Estudo da contribuição da drenagem pluvial urbana sobre a poluição marinha na cidade de Fortaleza, CE

Abstract

The final characteristics of the surface drainage of rainwater are dependent on the nature of the surfaces (streets and avenues, parks, plazas, rooftops, sidewalks, and soon), with which it comes into contact during the process flow as well as natural processes and human activities in river basins where they are coming from. A densely urbanized area this flow is directed from its collection in the streets until the shield drain, which empties into a body of water near or at sea in coastal cities. Whereas these galleries can represent point sources of pollution, this study aimed to analyze the effluents from storm drainage galleries of Fortaleza-CE, as well as their feathers dilution in the marine environment ahead. Because the local weather be well defined, the samples were collected during the rainy season and the dry season. Urban stormwater drainage showed a greater concentration of nutrients in the dry season (10.38 mg N-NO3 -/L, 4.90 mg N-NH3/L) in the wet season (5.96 mg N-NO3 -/L, 3.47 mg N-NH3/L), indicating dilution during precipitation events. Among the ecotoxicological assessments, the acute and chronic effects were observed, noting that the EC50 showed greater clarity regarding the correlation with the nutrients, and provide reference values for the effect of toxicity (EC50-24h 27.54% of the effluent in the period rainy; EC50-24h 23.11% in the dry season). The correspondence of the effects of stormwater drainage sea plumes were not clearly established, nor for nutrients and for ecotoxicological assessments. The bathing, measured only in the plume region, was related to seasonality, with loss of quality bath during rainfall events (> 800 MPN E. coli/100mL). This fact can be explained by the contribution of domestic sewage typically overflowed to the stormwater drainage system during heavy rainfall events. Therefore rainfall has clear effect on the effluent of urban drainage, either by the accumulation of nutrients and contaminants that contribute to increased toxicity during the dry period, or by diluting effect on the drag nutrients and faecal contaminants in the rainy season.