Environmental context. Metal contamination in estuarine sediments can affect ecosystem health. Molluscs are commonly used as environmental indicators because they accumulate contaminants that cause adverse health effects. We investigated metal uptake and effects in the Sydney cockle, comparing exposure to contaminated lake sediments in situ and in laboratory aquariums. Although differences were observed between the different exposure types, all approaches were found to be valid for investigating metal health effects in this organism.

Environmental context. Environmental quality guidelines are often based on an ‘additive’ approach using single metal toxicity values. We evaluated the ‘additive’ approach by testing it on three priority pollutant metals (Ni, Cu, Cd), and found that the toxicity of the metal mixture was less than additive when dose was expressed as total metal concentration, but it was additive when dose was expressed as bioavailable metal. We suggest that for metal mixtures, a more realistic indicator of risk is provided by calculations based on the bioavailable form of metals.

Environmental context. Engineered copper nanoparticles are presently under development for various uses and may thus be finally released into the aquatic environment. Copper is well known to be both an essential and a toxic element for aquatic organisms. Here, we investigate the toxicity of copper nanoparticles to a green alga and compare it with the toxicity of dissolved copper.

Environmental context. The lanthanides are a group of heavy elements (from lanthanum to lutetium) increasingly used in many electronic consumer products and little is known about their environmental mobility and toxicity. In natural systems, these elements will bind to natural organic matter but metal toxicity is usually defined by the free metal ion concentration. Here, we propose a method based on sample equilibration with an ion-exchange resin to measure the free lanthanide ion concentration in the presence of natural organic matter.

Environmental context. Organic matter dissolved in water can mitigate toxic effects of copper, which should be taken into account when estimating risks of copper pollution. The composition of this organic matter, however, can vary widely, and these variations might also need to be taken into account. This work addresses the question of organic matter quality and demonstrates that only the amount and not the source influences copper toxicity – good news for risk analysis because it simplifies predictions of the effects of copper in specific receiving waters.

Environmental context. Surfactants, a pollutant class routinely introduced into aquatic environments, can be toxic to a variety of species. It is thus important to understand how surfactants’ toxicity is influenced by their interactions with other environmental constituents, including natural organic matter. We report the changes in toxicity of three surfactants to brine shrimp in the presence of unmodified and chemically modified humic acids.

Environmental context. Lead and mercury are toxic atmospheric pollutants emitted in large quantities since 1850. Accumulating lake and peat sediments capture the pollutants from the atmosphere and indirectly record changes in deposition through time. This study of four long-term sediment records addresses the questions, ‘What proportion of this atmospheric deposition is natural background?’ and ‘Does the archive faithfully represent true rates of atmospheric deposition?’

Environmental context. Calcium silicate was added to a forest watershed in New Hampshire, USA, to accelerate its recovery from acid rain. The acid–base status of soil and stream quality improved over the 12-year study, with the most pronounced response in the upper elevation and the upper soil of the watershed. A total of 95 % of the added calcium and 87 % of the added silica were retained in the watershed over the study period.