This work aimed to investigate the retention of atrazine and picloram, carried by surface flow, in riparian zones. The surface flow, containing a mixture of both herbicides and kaolin, was then simulated within riparian zones established in pine plantations in north-eastern Georgia, USA. Five plots were established within riparian zones, each with a different slope (2, 5, 10, 15 and 20%). The influence of the initial moisture and of the O horizon condition in herbicide retention was analyzed. An exponential model, commonly used for the estimate of biochemical demand of oxygen (BOD) and nutrients attenuation in overland flow treatment, was used to estimate the attenuation of kaolin and herbicides in riparian zones. The model allowed an accurate estimate of the attenuation of kaolin and atrazine from the surface runoff mixture along 10 m of riparian zone. Generally, slope showed the best correlation with retention of the pollutants presented in the runoff mixture within the riparian zone. The O horizon present in the steeper slopes improved the sedimentation of kaolin and the atrazine adsorption.
surface runoff; streamside vegetation; atrazine; picloram; O horizon
