Offshore produced water treatment by a biofilm reactor on the seabed: The effect of temperature and matrix characteristics.

In many industrial processes a large amount of water with high salinity is co-produced whose treatment poses considerable challenges to the available technologies. The produced water (PW) from offshore operations is currently being discharged to sea without treatment for dissolved pollutants due to space limitations. A biofilter on the seabed adjacent to a production platform would negate all size restrictions, thus reducing the environmental impact of oil and gas production offshore. The moving bed biofilm reactor (MBBR) was investigated for PW treatment from different oilfields in the North Sea at 10 °C and 40 °C, corresponding to the sea and PW temperature, respectively. The six PW samples in study were characterized by high salinity and chemical oxygen demand with ecotoxic effects on marine algae S. pseudocostatum (0.4%

Aquatic Ecotoxicity Testing of Nanoparticles-The Quest To Disclose Nanoparticle Effects.

The number of products on the market containing engineered nanoparticles (ENPs) has increased significantly, and concerns have been raised regarding their ecotoxicological effects. Environmental safety assessments as well as relevant and reliable ecotoxicological data are required for the safe and sustainable use of ENPs. Although the number of publications on the ecotoxicological effects and uptake of ENPs is rapidly expanding, the applicability of the reported data for hazard assessment is questionable. A major knowledge gap is whether nanoparticle effects occur when test organisms are exposed to ENPs in aquatic test systems. Filling this gap is not straightforward, because of the broad range of ENPs and the different behavior of ENPs compared to "ordinary" (dissolved) chemicals in the ecotoxicity test systems. The risk of generating false negatives, and false positives, in the currently used tests is high, and in most cases difficult to assess. This Review outlines some of the pitfalls in the aquatic toxicity testing of ENPs which may lead to misinterpretation of test results. Response types are also proposed to reveal potential nanoparticle effects in the aquatic test organisms.

Effect of Exposure Concentration and Growth Conditions on the Association of Cerium Oxide Nanoparticles with Green Algae.

The increasing release of engineered nanoparticles (NPs) into aquatic ecosystems makes it crucial to understand the interactions of NPs with aquatic organisms, such as algae. In this study, the association of CeO2 NPs with unicellular algae (Raphidocelis subcapitata) and changes to the cellular elemental profile were investigated using three exposure concentrations (1, 50, and 1000 µg CeO2/L) at two different algal growth conditions-exponential and inhibited growth (1% glutaraldehyde). After a 24 h-exposure, algal suspensions were settled by gravity and CeO2-NP/algae association was analyzed by single-cell inductively coupled plasma quadrupole mass spectrometry (sc-ICP-QMS) and ICP time-of-flight MS (sc-ICP-TOFMS). Concurrent detection of the cellular fingerprint with cerium indicated NP association with algae (adsorption/uptake) and changes in the cellular elemental profiles. Less than 5% of cells were associated with NPs when exposed to 1 µg/L. For 50 µg/L exposures in growing and inhibited cell treatments, 4% and 16% of cells were associated with CeO2 NPs, respectively. ICP-TOFMS analysis made it possible to exclude cellular exudates associated with CeO2 NPs due to the cellular fingerprint. Growing and inhibited cells had different elemental profile changes following exposure to CeO2 NPs-e.g., growing cells had higher Mg and lower P contents independent of CeO2 concentration compared to inhibited cells.

Separating toxicity and shading in algal growth inhibition tests of nanomaterials and colored substances.

Nanoparticles and colored substances can inhibit algal growth by light shading and chemical toxicity. This study presents two complementary approaches to account for shading in algal growth inhibition tests of engineered nanomaterials (ENMs) and colored substances. The first approach distinguishes between shading effects and toxicity by varying the light path in parallel algal growth inhibition tests. This Multiple Path-Length (MPL) test was applied to TiO2 ENMs and the colored substances sodium picramate and Rhodamine B. A left shifting of concentration-response curves, with increasing light path lengths, indicated shading for Rhodamine B, sodium picramate and TiO2 ENMs. EC50-values obtained at the shortest light path length were generally found best suited to quantify the toxicity of ENMs and colored substances. The second approach addresses shading at the cellular level, where particles can attach to the cell surface and affect photo-pigment content and composition. Pigments associated with photosystem I and II were determined at varying light intensities and concentrations of TiO2 ENMs. The photo-pigments that increased in response to physical shading, decreased after TiO2 ENMs exposure. This indicates that toxicity rather than cellular shading dominated the response of algae exposed to TiO2 ENMs. Additional tests were conducted with the nanomaterials CeO2 and goethite to evaluate the applicability of this approach to other ENMs. On this basis, we recommend MPL testing for determining EC50-values that are not confounded by shading in the test solution, and the pigment-based approach for investigating shading on the cellular level.

