Environmental context. Engineered nanomaterials are increasingly being used and their release to the aquatic environment poses potential risk. We review the research on transformations of engineered nanomaterial in the aquatic environment, and consider the implications of their release. The key factors defining the fate of engineered nanomaterials in aqueous systems are identified.

Environmental context. Increasing production and application of engineered nanoparticles has led to an increased potential for their environmental release, raising ecotoxicological concerns. To appropriately characterise the fate, effects and risks of engineered nanoparticles in environmental systems, methods are essential to characterise nanoparticles in complex biological matrices. This study reports a method that extracts nanoparticles from tissues of organisms, enabling their detection, quantification and characterisation.

Environmental context. Chirally enriched semiconducting single-walled carbon nanotubes (SWNTs) are some of the most utilised nanomaterials. Although chirality of SWNTs is known to influence their electronic properties and interfacial interaction, the interplay between chirality and surfactant structure in SWNT stability is not well understood. This study investigates these interactions, providing data to better assess the environmental fate of SWNTs.

Environmental context. Nanoparticles may be passed from primary producers to predators higher up the food chain, but little is currently known about this transfer. We studied the accumulation dynamics of silver nanoparticles by algae, and then from algae to zooplankton. Using the biodynamic approach, we reconstructed the accumulation process to show that diet is the primary route of uptake for silver nanoparticles.

Environmental context. Nanoparticles are present in growing volumes of consumer products and are suspected to be released into the environment at detectable levels. We focus on cerium dioxide nanoparticles and investigate their availability to fish from the water column, where we found increasing concentrations of natural organic material increased the ceria measured in the fish gills. This complex interaction between nanoparticle behaviour and uptake from environmentally relevant test systems is significantly understudied.

Environmental context. Trace elements are ubiquitous in natural waters where their levels are highly variable depending on natural factors and anthropogenic pollution. The chemical form of the element determines its behaviour in the environment and whether it is likely to pose a risk to environmental and human health. This paper focuses on elemental forms in freshwater systems: it reviews analytical methods, gathers available data, and assesses trends, needs and open issues in this field.

Environmental context. Despite being present at trace concentrations, arsenic and phosphorus are among the most important of freshwater contaminants. This research highlights the biogeochemical coupling of both elements in a New Zealand lake. We find that the mineralisation of organic residues coupled to the dissolution of colloidal iron and manganese hydroxides may be an important driver of the bioavailability of phosphorus and arsenic.

Environmental context. The cycling of iron plays an important role in pelagic boundary zones such as the oxic–anoxic interface where physical and chemical gradients occur. The turnover of iron in this zone depends on oxygen fluctuation and the duration of the fluctuation event. This study increases the understanding of biogeochemical iron transformation in such hotspots.

Environmental context. Humic acids, important components of natural organic matter in soils, sediments and aquatic media, can interact with the surface of minerals affecting key environmental processes. In the presence of calcium, humic acids can also interact among themselves leading to molecular aggregates. We demonstrate that a solid mineral surface facilitates the formation of humic acid aggregates, and thus surface aggregation occurs under conditions where normal aggregation in solution does not occur.

Environmental context. Common soil minerals, which often contain trace metals in contaminated environments, are thought to limit metal-related risks in the environment. We studied the stability of these contaminated minerals and found that the presence of plant-derived organic compounds can alter contaminant availability in such environments. Understanding how soluble organics may change trace metal availability helps to predict risk and potentially remediate such environments more efficiently.