Fate and risks of nanomaterials in aquatic and terrestrial environments.

Over the last decade, nanoparticles have been used more frequently in industrial applications and in consumer and medical products, and these applications of nanoparticles will likely continue to increase. Concerns about the environmental fate and effects of these materials have stimulated studies to predict environmental concentrations in air, water, and soils and to determine threshold concentrations for their ecotoxicological effects on aquatic or terrestrial biota. Nanoparticles can be added to soils directly in fertilizers orplant protection products or indirectly through application to land or wastewater treatment products such as sludges or biosolids. Nanoparticles may enter aquatic systems directly through industrial discharges or from disposal of wastewater treatment effluents or indirectly through surface runoff from soils. Researchers have used laboratory experiments to begin to understand the effects of nanoparticles on waters and soils, and this Account reviews that research and the translation of those results to natural conditions. In the environment, nanoparticles can undergo a number of potential transformations that depend on the properties both of the nanoparticle and of the receiving medium. These transformations largely involve chemical and physical processes, but they can involve biodegradation of surface coatings used to stabilize many nanomaterial formulations. The toxicity of nanomaterials to algae involves adsorption to cell surfaces and disruption to membrane transport. Higher organisms can directly ingest nanoparticles, and within the food web, both aquatic and terrestrial organisms can accumulate nanoparticles. The dissolution of nanoparticles may release potentially toxic components into the environment. Aggregation with other nanoparticles (homoaggregation) or with natural mineral and organic colloids (heteroaggregation) will dramatically change their fate and potential toxicity in the environment. Soluble natural organic matter may interact with nanoparticles to change surface charge and mobility and affect the interactions of those nanoparticles with biota. Ultimately, aquatic nanomaterials accumulate in bottom sediments, facilitated in natural systems by heteroaggregation. Homoaggregates of nanoparticles sediment more slowly. Nanomaterials from urban, medical, and industrial sources may undergo significant transformations during wastewater treatment processes. For example, sulfidation of silver nanoparticles in wastewater treatment systems converts most of the nanoparticles to silver sulfides (Ag2S). Aggregation of the nanomaterials with other mineral and organic components of the wastewater often results in most of the nanomaterial being associated with other solids rather than remaining as dispersed nanosized suspensions. Risk assessments for nanomaterial releases to the environment are still in their infancy, and reliable measurements of nanomaterials at environmental concentrations remain challenging. Predicted environmental concentrations based on current usage are low but are expected to increase as use increases. At this early stage, comparisons of estimated exposure data with known toxicity data indicate that the predicted environmental concentrations are orders of magnitude below those known to have environmental effects on biota. As more toxicity data are generated under environmentally-relevant conditions, risk assessments for nanomaterials will improve to produce accurate assessments that assure environmental safety.

Ecotoxicological assessment of sanitary sewer overflows and rainfall dynamics offers insights into conditions for potential adverse ecological outcomes.

Sewer overflows are an environmental concern due to their potential to introduce contaminants that can adversely affect downstream aquatic ecosystems. As these overflows can occur during rainfall events, the influence of rainwater ingress from inflow and infiltration on raw untreated wastewater (influent) within the sewer is a critical factor influencing the dilution and toxicity of the contaminants. The Vineyard sewer carrier in the greater city of Sydney, Australia, was selected for an ecotoxicological investigation of a sanitary (separate from stormwater) sewerage system and a wet-weather overflow (WWO). Three influent samples were collected representing dry-weather (DW), intermediate wet-weather (IWW) and wet-weather (WW). In addition, a receiving water sample was also collected downstream in Vineyard Creek (WW-DS) coinciding with a WWO. We employed direct toxicity assessment (DTA) and toxicity identification evaluation (TIE) approaches to gain comprehensive insights into the nature and magnitude of the impact on influent from rainwater ingress into the sewer. Three standard ecotoxicological model species, a microalga, Chlorella vulgaris, the water flea, Ceriodaphnia dubia and the midge larva, Chironomus tepperi were used for both acute and chronic tests. The study revealed variable toxicity responses, with the sample of influent collected in wet-weather displaying lower toxicity compared to the dry-weather sample of influent. Ammonia, and metals, were identified in dry weather as contributors to the observed toxicity, however, this risk was alleviated through rainwater ingress in wet-weather with further dilution within the receiving water. Based on toxicity data, dilutions of influent to minimise effects on C. vulgaris and C. dubia ranged from 1 in 12 in DW to 1 in 2.8 in WW, and further diminished in the receiving water to 1 in 1.8. The successful application of ecotoxicological approaches enabled the assessment of cumulative effects of contaminants in influent, offering valuable insights into the sanitary sewer system under rainwater ingress.

