The use of lichens and mosses as sentinel organisms for the determination of the airborne organic pollution in Western Pyrenees: The case of the Irati forest

Abstract

High mountain ranges are very sensitive environments. Due to their altitude, they are prone to receive pollution from long-range transport through the atmosphere. The Pyrenees is a good example of these mountain ranges that extend from the Matxitxako Cape (Basque Country) to the Creus Cape (Catalonia) with altitudes up to about 3400 m.

In this article, the ability of lichens and mosses to accumulate Persistent Organic Pollutants (POPs) and consequently, to serve as indicators of atmospheric organic pollution is investigated. For this purpose, 50 lichens and mosses were collected in the Irati Forest (Western Pyrenees), one of the largest and best-preserved beech and fir forests in Europe. One species of lichens (Parmelia sulcata) and one species of mosses (Hypnum cupressiforme) were collected from 10 different beech trees at each sampling point. A microwave assisted extraction of the samples with a mixture of 1:1 (v:v) acetone:hexane was done for the determination of 16 PAHs, 11 PCBs and 10 OCPs by GC-MS.

Generally, PAHs presented significantly higher concentrations (with a maximum concentration of 1190 ng/g in lichens and 585 ng/g in mosses) than PCBs (maximum concentration 220 ng/g in lichens and 587 in mosses) and OCPs (maximum concentration 550 ng/g in lichens and 692 in mosses) in both matrices. Regarding PAHs Ace, Flu, Flr, Nap and Phe presented in our study the highest concentrations in both mosses and lichens and with respect to PCBs and OCPs PCB-194 and HCH isomers stood out respectively.

The spatial distribution of POPs revealed that generally the distribution of POPs obtained with both matrices was similar, with a common hotspot located in the centre area of the Forest. Despite pollution from long-range transport through the atmosphere cannot be underestimated, the work presented here revealed that the urban and agricultural activities carried out in the proximities of the Irati Forest during decades have still effect in the air quality regarding PCBs and OCPs. As the analysis of mosses showed, in order to avoid high presence of PAHs in the atmosphere of the Irati Forest, activities related with combustion processes carried out around the forest have to be controlled.