Potential of Epiphytic Lichen Pyxine cocoes,as an Indicator of Air Pollution in Kolkata, India

The accumulation of trace elements in the thalli of epiphytic lichens can reveal levels of trace elements in the ambient air. This study assessed the trace elements in lichen species Pyxine cocoesfound in the urban and peri-urban areas of Kolkata. Trace elemental analysis was carried out using energy-dispersive X-ray fluorescence and proton-induced X-ray emission spectroscopy. Variable levels of elements like Mn, Fe, Cu, Zn, Cr, V and Pb, are detected in the thalli of P. cocoescollected from repressentative locations. Localization of trace elements in the thalli was confirmed by analysis using scanning electron microscope attached with EDX spectrometer. Several pollution indices such as enrichment factor, contamination factor (Cf) and pollution load index were estimated to evaluate the trace element contamination level of the ambient air at the sampling spots. PLI and Cf and values suggest deterioration or air quality that varies from moderate to high level of contamination. Ca, S, Pb, Sr and Cr, are highly enriched at urban sampling spots (1–9). High coefficient of variation values for Ca, S, Pb, Sr and Cr confirm their accumulation from local anthropogenic sources in the urban sampling spots (1–9). However, results of principal component analysis analysis have shown that sources of trace elements in the samples from urban areas include both vehicular emissions and anthropogenic activities. Higher concentration of trace elements in the lichen thalli collected from peri-urban locations is attributed to vehicular emissions from the highways and expressways running through these areas.