A Small-Scale Setup for Algal Toxicity Testing of Nanomaterials and Other Difficult Substances.

Ecotoxicity data is a requirement for pre- and post-market registration of chemicals by European and international regulations (e.g., REACH). The algal toxicity test is frequently used in regulatory risk assessment of chemicals. In order to achieve high reliability and reproducibility the development of standardized guidelines is vital. For algal toxicity testing, the guidelines require stable and uniform conditions of parameters such as pH, temperature, carbon dioxide levels and light intensity. Nanomaterials and other so-called difficult substances can interfere with light causing a large variation in results obtained hampering their regulatory acceptance. To address these challenges, we have developed LEVITATT (LED Vertical Illumination Table for Algal Toxicity Tests). The setup utilizes LED illumination from below allowing for a homogenous light distribution and temperature control while also minimizing intra-sample shading. The setup optimizes the sample volume for biomass quantification and does at the same time ensure a sufficient influx of CO2 to support exponential growth of the algae. Additionally, the material of the test containers can be tailored to minimize adsorption and volatilization. When testing colored substances or particle suspensions, the use of LED lights also allows for increasing the light intensity without additional heat generation. The compact design and minimal equipment requirements increase the possibilities for implementation of the LEVITATT in a wide range of laboratories. While compliant with standardized ISO and OECD guidelines for algal toxicity testing, LEVITATT also showed a lower inter-sample variability for two reference substances (3,5-Dicholorophenol and K2Cr2O7) and three nanomaterials (ZnO, CeO2, and BaSO4) compared to Erlenmeyer flasks and microtiter plates.

Revising REACH guidance on information requirements and chemical safety assessment for engineered nanomaterials for aquatic ecotoxicity endpoints: recommendations from the EnvNano project.

The European Chemical Agency (ECHA) is in the process of revising its guidance documents on how to address the challenges of ecotoxicological testing of nanomaterials. In these revisions, outset is taken in the hypothesis that ecotoxicological test methods, developed for soluble chemicals, can be made applicable to nanomaterials. European Research Council project EnvNano-Environmental Effects and Risk Evaluation of Engineered, which ran from 2011 to 2016, took another outset by assuming that: "The behaviour of nanoparticles in suspension is fundamentally different from that of chemicals in solution". The aim of this paper is to present the findings of the EnvNano project and through these provide the scientific background for specific recommendations on how ECHA guidance could be further improved. Key EnvNano findings such as the need to characterize dispersion and dissolution rates in stock and test media have partially been addressed in the updated guidance. However, it has to be made clear that multiple characterization methods have to be applied to describe state of dispersion and dissolution over time and for various test concentration. More detailed information is called for on the specific characterization methods and techniques available and their pros and cons. Based on findings in EnvNano, we recommend that existing algal tests are supplemented with tests where suspensions of nanomaterials are aged for 1-3 days for nanomaterials that dissolve in testing media. Likewise, for daphnia tests we suggest to supplement with tests where (a) exposure is shortened to a 3 h pulse exposure in daphnia toxicity tests with environmentally hazardous metal and metal oxide nanomaterials prone to dissolution; and (b) food abundance is three to five times higher than normal, respectively. We further suggest that the importance of considering the impact of shading in algal tests is made more detailed in the guidance and that it is specified that determination of uptake, depuration and trophic transfer of nanomaterials for each commercialized functionalization of the nanomaterials is required. Finally, as an outcome of the project a method for assessing the regulatory adequacy of ecotoxicological studies of nanomaterials is proposed.

