Correlation of atmospheric purity index to the diversity of lichens in the Horton Plains National Park, Sri Lanka

Horton Plains National Park (HPNP) has been declared as a world heritage site, because of its unique biodiversity. Die-back of certain areas of this park is widely believed to be due to acidic precursor depositions carried over from other parts of the country and also from neighboring countries. Air pollution data for the two pollutants, NO 2 and SO 2 were obtained from the passive air sampling method. The data revealed that the concentrations of ambient NO 2 and SO 2 were very low in the HPNP. The variations of ambient NO 2 and SO 2 concentrations during the study period showed insignificant positive correlation (p≥ 0.05) with the rainfall data. Considering the variations of these two pollutants with Relative Humidity and the number of vehicles visiting HPNP, both pollutants had insignificant positive correlation. The Index of Atmospheric Purity (IAP) value obtained for the whole area of the HPNP was 54.22. This value belongs to the quality level 5 which represents the ‘very low’ pollution level. The results including lichen distribution and air quality data could confirm that the ambient air quality at HPNP is very high. The high diversity of lichens and the minimum levels of air pollutants suggested that the forest health of HPNP is at a favorable level. Therefore, it is essential to maintain at least the current air pollution level of HPNP in order to conserve the forest and its biodiversity.