Co-Authors:
Jacobsen, C.S., Geological Survey of Denmark and Greenland, GEUS, Department of Geochemistry, Thoravej 8, 2400 Copenhagen NV, Denmark
Shapir, N., Geological Survey of Denmark and Greenland, GEUS, Department of Geochemistry, Thoravej 8, 2400 Copenhagen NV, Denmark, Volcani Center, Bet Dagan, Israel
Jensen, L.O., Geological Survey of Denmark and Greenland, GEUS, Department of Geochemistry, Thoravej 8, 2400 Copenhagen NV, Denmark
Jensen, E.H., Danish EPA, Copenhagen, Denmark
Juhler, R.K., Geological Survey of Denmark and Greenland, GEUS, Department of Geochemistry, Thoravej 8, 2400 Copenhagen NV, Denmark
Streibig, J.C., Royal Agricultural and Veterinary University, Copenhagen, Denmark
Mandelbaum, R.T., Volcani Center, Bet Dagan, Israel
Helweg, A., Danish Institute of Agricultural Sciences, Flakkebjerg, Denmark
Abstract:
The bioavailability of atrazine was evaluated in a Danish soil profile (Drengsted) using a combination of soil sorption, transport and mineralisation methods as well as inoculation using Pseudomonas ADP. Sorption of atrazine decreased markedly with depth as indicated by Kd values of 5.2 1 kg-1 for the upper soil and 0.1 1 kg-1 for the subsoils. The transport of atrazine was evaluated using soil TLC plates and the resulting Rf values were 0.1 for the upper soil and 0.9 for the subsoil. Only a relatively small amount of atrazine leached through undisturbed soil columns taken from the upper 60 cm. Inoculating with Pseudomonas strain ADP (1×106 CFU g-1 dry weight soil) revealed that the degradation of 0.01 ppm atrazine was fully completed (80% mineralisation) within 10 days in the subsoil, while it reached less than 15% in the upper soil. Over a period of 500 days, a total mineralisation of 37% of added atrazine in the upper soil was found (2 mg kg-1 incubated at 20° C). However, in the subsurface soil where 0.02 mg kg-1 of atrazine was incubated at 10°C, the degradation was slower, only reaching about 12%. Terbuthylazine mineralisation was found to be temperature-dependent and low (less than 5%) in the upper soil and very much lower in the subsoil. Desethylterbuthylazine was the most frequently found metabolite. Finally, Pseudomonas strain ADP inoculated into soils from different depths increased the mineralisation of terbuthylazine dramatically. Modelling using a "two-compartment model" indicated that desorption of terbuthylazine is the limiting step for its mineralisation.