# Particulate Matter Contamination of Bee Pollen in an Industrial Area of the Po Valley (Italy)
## 3 Results  
During the monitoring period, forager bees were observed collecting pollen from wild and cultivated plants present in the surroundings (e.g., _Taraxacum officinal_ or dandelion, _Prunus spinosa_ or blackthorn, Brassicaceae, _Zea mays_ or corn, _Mediago sativa_ or alfalfa) in the industrial area. All pollen grains collected from both the control and the industrial site displayed contamination by inorganic particles, with controls appearing to be scarcely contaminated (no more than three particles for grain pollen were detected), while the pollen from the industrial site was heavily contaminated. Airborne PM detected on pollen from the control site was composed exclusively of natural mineral phases (i.e., clay minerals and calcite, Figures S1 and S2). All pollen samples from the industrial site were contaminated with clay minerals, calcite, iron oxides/hydroxides, barite, and quartz (Table 1, Figure 3).  
Pollen grains contaminated by feldspar (Figure 4a), and Fe alloys (Fe-Cr and Fe-Cr-Mn) appeared less frequently (Table 1, Figure 4b-d).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Analyzed PM** & **Natural Source** &
\begin{tabular}{c} **Anthropogenic** \\ **Source** \\ \end{tabular} & **May** & **June** & **July** & **August** \\ \hline Clay minerals & + & agriculture & + & + & + & + \\ Calcite & + & incinerator, agriculture & + & + & + & + \\ Quartz & + & incinerator, agriculture & + & + & + & + \\ Iron oxides/Hydroxides & & traffic & + & + & + & + \\ Barite & & traffic & + & + & + & + \\ Feldspars & + & agriculture & + & & & + \\ Fe-alloy (Fe-Cr; Fe-Cr-Mn) & & traffic & + & & + & \\ Spherical dioxide & & incinerator & + & & & \\ Heavy metals (Zn, Pb, Sb, Sn) & & traffic, incinerator & + & & & \\ Gold & & incinerator & & + & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mineralogical phases and other PMs contaminating bee pollen collected in different months.  
Figure 3: Airborne PM collected on all pollen grains. (**a**) Two particles composed of iron oxides/hydroxides (arrowheads; 1.5 and 1.4 \(\upmu\)m) on alfalfa pollen. (**b**) A particle composed of iron oxides/hydroxides (arrowhead; 1.5 \(\upmu\)m) on pollen of a Brassicacea. (**c**) PM of barite (1.2 \(\upmu\)m). (**d**) A particle of quartz (10 \(\upmu\)m) on pollen grains of _Taraxacum officinal_. (**e**) PM of a clay mineral (6.9 \(\upmu\)m) on a pollen grain of _T. officinal_. (**f**) Pollen grains of _Medicago sativa_ and a Brassicaceae contaminated by PM of calcite (4.7 \(\upmu\)m). Corresponding EDX spectra are provided in the Supplementary Materials.  
PM containing Zn, Pb, and Sb (Figure 5a-c) and spherical PM composed of silicon dioxide (Figure 6d,e) were only occasionally present on bee pollen.  
Figure 4: (**a**) Particulate matter (PM) of feldspar (asterisk). (**b**) Particles of Fe-Cr-Mn (arrows, 1.3 \(\upmu\)m and 2.7 \(\upmu\)m) and Fe oxides/hydroxides (arrowhead, 1 \(\upmu\)m). (**c**) a submicrometric PM of Fe-Cr (arrowhead, 200 nm). (**d**) a particle of Fe-Cr-Mn (6.3 \(\upmu\)m). Corresponding EDX spectra are provided as Supplementary Materials.  
Figure 5: (**a**) Pollen grains of _Melicago sativa_ contaminated with PM of quartz (arrow, 4.2 \(\upmu\)m), clay mineral (asterisk, 2.9 \(\upmu\)m), and metallic Zn (arrowhead, 3.8 \(\upmu\)m). (**b**) PM containing lead (brighter areas). (**c**) PM of antimony oxide (2.7 \(\upmu\)m). (**d**,**e**) Round-shaped SiO\({}_{2}\) particles (4.2 \(\upmu\)m and 4.3 \(\upmu\)m).  
Interestingly, some grains collected in May appeared to be contaminated with gold particles (Figure 6).