Assessing the spatial and temporal water quality in the sub-basin of the Poxim river, Sergipe state, Brazil

The dynamics of the land use and cover in the Poxim river basin, in Sergipe, Brazil, is a determinant factor for reducing the superficial water quality. This study aimed to identify aspects of water quality related to the land use and cover in four different monitoring stations, in the rainy and dry season. The monitored parameters were pH, DO, BOD, COD, turbidity, total dissolved solids (TDS), total phosphorus, ammonia, nitrite and nitrate, between July 2009 and June 2010. Water samples were collected at four monitoring stations (E1, in the Poxim-Mirim River; E2, in the Poxim-Acu River; E3, in the main river, near the confluence of the two tributaries; and E4, at the Sanitation Company of Sergipe State water supply intake) and analyzed at the Laboratory of Analytical Chemistry of the Federal University of Sergipe State. The results were compared with Brazilian standards for fresh water quality (Class 2), according to CONAMA Resolution no 357/2005. BOD and COD showed a higher input of organic matter in the monitoring station E3. OD values were critical in all four stations. The nutrients nitrogen and phosphorus had higher concentrations at stations E1 and E2 (upper basin, with agricultural practices). In the lower basin, there is a considerable deterioration of water quality, possibly due to the urbanization process. The studied parameters indicate the low quality of water in the Poxim River basin and the need to adopt appropriate mitigation measures.