## 2 Materials and Methods
### GC-MS Analysis of PAHs  
PAHs were determined using a GC apparatus (Perkin Elmer CLARUS 690 (Shelton, CT, USA) with an MS detector, using an Elite 35 MS capillary column (5% diphenyl/95% dimethyl polysiloxane; 30 m length \(\times\) 0.32 mm i.d. \(\times\) 0.25 \(\upmu\)m film thickness). Helium was used as the carrier gas at a flow rate of 1.0 mL/min. After being held at 100 \({}^{\circ}\)C for 1 min, the cover temperature was increased to 250 \({}^{\circ}\)C at a rate of 6 \({}^{\circ}\)C/min. The temperature was raised to 330 \({}^{\circ}\)C at a rate of 10 \({}^{\circ}\)C/min and held for 10 min. The mass spectrometric analysis was conducted using a selective ion monitor (SIM) with electron ionisation (EI) at 70 eV; the temperatures of the ion source and interface were 270 \({}^{\circ}\)C and 330 \({}^{\circ}\)C, respectively. The range of \(m/z\) was measured from 47 to 450, and for each compound, the maximum abundant ion from the molecular ion cluster was measured. The quantification of the specific polycyclic aromatic hydrocarbons was achieved by comparing the retention times of the sample peaks to those of known standards (Table 1). Sixteen PAHs were analysed: naphthalene (Na), acenapthylene (Ac), acenapththenene (Ace), fluorene (Flu), phenanthrene (Ph), anthracene (An), fluoranthene (Fin), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), benzo[g,h,i]perylene (Bghi), dibenzo[a,h]anthracene (DahA), and indeno[1,2,3 \(-\)cd] pyrene (IP).  
The performance parameters of the methods used were verified by evaluating the following parameters: linearity, limit of detection (LOD) and accuracy. The limits of detection were calculated as three times the standard deviation of the blanks, and the values were 0.0001 ug/g (dried plant) and 0.0001 ug/L (infusion). Linearity was checked by constructing the calibration curves using spiked model solutions at different concentration levels. The calibration plots based on the linear regression analysis revealed good linear relationships between the peak area and concentrations, with correlation coefficients over 0.9900. Accuracy, expressed as the percentage of recovery, was evaluated via the analysis of filters spiked with a known concentration of standard PAH compounds, and the values were found in the range of 90-95%.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**PAHs** & **Retention Time** & _m/z_ & **Linearity (R2)** & **LOD (ug/g) dwt** \\ \hline Na & 7.25 & 128 & 0.9885 & 0.0001 \\ Ac & 13.70 & 152 & 0.9937 & 0.0001 \\ Ace & 14.50 & 154 & 0.9933 & 0.0001 \\ Flu & 16.57 & 166 & 0.9945 & 0.0001 \\ Ph & 20.36 & 178 & 0.9922 & 0.0001 \\ An & 20.56 & 178 & 0.9968 & 0.0001 \\ Fln & 25.04 & 202 & 0.9923 & 0.0001 \\ Pyr & 25.87 & 202 & 0.9980 & 0.0001 \\ BaA & 30.74 & 228 & 0.9972 & 0.0001 \\ Chr & 30.90 & 228 & 0.9946 & 0.0001 \\ BbF & 33.80 & 252 & 0.9840 & 0.0001 \\ BkF & 34.00 & 252 & 0.9734 & 0.0001 \\ BaP & 34.68 & 252 & 0.9858 & 0.0001 \\ Bghi & 37.20 & 276 & 0.9765 & 0.0001 \\ DahA & 37.40 & 278 & 0.9823 & 0.0001 \\ IP & 37.74 & 276 & 0.9756 & 0.0001 \\ \hline \end{tabular}
\end{table}
Table 1: Retention time, monitored ion, linearity and limit of detection (LOD) of PAHs.  
All experiments were carried out triplicate, and the data were presented as mean \(\pm\) standard deviation.