Home Introduction Physical Setting Urbanization Natural Hazards Mineral Resources Water System Environmental Quality - Ecosystem Impact > Pollution - Waste Management - Population Density Outdoor Recreation Everglades N.P. Coastal Zone Fish & Wildlife Miccosukee Indians Conclusion References

The disposal of solid wastes creates air and water pollution. [larger image]

Current methods of waste treatment in south Dade County have resulted in impairment and contamination of land, water, and air. Recreational, aesthetic, and commercial uses of these resources have been restricted and health endangered. In 1973, the largest recent typhoid outbreak in the United States, with more than 150 confirmed cases, occurred in the area. The outbreak resulted from contamination of drinking water by human waste. Water in most canals is unsafe for swimming and other contact sports because of bacterial contamination. Fishing and swimming in south Biscayne Bay were restricted in 1973 due to massive fish kills. Air pollution has increased sharply in recent years. In 1972 there were numerous incidents where high air-contaminant concentrations exceeded State and Federal Standards and reached “Alert Episode” concentration levels.

Fish kills become more numerous as water quality deteriorates. [larger image]		Important recreational opportunities are destroyed by polluted water. [larger image]

Agriculture has also contributed to pollution. The amount of land now (1973) in agricultural use in Dade County is about 92 square miles, mostly in the south part of the county.

Although economically important for south Dade, agriculture is a major source of pollution. [larger image]

Fertilizers and pesticides are the main agricultural contaminants. Nutrients, such as nitrogen and phosphorus and potentially toxic metals, such as copper, lead and arsenic from agricultural fertilizers, are leached from farm soils or are carried on soil particles into surface and ground waters. Pesticides are generally insoluble in water and are usually transported from farms either in runoff or on dust particles.

The urban environment constitutes the major source of solid, liquid, and gaseous waste. Per capita liquid and solid waste will increase while per capita gaseous wastes should decrease when Federal emission standards for automobiles are implemented.

Liquid waste production in south Dade County was more than 16 billion gallons in 1972. Half was discharged to septic tanks. Sewered areas are served by 29 treatment plants which discharge to the ocean, canals, and seepage ponds ^3/. The long-range master plan for south Dade County provides for replacement of the smaller privately owned treatment plants with four large facilities ^4/. While the four large plants are being constructed, however, south Dade County will allow construction of 200 additional small treatment plants that will provide 90-percent treatment efficiency. The treated effluent from these small plants will be discharged to pits. Some of this effluent will infiltrate the Biscayne aquifer.

Liquid waste is projected to increase about eight times between 1950 and 1990 in south Dade. [larger image]

Each person in south Dade County in 1970 generated about one ton of solid waste, or a total for the area of about 400 thousand tons per year. By 1990 the total solid waste will approach one million tons per year, according to recent projection (see graph). Disposing of this solid waste is difficult because of the geology and hydrology of the area.

In 1970, about 30 percent of the solid waste was incinerated while the remainder was disposed of in dumps and landfills mostly outside of the south Dade area ^5/. Most of the incinerators and dumps do not meet pollution code requirements. Malfunctioning incinerators emit toxic gases and particulate matter, and open dumps and landfills are esthetically unpleasant, susceptible to fires which pollute the air, and sources of contaminants to shallow ground water.

Solid waste is projected to increase almost 10 times between 1950 and 1990. [larger image]

Plants for solid-waste disposal in Dade County call for improved efficiency of incinerators and for sanitary landfills to replace open dumps. Estimated county costs for these needed improvements will exceed 100 million dollars in the next 20 years ^6/.

In south Dade County, about 80 percent of the airborne contaminants come from more than 260,000 vehicles, which use 220,000,000 gallons of gasoline each year. In addition, some contaminants from fuel combustion for heat and power reach the atmosphere.

The overstimulation of water-plant growth by excess nutrients produces great variations in the oxygen content of water during a single day. By day plants produce oxygen through photosynthesis, and at night they consume oxygen. The nightly demand for oxygen in combination with the oxygen requirements for decay of organic matter in treated sewage effluents can lower the oxygen content of water below levels that fish and other aquatic organisms require for survival.

