The average Hg concentration in surface sediment (0 - 4 cm) of 121 ng g' 1 was 2.5 
times higher than corresponding deep sediment (11-17 cm) concentrations. Post-1985 
Hg accumulation rates averaged 53 ^ig m' 2 y* 1 corresponding to a 6.4 (1.6 - 19.1, n = 
18) times rate increase since the year 1900. Mercury accumulation rates increase 
starting about 1940, due perhaps to mid-century alteration of the hydrologic structure 
of the Everglades, and to increased agricultural and urban development to the north and 
east. Further, the findings are similar to trends reported for lakes in Sweden, 
Minnesota, and Wisconsin, perhaps, indicating a global process that leads to similar 
accumulation rates over widely varying geographic regions. 
378 
