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We characterized the spatial and seasonal distributions of different phosphorus fractions in surface sediments from the Furo of Muriá estuary by chemical fractionation. Five phosphorus species were successfully separated: phosphorus bound to Fe/Al oxyhydroxides (non-apatite inorganic phosphorus (NAIP) ranging from 164.54 to 280.32 μg g-1), phosphorus bound to calcium (apatite phosphorus (AP) ranging from 63.02 to 102.80 μg g-1), inorganic phosphorus (IP, ranging from 227.21 to 378.61 μg g-1), organic phosphorus (OP, ranging from 30.33 to 135.88 μg g-1) and total phosphorus (TP, ranging from 257.54 to 507.73 μg g-1), in which 88% of TP is constituted by IP. Statistical results showed that seasonality was not a major factor influencing phosphorus concentrations. Considering the classification of estuarine sediment conditions, we can conclude that the TP concentrations found in Furo of Muriá do not yet indicate the risk of environmental deterioration.

Sediments in aquatic systems are indicators of contamination levels. Therefore, they play an important role in the assessment of the nature and intensity of human impact on aquatic environments. The objective of this work was to assess the levels of pollution by determining the concentrations of various metals and phosphorus forms in the sediments of Água Preta Lake, which supplies water to the Metropolitan Region of Belém, in north-eastern Brazil. Our data indicate non-uniform sedimentation with a large granulometric fraction of silt. The predominant form of phosphorus was inorganic phosphorus, to the detriment of the organic form. Observed mean concentrations of nickel, copper, lead, and zinc were lower than the PEL (Probable Effect Level). However, the highest observed concentrations of nickel and lead exceeded the prescribed TEL (Threshold Effect Level), which suggests pollution from an anthropogenic source.