Monitoring the water quality Formoso river of the Amazon Region – Brazil using principal component analysis

Abstract

The expansion of the agricultural frontier poses a major threat to the quality of water bodies and conservation and biodiversity of biomes. In the Tocantins-Araguaia, hydrographic region is located the largest irrigated flood type rice project in the world, and in the inter-harvest period, the area is still used for soybean production. Considering the great economic, environmental and social importance of the area, the objective of this study was to evaluate the water quality Considering the great economic, environmental and social importance of the area, the objective of this study was to evaluate the water quality of a river in the Amazon Region, Brazil, and to identify the critical pollution sites in the area of influence of the agricultural project. The monitoring occurred between April 2018 and February 2019, during periods of drought and drought. The water quality was evaluated based on the determination of 34 physical-chemical and 2 microbiological parameters. The comparison of the values obtained with the limits allowed by the legislation for class II waters pointed out samples with high total phosphorus values, which can lead to eutrophication phenomena, concentrations above the expected of metals such as Fe, Cu, and Mn and samples with low percentage of dissolved oxygen. The main component analysis (PCA) showed little variation along the river, i.e., homogeneity in the different points evaluated in the same collection; however, the comparison between collections with different seasonalities revealed quite divergent results, reinforcing that seasonal variations can aggravate the changes in the water quality of the river.