Urban activities intensify air pollution by increasing the amount of particulate matter (PM). The trees collect PM by adsorption on the leaf surface and simultaneously absorb inorganic components. In this research, we investigated the potential of the black pine as bioindicator of road traffic emissions in Cluj-Napoca (Romania). We defined three sites types with different exposure to the road traffic (streets, outskirts, parks) and a control site far from the city. We quantified 17 inorganic components (Al, B, Ba, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, Zn) by MP-AES (microwave-plasma atomic emission spectroscopy) technique in the one-year-old needles and we identified the best candidates for biomonitoring purposes. The concentration of Ba, Cr, Cu and Fe showed the most sensitive variations with the road traffic intensity. While in the streets the Ba, Cu and Fe increased by 2.8–3.5 times in relation to the control site, the Cr varied in the highest degree exhibiting ratios of 2.2 (parks), 3.3 (outskirts) and 6.3 (streets). The success of these elements lies in several characteristics: they are closely related to non-exhaust emissions, they are readily absorbed through the leaves rather than the roots, and they tend to accumulate in the needles instead of being relocated to other organs. The street maintenance activities caused considerable accumulation of Na in the trees from the roadsides, but had no impact over the trees from the parks. The elements originating mainly in the re-suspended urban dust (Ni, Pb, Sr) equally affected the pines from the streets and parks.

Among the various species of vegetation, conifers play an important role as a biomonitor of air pollution. The current study presents the determination of pesticides and polycyclic aromatic hydrocarbons in 15 conifer samples collected in August 2018 (summer season) from different regions in north Lebanon (Tripoli, Koura, Bcharre, and Akkar). Pollutants were extracted based on QuEChERS-SPME followed by liquid and gas chromatography-tandem mass spectrometry. Results showed that the samples collected from Bcharre region had the lowest concentration in both pesticides and polycyclic aromatic hydrocarbons with a total concentration of 50 and 66 ng g⁻¹, while the samples collected from the regions widely known by their agriculture (Akkar, Tripoli, and Koura areas) were the most polluted with concentrations of 231 and 422 ng g⁻¹, 192 and 370 ng g⁻¹, and 127 and 98 ng g⁻¹ for pesticides and polycyclic aromatic hydrocarbons respectively. This study revealed that conifers are suggested to be efficient biomonitors of contamination levels in the air.