Valorización de la efectividad de vermicomposts de residuos vitivinícolas y oleícolas en el control de plaquicidas en suelos

Resumo

The propose of the present work is to look for new alternatives to re-use organic wastes from winery, distillery and olive oil industries as organic amendments of agricultural soils to control the behaviour of pesticides in the environment. In some cases, the direct application of these wastes to soils is forbidden. To develop our objective, was therefore necessary to stabilize the organic matter. We designed different vermicomposting processes with the main wastes from these agricultural industries (vine-shoot, spentgrape marc, biosolid vinasse and alperujo or wet olive cake). To carry out this objective, several soil processes that take place after the application of pesticides were studied in unamended and amended soils. Preliminary investigations were carried out with the different wastes selected to evaluate their pesticides sorption capability with different chemical character. Four types of organic wastes samples consisting on unmixed or mixed wastes, vermicomposted or not vermicomposted, were tested as sorbents of anionic and no-ionic pesticides. The organic wastes samples were: spent grape marc, spent grape marc mixed with lees cake (ratio 1:1), biosolid vinasse mixed with vine shoots (ratio 2:1) and alperujo mixed with manure (ratio 4:1). The pesticides were four herbicides (sulfuron-methyl, metsulfuron-methyl, flazasulfuron and diuron) and one insecticide (imidacloprid). The vermicomposing process was more effective in the organic sample with low lignin content. The vermicomposted or not vermicomposted organic wastes showed a significant good sorption capacity of diuron and imidacloprid, but very light for anionic pesticides. The sorption constants of imidacloprid and diuron were no related with the humification degree of these organic wastes samples either with their organic carbon (OC) contents. The retention was mainly correlated with the lignins contents. The sorption kinetics of diuron and imidacloprid were determined in eight different soils with low organic carbon content. Sorption kinetic parameters were worked out from three of the four kinetic models selected: Pseudosecond order kinetic reaction, Elovich equation and Weber-Morris model. The pseudosecond order kinetic function closely conform the experimental kinetics. Imidacloprid sorption was less time-dependent than diuron but in both cases an apparent equilibrium was reached within 6 h. The sorption of imidacloprid correlated with silt and sand content and the cation exchange capacity, these properties are usually masked in soils with higher OC content. Diuron did not correlate any property; however, it was more sorbed than imidacloprid. Elovich equation fit to most of the experimental kinetics of soil samples describing two sorption steps. The Weber and Morris model showed an important boundary layer effect for diuron and pointed out that the partition of this molecule has also a major influence on the initial sorption stage. Sorption kinetics took place throughout different mechanisms related mainly to the chemical character of these pesticides.