Abstract
Due to their wide distribution and availability, plant leaves can be considered interesting candidates as biomonitoring substrates for the evaluation of atmospheric pollution. In addition, some species can also retain historical information, for example, related to environmental pollution, due to their leaf class age. In this study, the content of polycyclic aromatic hydrocarbons (PAHs) in Abies holophylla and Pinus tabuliformis needle samples in the function of their class age has been investigated to obtain information regarding the degradation constant for each PAH under investigation (α values ranging from 0.173 to 1.870) and to evaluate the possibility to correlate the presence of PAHs in needles with some important pollution environmental factors. Considering air pollutant variables registered in Jilin Province, interesting correlations (at 95% confidence level) have been found between coal consumption per year and anthracene contents in needles, while fluorene, phenanthrene, and anthracene results correlated with coal consumption. Furthermore, it has been demonstrated that the total PAH concentration in needles, for both species, increased with their age (from 804 to 3604 ng g-1 dry weight), showing a general tendency to accumulate these substances through years. PAH degradation rates increased instead with molecular complexity. This study could be considered a first trial to obtain historical environmental information by pine needles biomonitoring.
Highlights
The presence of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere represents one of the problems of major concern related to air pollution in recent decades
Due to the accumulating effect, ΣPAHs generally increase with the needle age, in accordance with the results obtained by previous works (Ratola et al 2010a; Odabasi et al 2015)
Using the PAH content in Abies holophylla needles, a mathematical model that considers a first–order PAH degradation process has been applied in order to obtain the minimum α value for each of the considered PAH
Summary
The presence of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere represents one of the problems of major concern related to air pollution in recent decades. PAHs determination, anyway, could encounter technical, physical, and economical limitations when active air samplers are used, while sampling tree components like needles, leaves and barks, suitable for the determination of the spatial distribution of PAHs, are usually employed only to measure the current levels of atmospheric PAHs (De Nicola et al.2011; Amigo et al 2011; Zhou et al 2014). Recent studies on the historical record of PAHs have been conducted in lake sediments and ice cores of specific areas (Wang et al 2008; Cai et al 2016), but these sampling sites impose several constraints, limiting the monitoring to specific conditions in terms of spatial recognition and time intervals. A unique and very useful characteristic of conifer needles is that they can grow up and last for several years, preserving the history of the environmental conditions
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