Objectif
The present project involves a follow up of the collaborative work undertaken within a program funded by INTAS (completed project N° 01-0186). The previous project aimed to establish the humic substances (HS) fractions of soil responsible for the photosensitising properties, and to test the capacity of compost humic-like substances (HLS) to degrade organic probes upon irradiation by solar light. The main objective of the present proposal is a comprehensive investigation (i) on the chemical nature of the main components of HS or HLS which determine the photochemical activity and (ii) on the photosensitising properties of HS and HLS toward herbicides. Various soil HS, their low MS fraction (which was found to be responsible for photodegradation of pesticides), their high and medium MS fractions (which do not possess this property) as well as HLS extracted from various organic wastes compost will be studied using modern biochemical and physical-chemical techniques. We shall also focus on the water-soluble fraction of soils (WFS) or composts (WFC) in view of possible valorisation in the field of pollutants elimination.
Photochemical experiments will be conducted under natural or simulated solar light in order to approach natural conditions. Reactive species will be identified using probe-molecules and scavenging techniques. In addition, we will investigate the photo-degradability of various pesticides to get a full view of photo-degrading properties of different HS samples. Further determination of photo-inductive properties of the most active fractions after removal from them of specific components will be performed. Simultaneously all soils and wastes HS, their fractions, WFS and WFC will be analysed by advanced structural characterization techniques: 3D fluorescence spectroscopy, IR, SERS, differential thermal analyses, pyrolysis/gas chromatography-mass spectrometry, EPR, 13C NMR technique. For comparison, standard techniques (e.g. UV-VIS spectral analysis, elemental composition, etc.) will be used as well.
This complex investigation will help to find out the main HS structural constituents, which possess the best photochemical degradation activity toward pesticides. The data obtained will increase reliability of monitoring and estimation of HS in pesticide-polluted agricultural lands and other terrestrial environments. Composted organic wastes containing HLS with high photo-inductive activity towards pollutants of the environment will be useful for a considerable improvement of wastes management especially in the implementation of the Stockholm Convention on Persistent Organic Pollutants.
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AUBIÈRE
France