FORMATION OF MERCURIC SULFIDE IN SOIL

Analysis of mercury-contaminated soil from the flood plain of East For k Poplar Creek (EFPC) in Oak Ridge, TN, using a scanning electron micr oscope (SEM) with energy-and wavelength X-ray dispersive spectroscopy (EDS/WDS) and a transmission electron microscope (TEM) with select are a electron diffraction (SAED) revealed the presence of submicron, crys talline mercuric sulfide (HgS) in the form of metacinnabar. The HgS fo rmed in place after the deposition and burial of mercury-contaminated soils. A reaction path model developed to describe the geochemical evo lution of the soil redox conditions during flooding predicted that the resultant pe and pH of the soil would be within the stability range o f HgS. The reaction of mercury with other metal sulfides or sulfhydryl groups in the soil may have also contributed to the formation of HgS. The formation of HSS is significant to the remediation efforts at EFP C because the toxicity, leachability, and volatility of mercury in soi ls is dependent on the solid phase speciation. Because the local hydro geochemical conditions are not unique, the formation of HgS at this si te has implications to other environments as well.