Insight into the composition of volcanic aerosols is gained from filter-based observations at Maïdo (see section 2.2.1.5). While the high-volume samplers were not operating during the first complete GEM depletion (shortly after 6 AM), which fell into the transition period between nighttime and daytime sampling, all plumes associated with GEM depletion events after 7:00 were captured in a PM0.95 daytime filter. The corresponding filter was sampling from 25 th April 07:00 to 29 th April 18:00. As no important volcanic influence was detected at Maïdo before the 29 th April (Figure ), it can be assumed that significant enhancements of mean concentrations in this sampling period (compared to the time before) can be attributed near-exclusively to volcanic plumes on the 29 th April.