Development and operation of a microprocessor based wet deposition monitor

A microprocessor-based system for monitoring wet deposition is described. The system makes real-time measurements of the conductivity and pH of 0.5 mm sequential rain samples. The samples are then stored on an event or sub-event basis for subsequent laboratory analysis. A brief review of some of the problems associated with collection and storage of rainwater for chemical analysis is given in the context of the current instrument. The system was operated for a six month period at a site in southeast England. The event resolution of the device enabled detailed study of acid deposition episodes and associated air mass back trajectories. The sub-event data enabled study of wet deposition scavenging processes and advective concentration changes. Rainfall chemistry and meteorological changes associated with frontal discontinuities were well characterised by the monitor.