title: Key role of the low molecular size fraction of soil humic acids for fluorescence and photoinductive activity.
abstract: The IHSS soil humic acid (HA) standard and two HAs from soils of very different origin (Chernozem and Ranker) were fractionated by tandem size-exclusion chromatography-polyacrylamide gel electrophoresis. From each HA, three fractions with different molecular sizes (MSs) and electrophoretic mobilities were obtained and investigated for their fluorescence properties and abilityto photoinduce the transformation of 2,4,6-trimethylphenol and herbicide fenuron. Regardless of the source of the HA, the two high MS fractions were found to be very weakly fluorescent. They photoinduced the degradations of fenuron and 2,4,6-trimethylphenol less efficiently than the bulk HA (10-50-fold and 1.4-5.3-fold, respectively). In contrast, the low MS fraction was proved to be fluorescent and to photoinduce the transformation of probes as least as efficiently than the bulk HA. These results show that (i) most of fluorophores and a great part of photoinductive chromophores are located in the low MS fractions of soil HAs and (ii) this distribution of photochemically active constituents may be characteristic across broad soil types.
authors.affiliation: Laboratoire de Photochimie Moléculaire et Macromoléculaire, UMR CNRS- Université Blaise Pascal 6505, 63177 Aubière Cedex, France. claire.richard@univ-bpclermont.fr
authors.forename: C
authors.initials: C
authors.lastname: Richard
authors.forename: O
authors.initials: O
authors.lastname: Trubetskaya
authors.forename: O
authors.initials: O
authors.lastname: Trubetskoj
authors.forename: O
authors.initials: O
authors.lastname: Reznikova
authors.forename: G
authors.initials: G
authors.lastname: Afanas'eva
authors.forename: J P
authors.initials: JP
authors.lastname: Aguer
authors.forename: G
authors.initials: G
authors.lastname: Guyot
mesh_terms: D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004784:Environmental Monitoring; D005453:Fluorescence; D006540:Herbicides / Q000032:analysis; D006812:Humic Substances / Q000032:analysis*; D008970:Molecular Weight; D010636:Phenols / Q000032:analysis; D010671:Phenylurea Compounds / Q000032:analysis; D010777:Photochemistry; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D006540:Herbicides; D006812:Humic Substances; D010636:Phenols; D010671:Phenylurea Compounds; D012989:Soil Pollutants; C010727:fenuron