Colloid transfer by subsurface drainage.

During the drainage season, significant quantities of suspended matter can be exported from a drain collector. Their nature has been determined with a methodology linking chemical analysis, X-ray diffraction, and electronic m icroscopy associated with image analysis. The majority of these particles a re smaller than 200 nm. They are composed of 2:1 phyllosilicates and iron p articles usually in amorphous form. Cs-137, phosphorus and organic matter c learly demonstrate the superficial origin of these particles. Drainage modi fies natural leaching of soil by exporting definitively particles from the soil profile. (C) 2000 Academie des sciences/Editions scientifiques et medi cales Elsevier SAS.