Evaluación del riesgo ecológico de los efectos de metales pesados y nutrientes contenidas en efluentes urbanos sobre los ecosistemas de la bahía de Puerto Príncipe (Haití)

The bay of Port-au-Prince is a body of water into which flow rain water and untreated urban wastewater from residential zones, and commercial and industrial activities. The presence of pollutants in untreated urban wastewater constitutes a hazard to aquatic organisms and can greatly affect the balance of the ecosystem of the bay. The aim of this study was: (i) to implement an environmental hazard assessment framework for untreated urban wastewater; (ii) and to apply it to urban wastewater discharged by an open channel of the combined sewage system of Port-au-Prince. COD, heavy metals, NO 3 -, PO 4 3-and dissolved oxygen were chosen as the main parameters for this assessment. 69 samples were collected from the experimental site from September 2003 to May 2005. High concentrations of NO 3 -(23 mg/L), PO 4 3-(62 mg/L) and COD (1500 mg/L) were detected. These concentrations are much higher than the threshold values set by the regulations relating to wastewater discharges into natural environments. Metals in solution were mostly below the detection limit of the apparatus used. DO contents were very low, highlighting heavy organic load, combined with a low dissolution rate in the water of the channel before discharge into the sea. In view to enriching these initial results, it is now necessary to carry out a thorough environmental hazard assessment of the wastewater channel discharge in Port-au-Prince bay and, in particular, establish the proportions of organic pollutants in the discharge by implementing ecotoxicity tests. In the future, it appears necessary to perform the physicochemical and ecotoxicological characterization of the contaminated sediments in the channel, in order to develop ecohydrological tools for managing the ecological hazards and risks related to effects of the channel's total pollution on the environment of Port-au-Prince.