Environmental context. The increased use of nanomaterials in industrial and consumer products requires robust strategies to identify risks when they are released into the environment. Aquatic toxicologists are beginning to possess a clearer understanding of the chemical and physical properties of nanomaterials in solution, and which of the properties potentially affect the health of aquatic organisms. This review highlights the main challenges encountered in aquatic nanotoxicity testing, provides recommendations for overcoming these challenges, and discusses recent studies that have advanced our understanding of the toxicity of three important OECD nanomaterials, titanium dioxide, zinc oxide and silver nanomaterials.

Environmental context. The ability of the soil nematode Caenorhabditis elegans to withstand a wide range of environmental conditions makes it an idea model for studying the bioavailability and effects of engineered nanomaterials. We critically review what has been learned about the environmental fate of engineered nanoparticles, their effects and their mechanisms of toxicity using this model organism. Future systematic manipulation of nanoparticle properties and environmental variables should elucidate how their interaction influences toxicity and increase the predictive power of nanomaterial toxicity studies.

Environmental context. Predicting the environmental implications of nanotechnology is complex in part because of the difficulty in studying nanoparticle uptake in organisms at environmentally realistic exposures. Typically, high exposure concentrations are needed to detect accumulation and effects. We use labelled Ag nanoparticles to determine whether Ag bioaccumulation responses are linear over concentrations likely to occur in the environment, and whether concentration-dependent changes in agglomeration and dissolution affect bioavailability.

Environmental context. The increasing use of engineered nanoparticles has led to concerns over potential exposure to these novel materials. Predictions of nanoparticle transport in the environment and exposure risks could be simplified if all nanoparticles showed similar deposition behaviour when coated with macromolecules used in production or encountered in the environment. We show, however, that each nanoparticle in this study exhibited distinct deposition behaviour even when coated, and hence risk assessments may need to be specifically tailored to each type of nanoparticle.

Environmental context. This study investigates the toxicity of cerium oxide nanoparticles to earthworms, key organisms in soil ecosystems. Cerium oxide did not affect survival or reproduction of the earthworms but did exert histological changes. We conclude that current soil guidelines, based simply on metal toxicity, appear to adequately protect against cerium exposure risk, at least for earthworms.

Environmental context. Sorption and oxidation reactions at mineral surfaces can substantially influence the mobility and toxicity of environmental contaminants. An understanding of the factors that control these reactions is crucial for predicting the fate of contaminant species. We investigate the reactivity of manganese oxides towards polycyclic aromatic hydrocarbons, persistent organic compounds of environmental concern.

Environmental context. Arsenoribosides are the major arsenic species in marine macro-algae, yet inorganic arsenic is the major arsenic species found in seawater. We investigated the degradation of arsenoribosides associated with Ecklonia radiata by the use of microcosms containing both natural and autoclaved seawater and sand. The decomposition and persistence of arsenic species was linked to the use of autoclaved seawater and sand, which suggests that arsenoriboside degradation is governed by the microbial composition of microenvironments within marine systems.

Environmental context. Mining operations release dissolved metals in waste streams which can present an environmental hazard as well as an economic loss. Large volumes of waste water and low levels of metals mean that highly effective materials such as nanoparticles or nanostructures need to be employed to remove the dissolved metals from the stream. The challenge in using nanotechnology lies in the recovery of the particles, as filtration proves ineffective; this article discusses use of magnetic composites as a potential solution to this challenge.

Environmental context. Dimethylsulfide, a trace gas produced by oceanic plankton, is a key chemical species in the global cycles of sulfur and aerosols, with implications that span marine ecology to climate regulation. Knowledge of what governs dimethylsulfide production in the surface ocean depends on our ability to measure concentration changes over time and depth. We describe a sampling and analytical system that provides continuous shipboard measurements of dimethylsulfide concentrations in high-resolution vertical profiles.

Environmental context. The toxicity of metals in the environment is greatly influenced by natural organic matter owing to its ability to bind metals to form complexes that can be immobile and non-bioavailable. Sound mathematical models are important to reliably predict the behaviour of such contaminants, and how they are affected by organic matter and other environmental colloids. Here a new model is discussed and compared with precedent ones.

Environmental context. Photolysis is one of the most important transformation pathways in natural ecosystem for enrofloxacin (Enro), which is a hazard for humans and other living organisms. The effects of NO₃^– and humic acid on Enro photolysis were found to be light-source dependent. These results are of significance toward the goal of providing insight into the transformation and fate of Enro in the environment.

Environmental context. Recently developed fast fluorescence detectors have opened the way to the development of element speciation mapping, i.e. X-ray absorption near edge spectroscopy (XANES) imaging, of environmental samples. This technique is potentially very informative but is also highly data intensive. Here, we used XANES imaging to explore the distribution of Cu species in biosolid materials, destined for agricultural use, as this is of importance in relation to the bioavailability and potential toxicity of this metal.