ABSTRACT
ABSTRACT Water availability restrictions are already a reality in several countries. This issue is likely to worsen due to climate change, predicted for the upcoming decades. This study aims to estimate the impacts of climate change on groundwater system in the Guarani Aquifer outcrop zone. Global Climate Models (GCM) outputs were used as inputs to a water balance model, which produced recharge estimates for the groundwater model. Recharge was estimated across different land use types considering a control period from 2004 to 2014, and a future period from 2081 to 2099. Major changes in monthly rainfall means are expected to take place in dry seasons. Most of the analysed scenarios predict increase of more than 2 ºC in monthly mean temperatures. Comparing the control and future runs, our results showed a mean recharge change among scenarios that ranged from ~-80 to ~+60%, depending on the land use type. As a result of such decrease in recharge rates, the response given by the groundwater model indicates a lowering of the water table under most scenarios.
ABSTRACT
O cultivo da cana-de-açúcar exige a utilização de herbicidas, destacando-se o Diuron e a Hexazinona. Alguns dos poços de abastecimento de Ribeirão Preto (SP) construídos no Aquífero Guarani estão situados em pontos de recarga, e a presença de solo de textura arenosa nessas áreas aumenta a vulnerabilidade da água subterrânea à contaminação por herbicidas. Neste trabalho foram monitorados alguns poços localizados na área de recarga e estudou-se a remoção de Diuron e Hexazinona por meio da adsorção em carvão ativado granular (CAG) e da pré-oxidação com cloro e dióxido de cloro em uma instalação piloto de escoamento contínuo. Verificou-se que o tempo de saturação do CAG no ensaio com a pré-oxidação foi inferior ao obtido no ensaio sem a pré-oxidação com ambos os oxidantes, possivelmente pela formação de subprodutos que competiram com a adsorção dos herbicidas.
The cultivation of sugarcane demands the use of herbicides such as Diuron and Hexazinone. Some supply wells from Ribeirão Preto, SP, Brazil, built in the Guarani Aquifer are located in recharge points, and the presence of sandy Quartzarenic Neosol in these areas increases the vulnerability of the groundwater to contamination from herbicides This paper reports the water quality monitored in some wells located in the recharge area and the removal of Diuron and Hexazinone by means of adsorption in granular activated carbon (GAC), preceded or not by preoxidation with chlorine and chlorine dioxide in a pilot plant. The results indicated that Diuron was more strongly adsorbed than Hexazinone and that the saturation time of the GAC in the test with preoxidation was shorter than in the test without preoxidation, which may have occurred mainly due to the formation of by-products that competed with the adsorption of the herbicides.