Sorção e liberação de fósforo em sedimento de fundo do Rio Coxipó-MT

Abstract

One of the environmental problems that is causing most concern is the decrease of drinking water as a result of pollution due to human activities. Among the potential pollutants, phosphorus, despite being a natural nutrient water, is present in some sources of contamination, raising concern about the risk of eutrophication of rivers and lakes. Coxipó River is one of the leading affluents of the Cuiaba River that plays an important role in the state of Mato Grosso regarding its water and land use. To evaluate the sorption, release and phosphorus forms in bottom sediment, sediment samples were collected in Coxipó-MT River upstream (P1) and downstream (P2) of the city of Cuiaba. The sediment samples were characterized chemically and granulometrically, and subsequently the fractionation and phosphorus sorption test were carried out. The chemical and particle size characterization showed a difference between the sediment samples mainly in the content of available phosphorus, showing the anthropic influence on their composition. The study of phosphorus fractionation showed that P-Org is the most frequently phosphorus form found in both study points, P1 (11.6 mg kg-1) and P2 (38.5 mg kg-1). Due to the large presence of limestone in the formation of this watershed, the Ca-P was the main inorganic fraction with values of 5.7 and 33.0 mg kg-1 for P1 and P2, respectively. The sorption test showed that both sediment samples present capacity of phosphorus retention, with maximum sorption of 27.78 mg kg-1 for P1 and 166.7 mg kg-1 for P2, according to the Langmuir equation model that best described the phosphorus sorption (r2 = 0.898 and 0.973). There was no influence of pH on phosphorus release by sediment and both had capacity to assist in the removal of phosphorus from the water column, depurating the river water before its encounter with Cuiaba River.