Comparing ecosystem gaseous elemental mercury fluxes over a deciduous and coniferous forest

Abstract

Sources of neurotoxic mercury in forests are dominated by atmospheric gaseous elemental mercury (GEM) deposition, but a dearth of direct GEM exchange measurements causes major uncertainties about processes that determine GEM sinks. Here we present three years of forest-level GEM deposition measurements in a coniferous forest and a deciduous forest in northeastern USA, along with flux partitioning into canopy and forest floor contributions. Annual GEM deposition is 13.4 ± 0.80 μgm⁻² (coniferous forest) and 25.1 ± 2.4 μgm⁻² (deciduous forest) dominating mercury inputs (62 and 76% of total deposition). GEM uptake dominates in daytime during active vegetation periods and correlates with CO₂ assimilation, attributable to plant stomatal uptake of mercury. Non-stomatal GEM deposition occurs in the coniferous canopy during nights and to the forest floor in the deciduous forest and accounts for 24 and 39% of GEM deposition, respectively. Our study shows that GEM deposition includes various pathways and is highly ecosystem-specific, which complicates global constraints of terrestrial GEM sinks.

Citation

​Zhou, Jun; Bollen, Silas W.; Roy, Eric M.; Hollinger, David Y.; Wang, Ting; Lee, John T.; Obrist, Daniel. 2023. Comparing ecosystem gaseous elemental mercury fluxes over a deciduous and coniferous forest. Nature Communications. 14: 2722. 9 p. https://doi.org/10.1038/s41467-023-38225-x.