Avaliação das frações de fosfato como indicadores de eutrofízação de águas superficiais

Abstract

This work consists of two chapters. In the first, it was aimed to evaluate the leveis of P in surface waters in several situations ofsoil use and management on Coastal Plains on the State ofEspírito Santo. This was done in order to obtain a diagnostic about the potential problem ofeutrophicationwith P in water bodies, and to assess which soil uses are responsible for it, if it exists. The study was done at Aracruz-ES, particularly, but not exclusively, on the Pilot Whatershed of Aracruz Celulose Inc. Three sampling sites within the watershed and six outside were chosen. Sampling was performed in the dry seasons of2003 and 2004 and in the rainy seasons of 2004 and 2005. The leveis ofP in the following forms were assessed: soluble orthophosphate (OPS), total orthophosphate (OPT), total soluble P (PST), total P (PT), total particulate P (PPT), soluble non-reactive P (PNRS), non-reactive particulate P (PNRP), and total particulate orthophosphate (OPP). The pH, electrolytic conductivity, Ca, Mg,Na, K, NOJ , NHJ, and NO2 were also evaluated. The results obtained in ali agricultural sites showed no evidences ofartificial eutrophication. High contents of P were observed at some sites, but are caused probably due to decomposition of natural existing organic matter. The exception are the urban stretches ofrivers, which are under anthropic eutrophication. Even those, nevertheless, show great variability as the leveis ofP are comparable to natural ones during part ofthe year. In the second chapter, the objective ofthe study was to evaluate the presence of P in water bodies at the Campus ofthe Federal University ofLavras to verify the presence ofeutrophication. Eight artificial lakes were chosen, representing the conditions ofsoil use and management. The samplings were accomplished monthly starting on Aug/2003 up to Dec/2004. The leveis of P were quantified and water characterization analysis were performed. The values of OPS were at ali times below those allowed by the CONAMA 357/05 Resolution Nevertheless, other fractions of P presented high contents, reflecting the soil conditions under rainfall. Episodes ofhigh P contents were momentary. In general, these water bodies may be considered ofexcellent quality conceraing the presence ofP. Soil management on the Campus and the treatment applied to effluents and waste waters appearsto be adequate regarding P.