these concentrations are believed to 

 result from contamination by nearby 

 galvanized metals (Waller and Earle 

 1975). All trace metal sampling 



sites are located near highways 

 and/or located with the objective 

 of measuring some local phenomena, 

 and thus very likely do not portray 

 regional conditions (Irwin and 

 Kirkland 1980). 



The pH of rainfall reported at 

 sites 1, 3, 4, and 5 within the 

 basin ranged from pH 5.2 to pH 8.7 

 (Irwin and Kirkland 1980). This 

 data should be viewed as only ap- 

 proximate due to the holding times 

 imposed. 



Data on selected pesticides and 

 industrial compounds monitored are 

 rather limited for the basin. Trace 

 amounts of PCB were reported at 

 sites 1 and 3, and malathion and 

 diazinon were just detectable at 

 site 4. Site 2 monitored at a camp- 

 ground near Florida City just south 

 of Homestead reported the presence 

 of a variety of pesticides, highest 

 of which were diazinon (mean concen- 

 tration = 0.26 ppb) and malathion 

 (mean = 0.47 ppb). The sampling 

 site is located to the east of the 

 Everglades National Park and sand- 

 wiched in between two major farming 

 areas dealing mainly in truck crops, 

 i.e., vegetables. Application of 



pesticides in this area is usually 

 done by aerial sprayers, providing 

 ample opportunity for atmospheric 

 contamination over the sampling 

 site. The values reported should be 

 considered conservative because of 

 the rapid breakdown of the organo- 

 phosphate compounds reported in 

 highest concentrations, such as 

 malathion. 



Counties. The results were applied 

 to other counties including Dade and 

 Monroe. Their review of historical 

 data for Miami and Homestead showed 

 very low values, with most readings 

 below the official detection thresh- 

 old of 0.01 ppm. Dade County's 

 projected 1980 rate of emissions 

 (1,164 grams/sec.) was the highest 

 of any south Florida county and 

 ranked ninth in the state. Dames 

 and Moore (1978) concluded, however, 

 that the 24-hour maximum concentra- 

 tions of SO2 are presently, and 

 will continue to be, far below 

 Florida and national air quality 

 standards, even at locations where 

 the maximum combined effects are 

 expected. 



Inversions occur when warm air 

 becomes caught below colder air, re- 

 sulting in the trapping of a stable 

 air column and thereby preventing 

 mixing or dilution of air pollutants 

 immediately above the ground. By 

 monitoring towers in and adjacent to 

 the basin, Gerrish (1973) concluded 

 that inland inversions form almost 

 every night, are much stronger than 

 those on the coast of south Florida, 

 and are strongest in the dry season. 

 Because of the diurnal nature of the 

 inversions, significant atmospheric 

 pollutant buildup seldom occurs; the 

 daily inversions are quickly dis- 

 persed by the dynamic wind and rain 

 patterns that exist over the basin 

 (Dames and Moore 1978). 



Dames and Moore (1978) studied 

 sulfur dioxides in the state of 

 Florida, concentrating their efforts 

 in Hillsborough, Duval, and Escambia 



45 