A Guideline Value for Dioxin-Like Compounds in Marine Sediments.

Sediments to be dredged as part of the installation of a harbor crossing in Sydney, Australia, contained measurable concentrations of dioxin-like compounds. To assess the suitability of these sediments for ocean disposal, a defensible sediment quality guideline value (SQGV) for dioxin-like compounds, expressed as pg toxic equivalent (TEQ)fish /g dry weight, was required. There were deemed to be too many uncertainties associated with a value derived using effects data from field studies. A similar issue was associated with values based on equilibrium partitioning from sediment to pore water, largely associated with the wide range of reported sediment:water partition coefficients. Greater certainty was associated with the use of a tissue residue approach based on equilibrium partitioning between sediment and organisms determined using tissue concentrations in fish, the most sensitive aquatic biota, and biota:sediment accumulation factors. The calculation of an appropriate SQGV used data for dioxin-like compounds in both fish and sediments from Sydney Harbor. A conservative SQGV for dioxin-like compounds of 70 pg TEQ/g dry weight was deemed to be adequately protective of biota that might be exposed to these contaminants in sediments at the ocean spoil ground. The approach is transferable to similar situations internationally. Environ Toxicol Chem 2023;42:257-271. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Tracking contaminants of concern in wet-weather sanitary sewer overflows.

Four representative sites in the greater city of Sydney, Australia, were selected for a study of the wet-weather overflow of sanitary (separate to stormwater) sewerage systems. Water samples were collected by autosamplers from up to eight wet weather overflow events over 16 months and from companion receiving water sites. The objective was to identify the risks posed by sewage contaminants to aquatic biota in the receiving waters, to aid in prioritising management actions. Twelve organic contaminants were identified in influents across the four sites under rainfall ingress diluted conditions, with measurements showing that the highest concentrations were restricted to the anti-inflammatory acetaminophen and the diabetes medication metformin. Lesser contaminants included theobromine, ibuprofen, sucralose, and three benzotriazoles (mainly 1-H benzotriazole). An assessment of the toxicity of the identified organic chemicals indicated that none appeared to pose concerns for ecosystem health before wet-weather ingress dilution, and this was even less likely after dilution in the receiving waters. Metal concentrations were low; however, ammonia concentrations in the influent did pose a risk to ecosystem health, although receiving water dilution diminished this risk at four of the five receiving water locations studied.

Improving the Measurement of Iron(III) Bioavailability in Freshwater Samples: Methods and Performance.

