A New Technique for the Passive Monitoring of Particulate Matter: Olive Pollen Grains as Bioindicators of Air Quality in Urban and Industrial Areas

A new technique for the passive monitoring of particulate matter was developed, exploiting olive pollen as a bioindicator. We tested the pollen bioaccumulation efficiency when exposed to atmospheric particulate at three different sites in the Umbria region (Central Italy). Pollen grains, placed into sampling holders, were exposed in Perugia, a polluted town impacted by traffic emissions; in Terni, an industrial hotspot; and at Monte Martano, a regional rural site. At the end of the exposure period, the daily deposition fluxes of the soluble and insoluble elements and soluble molecular ions present in particulate were determined, and the bioaccumulation factor (BAF) and bioaccumulation index over time (BAIt) were derived to validate the passive monitoring system, distinguish the deposition contribute from natural pollen composition, and interpret the temporal dependence of the pollen exposure to pollutants. We observed BAFs greater than 1, which means that bioaccumulation occurs, and pollen can be considered a good passive sampler for several crustal and anthropic ions and toxic elements at all sites. BAIt values greater than 1 were detected only for some of the ions and metals previously present in the pollen, like Ca, Cr, and Mn at Terni; and nitrate, Ca, and Mn at Monte Martano and Perugia.