Spatial distribution and heavy metal content of some bryophytes and lichens in relation to air pollution in Nigeria's Guinea Savanna

Use of bio-indicators in monitoring environmental quality in the West African sub-region is limited. In a study to evaluate the occurrence and distribution of bryophytes and lichens in relation to air pollution in Nigeria, three species each of bryophytes (Calymperes palisotii, Erpodium coronatum, B. leptophyllum) and lichens (Parmelia tinctorum, Physcia sp. and Trentifolia sp.) were encountered. For categories of plants, the number of species (diversity) and frequency of occurrence increased as one moved further away from the source point. Accumulation patterns of 13 heavy metals (across species) were generally similar, with 50% or more of these being accumulated up to the level of 500 mg/kg or above. While metals like Cr, Co, Ni, Sr, Y, Cu, Ph and Br, were accumulated in consistently higher proportions, others like Zn, As, Rb and Se were in consistently lower proportions.