In south Dade County, the highest concentrations of phosphate in the surface waters are shown on the map below.

The January 1973 survey showed higher concentrations of phosphates in the urbanized areas. [larger image]

Water moving through canals flushes nutrients into Biscayne Bay and provides fresh water which satisfies decay and respiration demands for oxygen. During the dry season, however, flow through the canals decreases sharply.

Nutrients flushed from farm and residential land cause thick algal blooms in canals. [larger image]

When nutrients build up in the stagnant canals, aquatic blooms, fish kills, noxious odors, and health hazards can occur. Increased urban water use decreases the amount of water available for flushing of the canal system. The combined impact of increased nutrient load and reduction in flushing action can seriously damage aquatic environments.

Biscayne Bay, the temporary repository of urban wastes, is now over enriched in phosphorus. It is low in nitrogen which indicates that additions of nitrogen probably regulate the rate of vegetative growth in the Bay. The amounts of phosphorus and nitrogen added to Biscayne Bay can be lessened by tertiary waste treatment.

A survey in January 1973 showed that concentrations of nitrate and phosphorus were highest in the urban areas of south Dade County. [larger image]

Lead and mercury are the two metals known to be accumulating in this area. Crude estimates suggest that more than 3,000 metric tons of lead are added to the area each year (see illustration below). Much of this is from automotive exhaust and is deposited within several hundred yards of the highways. Concentrations in bottom sediments of Biscayne Bay are low, ranging from 15 to 30 µ/kg (micrograms per kilogram; 1 µ/kg = 1 part per billion). Somewhat higher concentrations occur at the mouth of Miami River and Black Creek Canal, indicating that some lead is transported in runoff.

Approximate Lead Balance for Dade County, 1972 (Metric tons)

[larger image]

The 990 metric tons of lead settling in Dade County from automobile exhaust emissions, provides the greatest toxic metal hazard. About 310 metric tons of lead from exhaust emissions in Dade County settles in the land and waters of the Everglades Basin. Another 20 metric tons flows into Biscayne Bay and the ocean.

Biscayne Bay shows some contamination by mercury when compared with Florida Bay, an area remote from rapid development (see graph). Mercury in the bottom sediments of Florida Bay ranged from 10 to 40 µ/kg and averaged 10 µ/kg. Bottom sediments in Biscayne Bay ranged from less than 10 to 325 µ/kg and averaged 40 µ/kg of mercury.

Mercury is contained in bottom sediments of Florida and Biscayne Bays. 7/ [larger image]

The degree of mercury contamination in Biscayne Bay sediments is quite low compared to average levels reported in sediments from southern Lake Michigan (150 µ/kg) ^8/, the South Bay portion of San Francisco Bay (370 µ/kg) ^9/, or Minimata Bay, Japan, where 46 people died from mercury poisoning incurred by eating shellfish from mud containing 22,000 to 59,000 µ/kg. Nevertheless, the fact that mercury can build up to levels as high as 325 µ/kg in individual locales of Biscayne Bay is a matter of concern.

Nonpersistent pesticides, such as malathion or parathion, are most commonly used in Florida, especially in the south Dade area where they are applied in citrus groves and vegetable farms ^10/. In 1969-70, they were applied to about 11,900 acres of citrus groves and 47,000 acres of vegetable farms in Dade County ^11/. Approximately one million pounds of persistent pesticides were used annually on urban and agricultural land in the 1960's in Dade County ^12/.

Both persistent and nonpersistent pesticides are found in air, water, plants, and animals of south Dade County, with persistent ones such as DDT predominant. Concentrations are usually at trace levels or below detectable levels in water, but at higher levels in bottom sediments and biota. Concentrations in excess of 1,000 µ/kg have been found in birds and mammals ^13/. A concentration of over 16,500 µ/kg was measured in one bald eagle.

