Diel variation and pathways of gaseous mercury production in surface water and sediment–water interface of the Florida Everglades
Article
Ogunsola, SS, Oladipo, ME, Irizarry, N et al. (2026). Diel variation and pathways of gaseous mercury production in surface water and sediment–water interface of the Florida Everglades
. SCIENCE OF THE TOTAL ENVIRONMENT, 1015 10.1016/j.scitotenv.2026.181428
Ogunsola, SS, Oladipo, ME, Irizarry, N et al. (2026). Diel variation and pathways of gaseous mercury production in surface water and sediment–water interface of the Florida Everglades
. SCIENCE OF THE TOTAL ENVIRONMENT, 1015 10.1016/j.scitotenv.2026.181428
The production and evasion of dissolved gaseous mercury (Hg(0)) in the aquatic environment reduce pool of Hg available for methylation at the sediment-water interface (SWI) and increase atmospheric Hg for long-range transport. While photochemical reduction probably dominates Hg(0) production in photic surface water, the persistent presence (even at elevated levels) of Hg(0) in aphotic water, SWI, and sediment suggests the roles of microbial and dark chemical processes. This study was aimed to evaluate the relative importance of photochemical, microbial, and dark chemical processes for the production and distribution of Hg(0) in Everglades water, where organic matter attenuates light rapidly with increasing water depth. A diel variation in Hg(0) from surface water to SWI was examined using a new sampling device developed to preserve volatile Hg(0) in water at the SWI without disturbance and laboratory incubation and field microcosm experiments were conducted to assess gross and net Hg(0) reduction. Results indicated that Hg(0) levels declined throughout the day in both surface and SWI waters. However, surface water consistently exhibited higher Hg(0) concentrations compared to SWI. The Hg(0) concentrations ranged from 0.2 ng/L to 0.02 ng/L in surface water and 0.17 ng/L to 0.01 ng/L in the SWI. Photoreduction emerged as the dominant pathway for Hg(0) production in the Everglades, accounting for up to 70.8% of total Hg(II) reduction, surpassing both dark chemical and microbial processes, although these may contribute under certain conditions. Overall, our findings suggest that temperature-dependent Hg(0) evasion and re-oxidation of Hg(0), combined with photochemical Hg(II) reduction, play a major role in regulating Hg(0) concentrations in Everglades water and may significantly influence the broader Hg cycle in wetland ecosystems.
