Características geoquímicas do fósforo e suas especiações químicas nos sedimentos do furo do Muriá (região amazônica, Brasil).

Abstract

The Furo of Muriá is inserted in the Hydrographic Region of western northeast Atlantic Basin. The study area is a "hole" (“Furo”), a local expression to define a channel or hydrographic accident connecting lakes, or connecting a river to a lake or a river to itself, and in the latter case, out of the alluvial plain. The importance of estuaries such as the Furo of Muriá is in these environments have a great usefulness for society, as much in economic activities like fishing and navigation, as recreational. Among the nutrients carried to the estuaries, phosphorus is an element associated with organic matter that has great adsorption potential in the sediments of the estuarine zones. In this sense, the objective of this study is to determine the spatial and seasonal distribution of concentrations of non-apatite inorganic phosphorus (PINA), apatite phosphorus phosphorus (PO), total phosphorus (AP), inorganic phosphorus (PO), organic of the organic matter and granulometry in the surface sediments of the Furo Muriá estuary in the municipality of Curuçá in order to evaluate the distribution of these environmental variables in the study area and to identify if this sedimentary environment represents a potential deposit of phosphorus for the region. The sediment samples were collected using an Ekman-Birge dredger at fourteen points of the Furo Muriá in the months of March, June, September and December of 2015. Fourteen samples were collected each month, one for each point, totaling 56 samples. In the laboratory, the samples were processed in triplicates and the results expressed in μg.g-1 of phosphorus, where the organic matter content (OM) was obtained by gravimetry, the phosphorus species by Wiliams (1976) method, Total Phosphorus by the sum of all fractions, and granulometry by Suguio (1973) classic method. The phosphorus concentrations ranged from 164.54 to 280.32 μg.g-1 for NAIP, 63.02 to 102.80 μg.g-1 for AP, 227.21 to 378.61 μg.g-1 for IP, 30.33 to 135.88 μg.g-1 for OP and 257.54 to 507.73 μg.g-1 for TP, where 88% TP is composed by IP. Statistical results showed that seasonality was not a preponderant factor influencing phosphorus concentrations. Considering the classification of conditions for estuarine sediments, it is stated that the total phosphorus concentrations found do not yet represent a risk of environmental deterioration.