The toxicity of iron(III) in fresh waters has been detected at concentrations above the iron solubility limit, indicating a contribution of colloidal and particulate forms of iron(III) to the toxicity response. Current water quality guideline values for iron in fresh water are based on analytical determinations of filterable or total iron. Filtration, however, can underestimate bioavailable iron by retaining some of the colloidal fraction, and total determinations overestimate bioavailable iron measurements by recovering fractions of low bioavailability from suspended solids (e.g., iron oxides and oxyhydroxides) naturally abundant in many surface waters. Consequently, there is a need for an analytical method that permits the determination of a bioavailable iron fraction, while avoiding false-negative and false-positive results. Ideally, a measurement technique is required that can be readily applied by commercial laboratories and field sampling personnel, and integrated into established regulatory schemes. The present study investigated the performance of pH 2 and pH 4 extractions to estimate a bioavailable iron(III) fraction in synthetic water samples containing iron phases of different reactivities. The effects of aging on fresh precipitates were also studied. The total recoverable, 0.45-µm filtered, and pH 4 extractable fractions did not discriminate iron phases and age groups satisfactorily. Contrastingly, the pH 2 extraction showed specificity toward iron phases and aging (0.5-2-h interval). Extraction times above 4 h and up to 16 h equally recovered >90% of the spiked iron regardless of its age. Furthermore, <1% of the well-mineralized iron was targeted. The present study shows that a pH 2 dilute-acid extraction is a suitable candidate method to operationally define iron fractions of higher bioavailability avoiding false-negative and false-positive results. Environ Toxicol Chem 2023;42:303-316. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Applicability of Chronic Multiple Linear Regression Models for Predicting Zinc Toxicity in Australian and New Zealand Freshwaters.

Bioavailability models, for example, multiple linear regressions (MLRs) of water quality parameters, are increasingly being used to develop bioavailability-based water quality criteria for metals. However, models developed for the Northern Hemisphere cannot be adopted for Australia and New Zealand without first validating them against local species and local water chemistry characteristics. We investigated the applicability of zinc chronic bioavailability models to predict toxicity in a range of uncontaminated natural waters in Australia and New Zealand. Water chemistry data were compiled to guide a selection of waters with different zinc toxicity-modifying factors. Predicted toxicities using several bioavailability models were compared with observed chronic toxicities for the green alga Raphidocelis subcapitata and the native cladocerans Ceriodaphnia cf. dubia and Daphnia thomsoni. The most sensitive species to zinc in five New Zealand freshwaters was R. subcapitata (72-h growth rate), with toxicity ameliorated by high dissolved organic carbon (DOC) or low pH, and hardness having a minimal influence. Zinc toxicity to D. thomsoni (reproduction) was ameliorated by both high DOC and hardness in these same waters. No single trophic level-specific effect concentration, 10% (EC10) MLR was the best predictor of chronic toxicity to the cladocerans, and MLRs based on EC10 values both over- and under-predicted zinc toxicity. The EC50 MLRs better predicted toxicities to both the Australian and New Zealand cladocerans to within a factor of 2 of the observed toxicities in most waters. These findings suggest that existing MLRs may be useful for normalizing local ecotoxicity data to derive water quality criteria for Australia and New Zealand. The final choice of models will depend on their predictive ability, level of protection, and ease of use. Environ Toxicol Chem 2023;42:2614-2629. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A generic environmental risk assessment framework for deep-sea tailings placement.

Deep-sea tailings placement (DSTP) involves the oceanic discharge of tailings at depth (usually >100 m), with the intent of ultimate deposition of tailings solids on the deep-sea bed (>1000 m), well below the euphotic zone. DSTP discharges consist of a slurry of mine tailings solids (finely crushed rock) and residual process liquor containing low concentrations of metals, metalloids, flotation agents and flocculants. This slurry can potentially affect both pelagic and benthic biota inhabiting coastal waters, the continental slope and the deep-sea bed. Building on a conceptual model of DSTP exposure pathways and receptors, we developed a stressor-driven environmental risk assessment (ERA) framework using causal pathways/causal networks for each of eight pelagic and benthic impact zones. For the risk characterisation, each link in each causal pathway in each zone was scored using four levels of likelihood (not possible, possible, likely and certain) and two levels of consequence (not material, material) to give final risk rankings of low, potential, high or very high risk. Of the 246 individual causal pathways scored, 11 and 18 pathways were considered to be of very high risk and high risk respectively. These were confined to the benthic zones in the mixing zone (continental slope) and the primary and secondary deposition zones. The new risk framework was then tested using a case study of the Batu Hijau copper mine in Indonesia, the largest DSTP operation globally. The major risk of DSTP is smothering of benthic biota, even outside the predicted deposition zones. Timescales for recovery are slow and may lead to different communities than those that existed prior to tailings deposition. We make several recommendations for monitoring programs for existing, proposed and legacy DSTP operations and illustrate how georeferenced causal networks are valuable tools for ERA in DSTP.

