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publications > paper > tracing sources of sulfur in the florida everglades report

Tracing Sources of Sulfur in the Florida Everglades

Anne L. Bates,* William H. Orem, Judson W. Harvey, and Elliott C. Spiker

Note: This article was published in the Journal of Environmental Quality 31:287-299 (2002). Entire article is available in PDF format (0.3 MB). PDF files require the FREE Adobe Acrobat Reader ® to be read.


We examined concentrations and sulfur isotopic ratios (34S/32S, expressed as delta34S in parts per thousand [parts per thousand symbol] units) of sulfate in surface water, ground water, and rain water from sites throughout the northern Everglades to establish the sources of sulfur to the ecosystem. The geochemistry of sulfur is of particular interest in the Everglades because of its link, through processes mediated by sulfate-reducing bacteria, to the production of toxic methylmercury in this wetland ecosystem. Methylmercury, a neurotoxin that is bioaccumulated, has been found in high concentrations in freshwater fish from the Everglades, and poses a potential threat to fish-eating wildlife and to human health through fish consumption. Results show that surface water in large portions of the Everglades is heavily contaminated with sulfate, with the highest concentrations observed in canals and marsh areas receiving canal discharge. Spatial patterns in the range of concentrations and delta34S values of sulfate in surface water indicate that the major source of sulfate in sulfur-contaminated marshes is water from canals draining the Everglades Agricultural Area. Shallow ground water underlying the Everglades and rain water samples had much lower sulfate concentrations and delta34S values distinct from those found in surface water. The delta34S results implicate agricultural fertilizer as a major contributor to the sulfate contaminating the Everglades, but ground water under the Everglades Agricultural Area (EAA) may also be a contributing source. The contamination of the northern Everglades with sulfate from canal discharge may be a key factor in controlling the distribution and extent of methylmercury production in the Everglades.

*Corresponding author (

Related information:

SOFIA Project: Groundwater-Surface Water Interactions and Relation to Water Quality in the Everglades

SOFIA Project: Integrated Biogeochemical Studies in the Everglades: Nutrients and Sulfur

SOFIA Project: Integrated Geochemical Studies in the Everglades

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