Qualidade da água de três estuários tropicais expostos a diferentes níveis de urbanização

Resumo

Estuaries are environments of high biological productivity that provide diverse ecosystem services, such as food or shelter. Its water quality is fundamental for the development and maintenance as close as possible to the original ecological standards that guarantee these services. Thus, this study aimed to compare the water quality of three tropical estuaries with different occupation histories and degrees of urbanization. The Goiana, Capibaribe and Jaboatão rivers estuaries are located in Pernambuco State, Brazil. The variables analysed were: water temperature (ºC), pH, dissolved oxygen (mg L-1), oxygen saturation (%), biochemical oxygen demand (mg L-1), turbidity (NTU), colour (Pt / Co), salinity and total phosphorus (mg L-1). All data were obtained from the Pernambuco State Environmental Agency (CPRH) from 2006 to 2009, as part of its water quality monitoring program. The three estuaries, regardless of their conservation status, are under poor water quality conditions, with high levels of total phosphorus (0.18 mg L-1 Brazilian guidelines) and low dissolved oxygen concentrations (entre 0.0 and 6.7 mg L-1, present work). Even with seasonal changes and over the years, oxygen levels are often less than 2.0 mg / L-1 characterizing hypoxia - possibly helped by high water temperatures (24.5 to 30.0 oC). As a general scenario, even with different urban contribution, the three estuaries need attention regarding water quality. Results reflect the lack of basic sanitation in the three basins, regardless of their degree of urbanization. This situation adds to other impacts from the centuries old sugarcane plantations and milling, such as deforestation, fertilizer runoff, soil leaching and other polluting loads.