SALTWATER AQUIFER 



Figure 44. Schematic diagram of water budget in canals of the Florida Keys 

 (adapted from Chesher 1974 and Bailey et al. 1970). 



levels. High levels of p,p'DDT are 

 attributed to the pre-1968 mosquito 

 control spraying program. Pesticides 

 used for households, golf courses, 

 plant nurseries, and marinas may be 

 the reason for the other elevated 

 levels of pesticides (exceeding Mud 

 and O'Hara Key levels), but the spe- 

 cific sources were not identified 

 (Chesher 1974). 



Groundwater in the Florida Keys 

 is restricted to: (1) the shallow 

 groundwater regime consisting of 

 freshwater lenses interfacing with 

 brackish and marine groundwater 

 (Hanson 1980); and (2) deeper Flori- 

 dan Aquifer waters (Beaven and Meyer 

 1978). Groundwater nutrient concen- 

 trations are very similar to canal 

 waters (Doctor's Arm) monitored by 

 FDPC (1973), Chesher (1974), and 

 USEPA (1975). Floridan Aquifer 



wells in the Florida Keys contain 

 water with concentrations of 1,600 

 to 20,000 mg/l of chloride and 3,430 

 to 37,500 mg/l of dissolved solids 

 from samples taken at depths ranging 

 from 248 to 610 m (812 to 2,000 ft). 



Total nitrogen and phosphorus concen- 

 trations are similar to the shallow 

 aquifer and freshwater lens reported 

 on Big Pine Key (Hanson 1980). 



Table 22. Concentrations of pesticides 

 (ppb, dry weight) in canal 

 sediments from the Florida 

 Keys (adapted from Chesher 

 1974). 



108 



