the Everglades National Park (1, 3, 

 4) further south and closer to the 

 coast do not support this supposi- 

 tion. Higher calcium/bicarbonate 

 levels observed in this basin 

 (sites I, 3, 4) are believed to be 

 derived from fine rock and marl 

 soils (Waller and Earle 1975). 



Waller (1975) reports that bulk 

 precipitation comprises as much as 

 78% of the total annual input of 

 nitrogen and 90% of the input of 

 phosphorus to the conservation areas 

 north of the Everglades National 

 Park. The majority of the total 

 loading occurs during the wet season 

 due to the increased quantity of 

 rainfall. Concentrations in dry 



fallout, however, tend to increase 

 during the dry season (Echternacht 

 1975, Waller and Earle 1975). 

 Echternacht (1975), reviewing the 

 South Florida Water Management Dis- 

 trict's rainwater data, illustrated 

 this seasonal difference of nitrogen 

 and phosphorus concentrations. Peak 

 concentrations occur during spring 

 months, which are characterized by 

 high winds and low rainfall and, 

 therefore, high dry fallout condi- 

 tions (Table 8). Summer months, 

 during peak rainfall and maximum 

 dilution, show the lowest concen- 

 trations. Dilution, soil drying, 

 increased wind activity, and con- 

 tamination of collecting devices by 

 animals are believed to be the pri- 

 mary causes of the obscured season- 

 ality. Fire is also believed to be 

 a factor in enhancing the concentra- 

 tion of dry fallout in the dry sea- 

 son (Holle 1971, Waller and Earle 

 1975). 



The mean nutrient values for 

 total nitrogen as "N" are fairly 

 uniform for all sites; however, 

 phosphorus as "P" reported at sites 

 1 and 3 are the highest recorded in 

 the state's USCS monitoring network 

 (Irwin and Kirkland 1980; see Figure 

 19). These two sites are monitored 



monthly and are located close to 

 "natural" settings at the Everglades 

 National Park Research Center and at 

 Grossman Hammock in Shark River 

 Slough. Therefore it is suggested 

 that local biota, such as birds and 

 frogs, may be contaminating the 

 samples (Waller and Earle 1975, 

 Irwin and Kirkland 1980). Bulk pre- 

 cipitation data collected by the 

 South Florida Water Management Dis- 

 trict support the idea of contamina- 

 tion at sites 1 and 3 (Echternacht 

 1975). Davis and Wisniewski (1975) 

 reported nitrogen as "NO x " and 

 phosphorus (ortho as "P") at sites 

 in Homestead, Tamiami Trail (40 Mile 

 Bend), and the Everglades. The 

 values reported are much lower than 

 reported at sites 1 and 3 by Irwin 

 and Kirkland (1980). 



Table 8. Seasonal averages of nu- 

 trient species contained in 

 rainwater at Tamiami Trail 

 40 mile bend (adapted from 

 Echternacht 1975). 



Most trace metals in bulk pre- 

 cipitation are derived from dry 

 soils and fine rock material wafted 

 into the air by winds. Mercury and 

 arsenic, however, are believed 

 related to pesticide use on nearby 

 agricultural operations (Waller and 

 Earle 1975). Lead and iron are 

 attributed to motor vehicle activity 

 (Irwin and Kirkland 1980). Site 4 

 (Tamiami Trail, 40 Mile Bend) is the 

 only site in the basin monitored for 

 trace metals in bulk precipitation. 

 Of all trace metals, cadmium and 

 zinc show up in the most potentially 

 hazardous concentrations; however, 



44 



