The graphical presentation of lead isotope data for environmental source apportionment.

Lead isotope ratios are widely used to identify original sources of Pb in the environment. Such source apportionment depends on the ability to distinguish potential sources on the basis of their isotopic composition. However, almost all terrestrial Pb is co-linear in some of the plots i.e. (206)Pb/(208)Pb versus (206)Pb/(207)Pb and (206)Pb/(204)Pb versus (206)Pb/(207)Pb commonly presented in the literature. These diagrams are unable to distinguish more than two sources of environmental Pb. Linear trends in such plots are an inevitable consequence of the co-linearity of terrestrial leads and should not be taken necessarily to indicate simple binary mixing of sources. A more reliable test for multiple source mixing can be obtained from plots involving (206)Pb/(204)Pb, (207)Pb/(204)Pb and (208)Pb/(204)Pb and therefore requires measurements of the minor (204)Pb isotope.