International audience

International audience

International audience

peer reviewed | The effects of chronically enhanced (NH(4))(2)SO(4) deposition on ion concentrations in soil solution and ionic fluxes were investigated in a Picea abies plot at Grizedale forest, NW England. Soil cores closed at the base and containing a ceramic suction cup sampler were 'roofed' and watered every 2 weeks with bulk throughfall collected in the field. Treatments consisted of the inclusion of living roots from mature trees in the lysimeters and increasing (NH(4))(2)SO(4) deposition (NS treatment) to ambient + 75 kg N ha(-1) a(-1). Rainfall, throughfall and soil solutions were collected every 2 weeks during 18 months, and analysed for major cations and anions. NO(3)(-) fluxes significantly increased following NS treatment, and were balanced by increased Al(3+) losses. Increased SO(4)(2-) concentrations played a minor role in controlling soil solution cation concentrations. The soil exchange complex was dominated by Al and, during the experimental period, cores of all treatments 'switched' from Ca(2+) to Al(3+) leaching, leading to mean [Formula: see text] molar ratios in soil solution of NS treated cores of 0.24. The experiment confirmed that the most sensitive soils to acidification (through deposition or changing environmental conditions) are those with low base saturation, and with a pH in the lower Ca, or Al buffer ranges.

[Departement_IRSTEA]EEE [TR1_IRSTEA]E33-Maîtrise et gestion des déchets | International audience | It is well-known that heavy metals brought by intensive pig slurry applications 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 farming causes serious environmental problems ; it enables the soil to be used as a treatment medium to process pig slurry. Numerous pig slurry applications were performed from 1991 to 1995 on an experimental hydrologically-isolated field specially equipped to recover all the leachate. These applications approximately corresponded to the amount which might have been spread over one century. The Solepur process can be considered as a simulation model for what happens to metals in pig slurry under normal field conditions over a long period of time. This work measured the concentrations of Cu, Zn, Mn, Co, Fe, Cd in pig slurry, in soil and in drainage water, and the results are discussed. Total concentrations and specification data within the three different compartments were analysed and showed that Cu and Zn accumulate in the surface layer, whereas other metals, such as Mn and Co, dissolve and are washed away in the leachate. The increase in the bioavailability and toxicity of these metals as well as their impact on the environment are discussed. | Il est bien connu que les métaux-lourds apportés par des épandages intensifs de lisier de porc s'accumulent dans le sol ; l'étude de leur comportement est donc de la plus haute importance étant donné leur impact potentiel sur l'environnement. Le procédé Solépur a été développé en Bretagne (France), où l'élevage porcin engendre de sérieux problèmes environnementaux ; ce procédé utilise le sol comme un intermédiaire épuratif dans le traitement du lisier de porc. Des épandages répétés de lisier, correspondant approximativement à un siècle d'épandage, ont été réalisés de 1991 à 1995 sur un champ expérimental isolé et équipé de façon à récolter totalement l'eau de drainage. Cette étude est consacrée à la mesure des concentrations de Cu, Zn, Mn, Co, Fe et Cd dans le lisier de porc, le sol et l'eau de drainage. Les concentrations totales et celles résultant de la spéciation chimique sont analysées dans ces trois compartiments et permettent de montrer que certains métaux (Cu et Zn) s'accumulent dans la couche de surface, alors que d'autres (Co et Mn) sont lessivés. L'accroissement de leur toxicité et de leur biodisponibilité ainsi que leur impact sur l'environnement sont également discutés.