Metal Accumulation in Lichens as a Tool for Assessing Atmospheric Contamination in a Natural Park

Abstract

Motor vehicles passing through natural areas could contribute to the air pollution that most likely causes biodiversity losses and decreases air quality. This study assessed the impact of tourism on atmospheric metal pollution in Khao Yai National Park (KYNP), Thailand. Native thalli of the epiphytic lichen Parmotrema tinctorum were collected during the rainy period at a total of eleven sampling sites: three sites in forested (no traffic), four sites in accommodation (low-moderate traffic) and four sites in parking (moderate-high traffic) areas in KYNP. Nine traffic-related metals, including As, Cd, Cr, Cu, Fe, Pb, Sb, V and Zn, were detected using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of most metals did not show significant differences between the higher traffic intensity areas and the no traffic area, and the concentrations of the metals were in the range of their background concentrations. Only Cr and V, metals related to motor vehicles, were identified at the accommodation sites at significantly higher concentrations (Cr=3.4 µg/g, V=1.33 µg/g) than their baseline concentrations (Cr=1.4 µg/g, V=0.96 µg/g). These two metals have adverse effects on humans, plants, lichens and other organisms. Bioaccumulation ratios (B ratios) indicated that most metals at most sampling sites did not bioaccumulate. No metal demonstrated high or severe bioaccumulation. This result suggests that the impact of tourism on atmospheric metal pollution in the rainy period at the KYNP was modest. It also affirms the ability of lichen as an effective tool for assessing atmospheric contamination in natural areas.