Effect of the interaction between transplants of the epiphytic lichen Pseudevernia furfuracea L. (Zopf) and rainfall on the variation of element concentrations associated with the water-soluble part of atmospheric depositions

Water Soluble Bulk Deposition (WSBD) and Water Soluble Leaching (WSL) from Pseudevernia furfuraceathalli transplanted in a anthropized zone were separately collected in four locations where weatherstations were set up for monitoring rainfalls rate and daily temperature.The thalli were exposed for three months during which 13 major rainfalls took place. The concentrationsof 15 elements (Al, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Pb, As, Cd, Ti, Sn, Sb) were measured as well inWSBD and WSL as in the lichen thalli at the end of the exposure period. The total bioaccumulation ofeach element was significantly correlated with its % representation in both the lichen input (WSBD) andoutput (WSL). Elements with a small water-soluble input-pool were mostly taken up by the thalli(output/input < 1). Among the elements with a high input-pool, Zn was nearly systematically taken upwhile Al and Mn were lost (output/input > 1). Al showed a significant direct correlation with the increasein mm and hours of rainfall (i.e. transition from net loss to net uptake) while Mn showed an inversecorrelation (transition from net uptake to net loss), which may be due to element competition modulatedby water-stimulated lichen physiology. Al was strongly bioaccumulated while Mn showed a slight increasein exposed thalli. This suggests that rainfall-induced loss can result in an underestimation bylichen biomonitoring of element concentrations in atmospheric deposition and an increase in thebioavailability of potential toxic elements for other environmental compartments.