Implication of vitality, seasonality and specific leaf area on PAH uptake in moss and lichen transplanted in bags

In this work the moss Hypnum cupressiforme and the lichen Pseudevernia furfuracea were exposed in bags for six weeks alive and oven-devitalized during summer and winter; the content of 24 PAHs was quantified to evaluate the effect of vitality, seasonality and specific leaf area (SLA) on PAH uptake and profiling. Vitality was followed throughout the exposure by measuring PSII maximal photochemical efficiency (Fv/Fm). In summer, a limited PAH signal was detected, with no significant increase, or even loss, of these compounds. During winter, a significant increase of PAHs was measured in both biomonitors, especially in those devitalized, with a lower baseline PAH content compared to alive material. This result suggests that PAH uptake mostly relies on passive mechanisms. Accordingly, Fv/Fm demonstrated that moss and lichen exposed alive spent most of the exposure time in cryptobiosis. In both biomonitors 4-rings PAHs prevailed, followed by 2-3-rings in lichen and 5-6-rings in moss. Lichen performed better than moss, due to the ability to entrap PAHs in the body of thalli, preserving these compounds during the exposure. A formula was developed to express the accumulated PAHs in terms of flux, that resulted higher in lichen than in moss. Oven devitalized lichen exposed in winter provided the highest uptake, indicating that morphology, SLA and seasonality represent key parameters in PAH biomonitoring.