Short-Term Guideline Values for Chlorine in Freshwaters.

The current Australian and New Zealand default guideline value of 3 µg Cl/L for total residual chlorine in freshwaters is largely based on acute data converted to chronic data using a default acute to chronic ratio of 10, without consideration of chlorine decomposition. Given the rapid decomposition of chlorine, initially as hypochlorite and then as chloramine, it is appropriate to consider a guideline value based on short-term (acute) toxicity rather than one based on longer-term chronic data, as has been recommended for chlorine in marine waters. The literature on the fate of chlorine in drinking water discharged to freshwaters and on the ecotoxicity of total residual chlorine has been reviewed, and on the basis of this, revised default guideline values were derived for both hypochlorite and chloramine in freshwater using a species sensitivity distribution of toxicity data. The values for 95% species protection were 7 and 9 µg Cl/L as total residual chlorine, respectively. The former would apply to any total residual chlorine-containing effluent, but in the case of drinking water where dechlorination has been undertaken, the chloramine-based default guideline value is likely to be more appropriate. Both are likely to be conservative because they were largely based on toxicity testing under continuous flow-through conditions. They will apply at the edge of the mixing zone, and the variable receiving water concentration at this point might best be determined from a time-weighted average total residual chlorine concentration. Environ Toxicol Chem 2021;40:1341-1352. © 2021 SETAC.

Short-Term Guideline Values for Chlorine in Marine Waters.

Chlorination is commonly used to control biofouling organisms, but chlorine rapidly hydrolyzes in seawater to hypochlorite, which undergoes further reaction with bromide, and then with organic matter. These reaction products, collectively termed chlorine-produced oxidants (CPOs), can be toxic to marine biota. Because the lifetime of the most toxic forms is limited to several days, appropriate guideline values need to be based on short-term (acute) toxicity tests, rather than chronic tests. Flow-through toxicity tests that provide continuous CPO exposure are the most appropriate, whereas static-renewal tests generate variable exposure and effects depending on the renewal rate. There are literature data for acute CPO toxicity from flow-through tests, together with values from 2 sensitive 15-min static tests on 30 species from 9 taxonomic groups. These values were used in a species sensitivity distribution (SSD) to derive guideline values that were protective of 99, 95, and 90% of species at 2.2, 7.2, and 13 µg CPO/L respectively. These are the first marine guideline values for chlorine to be derived using SSDs, with all other international guideline values based on the use of assessment factors applied to data for the most sensitive species. In applying these conservative guideline values in field situations, it would need to be demonstrated that concentrations of CPOs would be reduced to below the guideline value within an acceptable mixing zone through both dilution and dissociation. Environ Toxicol Chem 2020;39:754-764. © 2020 SETAC.

Deriving a Chronic Guideline Value for Nickel in Tropical and Temperate Marine Waters.

The absence of chronic toxicity data for tropical marine waters has limited our ability to derive appropriate water quality guideline values for metals in tropical regions. To aid environmental management, temperate data are usually extrapolated to other climatic (e.g., tropical) regions. However, differences in climate, water chemistry, and endemic biota between temperate and tropical systems make such extrapolations uncertain. Chronic nickel (Ni) toxicity data were compiled for temperate (24 species) and tropical (16 species) marine biota and their sensitivities to Ni compared. Concentrations to cause a 10% effect for temperate biota ranged from 2.9 to 20 300 µg Ni/L, with sea urchin larval development being the most sensitive endpoint. Values for tropical data ranged from 5.5 to 3700 µg Ni/L, with copepod early-life stage development being the most sensitive test. There was little difference in temperate and tropical marine sensitivities to Ni, with 5% hazardous concentrations (95% confidence interval) of 4.4 (1.8-17), 9.6 (1.7-26), and 5.8 (2.8-15) µg Ni/L for temperate, tropical, and combined temperate and tropical species, respectively. To ensure greater taxonomic coverage and based on guidance provided in Australia and New Zealand, it is recommended that the combined data set be used as the basis to generate a jurisdiction-specific water quality guideline of 6 µg Ni/L for 95% species protection applicable to both temperate and tropical marine environments. Environ Toxicol Chem 2020;39:2540-2551. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Remediation criteria for gasworks-impacted sediments: Assessing the effects of legacy hydrocarbons and more recent metal contamination.

