BEHAVIOR OF METALS FOLLOWING INTENSIVE PIG SLURRY APPLICATIONS TO A NATURAL FIELD TREATMENT PROCESS IN BRITTANY (FRANCE)

It is well-known that heavy metals brought by intensive pig slurry app lications accumulate in the soil; because of their potential impact on the environment, studying their behaviour is of utmost interest. The Solepur process has been developed in Brittany (France) where pig farm ing causes serious environmental problems, it enables the soil to be u sed as a treatment medium to process pig slurry. Numerous pig slurry a pplications were performed from 1991 to 1995 on an experimental hydrol ogically-isolated field specially equipped to recover all the leachate . These applications approximately corresponded to the amount which mi ght have been spread over one century. The Solepur process can be cons idered as a simulation model for what happens to metals in pig slurry under normal field conditions over a long period of time. This work me asured the concentrations of Cu, Zn, Mn, Co, Fe and Cd in pig slurry, in soil and in drainage water, and the results are discussed. Total co ncentrations and speciation data within the three different compartmen ts were analysed and showed that Cu and Zn accumulate in the surface l ayer, whereas other metals, such as Mn and Co, dissolve and are washed away in the leachate. The increase in the bioavailability and toxicit y of these metals as well as their impact on the environment are discu ssed. (C) 1997 Elsevier Science Ltd.