CONCENTRAÇÕES E FORMAS DE FÓSFORO NA ÁGUA E SEDIMENTO DE RESERVATÓRIOS DE ABASTECIMENTO PÚBLICO NA BACIA DO RIO MAMANGUAPE, PARAÍBA, BRASIL.

Abstract

Eutrophication of anthropogenic or natural origin occurs due to the accumulation of nutrients such as phosphorus (P) and nitrogen (N), because in the excess they increase the number or excessive growth of aquatic plants and the flowering of toxic algae, with serious damages for multiple uses , with major global impacts on nature. Phosphorus is one of the most relevant elements in the establishment of the eutrophication process, reaching the aquatic environment through the launch of domestic effluents, industrial activities and transport of fertilizers from agricultural areas. The objective of this work was to evaluate the phosphorus content in the water and sediment of two reservoirs of public supply, in the Mamanguape River Basin, Paraíba, Brazil. Where the experiment was conducted, water and sediment samples were collected over a period of 12 months. The analyzed variables were pH, electrical conductivity, temperature and transparency were performed "in situ". In the laboratory, total phosphorus, orthophosphate in water and fractionation of phosphorus forms in the sediment were determined. The transparency and pH of the water were influenced by seasonality, evidencing the importance of this agent in the water quality dynamics. In the water the values of P-Total ranged from 23.01 μg / L in Mazagão I to 25.95 μg / L in Mazagão II, and P-Ort values of 7.26 μg / L μg / in Mazagão I for 7,84 in Mazagão II, where in most of the months, the reservoirs presented as oligotrophic, with low values of P-total and orthophosphate in the water, however, relatively high values were found in months of the dry period, where they were classified as as eutrophic. The values of P-total in the sediment varied between 1521.97 mg kg-1 and 4806.72 mg kg-1, high values and that reflect the great phosphorus load present in these environments. Fractionation indicated a predominance of P-inorganic, with values between 1434.14 mg kg-1 and 4298.79 mg kg-1, although a good part was in Apatítica form. On the other hand, the non-Apatitic fraction, potentially available for the water column, was influenced by the low pH values in the sediment, which favors its adsorption to iron and aluminum, so the lower the pH, the more acidic the sediment. In general, the results indicated a potential natural control in the release of phosphorus from the sediment, as well as its precipitation of the water column and immobilization in the sediment.