|
(20-05) Mass balance of diuron and linuron in an agricultural ecosystem simulated with a field lysimeter experiment. Guzzella, L.*,1, Rullo, S.1, Capri, E.2, Ferrari, F.2, Nazzari, M.3, 1 IRSA-CNR, Brugherio, Milan, Italy2 Università di Piacenza, Italy3 Università "La Sapienza", Roma, Italy ABSTRACT- Field experiments with "in situ" lysimeters aimed at evaluating the impact of weathered herbicides on the aquatic environment were performed. The behaviour of herbicides in water, soil and living organisms (worms) was studied and related to parameters regulating the various processes occurring in the agricultural and forestal ecosystem. The following processes were considered: adsorption and interactions of target compounds with both inorganic and organic soil components; transportation of the target compounds by airborne soil particles; biotic/abiotic degradation rate of target compounds in soil and water; bioaccumulation of herbicides in worms. The experimental research was undertaken by the installation of ten soil columns (20 and 40 cm of depth) isolated from the field with artificial border and equipped with water drainage bottom. The experimental field was located in Monza (MI), on the basis of the soil pedological and hydrological characteristics. After application to soil of two phenylurea herbicides, i.e. linuron and diuron, on June 2001, both soil and water samples were collected and analysed to determine residual concentrations of herbicide and related TPs, in order to verify the persistence and leaching capacity of the above herbicides in different soil horizons. Natural pluviometric conditions were followed in order to verify the groundwater vulnerability. Air volatilisation and herbicide drift during the application were also determined. A laboratory-acclimated worm population was used for bioaccumulation studies in order to verify the potential uptake of soil living organisms. An appropriate aliquot of worms was added to the soil monoliths before the herbicide application and successively analysed to determine the herbicide and their TPs contents. The results showed that 65% of diuron and 27% of linuron was lost due to the herbicide drift during the application. Herbicide recovery in the water lysimeters averaged to 0.08% for diuron and to 0.07% to linuron, as compared to the herbicide amounts that reached the agricultural soil. No volatilisation and bioaccumulation effects was observed for both the herbicides. A 80-90 day half-life time in soil samples was estimated for both the herbicides. Key words: lysimeter, linuron, diuron, aquifer |