Historical contamination of sediments from industries that commenced before environmental regulations were commonplace is prevalent in many large cities. This contamination is frequently overlain and mixed with more recent urban contamination. The remediation of contaminated sites is often a very expensive exercise and the final remediation criteria often reflect a trade-off between protecting human and ecological health and the finances of those deemed responsible for the site clean-up. In this study, we describe an assessment of estuarine sediments impacted historically by contamination from a gasworks site. The major historical sediment contaminants included polycyclic aromatic hydrocarbons (PAHs) and other petroleum-related hydrocarbons (TRHs). Elevated concentrations of metals exist throughout the city region due to historical pollution and ongoing urban stormwater discharges. Equilibrium partitioning models were used to consider the influence on the bioavailability of PAHs of both natural sedimentary organic carbon and forms of black carbon (pyrogenic carbon - coal tars, charcoal). The strongest predictor of the observed sublethal toxicity to amphipod and copepod reproduction was a combination of total PAHs and metals (primarily Cu, Pb and Zn). Total PAHs was the strongest predicting variable for toxicity to organism survival. While high total PAH concentrations were attributed to the former gas works, high background concentrations of metals existed throughout much of this region of the estuary. Thus, without remediation at the estuary-scale, resuspension of the surrounding sediments by tidal currents and boat movements is predicted to re-contaminate remediated areas with sediments that may continue to cause chronic toxicity due to metals. The assessment indicated that remedial actions that remove or isolate sediments that caused toxicity to benthic organism survival would lead to significant improvements in ecosystem health, but toxicity to organism reproduction may remain at similar levels that exist throughout much of this region of the estuary due to high metal concentrations.

Nanomaterials in the environment: behavior, fate, bioavailability, and effects.

The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

Ecotoxicology of manufactured graphene oxide nanomaterials and derivation of preliminary guideline values for freshwater environments.

The unique physical and chemical properties of graphene-based nanomaterials (GNMs) have inspired a diverse range of scientific and industrial applications. The market value of GNMs is predicted to reach $US 1.3 billion by 2023. Common to many nanomaterials, an important and unresolved question is the environmental consequences of the increases in GNMs use. The current deficiencies in studies reporting ecotoxicology data for GNMs include differences in analytical methodologies for quantification, no standardized test guidelines, differences in morphology of GNMs, the lack of Chemical Abstract Service numbers, and the quality of the reported data. The assessment of potential adverse effects on aquatic organisms typically relies on guideline values based on species sensitivity distributions (SSDs) of toxicity data. We present preliminary water quality guideline values for graphene oxide NMs in freshwaters. Data include 10 species from 7 phyla (bacteria and fungi were not included). The most sensitive organism was found to be the freshwater shrimp Palaemon pandaliformis. The derived guideline values for 99, 95, 90, and 80% species protection were 350, 600, 830, and 1300 µg/L, respectively. These results will contribute to the regulatory derivations of future water quality guideline values for graphene-based NMs. Environ Toxicol Chem 2018;37:1340-1348. © 2018 SETAC.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects-An updated review.

