Natural and pre-treatments induced variability in the chemical composition and morphology of lichens and mosses selected for active monitoring of airborne elements

To enhance the reliability of the moss and lichen transplant technique for active biomonitoring of trace metals in urban environments, we evaluated the natural variability in the chemical composition of the (epilithic and epiphytic) moss Hypnum cupressiforme and the epiphytic lichen Pseudevernia furfuracea from two reference areas in NE Italy. Green shoots of epilithic mosses and lobes of epiphytic lichens from larch branches showed rather homogenous composition and were selected for the exposure in nylon bags. As different physico-chemical pre-treatments are usually applied to selected cryptogamic material before its exposure, we also evaluated the effects of oven-drying at 120 °C for 24 h, washing in 1 N HNO3 solution, and in 0.5% NH4 oxalate solution at 85 °C for 15 h on the chemical composition and morphology of water-washed moss shoots and lichen lobes. Pre-treatments remarkably changed the chemical composition of selected materials but not their surface morphology.