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Updated: Sep 4, 2025
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An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium
Published on: December 17, 2018
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Diel mercury concentration variations in a mercury-impacted stream.
Scott C Brooks1, Ami L Riscassi2, Carrie L Miller3
1Oak Ridge National Laboratory, Environmental Sciences Division, PO Box 2008, MS 6038, Oak Ridge, TN, 37831-6038, USA. brookssc@ornl.gov.
Environmental Science. Processes & Impacts
|July 13, 2022
Summary
Mercury and methylmercury cycles in a contaminated creek show daily and seasonal patterns. Particulate mercury increased overnight in summer, while filtered methylmercury varied with season and time of day, influenced by biota and photochemistry.
Area of Science:
- Environmental Chemistry
- Aquatic Toxicology
- Biogeochemistry
Background:
- Mercury (Hg) and methylmercury (MMHg) contamination poses ecological risks.
- Understanding diel and seasonal dynamics is crucial for accurate mercury monitoring.
- Previous studies have not fully elucidated the influence of daily cycles on Hg and MMHg biogeochemistry in streams.
Purpose of the Study:
- To investigate the influence of the daily photocycle on mercury and methylmercury biogeochemical cycles.
- To assess seasonal variations in mercury and methylmercury dynamics.
- To identify key drivers of mercury and methylmercury cycling in a contaminated creek.
Main Methods:
- Bi-hourly sampling of filtered and particulate Hg and MMHg over 30-hour periods during summer and winter.
- Analysis of associated water chemistry parameters, including turbidity, total suspended sediment, pH, discharge, and dissolved organic carbon (DOC).
- Evaluation of mercury and methylmercury concentrations across distinct creek locations (forested, urban/suburban, industrial).
Main Results:
- Particulate Hg and MMHg concentrations doubled overnight in summer (excluding upstream industrial site), correlating with increased turbidity and suspended sediment.
- Filtered Hg (HgD) concentrations increased during daytime in unshaded areas, suggesting photochemical reactions.
- Filtered MMHg (MMHgd) exhibited significant diel patterns year-round, with summer peaks in the afternoon and winter peaks after sunset, influenced by water temperature and biofilm activity.
Conclusions:
- Biogeochemical mercury and methylmercury cycles respond to daily and seasonal cycles, driven by macrobiota activity, photochemistry, and water column conditions.
- Accurate long-term mercury monitoring requires consistent sampling timing.
- In situ turbidity measurements can effectively track diel dynamics of particulate mercury and methylmercury, while fluorescing dissolved organic matter is less effective.