The present review covers developments in studies of nanomaterials (NMs) in the environment since our much cited review in 2008. We discuss novel insights into fate and behavior, metrology, transformations, bioavailability, toxicity mechanisms, and environmental impacts, with a focus on terrestrial and aquatic systems. Overall, the findings were that: 1) despite substantial developments, critical gaps remain, in large part due to the lack of analytical, modeling, and field capabilities, and also due to the breadth and complexity of the area; 2) a key knowledge gap is the lack of data on environmental concentrations and dosimetry generally; 3) substantial evidence shows that there are nanospecific effects (different from the effects of both ions and larger particles) on the environment in terms of fate, bioavailability, and toxicity, but this is not consistent for all NMs, species, and relevant processes; 4) a paradigm is emerging that NMs are less toxic than equivalent dissolved materials but more toxic than the corresponding bulk materials; and 5) translation of incompletely understood science into regulation and policy continues to be challenging. There is a developing consensus that NMs may pose a relatively low environmental risk, but because of uncertainty and lack of data in many areas, definitive conclusions cannot be drawn. In addition, this emerging consensus will likely change rapidly with qualitative changes in the technology and increased future discharges. Environ Toxicol Chem 2018;37:2029-2063. © 2018 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Trophic transfer of metals in a seagrass food web: Bioaccumulation of essential and non-essential metals.

Metal concentrations are reported for a seagrass ecosystem receiving industrial inputs. δ13C and δ15N isotope ratios were used to establish trophic links. Copper concentrations (dry mass) ranged from <0.01 µg/g in fish species to 570 µg/g (µâ€¯= 49 ±â€¯SD = 90 µg/g) in the oyster Saccostrea glomerata. Zinc concentrations ranged from 0.6 µg/g in the seagrass Zostera capricorni to 10,800 µg/g in the mud oyster Ostrea angasi (µâ€¯= 434 ±â€¯1390 µg/g). Cadmium concentrations ranged from <0.01 µg/g in fish species to 268 µg/g in Ostrea angasi (µâ€¯= 6 ±â€¯25 µg/g). Lead concentrations ranged from <0.01 µg/g for most fish species to 20 µg/g in polychaetes (µâ€¯= 2 ±â€¯3 µg/g). Biomagnification of metals did not occur. Organisms that fed on particulate organic matter and benthic microalgae had higher metal concentrations than those that fed on detritus. Species physiology also played an important role in the bioaccumulation of metals.

Derivation of water quality guidelines for priority pharmaceuticals.

Pharmaceuticals can enter freshwater and affect aquatic ecosystem health. Although toxicity tests have been carried out for the commonly used pharmaceuticals, evidence-based water quality guidelines have not been derived. High-reliability water quality guideline values have been derived for 4 pharmaceuticals-carbamazepine, diclofenac, fluoxetine, and propranolol-in freshwaters using a Burr type III distribution applied to species sensitivity distributions of chronic toxicity data. Data were quality-assured and had to meet acceptability criteria for "chronic" no-observed-effect concentrations or concentrations affecting 10% of species, endpoints of population relevance (namely, effect endpoints based on development, growth, reproduction, and survival). Biomarker response data (e.g., biochemical, histological, or molecular responses) were excluded from the derivation because they are typically not directly relevant to wildlife population-related impacts. The derived guideline values for 95% species protection were 9.2 µg/L, 770 µg/L, 1.6 µg/L, and 14 µg/L for carbamazepine, diclofenac, fluoxetine, and propranolol, respectively. These values are significantly higher than the unknown reliability values derived for the European Commission, Switzerland, or Germany that are based on the application of assessment factors to the most sensitive experimental endpoint (which may include biochemical, histological, or molecular biomarker responses) of a limited data set. The guideline values derived in the present study were not exceeded in recent data for Australian rivers and streams receiving pharmaceutical-containing effluents from wastewater-treatment plants. Environ Toxicol Chem 2016;35:1815-1824. © 2015 SETAC.

Derivation of a water quality guideline for aluminium in marine waters.

