|
|---|
INSIDE
|
 |
|
Montevideo is justifiably proud of its urban beaches which lie, in long stretches, along the Uruguayan capital's frontage on the River Plate. But pride has been invaded by concern in recent years as routinely taken samples began to show coliform bacteria in excess of 3,000 per 100 millilitres. This level of bacterium indicates the presence of sewage, but its exact source was unknown.
The River Plate is an unusual river. It would be a sea if its water was clear and salty. In fact it is a giant basin formed by the outflow of two great rivers, Parana and Uruguay. Shaped like an inverted funnel it flows in a northwest-southeast direction, between Argentina and Uruguay, into the Atlantic Ocean. Where the brown river meets the blue ocean it is more than 100 kilometres wide.
Nor are the pollution problems of the River Plate limited to organic matter. The vast basin is brimming with industrial wastes from hundreds of small tanneries around Montevideo Bay and effluent from Uruguay's premier port. The once popular beach resort of Carasco has been closed for many years because of high pollution. Most of Montevideo's 1.5 million people live quite close to the river and the basin is heavily used for fishing and recreation. But resources and data to address growing environmental problems are limited and much remains unknown.
Montevideo has been constructing a modern sewage system for many years but it remains incomplete. A lot of raw sewage is deposited into two small rivers, Pantanoso and Miguelete, which pollute Montevideo Bay and the River Plate. The main part of the present engineered disposal system uses a well-tried technology called an "outfall" that pipes sewage from a coastal station and discharges it in the Plate, several kilometres away and at a depth of about 10 metres. Sewage is discharged at a pressure calculated to disperse it so that bacteria die-off is achieved.
Tracking the movements of sewage and other pollution in this vast expanse is a herculean high tech task. An IAEA technical co-operation project that began in 1991 used isotopic techniques to establish that sewage from far out in the river could flow back infrequently to the beaches when specific riverflow, tides, winds and ocean currents combined. But it has also confirmed, happily, that the outflow system is functioning well. Project-generated data on the river dynamics are being used as inputs in city plans by the Uruguayan Ministries of environment, health, and industry as well as the Montevideo Municipal Authority. They are now working in partnership with the directorate of nuclear technology (DINATEN), which is the IAEA's counterpart to monitor pollution and plan remedial action.
Through project-provided training, know-how and technology - including gamma counters, a gamma detection system and an automatic multi-sample analyser, and devices for water sampling at various depths - DINATEN and the municipal authority have improved their environmental monitoring capabilities.
Other IAEA technical co-operation projects have been planned to help in a systematic manner. While the initial project focused on water flow patterns, a second, now being completed, used isotopes and fluorescent tracers at various points of the basin and ocean side of the city, to study the movement of sediment. A new project, expected to start in 1997 will analyse the contaminant load of sediment in and around the bay and the 'age' of the contaminants so that the planners know what has been deposited there in the past 30-40 years. Expert services and training will be provided to prepare the very special field equipment such as dredges with detectors, and to do the tracer injections and measurements. The technique to date sediment using environmental lead-210 will be applied for the first time in the basin.
Step by step the scientific evidence generated through isotopic techniques is providing the foundation for the Uruguayan authorities to formulate sound environmental policies and take effective remedial action. It is a long-term process requiring a solid developmental partnership - one that the IAEA has committed itself to in Uruguay and in many other developing Member States.
| Contents | HomePage | WorldAtom | TecAtom |