Buildup of persistent insecticides in some birds causes metabolic upset in their reproductive processes. Increasing concentrations of DDT are coincidental with death and decreasing numbers of some species, particularly hawks, eagles, and pelicans. Even though local use of DDT and other persistent insecticides is decreasing, a buildup may continue for years as a result of the long life of some pesticides (up to 20 years for the DDT family) and as a result of extensive use in other parts of the world and ultimate atmospheric transport to Dade County. This is of particular concern in the Everglades National Park because birds are an important attraction.

DDE occurs in the near-shore bottom sediments of the northern half of Biscayne Bay. [larger image]

Pesticides accumulate in humans to levels thousands of times greater than those in the water they drink and the food they eat. Average concentrations of total DDT in human fat from Caucasians more than 5 years old in Dade County was 8.4 µ/kg ^15/. For comparison, concentrations in Caucasians from 22 other States ranged from 3.98 to 13.23 µ/kg. States with warm climates had higher averages (9.21 µ/kg) than States with cool climates (4.85 µ/kg ^15/). The effects of such concentrations on human health are not known.

Most inland canals, lakes, and ponds in south Dade County are unsafe for swimming and contact sports because of fecal contamination. Feces often contain pathogenic bacteria and viruses. Only three of ten major canals are considered safe for swimming; and only ocean beaches are generally recommended for water-contact sports. Also significant is the fact that during the dry season the canals provide recharge directly to the Biscayne aquifer. Because water supplies are withdrawn from this aquifer, a potential exists for contamination of public water supplies.

Bacteria and viruses have been detected repeatedly at ocean outfalls for untreated sewage, but no pathogenic viruses have been detected at outfalls for treated sewage. Preliminary data from a limited study have also failed to indicate pollution of ground water by effluent from septic tanks.

Because of bacterial and viral contamination, commercial shellfishing for direct marketing is prohibited along the entire east coast of south Florida.

Thermal pollution in the south Dade area is from two fossil fuel and one nuclear power plants at Turkey Point; The fossil-fuel units require 1,270 cfs of cooling water and raise the water temperature 12°F 16/. The nuclear unit requires 4,250 cfs and raises the water temperature 16°F. Investigations by the University of Miami and the Environmental Protection Agency show that the release of heat from the existing fossil-fuel plants has affected the biota of south Biscayne Bay. Plankton, benthic algae, sea grasses, benthic invertebrates, and fish were all significantly affected by elevated temperatures near the discharge area. The most obvious effects were the decreases in the number of algal species and the death of sea grasses over an area of several hundred acres of bay bottom. In general, animals were adversely affected by temperatures above 91°F. A huge system of canals under construction on a 10-square-mile area will serve as a cooling radiator for the heated water, which will then be recycled (see photograph). This will reduce significantly the thermal loading of Biscayne Bay in the vicinity of Turkey Point.

Shown here is a false color infrared photo of the coastal area at Turkey Point. The photo is from the National Aeronautics and Space Administration. [larger image]

The extensive system of canals is used to cool water from the nuclear power plant at Turkey Point. This image is from the National Aeronautics and Space Administration. [larger image]

The major source of air pollution is the automobile. Increased traffic will cause increased deterioration of air quality in south Dade. [larger image]

In the past, it was generally assumed that because of prevailing sea breezes, Dade County's air had an unlimited potential for dispersing airborne pollutants. Daily observations during the past 10 years indicate that haze is slowly increasing.

This increase is due to the increase in motor vehicles as well as the expanding industrial activities. About 80 percent of the 950,000 tons of pollutants emitted to the air in 1971 was from motor vehicles; the remainder came from industrial and commercial sources, mainly fuel combustion for heat and power generation, incineration, and open fires.

In general, the concentration of pollutants in air over Dade County is less than that over other large metropolitan areas. However, the significant increase in oxidants, oxides of nitrogen, and sulfur dioxide and a possible increase in airborne lead near expressways in 1972 indicate a deteriorating air quality.

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