The research goals were achieved through the application of the

Fig. 8. Spatial and temporal variations of phosphate in the years 2006 and 2011. Axis concentrations expressed on UNC 0631 logarithmic scale.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 9. Spatial variation of phosphate during the spring (a), summer (b), fall (c) and winter (d) in 2006 and 2011.Figure optionsDownload full-size imageDownload as PowerPoint slide
3.2.2. Nitrate
Nitrate concentrations were higher in 2011 than in 2006 (Table 5). The behavior of nitrate variation in 2006 had higher concentration on the northern lagoon area, followed by a decrease in the central region and a slight increase in the estuarine region. For 2011, there was a gradual decrease in nitrate concentration from the northern region of the lagoon; however, from central region to the estuary concentrations remained high during winter and low during the summer.
The differences in nitrate concentration between the two years were more evident in the northern and central region. The highest concentration variations around the annual average concentration occurred near the Camaquã River outlet (represented by São Lourenço station) and the lowest was at the estuarine region in both years; however, in 2006 the variation of nitrate over the year was lower than 2011, and its concentration was extremely low between summer and fall and high between spring and winter. Fig. 10 and Fig. 11 show, respectively, the temporal evolution of nitrate in both years for some points and the spatial variation of nitrate on spring, summer, fall and winter.