SUMMARY
Rainwater sequential sampler instruments can be very useful in characterizing the variability in rainwater composition, which can occur over relatively short time periods. The main aim of this study was to develop a low-cost volume-based sequential rain sampler for the assessment of variations in the chemical composition of rainwater during individual rain events in one place. In order to evaluate the performance of the apparatus a few tests were conducted under field conditions in Coimbra (Portugal). Rainy periods were analysed in relation to the following physicochemical parameters: electrical conductivity, pH, turbidity, nitrates, sulphates and chloride. The results showed that the rainwater composition varied over time; moreover, some parameters were found to be highest at the beginning of the rainy period, followed by a rapid decline of the initial value and then remained approximately constant. The findings suggest that the rainwater sequential sampler is a low-cost solution tool that can be useful for non-continuous assessment of intra-event rainwater composition variability.