A trace amount of lead on adsorbent Mg6Fe2(OH)16(CO3)¥3H2O was selectively monitored by XAS combined with a fluorescence spectrometer. In the presence of dominant scattered and emitted X-rays derived from heavy elements (Fe and Mg), large quantities of heavy elements predominantly absorb the incident photons and the X-ray fluorescence derived from trace amounts of elements is very weak compared to scattered + emitted X-rays derived from heavy elements. Pb L alpha1 emission was counted during XAS measurements with a fluorescence spectrometer of energy resolution of 1.1 eV. Obtained spectrum was compared to the spectra for standard Pb(2+) compounds. The ion exchange mechanism FeO(OH) + Pb(2+) --> FeO-OPb(+) + H(+) was rejected, but a eutectic mixture of PbCO3 and Pb(OH)2 may be coagulated on the basic surface of adsorbent.