An Examination of Total and Methyl Mercury fate and transport in the Florida Everglades Using a Eulerian Approach

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1 An Examination of Total and Methyl Mercury fate and transport in the Florida Everglades Using a Eulerian Approach Mike Tate 1, Dave Krabbenhoft 1, Morgan Maglio 1, John DeWild 1, Jacob Ogorek 1, Charlie Thompson 1, Bill Orem 2, and George Aiken 3, Carl Fitz 4 1. USGS, Middleton, WI 2. USGS, Reston, VA 3. USGS, Boulder, CO 4. University of Florida U.S. Department of the Interior U.S. Geological Survey

2 An Eulerian approach provides a significant challenge to demonstrate a linked hydrobiogeochemical level of understanding Wet & Dry Hg Deposition Total Hg Hg o Evasion MeHg Mass Hg flux in Settling & sorbtion Diffusion Mass Hg flux out Mass MeHg flux in Hg Photo-demethy Mass MeHg MeHg flux out Diffusion Flow Direction Flow Direction

3 Water Quality Gradients along Flow Paths (Eulerian Approach) from Internal and External Forcing Factors At the top of the system, runoff from DOC agricultural Gradient fields (mg/l) is enriched Nin several QW constituents, notably S sulfate and DOC for Hg research For this study, we start and the release points of canal water into the marsh at two locations in WCA- 2A ~1 and WCA-3A ~5 Follow independently (EDEN) prescribed flow paths and document changes Check observations against modeled results for verification Legend 3A Transect Sites 2A Transect Sites Sulfate Concentration >1 mg/l 1-5 mg/l 2-1 mg/l.5-2 mg/l Agricultural Fields 3A ENP LNWR 2A

4 Total Hg Concentrations in Surface Water 5 4 2A Transect Surface Water July 212 Surface Water May 213 Surface Water Aug A Transect Surface Water May 213 Surface Water Aug 214 HgT (ng/l) 3 2 HgT (ng/l) Distance from L-28 Canal (km)

5 MeHg Concentrations in Surface Water 2. 2A Transect Surface Water July 212 Surface Water May 213 Surface Water Aug A Transect Surface Water May 213 Surface Water Aug MeHg (ng/l) 1. MeHg (ng/l) A Transect Canal Surface water is initially low in mehg. MeHg reaches maximum 3-5km from canal MeHg porewater concentrations are generally low and only show modest increase downstream Distance from L-28 Canal (km) 3A Transect Maximum mehg concentration is observed within the first 2-3km from the canal MeHg decreases toward the center of the marsh. Near the S-12, mehg marginally increases.

6 Is there a link between MeHg transect trend and Sulfate Yes! A Transect July 212 May 213 Aug A Transect May 213 Aug 214 SO 4 (mg/l) 4 3 SO 4 (mg/l) Distance from L-28 Canal (km)

7 MeHg vs. Sulfate in Surface Water A Transect May 213 Aug A Transect July 212 May 213 Aug 214 MeHg (ng/l) MeHg (mg/l) SO4 (mg/l) SO4 (mg/l)

8 Goldilocks Distribution Relationship between MeHg, SO 4 and DOC

9 Model Results for HgT in WCA 2A Total Hg per transect segment (ug) Observed Surface Water HgT Observed Surface Water Hg Wet Deposition Dry Deposition Hg Re-emission Gross Atmospheric Deposition Net Atmospheric Deposition Adsoption to Surfaces Predicted Surface Water Hg

10 Model Results for HgT in WCA 2A Total Hg per transect segment (ug) Wet & Dry Deposition Observed Surface Water Hg Wet Deposition Dry Deposition Hg Re-emission Gross Atmospheric Deposition Net Atmospheric Deposition Adsoption to Surfaces Predicted Surface Water Hg

11 Model Results for HgT in WCA 2A Total Hg per transect segment (ug) Total Gross Atmospheric Deposition Observed Surface Water Hg Wet Deposition Dry Deposition Hg Re-emission Gross Atmospheric Deposition Net Atmospheric Deposition Adsoption to Surfaces Predicted Surface Water Hg

12 Model Results for HgT in WCA 2A Total Hg per transect segment (ug) Hg Removal Processes Observed Surface Water Hg Wet Deposition Dry Deposition Hg Re-emission Gross Atmospheric Deposition Net Atmospheric Deposition Adsoption to Surfaces Predicted Surface Water Hg

13 Model Results for HgT in WCA 2A Observed vs. Predicted Surface Water Hg Total Hg per transect segment (ug) Observed Surface Water Hg Wet Deposition Dry Deposition Hg Re-emission Gross Atmospheric Deposition Net Atmospheric Deposition Adsoption to Surfaces Predicted Surface Water Hg

14 Summary: Use of an Eulerian sampling approach has provided new and confirmation insights into Hg cycling processes in the Everglades Coupling spatial and temporal information with field measurements links our physical and process-based understanding of Hg cycling in the Everglades. A restored Everglades with enhanced sheet-flow (DECOMP), studies employing Eulerian frameworks will have application for forecasting future conditions.