Balanço de nutrientes da água do açude Pentecoste (Pentecoste,Ceará, Brasil) no período de março a dezembro de 2002

Abstract

The Pentecoste reservoir is located in Pentecoste, at Ceará state, Brazil. It has a subject to flooding area of about 5,486 ha with 7.2 m average deep and capacity to store 395,638,000 m3 water. The aim of this work was to evaluate the nutrient levels of the Pentecoste reservoir. Water samples were collected in four stations at the surface and 2 m deep, every month from March to December 2002. The obtained data were submitted to a Pearson's correlation analysis with 1 and 5% significance level. Nutrient concentrations kept inside of the tolerated level for aquatic organisms. Total ammonia concentrations varied from 0.0122 to 1.12 mg.L-1, nitrites concentrations from 0.0066 to 0.0726 mg.L-1, nitrates from 0.00 to 2.64 mg.L-1, and phosphates from 0.00 to 0.61 mg.L-1. E1 station presented the highest nutrient concentrations. Correlation analysis showed that river mouth stations were strongly affected by precipitation and an increase in water volume resulted in a decrease of nutrient concentrations. Chemical oxygen demand values observed at E3 and E4 stations presented positive correlation with total ammonia, nitrites, nitrates and phosphates concentrations. Data analyses also showed that organic matter was a potential source of nitrogen and phosphates for this aquatic environment.