Caribbean Water Science Center Science Plan 1999

Fate and Transport of Contaminants

The Caribbean District has conducted synoptic surveys of surface water, ground water, and water quality and stream, reservoir and estuary sediments that have shown the persistence of contamination in fluvial, lacustrine, estuarine, and ground-water systems.   Among the pollutants found are mercury, lead, arsenic, PCB’s, DDT, and trichloroethylene.  However, only one of these studies, the Vega Alta ground-water transport model, tracks the movement of volatile organic compounds from the source through the upper aquifer.  The other studies have been synoptic surveys of sediment characterization.  More definitive studies of the fate and transport of contaminants are needed.

Information Needs and Deficiencies

1. There is a lack of knowledge of the complete geographic distribution of many contaminates.
   
   
2. The drinking water systems in Puerto Rico have been found to contain varying levels of trihalomethanes and other disinfection by-products.  There is a lack of understanding of the source and concentrations of the precursors to disinfection by-products.
   
   
3. In Puerto Rico there are many abandoned landfills and clandestine dump sites.   There is a need to study the fate and transport of toxic material that may have been deposited in these sites.
   
   
4. Half of the households in Puerto Rico are unsewered. The impact of the unsewered households on the streams in Puerto Rico is unknown.
   
   
5. The impact of herds of beef and dairy cattle in Puerto Rico on surface water quality is unknown.
   
   
6. A recent study in north-central Puerto Rico indicates that about 90 percent of the nitrogen applied as fertilizer is in transit in the vadose zone.  Further studies are needed to determine the amount of nitrate in storage in the vadose zone and its rate of movement toward the water table in both unsewered communities and agricultural areas.

Program Opportunities

1. Propose to conduct island-wide surveys of the concentration of metals and persistent organic contaminants in ground water and lacustrine and estuarine sediments. Particular attention should be given to areas downstream from industrialized and agri-business zones.
   
   
2. Propose to conduct a study to determine the source and concentrations of the precursors to disinfection by-products.
   
   
3. Propose to study the fate and transport of toxic material that may have been deposited in the many abandoned landfills and clandestine dump sites in Puerto Rico.
   
   
4. Conduct a study of the effects of unsewered households on the microbiological and chemical quality of streams in Puerto Rico.
   
   
5. Conduct a study of the impact of cattle on stream eutrophication and micro-biological quality in Puerto Rico.
   
   
6. Conduct studies to determine the amount of nitrate in storage in the vadose zone and its rate of movement toward the water table in both unsewered communities and agricultural areas within different hydrogeological conditions (volcanics, coastal alluvial plain, and karst).

Next: Water Resources in Coastal Areas

• Caribbean Water Science Center Home Page
• Caribbean Water Science Center Science Plan Table of Contents