Assessment of the Potential for Release of Mercury From FGD-Gypsum When Applied As a Soil Amendment.

The primary focus of this study was to quantify mercury (Hg) released to air from flue gas derived gypsum (FGDG) when amended to planted and bare agricultural soils.  The potential for methyl mercury (MeHg) production, and Hg uptake by plants in soils amended with FGDG, was also investigated.  FGDG from three coal fired energy generating facilities were homogenized into three soils at 4.5, 45, and 170 t ha-1, and applied at 4.9 t ha-1 as a thin layer to simulate tilled and no-till applications, respectively.  Hg flux was measured from unamended and FGDG amended soils on a seasonal time step over one year, and after disturbing, watering and planting.  MeHg in soil, irrigation drainage, and total Hg (THg) in plant tissues were quantified.  Results must be interpreted within the confines of the experimental setting, and materials used for this study.  THg concentrations in soils homogenized with FGDG were below those considered to be natural background values (< 100 ng g-1).  Emissions from amended soils were higher initially relative to unamended soils but became similar over time for all application rates.  Significantly less Hg (2%) was lost to the air from FGDG amended to soils than from the pure FGDG material (30 to 70%) over a year.  THg and MeHg in irrigation drainage and THg concentrations measured in plants were similar for amended and unamended soils.