This study employs measurements of atmospheric Hg0 concentrations and exchange fluxes (i.e., uptake and emissions) in a forest near Petersham, MA to analyze trends in Hg0 for multiple years. Hypotheses are that (i) fluxes of Hg0 will follow diel and seasonal patterns similar to that of carbon dioxide (CO2) which is dominated by plant uptake; that (ii) the ecosystem will represent a net sink for Hg0 over the course of a year as a result of canopy uptake; and that (iii) ecosystem-level Hg0 fluxes can be partitioned into contributions of canopies and underlying soil fluxes. Fluxes are measured using a micrometeorological flux-gradient approach whereby Hg0 is measured at two heights above the forest to infer about fluxes. In addition, other trace gases such as carbon dioxide as well as micrometeorological data are collected. Seasonal and diurnal trends in the data are analyzed and sorted by meteorological conditions present at the time of measurement using statistical programs such as Stata, Python, and Excel. Preliminary canopy measurements indicate diel and seasonal concentration and flux Hg0 patterns are largely decoupled from that of CO2, indicating that Hg0 uptake may be unrelated to stomatal uptake. In addition, midday Hg0 emissions indicate an importance of Hg0 emissions via photochemical processes. Overall, we find that this forest served as a small net source of Hg0 of 1.1 μg m-2 yr-1, although this estimate has large uncertainty. Preliminary soil gradient analysis indicate a net summertime deposition of Hg0 in soils that still needs to be quantitatively constrained using turbulence characteristics. We conclude that this forest unexpectedly serves as a small Hg0 source, which is inconsistent with other studies that predict forests to serve as significant Hg0 sinks.
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