Anatomical, physiological, and chemical alterations in lichen (Parmotrema tinctorum (Nyl.) Hale) transplants due to air pollution in two cities of Brahmaputra Valley, India.

The lichen species Parmotrema tinctorum (Nyl.) Hale was transplanted in two cities-Tezpur (small) and Guwahati (large)-of the Brahmaputra Valley to assess the impact of air pollution on the anatomy and physiology, and accumulation of pollutants. Significant damage to the anatomy was observed in samples, and the degree of damage was found to be higher in the transplants of the larger city. In the lichen transplants from locations having high traffic density, the total chlorophyll content was found to fall; on the contrary, electrical conductivity was found to be higher. The exposed-to-control ratio showed severe accumulation of Cd in all the transplants. Elements such as Cd, Pb, and Zn were found to be enriched in all the lichen samples from both Guwahati as well as Tezpur city. Besides, Cr, Cu, K, and Ni were also realized to be enhanced to a moderate extent. The correlations of indicator metal species pairs showed that anthropogenic influence was quite clear.

Biomonitoring by epiphytic lichen species-Pyxine cocoes (Sw.) Nyl.: understanding characteristics of trace metal in ambient air of different landuses in mid-Brahmaputra Valley.

This study presents a comparative assessment of the trace metal air pollutants of urban, peri-urban, and rural areas of the Brahmaputra Valley plain in the Eastern Himalayan region using biomonitoring of Pyxine cocoes. In situ collection of the thalli growing on Bombax sp. from representative locations was done, which was analyzed for Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn using ICP-OES. The metals, viz. Cd, Cr, Ni, Pb, and Zn, were highly enriched, indicating anthropogenic influences. The coefficients of variation (CV) of Co, Cr, and Ni were also high, pointing at their accumulation from local sources. Influence of local sources was also observed for Cd, Fe, and Mn in peri-urban and Cd in urban samples. Metals related to automobiles were accumulated in greater volume in samples of peri-urban locations, which implies the impact of the highway that runs through these locations and other associated human activities. The samples of urban areas were found to be enriched with metals originating from both vehicular emissions and road dust. Also, accumulations of Co, Cr, Cu, Fe, Mn, and Ni in the lichen thalli were found to be around tea gardens. Inter-species correlations were found to be positively significant for most of the elements. Principal component analysis (PCA) of the metal data revealed that vehicular emission and coal burning, street dust, and crustal dust were the major sources of trace metals in the ambient air of the region.