Transport and transformation of 14C-terbuthylazine in subsurface gravel under saturated and unsaturated water flowing conditions

14C-Terbuthylazine was applied to subsurface gravel in laboratory columns at a rate corresponding to 0.67 kg/ha, and in an outdoor lysimeter at a rate corresponding to 0.30 kg/ha. In the columns, the transport was investigated both under saturated and unsaturated water flowing conditions, and in the lysimeter, under unsaturated conditions only. The retardation factor was smaller under saturated (Rf = 2.4) than under unsaturated (Rf = 5.1) conditions whereas recoveries decreased in the order saturated column (W = 59.7%) > unsaturated column (W = 31.7%) > lysimeter (W = 15.4%). Deethylterbuthylazine was formed during the transport and exhibited a lower retardation factor than terbuthylazine.