toxicity in estuaries is challenging due to the multitude of stressors, both natural and anthropogenic. The Toxicity Identification and Evaluation (TIE) is a suitable way of determining causes of toxicity of sediments, but it poses difficulties since its application is labour intensive and time consuming. The aim of this study is to evaluate the diagnosis provided by a TIE based on microscale embryotoxicity tests with interstitial water (IW) to identify toxicants in estuarine sediments affected by multiple stressors. TIE showed toxicity due to different combinations of metals, apolar organic compounds, ammonia and sulphides, depending on the contamination source closest to the sampling station. The microscale TIE was able to discern different toxicants on sites subject to different contamination sources. There is good agreement between the results indicated in the TIE and the chemical analyses in whole sediment, although there are some disagreements, either due to the sensitivity of the test used, or due to the particularities of the use of interstitial water to assess the sediment toxicity. The improvement of TIE methods focused on identifying toxicants in multiple-stressed estuarine areas are crucial to discern contamination sources and subsidise management strategies.

Multivariate Analysis of Sediment Toxicity in an Ocean Ecosystem: A Southern California Bight Case Study

Contaminated sediments can negatively affect aquatic organisms and beneficial uses of coastal regions. Monitoring programs typically collect many indicators of sediment toxicity, yet multivariate approaches that comprehensively evaluate data across heterogeneous spatial environments are frequently not performed. In this paper, we explore a multivariate approach to show that a list of suspected drivers of sediment toxicity to native Mytilus galloprovincialis (mussel) and Eohaustorius estuarius (a marine amphipod) population can be narrowed down without excluding samples, and that redundancies in sampling sites can be identified and isolated. Using a 153 × 28 data matrix assembled from a southern California-wide bight monitoring program, we demonstrate by this approach that Port of Los Angeles (PLA) and San Diego Bay (SDB) contained the most toxic sediments in the bight in 2008, the nature of which was unique to each locality. (Note: Little toxicity was observed here in 2013 and 2018.) In PLA sediments, mussels were more affected than amphipods, with higher survivability associated with low Hg and Sn levels. Conversely, amphipods had higher mortality than mussel embryos in SDB sediments, with higher survivability associated with low Be and Co levels. Nitrogen, organic content, and finer sediment particles were not related to the survivability of these organisms.

Seasonal Toxicity Observed with Amphipods (Eohaustorius estuarius) at Paleta Creek, San Diego Bay, USA

To assess potential impacts on receiving systems, associated with storm water contaminants, laboratory 10-d amphipod (Eohaustorius estuarius) survival toxicity tests were performed using intact sediment cores collected from Paleta Creek (San Diego Bay, CA, USA) on 5 occasions between 2015 and 2017. The approach included deposition-associated sediment particles collected from sediment traps placed at each of 4 locations during the 2015 to 2016 wet seasons. The bioassays demonstrated wet season toxicity, especially closest to the creek mouth, and greater mortality associated with particles deposited in the wet season compared with dry season samples. Grain size analysis of sediment trap material indicated coarser sediment at the mouth of the creek and finer sediment in the outer depositional areas. Contaminant concentrations of metals (Cd, Cu, Hg, Ni, Pb, and Zn) and organic compounds (polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], and pesticides) were quantified to assess possible causes of toxicity. Contaminant concentrations were determined in the top 5 cm of sediment and porewater (using passive samplers). Whereas metals, PAHs, and PCBs were rarely detected at sufficient concentrations to elicit a response, pyrethroid pesticides were highly correlated with amphipod toxicity. Summing individual pyrethroid constituents using a toxic unit approach suggested that toxicity to E. estuarius could be associated with pyrethroids. This unique test design allowed delineation of spatial and temporal differences in toxicity, suggesting that storm water discharge from Paleta Creek may be the source of seasonal toxicity. Environ Toxicol Chem 2019;39:229-239. © 2019 SETAC.

