The investigations were carried out on quartz after trapping lead as described in Section 2.3.6. C(1s) signal was used as an internal energy calibrant at 284.5 eV binding energy, C(1s) peak was observed at 287.7 eV in the presence of Pb. Hence, C(1s) shift was found to be +3.2 eV. XPS spectrum of Pb on quartz surface can be seen in Fig. 2(a). Pb(4f7/2) and Pb(4f5/2) peaks were observed at 142.9 eV and 147.8 eV, respectively. By subtracting the C(1s) shift from these peaks corrected Pb(4f7/2) and Pb(4f5/2) peaks were found as 139.7 eV and 144.6 eV, respectively. In a study on Pb(II) species adsorbed on alumina, for 6 samples, the range of values for Pb(4f7/2) and Pb(4f5/2) peaks were 139.5–140.1 eV and 144.3–144.7 eV, respectively [29]. Therefore, the peaks observed in Fig. 2(a) can be assigned to Pb(II), illustrating that the oxidation state of Pb in species trapped on SQT surface is +2.