Fig. 5. Isotope/isotope ratios of size-fractioned (4 to 0.037 mm) samples measured by inductively coupled plasma mass spectrometry (ICP–MS) from four of the urban phytoremediation test plots and the nonurban residence with an isolated Pb-based paint source. Error bars represent analytical uncertainty. The proposed end-member isotopic compositions for Pb-based paint and leaded gasoline are from Rabinowitz (1986). The plotted symbols represent the mean and the shaded ellipses represent the standard deviation. Ayuso et al. (2004) represents the atmospheric Pb composition in the USA in the 1970s and Mississippi Valley Type ore.