Abstract
Sao Paulo State is the main sugar cane producer and these agricultural activities are carried out in predominantly sandy soils, which require large amounts of phosphate fertilizers and amendments. This work evaluated the fertilizer-effect on the Al, Ba, Fe, Mn and Ni released in a watershed with influence of sugar cane crops in the Sao Paulo State, Brazil, namely the Monjolo Grande Stream basin. Five surface water sampling campaigns were carried out at the mouth of Monjolo Grande Stream in February, April, June, September and November 2010, characterizing the following parameters: discharge, pH, temperature, electric conductivity, dissolved oxygen and total and dissolved concentrations of Al, Ba, Fe, Mn and Ni. Approximately 99% of Al and Fe are transported annually in association with suspended sediments carried to the Monjolo Grande Stream by sheet erosion. The results also demonstrated that the increasing Al, Ba, Fe and Mn concentrations dissolved in the waters of the Monjolo Grande Stream basin in the wet season are associated to phosphate fertilizers and amendments that are used extensively in agrichemical activities. However, with the current application rates, there has been no increase in the dissolved concentrations of these metals at levels that could pose risks to human health.
Highlights
Over the past centuries, Brazil’s Southeast and Midwest regions have undergone various environmental impacts associated with land use changes, mainly due to the removal of natural vegetation of the Cerrado region for agropastoral activities and coffee cultivation in the nineteenth century
This work evaluated the fertilizer-effect on the Al, Ba, Fe, Mn and Ni released in a watershed with influence of sugar cane crops in the São Paulo State, Brazil, namely the Monjolo Grande Stream basin
The results demonstrated that the increasing Al, Ba, Fe and Mn concentrations dissolved in the waters of the Monjolo Grande Stream basin in the wet season are associated to phosphate fertilizers and amendments that are used extensively in agrichemical activities
Summary
Brazil’s Southeast and Midwest regions have undergone various environmental impacts associated with land use changes, mainly due to the removal of natural vegetation of the Cerrado region for agropastoral activities and coffee cultivation in the nineteenth century. The sugar cane crops require large amounts of phosphate fertilizer applications (NPK-5:25:25) and amendments, such as KCl, limestone and phosphogypsum. These materials are water soluble and, can result in several metal leaching processes (i.e. Al, Ba, Fe, Mn and Ni) [3], including radioactive elements [4], in the surface waters from a watershed. Another adverse effect of sugar cane crops is the increased of the sediment transport to watercourses, causing their sedimentation. The changes in aquatic systems linked to sugar cane crops have an anthropogenic impact on these environmental systems, promoting different effects at different biological, economic, social and public health levels
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