Be. Rood et al., MERCURY ACCUMULATION TRENDS IN FLORIDA EVERGLADES AND SAVANNAS MARSH FLOODED SOILS, Water, air and soil pollution, 80(1-4), 1995, pp. 981-990
Global and regional increases in atmospheric mercury (Hg) concentratio
ns have previously been identified as the cause of increased mercury a
ccumulation rates in north temperate lakes in Sweden, Wisconsin, and M
innesota. Atmospheric deposition can often account for elevated Hg con
centrations in fish from these systems. Mercury levels in sportfish co
llected from some areas of the Florida Everglades and Savannas Marsh e
xceed limits that are acceptable for human consumption. Forty five soi
l cores and soil grab samples were retrieved from the Everglades and S
avannas Marsh wetlands. Eighteen sediment cores were dated radiochemic
ally with Pb-210 and Cs-137 using gamma-ray spectroscopy to determine
modem and historic mercury accumulation rates for these subtropical we
tland systems. Recent (''post-l985'') Hg accumulation rates averaged 5
3 mu g m(-2) y(-1) (23 to 141,n = 18) corresponding to an average-rate
increase of 4.9 times (1.6 to 19.1) over those observed around the tu
rn of the century. This accumulation seems to result more from either
global or regional atmospheric deposition rather than from lateral tra
nsport via overlying surface water. The trends for mercury accumulatio
n match those reported for lakes in Sweden and the northern United Sta
tes, even though these systems are distinctly different in their clima
te, vegetational composition,and location. We provide the first data o
n accumulation of mercury in subtropical wetland systems, and demonstr
ate the feasibility of radiochemical dating of wetland sediment.