Polycyclic aromatic hydrocarbons and potentially toxic elements in transplanted lichen <i>Pyxine cocoes</i> as indicator of air pollution in Lucknow City, India

Air pollution has emerged as a serious global issue driven by rapid urbanization and industrialization. This study aims to evaluate the air quality of Lucknow, a fast-growing city in North India, using lichen <i>Pyxine cocoes</i> (Sw.) Nyl. Lichen specimens collected from the relatively unpolluted area of Malihabad were transplanted for 30 days at 10 sites in Lucknow City with varying traffic volumes. The concentrations of potentially toxic elements (Fe, Al, Mn, Zn, Cu, Pb, Ni, Cr, Co, and Cd) were determined using an ICP-MS, while PAHs were examined through HPLC. Additionally, the physiological status of the lichen specimen was assessed by analyzing chlorophyll content, chlorophyll degradation, and photosynthetic efficiency (<i>F</i>_v/<i>F</i>_m). A total of 15 PAHs were detected in the transplanted lichens with molecular weights varying from 0.006-6.265 μg g^-1 (low), 0.001-17.027 μg g^-1 (medium), and 3.957-20.862 μg g^-1 (high). In contrast, significantly increased amounts of potentially toxic elements such as iron (4.42-5.38 μg L^-1), aluminum (3.52-4.38 μg L^-1), manganese (99.42-136.35 μg g^-1), and zinc (77.67-83.82 μg g^-1) were detected in sites Alambagh Chauraha, IT crossing and Polytechnic Chauraha. In all the specimens, chlorophyll a (5.17 μg L^-1), chlorophyll b (2.21 μg L^-1), and total chlorophyll (7.38 μg L^-1) were significantly decreased and degraded (0.53 μg g^-1). The results once again demonstrate that transplanted <i>P. cocoes</i> as a sensitive and reliable bioindicator of PAHs and potentially toxic elements induced air pollution in Lucknow City.