Contribution à la connaissance des sources et de la dynamique des quelques polluants prioritaires organiques dans l'écosystème sol
The aim of the present work is to study the sources and the dynamics of several organic priority pollutants in the soil's ecosystem. The principal organic pollutants studied are the polycyclic aromatic hydrocarbons (PAH) and the polychlorinated biphenyls (PCB). The PAHs contain carcinogenic substances and have a natural as well as an anthropogenic origin. They are produced, among others, by incomplete burning of fossil fuels or all other types of organic substances. PCBs are strong enzymatic inducing agents. They have a purely anthropogenic origin and are used mainly as dielectric fluids in electric transformers. The first chapter of this work gives some information about the production mechanisms, the sources and the toxicity of PAHs and PCBs. Their degradation pathways in the soil ecosystem are also discussed. The second chapter is based on the realization of total, 3 dimensional fluorescence figures of samples which contain PAHs. The program which is used was initially created for geodetic and photogrammetric purposes. The third chapter studies the inputs of organic micropollutants in agricultural soils. One of the most important PAH and PCB sources in soil ecosystems are atmospheric precipitations. The influence of sewage sludge spreading and the use of animal manure and mineral fertilizers in the contamination of soils by PAHs and PCBs are also investigated. The fourth chapter deals with the impact of PAHs on soil micro-organisms. Two respirometric tests are used to show the determinant effect which the soil structure plays in relation to the availability of PAHs on the activity of micro-organisms. The fifth chapter deals with the transfer of PAHs from the soil to earthworm tissues. By means of mass-spectrometry, modifications of the proportions of pollutants are shown in the earthworm tissues as opposed to that of the soil in which they live. The last chapter underlines the most important results of this work and draws the conclusions.