Environmental context. Metal toxicity to marirne organisms is largely controlled by organic ligands (L) although the source, structure and stimuli of most ligands remain unknown. We studied trends in Cd and Zn complexing ligands in a near-pristine Irish estuary to gain clues on the identity of L in natural waters. The evidence suggests the naturally occurring Cd ligands include fulvic acids whereas the Zn ligands are likely to be exuded from seaweeds. Further research is required to determine their exact identity.

Environmental context. Identifying the source and stimuli responsible for organic ligands in seawater is crucial to understanding trace metal availability. Voltammetric techniques were employed to characterise the water chemistry of seaweed cultures exposed to low levels of Cu or Zn over 7 days. The results suggest that seaweeds are a potential source of metal complexing ligands and Cu and Zn appear to stimulate ligand production; further research is required to determine if this is applicable to macroalgae and metals outside this study.

Environmental context. The low concentration of iron in the oceans limits growth of phytoplankton. Dissolved organic molecules, called ligands, naturally present in seawater, bind iron thereby increasing its solubility and, consequently, its availability for biological uptake by phytoplankton. The characteristics of these ligands are determined indirectly with various mathematical solutions; we critically evaluate the underlying method and calculations used in these determinations.

Environmental context. Metal contamination of seawater can present severe environmental problems owing to the high toxicity of metals and their persistence in the environment. This study explores the possibility of analysing lead in seawater media using two recently developed electrochemical methods. The methods are shown to be very useful tools to monitor the behaviour and fate of lead and other metals in seawater.

Environmental context. Electroanalytical methods have found wide application in trace metal speciation analysis in environmental systems. The need to find functional alternatives to mercury electrodes for in situ speciation studies has encouraged the use of bismuth as a solid-state electrode substrate. We demonstrate the utility of bismuth electrodes for quantitative dynamic speciation analysis.

Environmental context. We determined seasonal changes in the organic matter content of the northern Adriatic with newly applied electrochemical techniques able to measure catalytically active organics. The inflow of the Po River and its nutrient load are responsible for the observed changes in the type and concentrations of organic matter in the area.

Environmental context. The electrochemical detection of many sulfur compounds in natural waters is based on the deposition of a HgS layer at the Hg electrode. In samples containing metal ions in excess of sulfide species, electrochemical exchange reactions between the HgS and the metal ion produce metal-sulfide voltammetric peaks. These peaks can easily be misinterpreted as dissolved sulfide species, and hence do not reflect the bulk state of the solution.

Environmental context. Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic and mutagenic compounds found in the atmosphere, soil, sediments and water. They can bioaccumulate in marine organisms where they pose a threat to the health of the organisms. We are developing a low-cost and simple electrochemical method to monitor the concentrations of these compounds in the aquatic environment.

Environmental context. The dramatic change in physical and chemical characteristics that substances experience at reduced length scales (1–100 nm), together with a potential risk of ecotoxicity, are two of the reasons for the scientific interest in nanoparticles. The current understanding of the behaviour and fate of nanoparticles in natural waters is limited because of a lack of efficient methods for their characterisation. Electrochemistry is a promising tool for the determination and characterisation of nanoparticles in the natural environment.

Environmental context. In anoxic environments FeS is both an important mediator in the Fe and S biogeochemical cycles and plays a vital role in controlling the scavenging and availability of many trace metals. Electrochemical detection of colloidal and particulate FeS in natural waters can be done by voltammetric measurements. The recorded anodic waves, however, are rather qualitative and lack information on the FeS concentration and size distribution.

Environmental context. Sorbing nanoparticles can have a significant effect on the speciation of small ions and molecules in the environment. The reactivity of nanoparticulate-bound species can differ significantly from that of their molecular or colloidal counterparts. We present a conceptual framework that describes the chemodynamics and lability of nanoparticulate metal complexes over a wide range of experimental timescales and environmental conditions.