The Science of the Total Environment, 81/82 (1989) 143-156 143 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands SPECTROSCOPIC AND COMPOSITIONAL COMPARATIVE CHARACTERIZATION OF I.H.S.S. REFERENCE AND STANDARD FULVIC AND HUMIC ACIDS OF VARIOUS ORIGIN 1 2 1 1 N. SENESI , T.M. MIANO , M.R. PROVENZANO and G. BRUNETTI 1 Istituto di Chimica Agraria, Universit~ di Bari, Bari (Italia) 2 Istituto di Chimica Agraria e Forestale, Univ. di Basilicata, Potenza (Italia) SUMMARY Eleven standard and reference fulvic acids (FA) and humic acids (HA) of aquat- ic and terrestrial origin from the collection of the International Humic Substan- ces Society have been studied by chemical and spectroscopic methods. Aquatic HA appear richer in 0 and lower in C than terrestrial HA, while the opposite is gen- erally true for the corresponding FA. The N content of aquatic samples is always much lower, and C/N ratio and E4/E 6 ratio much higher than those of terrestrial samples. The infrared spectra of all samples but soil HA are qualitatively simil- ar one to another, but they differ mainly in the relative intensity of carboxyl, aromatic and aliphatic group bands. Fluorescence of terrestrial HA occurs at higher wavelengths than terrestrial FA and aquatic HA and FA in both emission and excitation modes, while synchronous-scan spectra appear more resolved and inform- ative. ESR spectra are featured by resonances consistent with conjugated semiqui- none free radicals and Fe(III) ions, the latter resonance being generally more intense for terrestrial than for aquatic samples. INTRODUCTION A primary purpose of the International Humic Substances Society (IHSS), as stated in the Bylaws, is to "establish and maintain a collection of standard and reference samples of humic substances" (ref. i). Up-to-date, this task has been successfully accomplished by the isolation of a number of terrestrial and aquatic fulvic acids (FA) and humic acids (HA) of various nature and origin (ref. 2), which are accessible to researchers worldwide. Unique features of the collection are the carefully chosen and specifically designated source materials, and the carefully controlled and IHSS-supervised, fully documented isolation and purific- ation of FA and HA (ref. 2). Furtherly, the availability of the bulk solid source materials allows the comparison of different extractive methods. One of the major benefits that results from the existence of this collection is the possibility of critically compare the experimental results of humic subst- ances researchers worldwide. The basic characterization of the samples, according 0048-9697/89/$03.50 © 1989 Elsevier Science Publishers B.V.