Biomonitoring of airborne persistent organic pollutants using lichens

Lichens, symbiosis of fungi and algae and/or cyanobacteria, have been considered outstanding accumulators of atmospheric persistent organic pollutants (POPs). While the alga seems to play an active role in uptake of gas phase compounds, the fungus seems to play a more passive role acting as an accumulator of particle-bound compounds. This dual behaviour is very helpful, as it may work as a 2-in-1 tool to monitor airborne POPs. Attempting to understand the processes involved in the air-to-lichen transfer of POPs, the concentrations in lichens have been related to the ones measured by means of active and passive air samplers. Understanding how POPs reach lichens’ surface, how they enter into the lichen thallus, where inside the lichens they accumulate and how concentrations in lichens relate to levels in air, is the first step to accurately understand the usage of lichens to monitor atmospheric POPs. In this chapter we explore the state-of-the-art of these aspects, as well as providing an overview of the main studies using lichens as biomonitors of POPs, including how lichens have been used for source apportionment.