Affiliations: Department of Environmental Science, Tezpur
University, Tezpur – 784028, India | Lichenology Laboratory, National Botanical Research
Institute (CSIR), Lucknow – 226001, India
Abstract: Lichens are indicator species of air quality of a locality. Estimate
of heavy metal (HM) accumulation in lichens offers an indirect measure of their
levels in the atmosphere. Accumulated HMs of lichen thalli of 16 species
belonging to 10 genera and their phorophytes of two characteristic areas of
Brahmaputra valley were studied. Acid digested samples of thalli and
phorophytes were analysed for Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb by ICP-OES.
Mean concentrations of the HMs were found to be higher in lichens at the area
situated close to the downtown area of the city and the Brahmaputra River.
Accumulation of Cd, Cu, Fe and Ni were found to be higher in lichen thalli;
however, leaves accumulated higher levels of Co and Mn. Linear regression
analysis shows poor dependency of the thalli on their phorophytes indicating
accumulation of metals from atmosphere. The extent of enrichment in the lichen
thalli, which was evaluated by calculating enrichment factors (EFs) revealed
moderate enrichment of Cr, Cu, Ni and Pb; however, Cd was found to be highly
enriched. Ecological risk posed by the heavy metals were calculated and it was
found that Principal Component Analysis (PCA) of the data set identifies three
contributing sources: coal-fired industrial emission, crustal dust blown from
dry river bed and vehicular emission.
Keywords: Air pollution, biomonitoring, lichen, Tezpur, source apportionment
