Assessment of the marapendi lagoon water quality in Rio de Janeiro/RJ

Abstract

Coastal lagoons are natural environments localized between the continent and the ocean, being of great importance to human beings due to a series of services provided, besides serving as rainwater receiving bodies. However, these zones have been subjected to constant degradation processes due to human activity. This study had as its main goal performing the environmental diagnosis of Marapendi lagoon (Rio de Janeiro city), using as a basis the water quality historical data from three monitoring stations, from 2010 until 2017. The variables used were the Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), Total Phosphorus (TP), Nitrogen Series and thermotolerant coliforms. The data was compared with the patterns stablished by the legislation and the obtained results for all physicochemical parameters do not comply with the patterns established by the legislation in most of the time studied showing that the lagoon finds itself in bad environmental conditions, mainly due to the accelerated eutrophication process caused by the constant untreated sewage discharge into the water body. The eastern part of the lagoon, due to its greater influence of the tidal regime, presented the lowest values considering the analyzed parameters. However, the point located upstream of the lagoon presented the worst quality, due to partial silting up of this region and that can be justified by the low renewal capacity of its waters.