## 2 Materials and Methods
### Samples Processing and Analysis  
The soluble fractions were extracted in ultrapure water (18.2 M\(\Omega\)/cm) and quantified, respectively, by ion chromatography and ICP-QOMS. The freshly harvested pollen and POL and CNT samples were extracted twice by shaking with 14 mL of water for 2 min. The resulting extracts were centrifuged at 10,000\(\times\)\(g\) for 20 min at 17 \({}^{\circ}\)C, and the supernatants were divided into two aliquots: one was filtered (0.2 \(\upmu\)m) and used to assess the soluble cationic and anionic species by suppressed ionic chromatography (AQUION and ICS-2100 Dionex supplied by ThermoFisher Scientific, Waltham, MA USA) and the other, after acid digestion in an HNO\({}_{3}\):H\({}_{2}\)O\({}_{2}\) mixture (4:2) assisted by a microwave oven (MARS 6 Microwave Digestion System, CEM Corporation, Matthews, NC, USA), wasused to determine the soluble metals present by using the triple quadrupole Agilent 8900 ICP-MS-QQQ instrument (Agilent Technologies, Santa Clara, CA USA)equipped with a collision/reaction cell (CRC) and connected to an SP4 autosampler. In addition, the total metal concentrations were quantified by ICP-QQQMS spectroscopy, analyzing microwave digestions in HNO\({}_{3}\) and H\({}_{2}\)O\({}_{2}\) (4.2) of aqueous dispersions (20 mL) of pollen and CNT samples shaken for 2 min. Details of the acid digestion procedure can be found in [PERSON] et al., 2023 [42]. Element analysis. Commercially produced standard solutions (ICP multielement standard solution CertiPUR(r), 1000 ppm, Merck Chemicals, and Reagents GmbH, Darmstadt, Germany) in nitric acid and internal standard solution (Internal standard mix for ICP-MS systems, 100 ppm, 6-Li, Sc, Ge, Rh, In, Tb, Lu, Bi, Agilent Technologies, Santa Clara, CA USA) were used to prepare appropriate elemental calibration standards. An ordinary least-squares regression model (OLSR) was used for calibrations. Linearity between intensity and concentration was observed in the range of 1-10,000 ppt (R\({}^{2}\) > 0.999). Instrument detection limits, based on the calibration curve method, were estimated to be 12 for Cr, 26 for Mn, 41 for Fe, 2 for Co, 15 for Ni, 1 for Cu, 175 for Zn, 3 for Pb, 5 for Cd 12 for Ba, 24 for Sr, 293 for Si, and 611 ppt for Al. Experimental repeatability was calculated by performing three replicate analyses of two multi-element standards solutions (0.5 and 1 ppb). The metal RSDs obtained by the repeatability test were 2.6-13.0%. The accuracy of the analytical method was obtained using standard reference material (ERM\({}^{\oplus}\)-BB422 fish muscle, European Commission, JRC, Geel, Belgium). The metal concentrations agreed with the certified value, and recovery fell in the range of 80-120%. Analytical quality control included the analysis of a digestion reagent blank with each batch of 12 samples. Ion analysis. Multi-ion calibration standards were prepared from single-component standard solutions for IC (Fluka-TraceCERTTM, 1000 \(\pm\) 4 ppm, Honeywell International Inc, Charlotte, NC, USA). Linearity between peak area and concentration was observed in the range of 0.05-1 ppm for the soluble cationic and anionic species (R\({}^{2}\) > 0.999) using a 500 \(\mu\)L loop. Instrument detection limits, based on the calibration curve method, were estimated to be 0.01 for MSA, nitrite, and sulfate; 0.02 for Li\({}^{+}\), Cl\({}^{-}\), Br\({}^{-}\), nitrate, and phosphate; 0.03 for Na\({}^{+}\) and Mg\({}^{2+}\); 0.04 for K\({}^{+}\), oxalate, and F\({}^{-}\); 0.05 for formate; 0.07 for ammonium; and 0.4 ppm for Ca\({}^{2+}\). Experimental repeatability and accuracy of the analytical method were calculated by performing three replicate analyses of a multi-element standards solution (1 ppm). The ion RSDs obtained by the repeatability test were 2.6-19.8% for anionic and 2.2-8-4% for cationic species, and recovery fell in the range of 90-106% for anions and 90-102% for cations. All reagents were of analytical- or, whenever available, suprapure-grade quality and were from VWR Chemicals (Radnor, PA, USA).