Volume 13 Number 3 2016
Peter Campbell Tribute
Environmental context. The concentration of a free metal cation has proved to be a useful predictor of metal bioaccumulation and toxicity, as represented by the free ion activity and biotic ligand models. However, under certain circumstances, metal complexes have been shown to contribute to metal bioavailability. In the current mini-review, we summarise the studies where the classic models fail and organise them into categories based on the different uptake pathways and kinetic processes. Our goal is to define the limits within which currently used models such as the biotic ligand model (BLM) can be applied with confidence, and to identify how these models might be expanded.
EN15104Developing a sentinel mollusc species for toxicity assessment: metal exposure, dose and response – laboratory v. field exposures and resident organisms
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.
EN15124Evaluating the concentration addition approach for describing expected toxicity of a ternary metal mixture (Ni, Cu, Cd) using metal speciation and response surface regression
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.
EN15132Toxicity of engineered copper (Cu0) nanoparticles to the green alga Chlamydomonas reinhardtii
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 chemical speciation of metals strongly influences their transport, fate and bioavailability in natural waters. Analytical measurement and modelling both play important roles in understanding speciation, while modelling is also needed for prediction. Here, we analyse a large set of data for fresh waters, estuarine and coastal waters, and open ocean water, to examine how well measurements and modelling predictions agree.
EN15136Determination of the free-ion concentration of rare earth elements by an ion-exchange technique: implementation, evaluation and limits
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. Many trace metals including lead are only sparingly soluble in seawater and may exist in both dissolved and particulate forms (e.g. as precipitates). Aquatic organisms may experience different toxic effects from exposure to dissolved and particulate trace metals. This study reports the limits to lead solubility in seawater that influence the exposure to these forms of lead in the field and the laboratory.
EN15123Influence of dissolved organic matter (DOM) source on copper speciation and toxicity to Brachionus plicatilis
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.
EN15108Surfactant toxicity to Artemia franciscana and the influence of humic acid and chemical composition
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?’
EN15113Long-term responses in soil solution and stream-water chemistry at Hubbard Brook after experimental addition of wollastonite
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.