The Effect of Sulfate and Sulfide on Mercury Methylation in Florida EvergladesEPA Grant Number: U915152
Title: The Effect of Sulfate and Sulfide on Mercury Methylation in Florida Everglades
Investigators: Benoit, Janina M.
Institution: University of Maryland
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 1997 through January 1, 2000
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Fellowship - Oceanography , Academic Fellowships , Aquatic Ecosystems
The overall objective of this research project is to investigate how pore water sulfate and sulfide control methylmercury (MeHg) production and accumulation in sediments. The specific objective of this research project is to determine how the addition of sulfate and sulfide affect Hg methylation rates in Florida Everglades sediments.
Experimental additions of sulfate and sulfide to ambient sediments, along with measurements of pore water chemistry, were used to study the effect of these two constituents on Hg methylation in the Florida Everglades. Cores were collected from three sites along a nutrient and sulfate gradient caused by runoff from the agricultural region at the northern edge of this wetland. The sites exhibited a range in ambient pore water sulfate from <1 µM (TS7), to 2 µM (LOX), to 17 µM (3A15). Results indicate that addition of sulfate stimulated Hg methylation at the two low ambient sulfate sites (TS7 and LOX). At TS7, sulfate addition did not result in an increase in pore water sulfide, and at LOX a fivefold increase was observed, but sulfide levels did not become high enough to inhibit methylation. At 3A15, modest increases in sulfide lowered rates of Hg methylation; added sulfate reduced MeHg production rates. Results indicate that processes that lead to the sequestration or reoxidation of sulfide may have an important effects on MeHg formation in aquatic sediments.