Using mosses and lichen to study roadside pollution and the correlation of toxic elements and elevation in a mountainous area of Guizhou, China

Using mosses and lichen to study roadside pollution and the correlation of toxic elements and elevation in a mountainous area of Guizhou, China

In this study, three moss species (Bryum argenteum, Rhynchostegium subspeciosum and Orthotrichum dasymitrium) and one lichen species (Parmelia saxatilis) were sampled to monitor the levels of toxic elements along a section of a gorge road for assessing the enrichment ability of these species and the effects of toxic elements at different elevations. Hierarchical clustering was used to classify samples based on geographic data and ICP-MS to determine the contents of toxic elements in each plant. Based on the obtained levels of enrichment factors (EF), metal accumulation index (MAI) and geoaccumulation index (Igeo), Bryum argenteum (highest MAI and Igeo) was identified as the most suitable biomonitoring species. PMF source analysis showed that the main pollution sources were traffic dust (45%) and other traffic emissions (43%). Road pollution was alarming as high Pb, As and Cr levels were detected as the most important pollutants. The levels of toxic element depositions along the road of the Karst gorge area increased with rising elevation. The vertical distribution of pollutants was affected by temperature, topography, dominant winds and pollutant emissions. However, some variations in the distribution in similar areas were also observed.