Environmental context. The free Zn ion concentration in environmental aqueous systems is an important factor in determining Zn deficiency or toxicity to organisms as this species is directly bioavailable. The permeation liquid membrane technique, a tool to measure either free or bioavailable metal concentrations in solution depending on its setup, was evaluated for the first time for Zn speciation in simplified plant nutrient solutions. The technique is low-cost and applicable to a broad range of aqueous samples.

Environmental context. Marine dissolved organic matter plays a key role in the global carbon cycle. Questions remain, however, as to the influence of anthropogenic activities on its composition and distribution in coastal waters. It was found that dissolved organic matter in the vicinity of a municipal sewage effluent (Marseilles City, France) contained a high proportion of protein-like material, thereby demonstrating the influence of human activities on coastal dissolved organic matter.

Environmental context. When surface water is disinfected to produce potable drinking water, toxic by-products are generated by reaction with naturally occurring organic matter. The production of trihalomethane disinfection by-products was investigated for different types of well-characterised organic matter from various geographic locations. Increased understanding of the character of organic matter dissolved in water is needed for improving the ability to provide safe water and protect public health.

Environmental context. The size of soil colloids is – among other characteristics – crucial for the mobility of associated contaminants. We analysed the effect of liming on the size of colloids mobilised from strongly contaminated shooting-range soils using multi-stage tangential ultrafiltration (MTUF) for the size fractionation of dispersed soil colloids. Our results indicate the high analytical potential of MTUF and show that liming induces the aggregation of colloids, thereby decreasing the mobilisation of colloid-bound Sb and As, but increasing colloidal Pb.

Environmental context. Exchange processes at the water–sediment interface can release metals to riverine waters, having negative effects on organisms in the water column. We investigate the geochemical processes and metal exchange between the surface sediment and the overlying water under metal contamination conditions. Results suggest that the sediment can be a significant source of metal pollution in aquatic systems, particularly during anoxic events.