Five solid-waste landfills and an open burning dump were studied in Puerto Rico to obtain physical, chemical and biological data on leachates, give an overview of their pollution potential, and determine the adequacy of monitoring at these or similar sites. These sites are operated by the municipal governments of Arecibo, Caguas, Cayey, Humacao, Mayaguez and Guayama. The bulk of waste is of domestic origin but wastes from local industries and institutions are also handled. Data were collected between February and July 1976.

Parameters measured included temperature, specific conductance, pH, color, common ions, cyanide, macronutrients (nitrogen and phosphorus species), total organic carbon, dissolved oxygen, BOD5 (biochemical oxygen demand), COD (chemical oxygen demand), total and fecal conform, trace metals, and phenols.

The results obtained indicated that leachate from most sites is enriched in common ions, macronutrients, and trace metals. A sample obtained from runoff at the Cayey landfill was the only one with an acidic pH (5.8). It had a common ion concentration of 10,750 mg/L (milligrams per liter), or twice that found in leachate contained within the buried refuse. The leachate from the Caguas site had the highest common ion concentration (12,520 mg/L).

Maximum values for other parameters were as follows: Temperature, 33°C (or about 10°C above ambient ground-water temperature); specific conductance, 19,200 micromhos per centimeter; color, 2,200 units; cyanide, 30 ug/L (micrograms per liter); total nitrogen, 600 mg/L; total phosphorus, 4.3 mg/L; total organic carbon, 500 mg/L; 5-day biochemical oxygen demand, 5,540 mg/L; chemical oxygen demand, 3,000 mg/L; total coliform bacteria, 410,000 colonies per 100 milliliters; fecal coliform bacteria, 14,000 colonies per 100 milliliters; total arsenic, 54 ug/L; total cadmium, 15 ug/L; total chromium, 1,600 ug/L; total lead, 1,10C ug/L; total mercury, 2.6 ug/L; total nickel, 1,300 ug/L; and total phenols, 1,100 ug/L.

Pollution of water resources is limited to the periphery of the sites. A major problem throughout seems to be related to operating methods. Under the conditions found, large quantities of rainwater and runoff could be available for leachate production. Generation of leachate may not be significant at present probably because of the recent establishment of the landfills (less than 5 years).

Monitoring at these or similar sites in Puerto Rico can be limited to defining present baseline water-quality conditions and implementation of a sampling program. Baseline data could be limited to specific conductance, pH, color, common ions, and dissolved oxygen. A scheduled sampling program could be limited to specific conductance readings and measurement of concentration of bicarbonate, chloride, and dissolved oxygen.