| Popis: |
Five pesticides, atrazine, diazinon, hexazinone, procymidone, and terbuthylazine, were applied to a Kiripaka bouldery clay loam located near Whangarei, Northland, New Zealand, and a Himatangi sand located near Palmerston North, Manawatu, along with bromide and deuterated water as tracers. Their transport and persistence were monitored for 18 months using soil sampling down to a maximum of 1 m and 8 suction cups at each site located between 0.2 and 1.5 m down the profile. There was rapid leaching of the tracers as well as hexazinone at both sites. Procymidone was much less mobile than the tracers but was very persistent, with significant amounts still present in the profile after 18 months. Atrazine, terbuthylazine, and diazinon had relatively low persistence, mainly due to rapid degradation, and possibly volatilisation for diazinon, with < 10% remaining after 6 months at both sites. There was evidence of preferential flow at the Northland site, which is consistent with the highly structured soil profile and intense rainfall that occurred at the site in the month following pesticide application. Batch sorption experiments measured lower Koc values for the topsoil samples than generally observed in the literature for all 5 pesticides. This indicates that these pesticides will be much more mobile in the Northland Kiripaka soil and slightly more mobile in the Manawatu Himatangi soil than would be expected from the literature values. |
