Heavy metal accumulation and the practical application of lichens as bioindicators for heavy metal pollution in surface soil

Abstract

Levels of trace element pollution in surface soil have been estimated using soil analyses and leaching tests. These methods may reveal different results due to the effect of soil properties on the elemental availability. Therefore, this study advocates an alternative method for monitoring and assessment of trace element pollution in surface soil using terricolous fruticose lichens. Lichens and their substrata were analyzed using particle induced X-ray emission (PIXE), inductively coupled plasma-mass spectrometry (ICP-MS) and XRF to clarify the relationships between Cu, Zn, As and Pb concentrations in lichens and soils, including their absorption properties. Concentrations of these elements in the lichens were positively correlated with those in the soils regardless of lichen species, location, habitat, or conditions of soils. The analyzed lichens had neither competitive nor antagonistic properties in their elemental absorption, which made them good bioindicators of trace element pollution in surface soil. The distribution maps of average Cu, Zn, As and Pb concentrations at each sampling region was detected at almost all of the Cu, Zn and As pollution of the soils. Therefore, lichens could be used in practical applications to monitor Cu, Zn and As pollution in surface soils.