Soil and organic wastes: transformation of olive oil mill waste water and clay particle aggregation

This study investigated organic transformations, aggregate formation and their stability in water, in two different clays (kaolinite and montmorillonite) incubated with fresh olive mill wastes (OW). Clays and OW were incubated for 90 days and subjected to wetting and drying cycles. The organic matter transformations was characterized by solid state CP/MAS NMR spectroscopy. Aggregation was assessed on selected sizes of clay aggregates obtained after incubation by pore size distribution (Hg intrusion + N2 adsorption techniques) and by aggregate stability in water measurements. Organic matter from incubated OW clay samples of both clay types has shown enrichment of alkyl groups and decrease of O-alkyl. Incubation of OW with kaolinite promoted an increase of aggregation and aggregate stability in water. The mineralogy of clays can substantially influence both the transformation of organic matter and the aggregation processes that, in turn, could affect the amendment properties of OW applied to soils.