Airborne chemical elements: correlation between atmospheric levels and lichen content

Concentrations of As, Cd, Co, Na, Sb, Se and Zn have been measured in atmospheric particulate matter and Parmelia sulcata Taylor transplants at a suburban and industrial area. Levels in particulate matter were found to be much lower than European target values, Californian Acute Inhalation Reference Exposure Levels and Ontario's Ambient Air Quality Criteria. Correlations between elemental content in lichens and particulate matter (PM2.5, PM2.5-10 and PM10) were investigated. For the majority of the studied elements, the best correlations were obtained by plotting data from a lichen exposure system, allowing free influx, against the sum of monthly averages from the first month of exposure till the month of collection. All the significant correlations found were positive, suggesting that element availability contributes to enhance accumulation. The existence of significant correlation is most likely to be proven if strong gradients of chemical elements content in lichen transplants are detected.