A comparative study of lichen biochemistry and air pollution status of urban, semi urban and industrial area of Hooghly and Burdwan district, West Bengal

Lichens are group of nonvascular plants. Lichen absorbs water and nutrient passively from their environment. Because of this lichens are particularly sensitive to environmental factors such as temperature, water availability, and air pollutants and/or by substances accumulates in lichen from the environment through variety of mechanisms including particulate trapping, ion exchange, extracellular electrolyte adsorption, hydrolysis and intra cellular uptake. Air pollution control is more complex than most other environmental changes. A study has been done to evaluate the air pollution status by means of lichen through the biochemical variability of three macro environment (semiurban area Arambagh, urban area Burdwan and industrial area Durgapur). The study results revealed that there exist inverse relationship between pollutant load and pigment content (chlorophyll and carotenoid content). Average concentration of chlorophyll ‘a’, ‘b’, and total chlorophyll was found in following order, Site-II>Site-III>Site-I. From the result of Chlorophyll Stability Index (CSI) it has been found that the chlorophyll degradation is highest in Site-II followed by Site-III and lowest in Site-I. There is a strong inverse relationship of chlorophyll content in lichen with SO2 and NOx but the level of SPM found highest in Site-I followed by Site-III and lowest in Site-II. Moreover, biochemical constituents (protein, sugar, phenol and proline) of all the representative samples were also vary from site to site. The study results reveal that the amount of soluble sugar was highest recorded at Site-III followed by Site–I and lowest in Site-II. Again correlation study indicates that there is positive relationship between soluble sugar and phenol content at 5% level of significance. Therefore, it also indicates that the lichen metabolite and other physiological action monitored by SO2, NOx and SPM level in the air. Studies showed that the semiurban area was under more vulnerable condition than industrial and urban area of Hooghly and Burdwan district. Moreover the micrograph study of representative lichen samples directly proved that lichen structure affected by air pollutants, but the extent of deformation exclusively depends on the level of pollutants present in the air. Results also suggest that different level of air pollutants (SO2, NOx and SPM) affect the biochemical parameters of lichen, but more extensive study is needed to confirm the relationship between air pollution status and lichen biochemistry.