Environmental context. The need to describe the Earth’s system or any of its components with a quantity that has units of time is ubiquitous. These quantities are used as metrics of the system to describe the response to a perturbation, the cumulative effect of an action or just the budget in terms of sources and sinks. Given a complex, non-linear system, there are many different ways to derive such quantities, and careful definitions are needed to avoid mistaken approximations while providing useful parameters describing the system.

Environmental context. Metal–carbonato complexes have been reported to contribute to metal uptake and toxicity in aquatic organisms. We show that in the presence of lead–carbonato complexes, Pb internalisation by the microalga Chlamydomonas reinhardtii is higher than that predicted on the basis of the free Pb²⁺ concentration. This effect, which was not observed for another microalga that takes up Pb more slowly, is attributed to the very high rates of Pb uptake by C. reinhardtii, which result in diffusion limitation.

Environmental context. Phytoplankton form the base of marine food-webs, and hence they have been proposed as the likely source of many arsenic compounds found in marine animals. Because of the difficulties associated with field experiments with phytoplankton, attempts to test this hypothesis have relied mainly on laboratory experiments. This study assesses the environmental validity of this research approach by investigating the influence of the culturing experimental protocol on the uptake, accumulation and biotransformation of arsenic by marine phytoplankton.

Environmental context. Mercury is a very hazardous substance for human and environmental health. Systematic long-term direct measurements in the atmosphere can provide valuable information about the effect of emission controls on the global budget of atmospheric mercury, and offer insight into source–receptor transboundary transport of mercury. A complete setup for the measurement of the four most relevant atmospheric mercury species (total gaseous mercury, gaseous oxidised mercury, particle-bound mercury, and gaseous elemental mercury) has been operating at the rural background site of Waldhof, Germany, since 2009. We present the dataset for 2009–2011, the first full-speciation time series for atmospheric mercury reported in Central Europe.

Environmental context. 4-tert-Butylphenol, an environmental endocrine disruptor, can be taken in by humans and animals resulting in reproductive and developmental problems. We report a theoretical study on the degradation mechanism of 4-tert-butylphenol in the atmosphere, and calculate the atmospheric lifetime of this chemical. The data will help our understanding of the behaviour of 4-tert-butylphenol in the environment and thereby provide valuable information about its possible effect on human health.

Environmental context. Organic hydrophobic compounds are present in water in low concentrations, and they can be analysed by means of a preconcentration technique called solid phase microextraction. We investigate the role and role of sorbing nanoparticles on the solid phase microextraction analysis of organic compounds. Our results show that nanoparticles are capable of partitioning between water and the solid phase and aggregate at the interface leading, most probably, to substantial overestimation of the original sample concentration.

Environmental context. The increasing use of sun-creams containing UV-filtering chemicals has led to increased inputs of these compounds to the aquatic environment. Chlorinated waters can convert these chemicals into chlorinated products whose toxic effects are of primary concern. To better understand the environmental fate of sun-cream chemicals, we studied the stability of two UV-filtering compounds under varying conditions of pH, chlorine concentration, temperature, dissolved organic matter and solar irradiation.

Environmental context. Benzotriazoles are chemicals widely used to inhibit corrosion in various industrial processes and in household products. They persist in aquatic environments, even under UV irradiation, and thus there is a need to improve their photolytic degradation to minimise the environmental exposure risks. We investigated the effects of four iron–carboxylate complexes on the UV photodegradation of three benzotriazoles in aqueous solutions and show that they significantly increase the degradation rates of benzotriazoles.