Bioaccumulation of lead by the lichen Acarospora smaragdula from smelter emissions

Accumulation of lead in the crustose lichen Acarospora smaragdula sensu Int o is reported in the vicinity of an ore-processing plant where it is subjec ted to acidification and metal particulate fallout. A combination of light microscopy, X-ray element mapping, field emission scanning electron microsc opy (FESEM) and other analytical techniques identifies Ph accumulation with in specific fungal tissues derived from smelter particles (PM10s). No Pb wa s detected within the photobiont layer. Our studies suggest that Ph is high ly mobile under the prevailing acidic conditions, and is fixed within the l ichen cortex and melanized apothecia. Lead is also accumulated within the m edulla and at the rock-lichen interface where it may precipitate as amorpho us botryoidal encrustations on medullary hyphae and iron-rich particles. Mo dern FESEMs and microprobes enable analysis of minute quantities of materia l, and are important tools in understanding the fate of metals within liche ns necessary to develop their use as predictive and sensitive bioindicators of aerial particulate contaminants. We suggest that crustose lichens, hith erto largely ignored in metal pollution studies, may be useful bioindicator s of aerial particular contaminants in polluted areas where macrolichens ar e absent.