Lichens biomonitoring as feasible methodology to assess air pollution in natural ecosystems: Combined study of quantitative PAHs analyses and lichen biodiversity in the Pyrenees Mountains

Abstract

The air quality in the Aragón valley, in the central Pyrenees, has been assessed by evaluation of lichen biodiversity and mapped by elaboration of the Index of Air Purity (IAP) based on observations of the presence and abundance of eight kinds of lichen with different sensitivity to air pollution. The IAP values obtained have been compared with quantitative analytical measures of 16 PAHs in the lichen Evernia prunastri, because this species was associated with a wide range of traffic exposure and levels of urbanization. Analyses of PAHs were carried out by the DSASE method followed by an SPE clean-up step and GC-MS analysis. The concentration of total PAHs found in lichen samples from the Aragón valley ranged from 692 to 6420 ng g(-1) and the PAHs profile showed predominance of compounds with three aromatic rings. The influence of the road traffic in the area has been shown because values over the median concentration of PAHs (>1092 ng g(-1)), percentage of combustion PAHs (>50%), and equivalent toxicity (>169) were found in lichens collected at places exposed to the influence of traffic. The combination of both methods suggests IAP as a general method for evaluating the air pollution referenced to PAHs because it can be correlated with the content of combustion PAHs and poor lichen biodiversity can be partly explained by the air pollution caused by specific PAHs.

Biomonitoring of Airborne Heavy Metal Contamination

“…Because of their high sensitivity toward specific pollutants and ability to store contaminants in their biological tissues, lichens are defined as bioindicators and/or bioaccumulators, respectively. Lichen form conspicuous gray, green, orange, or red patches on trees or rockes (Blasco et al, 2008).…”

“…10; 1≤f ≤ 10). The IAP-index was calculated separately for each sampling site (Blasco et al, 2008;Zechmeister & Hohenwallner, 2006). The frequency method makes it possible to predict pollution levels with a certainty of over 97% (Conti & Cecchetti, 2001).…”

Comparison of Pine Needles and Mosses as Bio-Indicators for Polycyclic Aromatic Hydrocarbons

“…Pine needles are suitable for the evaluation of long-term trends in atmospheric PAHs [11], while it has been proposed that lichens may be useful for the fingerprinting of multisource atmospheric PAH pollution [16] and for the assessment of air quality in natural ecosystems [19]. However, the abilities and usefulness of bio-indicators differ on a caseby-case basis.…”

“…This approach is based on the concept that the amounts and composition of contaminants in plants provide accumulative and timeintegral estimates of the concentrations of airborne contaminants [10]. In particular, pine needles [3,8,[11][12][13][14][15], lichens [16][17][18][19], and mosses [7,[20][21][22][23][24][25][26] are good bio-in-dicators of airborne contaminants.…”

Analysis of Lichen Metabolites, a Variety of Approaches

“…Therefore, GC-MS air pollution assessment techniques were applied to detect polycyclic aromatic hydrocarbons within different Pyrenean lichens (Blasco et al 2008) or within Italian alpsdwelling lichens (Nascimbene et al 2014). …”