Arisvaldo Vieira Méllo Júnior

Herbicidas no alto Rio Poxim, Sergipe e os riscos de contaminação dos recursos hídricos

Increased agricultural activity in watershed areas has been causing concern over contamination by herbicides in agricultural areas. The problem becomes more important when contamination can affect water for human consumption, as happens with water from the Poxim river, which supplies the city of Aracaju, capital of the State of Sergipe. The aim of this study was to evaluate the risk of contamination by herbicides to both surface and groundwater in the upper sub-basin of the Poxim River, and to detect the presence of the active ingredients Diuron and Ametrine up-river from the sugar-cane plantations. Risk analysis was carried out using criteria from the Environmental Protection Agency (EPA), the GUS index, and the GOSS method. It was observed that several active ingredients are at risk of leaching, demonstrating the importance of monitoring the river to control both the quality of water and the frequency and volume of herbicides used in the region. Based on the results, monitoring was carried out bi-monthly from July 2009 to July 2010 at two sampling points. Water samples were analyzed in the laboratory, where the presence of Diuron and Ametrine was noted. Water quality in the Sub-basin of the Rio Poxim is being influenced by the use of herbicides in the region. There was an increase in herbicide concentration in the surface water during the rainy season, possibly caused by soil runoff.

Impactos da construção da usina hidrelétrica de Sobradinho no regime de vazões no Baixo São Francisco

A regularizacao das vazoes no baixo Rio Sao Francisco e atribuida as barragens construidas ao longo do seu curso. Neste artigo e avaliada a magnitude das alteracoes no regime de vazoes do rio, provocadas pela construcao do reservatorio de Sobradinho utilizando-se curvas de permanencia de cotas e vazoes como ferramenta de analise. O trecho estudado tem extensao de 197 km, desde a estacao de Piranhas,AL, ate a foz do rio no Oceano Atlântico. Foram utilizadas series historicas de cotas e vazoes de quatro estacoes fluviometricas que tiveram suas curvas-chave corrigidas com referencia de nivel IBGE. A construcao de sobradinho causou uma reducao percentual media de 6 a 12% nas cotas maiores (C5) e uma elevacao de 20 a 32% nas cotas menores (C95). Houve reducao de 9% na vazao maxima (Q5) e aumento de 27% na vazao minima (Q95). As vazoes Q5 e Q95 foram de 5.652 e de 1.231 m3 s-1 na estacao de Pao de Acucar para o periodo apos Sobradinho. Os resultados mostram que a regularizacao do regime de vazoes apos a construcao de Sobradinho minimizou os efeitos das grandes cheias nas regioes a jusante mas tambem vem afetando negativamente atividades tradicionais das populacoes ribeirinhas, como a pesca, navegacao e agricultura.