Natural organic matter exerts a powerful control on chemical conditions in waters and soils, affecting pH and influencing the biological availability, transport and retention of metals. To quantify the reactions, we collated a wealth of laboratory data covering 40 metals and acid–base reactions, and used them to parameterise the latest in a series of Humic Ion-Binding Models. Model VII is now available to interpret field data, and contribute to the prediction of environmental chemistry.

Explosive volcanic eruptions may have significant environmental repercussions for many Earth system cycles, particularly the water cycle. We investigate the potential contribution to local geochemical fluxes through water of five historical eruptions that occurred over a 20-year period in the Southern Andes. In all five cases, the major potentially toxic trace elements were arsenic, copper, fluoride, molybdenum, nickel, lead and zinc.

Mineral dust aerosol is both an efficient scatterer of solar radiation, potentially cooling the planet, and a moderate absorber, potentially warming it: the exact balance is both uncertain, and geographically variable. Australian desert soils are noticeably more reddish than most Northern Hemisphere deserts, most probably a result of enhanced iron mineralogy. This paper contains results from a field campaign designed to increase our understanding of the chemistry of Australian mineral dust aerosol, especially in relation to iron and salt.

Persistent organic pollutants (POPs) are potentially toxic chemicals capable of long distance transport and are often found far from their source. Little is known of their behaviour in Antarctica, where the marine plankton food web is driven by strong seasonal variations in solar radiation. Here the first dynamic coupled ecosystem–fugacity model to describe how POPs distribute through the Antarctic environment is presented. The model is used to identify the important processes that govern the presence of hexachlorobenzene in Antarctic plankton.

Environmental metabolomics is an emerging field that examines the metabolic changes in organisms in response to potential environmental stressors. In this study, nuclear magnetic resonance spectroscopy is used to investigate earthworm metabolic responses to sub-lethal exposure of environmentally persistent pesticides. The study identifies two toxic modes of action elicited by the pesticides, and highlights the potential of metabolomics for the chemical assessment of persistent environmental contaminants.

Methods for determining iron species are integral to investigations of iron cycling processes in the environment. Capillary electrophoresis is an effective tool for determining the concentrations of various iron species in solution, but the separations are highly dependent on the electrolyte composition. This study reports the use of capillary electrophoresis to separate and quantify distinct Fe^II and Fe^III complexes with polyaminocarboxylates.

Speciation of trace metals in the oceans is typically explained by invoking the concept of metal binding to specific organic ligands. Here, using a speciation model widely used for freshwaters, we assess the extent to which non-specific humic-type ligands found in the ocean may explain chemical speciation of cationic metals. We found that the model can give good fits in some cases, and that experimental results do not give consistent variation from the model. This has implications for the way that the availability of trace elements is considered in ocean environments.

Cadmium(II) is considered as one of the most dangerous pollutants in natural waters. We performed a complete study on the interactions of cadmium(II) with inorganic components of natural waters, by using new experiments and some literature data. The body of results can be considered an improvement in modelling the inorganic speciation of cadmium(II) in natural waters.