Not all that glitters is gold-Electron microscopy study on uptake of gold nanoparticles in Daphnia magna and related artifacts.

Increasing use of engineered nanoparticles has led to extensive research into their potential hazards to the environment and human health. Cellular uptake from the gut is sparsely investigated, and microscopy techniques applied for uptake studies can result in misinterpretations. Various microscopy techniques were used to investigate internalization of 10-nm gold nanoparticles in Daphnia magna gut lumen and gut epithelial cells following 24-h exposure and outline potential artifacts (i.e., high-contrast precipitates from sample preparation related to these techniques). Light sheet microscopy confirmed accumulation of gold nanoparticles in the gut lumen. Scanning transmission electron microscopy and elemental analysis revealed gold nanoparticles attached to the microvilli of gut cells. Interestingly, the peritrophic membrane appeared to act as a semipermeable barrier between the lumen and the gut epithelium, permitting only single particles through. Structures resembling nanoparticles were also observed inside gut cells. Elemental analysis could not verify these to be gold, and they were likely artifacts from the preparation, such as osmium and iron. Importantly, gold nanoparticles were found inside holocrine cells with disrupted membranes. Thus, false-positive observations of nanoparticle internalization may result from either preparation artifacts or mistaking disrupted cells for intact cells. These findings emphasize the importance of cell integrity and combining elemental analysis with the localization of internalized nanoparticles using transmission electron microscopy. Environ Toxicol Chem 2017;36:1503-1509. © 2016 SETAC.

Behavior and chronic toxicity of two differently stabilized silver nanoparticles to Daphnia magna.

While differences in silver nanoparticle (AgNP) colloidal stability, surface potential, or acute aquatic toxicity for differently stabilized AgNP have often been reported, these have rarely been studied in long-term ecotoxicity tests. In the current study, we investigated the chronic toxicity of AgNP to Daphnia magna over a 21-day period with two different stabilizers (citrate and detergent), representative for charge and sterical stabilizers, respectively. This was coupled with a series of short-term experiments, such as mass balance and uptake/depuration testing, to investigate the behavior of both types of AgNP during a typical media exchange period in the D. magna test for chronic toxicity. As expected, the sterically stabilized AgNP was more stable in the test medium, also in the presence of food; however, a higher uptake of silver after 24h exposure of the charge stabilized AgNP was found compared to the detergent-stabilized AgNP (0.046±0.006µgAgµgDW(-1) and 0.023±0.005µgAgµgDW(-1), respectively). In accordance with this, the higher reproductive effects and mortality were found for the charge-stabilized than for the sterically-stabilized silver nanoparticles in 21-d tests for chronic toxicity. LOEC was 19.2µgAgL(-1) for both endpoints for citrate-coated AgNP and >27.5µgAgL(-1) (highest tested concentration for detergent-stabilized AgNP). This indicates a link between uptake and toxicity. The inclusion of additional short-term experiments on uptake and depuration is recommended when longer-term chronic experiments with nanoparticles are conducted.

Chronic toxicity of silver nanoparticles to Daphnia magna under different feeding conditions.

Despite substantial information on the acute toxicity of silver nanoparticles (AgNP) to aquatic organisms, little is known about their potential chronic effects and the applicability of current test guidelines for testing nanomaterials. The purpose of this study was to study the influence of food availability on toxicity. This was done through a series of Daphnia magna 21-day reproduction tests (OECD 211) using 30 nm citric acid stabilized AgNP aimed at studying the influence of food abundance on the reproductive toxicity of AgNP in D. magna. The experiments were carried out as static renewal tests with exposure concentrations from 10 to 50 µg Ag/L, and test animals were fed green algae Pseudokirchneriella subcapitata in low and high food treatments. The endpoints recorded were survival, growth of parent animals and number of live neonates produced. Detrimental effects of AgNP on survival, growth and reproduction were observed in concentrations higher than 10 µg Ag/L, whereas the animals exposed to 10 µg Ag/L had larger body length and produced more offspring than controls at both food treatments. High food treatment resulted in higher animal survival, growth and reproduction compared to result found for low food treatment.