ASSESSMENT OF AIR POLLUTION TOLERANCE INDEX AND LEAF STRUCTURE OF SELECTED PLANT SPECIES AROUND UDAYAPUR CEMENT FACTORY, NEPAL

Abstract

Present study investigate the effect of cement dust on plants physiology and morphology around Udayapur Cement Factory. Plants can be both bio-indicator and tolerant in order to control the air pollution in urban and industrial areas. Eight commonly available plant species of tree and shrub were selected from study area. Plant species were collected from four directions and four different radial distances from the factory viz. (0-250 m), (250-500 m), (500-750 m) and (750-1000 m) from the Udayapur Cement Factory. To study the relative tolerance of plants towards air pollutants, four parameters namely ascorbic acid, leaf extract pH, total chlorophyll and relative water content were measured and computed together to calculate air pollution tolerance index (APTI). The characteristics of leaf structure (stomatal length, breadth and density and specific leaf area) were also studied. The APTI values of most of the plant species increased significantly at distance near to the factory at 0-250 m distance. All the tree species showed high APTI values in eastern direction and among the shrub species studied Colebrookea oppositifolia and Clerodendrum viscosum had high APTI values at northern direction, Melastoma melabathricum showed high APTI values in eastern direction and Phoenix acaulis had high APTI values at western direction. Most of the species showed high APTI values in east direction which indicates high air pollution in this direction, which may be due to the presence of road between the forests in order to transport cement from the factory as well as the dust emission from the factory and also the direction of westerly wind. Based on APTI values three tree species (Casearia graveolens, Cassia fistula and Shorea robusta) and two shrub species (Colebrookea oppositifolia and Phoenix acaulis) were found to be tolerant species with APTI values ranging above seventeen. Derris elliptica was considered as intermediate species with APTI value ranging between twelve and sixteen. Likewise, shrub species namely Melastoma melabathricum and Clerodendrum viscosum measured APTI value less than eleven and were kept under sensitive category. The data of stomatal density showed increasing trend and stomatal length and breadth showed decreasing trend while moving near to the cement factory (0-250 m). SLA of all plant species decreased near the cement factory.