DETERMINATION OF TRACE-ELEMENTS IN LICHENS BY INSTRUMENTAL NEUTRON-ACTIVATION ANALYSIS

Instrumental neutron activation analysis has been applied to analyze e piphytic specimens of the lichen Canoparmelia texana. Samples collecte d from the barks of the trees were previously cleaned, lyophilized and ground to be irradiated under a thermal neutron flux in the IEA-R1 nu clear reactor. Elements Al, As, Br, Ca, Cd, Cl, Co, Cr, Cs, Fe, Hf, K, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Mg, Mn, Na, Rb, Sb, Sc, Se, Th, Ti, U , V and Zn were determined quantitatively by using short arid long irr adiations. Comparisons were made between the results for washed and un washed samples as well as those collected in two different years, from individual palm trees and also from different sites of Sao Paulo Stat e. ?he precision and the accuracy of the method were evaluated by anal yzing NIST 1572a Citrus Leaves, IAEA 336 Lichen and USGS W-l Rock refe rence materials.