Metal risk assessment of industrialized harbors and coastal marine waters requires the application of robust water quality guidelines to determine the likelihood of biological impacts. Currently there is no such guideline available for aluminium in marine waters. A water quality guideline of 24 µg total Al/L has been developed for aluminium in marine waters based on chronic 10% inhibition or effect concentrations (IC10 or EC10) and no-observed-effect concentrations (NOECs) from 11 species (2 literature values and 9 species tested including temperate and tropical species) representing 6 taxonomic groups. The 3 most sensitive species tested were a diatom Ceratoneis closterium (formerly Nitzschia closterium; IC10 = 18 µg Al/L, 72-h growth rate inhibition) < mussel Mytilus edulis plannulatus (EC10 = 250 µg Al/L, 72-h embryo development) < oyster Saccostrea echinata (EC10 = 410 µg Al/L, 48-h embryo development). Toxicity to these species was the result of the dissolved aluminium forms of aluminate (Al(OH4 (-) ) and aluminium hydroxide (Al(OH)3 (0) ) although both dissolved, and particulate aluminium contributed to toxicity in the diatom Minutocellus polymorphus and green alga Dunaliella tertiolecta. In contrast, aluminium toxicity to the green flagellate alga Tetraselmis sp. was the result of particulate aluminium only. Four species, a brown macroalga (Hormosira banksii), sea urchin embryo (Heliocidaris tuberculata), and 2 juvenile fish species (Lates calcarifer and Acanthochromis polyacanthus), were not adversely affected at the highest test concentration used.

Modeling food web structure and selenium biomagnification in Lake Macquarie, New South Wales, Australia, using stable carbon and nitrogen isotopes.

As a consequence of coal-fired power station operations, elevated selenium concentrations have been reported in the sediments and biota of Lake Macquarie (New South Wales, Australia). In the present study, an ecosystem-scale model has been applied to determine how selenium in a seagrass food web is processed from sediments and water through diet to predators, using stable isotopes (δ(13) C and δ(15) N) to establish the trophic position of organisms. Trophic position, habitat, and feeding zone were examined as possible factors influencing selenium bioaccumulation. Selenium concentrations ranged from 0.2 µg/g dry weight in macroalgae species to 12.9 µg/g in the carnivorous fish Gerres subfasciatus. A mean magnification factor of 1.39 per trophic level showed that selenium is biomagnifying in the seagrass food web. Habitat and feeding zone influenced selenium concentrations in invertebrates, whereas feeding zone was the only significant factor influencing selenium concentrations in fish. The sediment-water partitioning coefficient (Kd ) of 4180 showed that partitioning of selenium entering the lake to particulate organic material (POM) is occurring, and consequently availability to food webs from POM is high. Trophic transfer factors (invertebrate = 1.9; fish = 1.2) were similar to those reported for other water bodies, showing that input source is not the main determinant of the magnitude of selenium bioaccumulation in a food web, but rather the initial partitioning of selenium into bioavailable POM. Environ Toxicol Chem 2015;34:608-617. © 2014 SETAC.

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.

Effect of declining toxicant concentrations on algal bioassay endpoints.

Sorption, degradation, volatilization, and uptake by test organisms cause concentrations of many toxicants to decline during toxicity testing. Despite the recognition of this occurring, nominal, measured initial or time-averaged concentrations are commonly used for the calculation of inhibitory or effect concentrations from toxicity test data. Because a premise of constant exposure is assumed but not met in these calculations, the toxicity of the test water may be significantly underestimated. Laboratory experiments using a 72-h algal growth inhibition bioassay and copper as a toxicant are used to demonstrate that calculated inhibitory concentrations will often be underestimated twofold if losses of copper occurring over the 72-h test duration are not considered. A simple model is presented for toxicant concentration decline and for the relationship between algal growth rate and toxicant concentration. This model is used to demonstrate the magnitude that calculated inhibitory concentrations may be underestimated if concentration declines are not considered for a series of different concentration decline scenarios. For a toxicant whose concentration declines exponentially to less than 5% of its original value within 36 h of a 72-h test, the inhibitory concentration is shown to be underestimated by a factor of 50.