Understanding the bioavailability of pyrethroids in the aquatic environment using chemical approaches

Pyrethroids are a class of commonly used insecticides and are ubiquitous in the aquatic environment in various regions. Aquatic toxicity of pyrethroids was often overestimated when using conventional bulk chemical concentrations because of their strong hydrophobicity. Over the last two decades, bioavailability has been recognized and applied to refine the assessment of ecotoxicological effects of pyrethroids. This review focuses on recent advances in the bioavailability of pyrethroids, specifically in the aquatic environment. We summarize the development of passive sampling and Tenax extraction methods for assessing the bioavailability of pyrethroids. Factors affecting the bioavailability of pyrethroids, including physicochemical properties of pyrethroids, and quality and quantity of organic matter, were overviewed. Various applications of bioavailability on the assessment of bioaccumulation and acute toxicity of pyrethroids were also discussed. The final section of this review highlights future directions of research, including development of standardized protocols for measurement of bioavailability, establishment of bioavailability-based toxicity benchmarks and water/sediment quality criteria, and incorporation of bioavailability into future risk assessment and management actions.

Using spatial and temporal variability data to optimize sediment toxicity identification evaluation (TIE) study designs

Toxicity tests are an important aspect of sediment quality assessments, but knowledge of the cause of toxicity is needed to determine effective management actions. Toxicity identification evaluation (TIE) methods were developed to meet this need. While TIE method manuals provide information on the procedures, little information on study design is presented. The level of variability associated with performing TIEs and how to account for it is also not addressed. The goal of this study was to collect data on both the spatial and temporal variability associated with sediment TIEs by use of the amphipod Eohaustorius estuarius 10-day survival test and then apply that information to make recommendations for designing future TIE studies. Ten stations were sampled at Consolidated Slip in Los Angeles Harbor, California, with samples collected 2 months apart. In the first stage, TIEs were conducted on whole sediment and pore water from 3 of the most toxic stations. In the second stage, focused TIEs were conducted on whole sediment from all stations. Chemical analysis for metals and organic contaminants was also performed. With a weight of evidence approach, it was determined that pyrethroid pesticides were the likely cause of toxicity, with a lesser contribution from polycyclic aromatic hydrocarbons (PAHs). Results of the individual TIEs fell into 3 broad categories: TIEs in which treatments for organic chemicals and pyrethroids were effective; TIEs in which the treatment for pyrethroids was not effective but the treatment for organic contaminants was effective; and TIEs in which the treatment for pyrethroids was effective but the treatment for organic contaminants was not. This variability was used to calculate that at least 3 TIEs were necessary to make a confident assessment of the cause of toxicity. There was not substantial temporal variability in the TIE outcomes. Other recommendations are made regarding effective TIE study design. Integr Environ Assess Manag 2019;15:248-258. © 2018 SETAC.

Risk assessment of pesticides in estuaries: a review addressing the persistence of an old problem in complex environments

Estuaries, coastal lagoons and other transition ecosystems tend to become the ultimate reservoirs of pollutants transported by continental runoff, among which pesticides constitute the class of most concern. High amounts of dissolved and particulated organic matter greatly contribute to the accumulation of pesticides that eventually become trapped in sediments or find their way along food chains. Perhaps not so surprisingly, it is common to find elevated levels of pesticides in estuarine sediments decades after their embargo. Still, it remains challenging to address ecotoxicity in circumstances that invariably imply mixtures of contaminants and multiple factors affecting bioavailability. Despite advances in methods for detecting pesticides in waters, sediments and organisms, chemical data alone are insufficient to predict risk. Many researchers have been opting for ex situ bioassays that mimic the concentrations of pesticides in estuarine waters and sediments using a range of ecologically relevant model organisms, with emphasis on fish, molluscs and crustaceans. These experimental procedures unravelled novel risk factors and important insights on toxicological mechanisms, albeit with some prejudice of ecological relevance. On the other hand, in situ bioassays, translocation experiments and passive biomonitoring strive to spot causality through an intricate mesh of confounding factors and cocktails of pollutants. Seemingly, the most informative works are integrative approaches that combine different assessment strategies, multiple endpoints and advanced computational and geographical models to determine risk. State-of-art System Biology approaches combining high-content screening approaches involving "omics" and bioinformatics, can assist discovering and predicting novel Adverse Outcome Pathways that better reflect the cumulative risk of persisting and emerging pesticides among the wide range of stressors that affect estuaries.

