Biomonitoring spatial and temporal impact of atmospheric dust from a cement industry.

The objective of this work was to evaluate the spatial and temporal impact of dust-pollution in the vicinity of a cement industry, located in an area with dry climate. The spatial impact integrated over time was evaluated from the concentrations of Ca, Fe and Mg in in-situ Xanthoria parietina. The temporal pattern was assessed through one-month transplants of the lichen Ramalina canariensis. Four potential sources of atmospheric dust were evaluated: the limestone-quarry; the unpaved roads, the deposit area and the cement mill. Calcium concentration in lichens was considered the best cement-dust indicator. Different types of dust (clinker and grinded-limestone-dust) resulted in different time-patterns of Ca accumulation, which was also related with the different influence that wet and dry periods have in the lichen accumulation process. The dust pollution was found to be deposited locally and dependent on: the nature of dust particles and the volume and frequency of precipitation.

Nitrogen uptake in relation to excess supply and its effects on the lichens Evernia prunastri (L.) Ach and Xanthoria parietina (L.) Th. Fr.

The aim of this study was to compare the physiological responses to increased nitrogen (N) supply between the nitrophytic lichen Xanthoria parietina (L.) Th. Fr. and the acidophytic lichen Evernia prunastri (L.) Ach. The two lichens were exposed to a weekly dosage of 0.05, 0.1, 0.2, 0.6 or 2.4 g N m(-2) for 2 months, administered as NH(4)NO(3) dissolved in artificial rainwater (1 l m(-2)). After the treatments, in vivo chlorophyll a fluorescence was determined to assess vitality; concentrations of total N, ammonium, nitrate and dominant amino acids, including glutamate, glutamine and arginine, were quantified in order to follow changes in N status; and the polyols ribitol, arabitol and mannitol were quantified to follow changes in the lichens' carbon (C) status. The uptake of N was quantified by labelling the fertiliser with (15)N in the ammonium position; chlorophyll a was used as an indirect marker for algal activity, and ergosterol as an indirect marker of fungal activity. Nitrogen uptake was higher in E. prunastri than in X. parietina, although the latter species may have used the mannitol reserves to obtain C skeletons and energy for N assimilation. Chlorophyll a and ergosterol concentrations remained unaltered in X. parietina irrespective of N dosage while ergosterol decreased with increasing N uptake in E. prunastri. The latter species had accumulated a large pool of ammonium at the highest N dosage, whilst in X. parietina a significant nitrate pool was instead observed. Taken together, these short-term responses to high N supply observed in the two lichens, and the differences between them, can partly explain the higher tolerance of X. parietina towards increased atmospheric N levels.