Biological effects of ammonia released from a composting plant assessed with lichens.

During composting of organic wastes, a certain amount of nitrogen can be locally released as NH4+/NH3 to the environment. In this study we investigated whether ammonia emissions from industrial composting may influence the surrounding environment, using lichens as bioindicators. To the purpose, samples of N-tolerant and N-sensitive lichens, namely Xanthoria parietina and Evernia prunastri, were transplanted for 1 – 3 months along transects at increasing distance (0 – 400 m) from a compost facility in Tuscany (central Italy). We investigated the physiological response of the transplants by means of the chlorophyll a fluorescence emission in the photobiont, the damage endured by cell membranes (measured as electrolyte leakage) and the overall viability of the mycobiont assessed by the enzymatic activity of dehydrogenase. We measured ammonia emissions with passive samplers around the facility and assessed the condition of lichen communities, actually dominated by meso-acidophilous lichens, using diversity indices. N-tolerant and N-sensitive lichens reacted differently: the N-tolerant X. parietina was not affected by the proximity to the facility and some physiological parameters even showed a higher performance; on the other hand the mesophilous N-sensitive E. prunastri showed a higher performance with increasing distance from the source. Such data would suggest in the near future a likely shift from oligotrophic to nitrophilous lichen communities in the surroundings of the facility.