Enantiomer-specific measurements of current-use pesticides in aquatic systems

Some current-use pesticides are chiral and have nonsuperimposable mirror images called enantiomers that exhibit identical physical-chemical properties but can behave differently when in contact with other chiral molecules (e.g., regarding degradation and uptake). These differences can result in variations in enantiomer presence in the environment and potentially change the toxicity of pesticide residues. Several current-use chiral pesticides are applied in urban and agricultural areas, with increased potential to enter watersheds and adversely affect aquatic organisms. The present study describes a stereoselective analytical method for the current-use pesticides fipronil, cis-bifenthrin, cis-permethrin, cypermethrin, and cyfluthrin. We show use of the method by characterizing enantiomer fractions in environmental sample extracts (sediment and water), and laboratory-dosed fish and concrete extracts previously collected by California organizations. Enantiomer fractions for most environmental samples are the same as racemic standards (equal amounts of enantiomers, enantiomer fraction = 0.5) and therefore are not expected to differ in toxicity from racemic mixtures typically tested. In laboratory-derived samples, enantiomer fractions are more frequently nonracemic and favor the less toxic enantiomer; permethrin enantiomer fractions range from 0.094 to 0.391 in one type of concrete runoff and enantiomer fractions of bifenthrin in dosed fish range from 0.378 to 0.499. We use enantiomer fractions as a screening tool to understand environmental exposure and explore ways this uncommon measurement could be used to better understand toxicity and risk. Environ Toxicol Chem 2018;37:99-106. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

A New Film-Based Passive Sampler for Moderately Hydrophobic Organic Compounds

Passive samplers for moderately hydrophobic organic compounds (MHOCs) (i.e., log K_ow ranging from 2 to 5) are under-developed compared to those that target polar or strongly hydrophobic compounds. The goal of this study was to identify a suitable polymer and develop a robust and sensitive film-based passive sampler for MHOCs in aquatic systems. Poly(methyl methacrylate) (PMMA) exhibited the highest affinity for fipronil and its three metabolites (i.e., fipronils) (log K_ow 2.4-4.8) as model MHOCs compared with polyethylene and nylon films. In addition, a 30-60 min treatment of PMMA in ethyl ether was found to increase its sorption capacity by a factor of 10. Fipronils and 108 additional compounds (log K_ow 2.4-8.5) reached equilibrium on solvent-treated PMMA within 120 h under mixing conditions and their uptake closely followed first-order kinetics. PMMA-water partition coefficients and K_ow revealed an inverse parabolic relationship, with vertex at log K_ow of 4.21 ± 0.19, suggesting that PMMA was ideal for MHOCs. The PMMA sampler was tested in an urban surface stream, and in spiked sediment. The results demonstrated that PMMA film, after a simple solvent swelling treatment, may be used as an effective passive sampler for determining C_free of MHOCs in aquatic environments.

Application of sediment toxicity identification evaluation techniques to a site with multiple contaminants

Sediment toxicity identification evaluations (TIEs) are conducted to determine causes of adverse effects observed in whole-sediment toxicity tests. However, in multiple contaminant scenarios, it is problematic to partition contributions of individual contaminants to overall toxicity. Using data from a site with multiple inputs and contaminants of concern, the authors describe a quantitative approach for the TIE process by tracking toxicity units to determine whether all toxicity is accounted for. The initial step established the level of toxicity associated with the whole sediment and then partitioned sources of toxicity into general contaminant classes (e.g., ammonia, metals, nonpolar organic compounds). In this case, toxicity was largely the result of nonpolar organics, so the sediments were extracted and the extracts added back into dilution water and tested to confirm recovery of toxicity. Individual fractions were then generated using a solvent gradient and tested for toxicity. Fractions of interest were evaluated with gas chromatography/mass spectrometry to identify specific constituents associated with toxicity. Toxicity units associated with these constituents were then evaluated to determine probable associations with cause and whether all toxicity was accounted for. The data indicated that toxicity was associated with 2 contaminant classes, representing legacy compounds and contaminants of emerging concern, with the contribution of each varying across the site. Environ Toxicol Chem 2016;35:2456-2465. © 2016 SETAC.