ORIGINAL PAPER Fluorescence analysis of humic-like substances extracted from composts: influence of composting time and fractionation C. Richard Æ G. Guyot Æ O. Trubetskaya Æ O. Trubetskoj Æ M. Grigatti Æ L. Cavani Received: 22 May 2007 / Accepted: 15 January 2008 / Published online: 13 February 2008 Ó Springer-Verlag 2008 Abstract Humic-like acids (HLA 0 , HLA 70 , HLA 130 , HLA 730 ) were extracted from composts obtained from sewage sludges and trimmings after 0, 70, 130 and 730 days of composting, respectively. In addition, HLA 130 was fractionated using SEC-PAGE set-up. Fluorescence spectroscopy revealed that HLA 0 was the only sample to contain emission bands characteristic of protein-like com- pounds (k exc /k em : 280/350) and chlorophyll (k exc /k em : 420/ 660). Emission intensities above 400 nm and HIX both varied in the order: HLA 70 [ HLA 130 [ HLA 730 [ HLA 0 and increased as the fraction molecular size decreased. Thus, the formation of long wavelength emitting fluoro- phores during composting is connected to the humification process. These fluorophores are mainly concentrated in the low molecular size fraction obtained by SEC-PAGE fractionation of composts. Keywords Compost humic-like substances Á Composting time Á SEC-PAGE fractionation Á Excitation–emission matrix Introduction The organic wastes composting provides the possibility to supply nutrients and large quantities of organic matter to soil for improving soil physical–chemical and biological properties. However, for a proper and safe use composts need to be better known and characterized. In particular information on chemical modifications during composting would be of great interest. Organic matter from compost is a very complex mixture as that of soil or water. Several techniques are used to achieve compost organic matter characterization but it remains a big challenge. Fluorescence is a non-destructive technique that pro- vides useful information on the emitting compounds. It has been largely applied to dissolved organic matter from soil and water giving samples fingerprints generally function of material origin (Coble 1996; Peuravuori et al. 2002; Chen et al. 2003; Alberts and Takacs 2004). In particular, excitation-emission matrix (EEM) allows a 3-D full description of fluorescence properties of samples. Moreover, fluorescence was proposed as a useful tech- nique for quantifying the humification degree of humic materials postulating that condensed molecules emit at longer wavelength than less condensed molecules. For this purpose several indexes were developed (Zsolnay et al. 1999; Kalbitz et al. 1999; Milori et al. 2002). A com- parison of these indexes on different organic alkaline extracts obtained from diverse materials (humic sub- stances, composted and non-composted materials) was presented (Fuentes et al. 2006). C. Richard (&) Á G. Guyot Laboratoire de Photochimie Mole ´culaire et Macromole ´culaire, UMR No 6505, CNRS, Universite ´ Blaise Pascal, 63177 Aubie `re Cedex, France e-mail: claire.richard@univ-bpclermont.fr O. Trubetskaya Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 142290, Moscow, Pushchino, Russia O. Trubetskoj Institute of Fundamental Problems in Biology, Russian Academy of Sciences, 142290, Moscow, Pushchino, Russia M. Grigatti Á L. Cavani Dip. di Scienze e Tecnologie Agroambientali, Alma Mater Studiorum, Universita ` di Bologna, Viale G. Fanin, 40, 40127 Bologna, Italy 123 Environ Chem Lett (2009) 7:61–65 DOI 10.1007/s10311-008-0136-3