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Soil profiles near watercourses that drain rural areas with agricultural lands and pastures, as well as recreational zones and densely populated industrial centers, are directly influenced by human activities. Therefore, these soils condition the contamination dynamics of the aforementioned watercourses in a remarkable way. The present study deals with soils belonging to a first order subbasin. Pedons representative of positive areas located in slopes (B) and of alkaline sites close to the alluvial plane (T) were selected as study sites. In both cases, the land is used for extensive farming. Composite samples of the upper 5 cm of both soil types were treated either with vermicompost or phosphate fertilizer to study the effect of the addition of these elements on the runoff dynamics of heavy metals. Experiments using a rainfall simulator that formed drops on runoff microplots containing soil samples were carried out under laboratory conditions. The runoff obtained was analyzed for lead (Pb), zinc (Zn), cadmium (Cd), and nickel (Ni), both dissolved and particulate, following the Community Bureau of Reference (BCR) adaptation of the sequential extraction procedure. From these results, it was concluded that the use of high amounts of organic amendment produced important effects on the surface condition of the soils that determine a highly significant reduction in the delivery of suspended solids to watercourses. Amendments, however, may release heavy metals that flow through runoff avenues either as particulate or dissolved forms. Most of the heavy metal concentration is

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Soil erosion is a global concern because of its consequences for the environment and the economy of countries. In the Argentine Pampas Region, soil erosion process is a priority issue, although there is little information about sediment concentration (SC) in agricultural catchments. The study aimed at assessing the factors that have a major influence on SC and discussing the dynamics of hydrological and sedimentological connectivity during 2012, a year with precipitation over the mean and significant erosive events. The study was conducted in a watershed of Buenos Aires province, Argentina. A linear regression model, that considered autocorrelation, was obtained. Maximum rainfall intensity in 30 minutes and peak flow were related to SC. An analysis of satellite images was carried out to discuss the hydrological connectivity, and a connectivity index was calculated to assess changes in sedimentological connectivity. The analyses suggested increments in hydrological and sedimentological connectivity, associated with the drainage area expansion and with water erosion rills. Hydrological connectivity is needed for sedimentological connectivity. However, increments in sedimentological connectivity may have been conditioned by the input of energy to detach and to transport particles. This may have been evidenced when flows exceeded a threshold runoff coefficient.