Effet d'apports de composts sur la disponibilité de micropolluants métalliques et organiques dans un sol cultivé

Abstract

The effects at medium term of repeated compost spreading on cultivated soil on the physico-chemical characteristics and biologicalactivity, including soil microflora and earthworm population, have been studied in a field experiment started in 1998. The composts areorganic amendments that increased soil fertility. They brought also small concentrations in heavy metals (HM) and organic micropollutants(Polycyclic aromatic hydrocarbons, PAH). Their repeated applications could disturb the biological functioning of a soil, in relationwith progressive accumulation of pollutants. After 9 years of experimentation, 5 spreading of sludge compost and municipal solid wastecompost have modified physico-chemical characteristics of soil such as pH, organic matter contents… Total Cu and Zn concentrationsin soil also significantly increased. Such evolution was not noticeable for the other HM and PAH. The PAH concentration in soil correspondedto usual concentrations found in cultivated soils. The particulate organic matter [50 μm -5 mm] increased in soil after compostapplication, mainly with sludge compost. The HM and PAH concentrations were larger in this particulate organic matter compared to totalsoil. The fraction of HM extractable with EDTA increased compared to control more than total HM in soil receiving composts. Howeverthe exchangeable fraction of HM (< 1 % total HM) was mitigated by the effect of compost on soil pH. The effects of compost applicationon microflora and earthworm population are presented in other papers of the present journal.