Several studies have pointed to the potential benefits of riparian vegetation as buffer zones for agricultural and industrial pollutants harmful to aquatic ecosystems. However, other studies have called into question its use as an ecological filter, questioning the widths and conditions for which they are effective as a filter. In this work, we have investigated the buffering capacity of the riparian one to retain pesticides in the water-saturated zone, on 27 sites composed by riparian buffer zones with different vegetation structure (woody, shrubs, or grass vegetation) and width (12, 36, and 60 m). Five pesticides were analyzed. The effectiveness of the filtering was largely influenced by the width and vegetation type of the buffer zone. In general, decreasing pesticide removal followed in this order wood > shrubs > grass. The 60 m woody buffer zone was the most effective in the removal of all the pesticides. Only atrazine was detected in this case (0.3 μg L(-1)). Furthermore, a linear correlation (R (2) > 0.97) was observed in their removal for all compounds and buffer zones studied. Thus, preserving the woody vegetation in the riparian zone is important for watershed management and groundwater quality in the no-tillage system in temperate climate.

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Purpose Riparian zones are identified as mitigation areas of agricultural pollutants to river ecosystems. However, the mitigation mechanisms of these pollutants remain unclear mainly on the effects of different types of riparian vegetation and its organic matter content in the pollutants removal process. This study aims to assess the content of organic matter in soils composed of woody vegetation and grass and its effects on four pesticides adsorption. Adsorption studies were conducted in soil collected in riparian vegetation areas composed of grass and trees under the influence of an agricultural area. Methods The analyses were performed in 21 shakers containing 100 g soil and a L of water previously contaminated with pesticide that were stirred for 30, 60, 120, 240, 360, 720, and 1440 min. A study was made of maximum adsorption capacity using the time 360 min and the concentrations of 5, 20, 40, and 50 μg L −1. Results The soils of woody vegetation areas had a higher concentration of organic matter as compared with grass areas, and time 360 min achieved the highest adsorption capacity with minimum values of 84% adsorption for the area of land made up of trees and 67% for grass areas. The soils of woody vegetation areas had a higher concentration of organic matter as compared with grass areas, time 360 min. Conclusion The best adsorption capacity was obtained with minimal adsorption amounts of 84% to the area of soil composed of 67% for trees and grass areas.