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Harvard Forest Research Project 2022

  • Title: Mercury accumulation in the Harvard Forest soils
  • Principal investigator: Daniel Obrist (daniel_obrist@uml.edu)
  • Institution: University of Massachusetts - Lowell
  • Primary contact: Daniel Obrist (daniel_obrist@uml.edu)
  • Team members:
  • Abstract:

    The overall goal of this project is to quantify net atmosphere-surface exchange of gaseous elemental mercury (Hg[0]) in two remote forests for one full year each, providing the first such records in non-polluted forests and leading to transformative progress in constraining Hg(0) sinks (atmospheric dry deposition) and sources (e.g., re-emissions) across landscapes.
    The first objective is to quantify the magnitude and temporal dynamics of net gaseous dry Hg(0) deposition (sum of gross deposition minus emission) in two forests with different seasonality, a deciduous temperate forest and an evergreen boreal forest. Net Hg(0) deposition will be measured using micrometeorological measurements on large towers, the only available method for direct, non-intrusive and time-extended measurements of net Hg(0) exchange at the ecosystem level encompassing all underlying sinks and sources. The second objective is to partition Hg(0) fluxes into canopy and soil contributions via deployment of two corresponding flux systems. One system will be deployed above the forest canopy to measure ecosystem-level Hg(0) exchange; a second system will be deployed below the canopy to quantify soil contributions. Canopy Hg(0) fluxes will be calculated by difference. Flux partitioning will provide annual, seasonal and diurnal Hg(0) sink (e.g., to canopies) and source strengths (e.g., from soils) needed to constraint Hg(0) deposition in global and regional chemical transport models. The third goal is to elucidate pathways of deposition by comparing Hg(0) fluxes to those of carbon dioxide, ozone, water vapor, and carbonyl sulfide.