a b s t r a c tRiparian buffer zones have the potential to capture chemical contaminants and to mitigate detrimental side-effects in aquatic ecosystems derived from excess fertilizers used in agro-food production. No-till farming systems are well known agricultural practices and are widely used in temperate areas. In that regard, different settings and widths of riparian buffer zones (12, 24, 36, 48 and 60 m) with woody vegetation, shrubs or grasses were assessed. The methodology was comprised of the evaluation of a large number of experimental sites and the sampling was conducted after the first rain period and respective fertilizer applications. The results point to the fact that effectiveness is largely controlled by buffer zone width and vegetation type. Indeed, buffer zones with 60 m width composed of woody soils were more effective in phosphorus (99.9%) and nitrogen (99.9%) removal when compared to shrub (66.4% and 83.9%, respectively) or grass vegetation (52.9% and 61.6%, respectively) areas. Woody vegetation has deep rooting systems and woody soils have a higher content of organic matter when compared to grass and shrubs areas.

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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