Lichens (Parmelia sulcata) time response model to environmental elemental availability

Parmelia sulcata transplants, collected in a non-polluted area, were expose d to new atmospheric conditions at six stations, of which five were located near power plants and one at an unpolluted area. Data were collected for a 1-year period, on rainfall, airborne particulates, elemental deposition an d on lichen elemental composition. The study was carried out to quantify th e relationships between elemental availability and elemental accumulation i n lichens. A mathematical model was developed, involving a simple represent ation of the lichen, and a memory loss function which describes the time re lations for the lichen's progressive representation of its new ambient cond itions. The collected data set was used to test the model. The results indi cate that the environmental data on Na, Al and Pb could be reproduced and p redicted by the model, including the variability patterns. Half-memory time s were calculated for Na, Al and Pb as 200, 500 and 600 days, respectively, based on using all station data. However, further improvements are still n eeded, including the clarification of differences in model outcomes between stations. (C) 1999 Elsevier Science B.V. All rights reserved.