Observed and Modeled Mercury and Dissolved Organic Carbon Concentrations and Loads at Control Structure S-12D, Florida Everglades, 2013–17
- Document: Report (4.90 MB pdf)
- Appendix 1 (457 kB pdf) — Model Archive Summary for Dissolved Organic Carbon Concentrations at Station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida
- Appendix 2 (535 kB pdf) — Model Archive Summary for Filtered Mercury Concentrations at Station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida
- Appendix 3 (481 kB pdf) — Model Archive Summary for Filtered Methylmercury Concentrations at Station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida
- Appendix 4 (408 kB pdf) — Model Archive Summary for Particulate Mercury Concentrations at Station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida
- Appendix 5 (379 kB pdf) — Model Archive Summary for Particulate Methylmercury Concentrations at Station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida
- Appendixes 1 –5 in pdf format (zip)
- Appendixes 1 –5 in rtf format (zip)
- Data Release: USGS data release — Calculated mercury and carbon concentrations, USGS station 254543080405401: Tamiami Canal at S-12D Near Miami, Florida, 2013–2017
- Download citation as: RIS | Dublin Core
Mercury (Hg) has been a contaminant of concern for several decades in South Florida, particularly in the Florida Everglades. The transport and bioavailability of Hg in aquatic systems is intimately linked to dissolved organic carbon (DOC). In aquatic systems, Hg can be converted to methylmercury (MeHg), which is the form of Hg that bioaccumulates in food webs. The bioaccumulation of MeHg poses significant health risks to wildlife and humans. Fish consumption advisories triggered by elevated Hg levels first appeared in the 1980s in South Florida. Multiple structures regulate freshwater distribution to Everglades National Park, including S-12D. This report summarizes seasonal and annual concentration and load data from late September 2013 to April 2017 for the total of (1) filter-passing total mercury (FTHg), (2) filter-passing methylmercury (FMeHg), (3) particulate total mercury (PTHg), (4) particulate methylmercury (PMeHg) and, (5) DOC discharged through control structure S-12D. The loads of Hg fractions and DOC at control structure S-12D were determined by pairing discharge data with constituent concentrations estimated by empirical models based on surrogate in situ water-quality measurements.
Calculated concentrations of DOC ranged from 12.8 milligrams per liter (mg/L) to 27.9 mg/L with a mean of 18.8 mg/L during the study period. Annual loads of DOC ranged from 3,950 tons in 2015 to 10,900 tons in 2016. DOC loads increased linearly with an increase in flow, and the highest monthly DOC load of 1,630 tons was observed in February 2016.
Calculated concentrations of FTHg ranged from 0.35 to 1.55 nanograms per liter (ng/L) with a mean of 0.85 ng/L during the study period. Calculated concentrations of FMeHg ranged from 0.06 ng/L to 0.24 ng/L with a mean of 0.14 ng/L during the study period. Generally, FTHg and FMeHg concentrations were lower during periods of decreased flow and higher during periods of increased flow. Calculated PTHg concentrations ranged from 0.09 ng/L to 4.19 ng/L with a mean of 0.58 ng/L during the study period. Calculated PMeHg concentrations ranged from below the limit of detection <0.01 ng/L to 0.29 ng/L with a mean of 0.03 ng/L during the study period.
Loads of Hg were often zero or lowest from November to May, owing to the lack of flow or low-flow conditions. FTHg and FMeHg loads increased linearly with an increase in flow and typically were highest from June to October. During periods of increasing flow or following changes in gate operations, PTHg and PMeHg constituted a greater percentage of the total Hg load. Annual loads of total Hg (filter-passing and particulate) ranged from 254 grams in 2015 to 658 grams in 2016. FTHg was the predominant contributor to the total Hg load. Information presented herein provides the first assessment of DOC and Hg loads to Everglades National Park through control structure S-12D using continuous in situ measurements of discharge and constituent surrogates and compares the surrogate model approach to loads calculated from monthly sampling. Analysis of calculated and observed loads demonstrates the significance of flow data on calculating constituent loads.
Booth, A.C., Poulin, B.A., and Krabbenhoft, D.P., 2020, Observed and modeled mercury and dissolved organic carbon concentrations and loads at control structure S-12D, Florida Everglades, 2013–17: U.S. Geological Survey Open-File Report 2020–1092, 27 p., https://doi.org/10.3133/ofr20201092.
ISSN: 2331-1258 (online)
Table of Contents
- Study Methods
- Analyses of Field and Laboratory Measurements
- Channel Cross-Sectional Variability
- Empirical Models
- Dissolved Organic Carbon Concentrations and Loads
- Mercury Concentrations and Loads
- Comparison of Observed Loads to Calculated Loads
- Comparison of Traditional Discrete Sampling to Surrogate Approach
- Summary and Conclusions
- References Cited
- Appendixes 1–5
|Publication Subtype||USGS Numbered Series|
|Title||Observed and modeled mercury and dissolved organic carbon concentrations and loads at control structure S-12D, Florida Everglades, 2013–17|
|Series title||Open-File Report|
|Publisher||U.S. Geological Survey|
|Publisher location||Reston, VA|
|Contributing office(s)||Caribbean-Florida Water Science Center, Upper Midwest Water Science Center|
|Description||Report: vi, 27 p.; Appendixes; Data Release|
|Online Only (Y/N)||Y|
|Additional Online Files (Y/N)||Y|
|Google Analytic Metrics||Metrics page|