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Investigating Mercury Dissolution in Soil Columns: The Role of Pe on Hg Transformations

This study explores the effects of redox potential (pe) on the transformations of mercury (Hg) in soils, emphasizing both abiotic and biotic processes. We aim to quantify the impact of pe on the dissolution and transport of dissolved and transformed Hg in controlled conditions. Utilizing soil columns that replicate watershed zones, we analyze various soil compositions and metabolic processes, including denitrification and methanogenesis. Our results will inform future studies on Hg behavior under varying environmental conditions, enhancing understanding of its ecological implications.

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Investigating Mercury Dissolution in Soil Columns: The Role of Pe on Hg Transformations

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  1. Mercury Dissolution Studies in Soil Columns as a Function of pe Matthew Fox Dr. S. Grimberg

  2. Objectives • Predict the effect of pe on abiotic/biotic Hg transformations in sediments • Net effect of pe on Hg in controlled pe conditions: • Dissolved Hg • Transformed Hg • Transported Hg

  3. Soil Composition Aerobic Metabolism: Oxidation of organic matter Denitrification: Sulfate Reducing Conditions: Sulfate reducing bacteria causing Hg Methylation Methanogenesis: *Modified from Dr. Kim Shulz: www.esf.edu/efb/schulz/ Limnology/RedoxReac2.jpg

  4. Abiotic and Biotic Column Conditions Anaerobic: Sulfur couple Variable column Anaerobic: Nitrogen couple Aerobic Eh Range (mV) • The columns model the soil zones within the watershed 200 to 800 50 to 750 -650 to -200

  5. Column Setup • Measure pH/pe before and after column • Outflow will be into a sealed container to reduce contamination • Many samples for HgT and a few samples for MeHg pH/ORP meter N2 Purge + Disp. Pump Ready for Hg analysis Media solution Flow through cell Column

  6. Experimental Stages • Quartz sand: • vary pe, DOC in abiotic environment Obtain stable reproducible results. • Quartz sand w/ HgS: • vary pe, DOC in abiotic and biotic environment • Soil: • vary pe, DOC in biotic environment • Soil w/HgS: • vary pe, DOC in biotic environment 1. 2. 3. 4.

  7. Expected Relative Output from Columns

  8. Accomplished to Date • Collected Soil samples next to Sunday Lake • Collected Influent and Effluent water/DOC samples, filtered through 5.0 and 0.45 mm, storing frozen • Experimental setup for two columns with automatic data logging capabilities • Determined the mV effect of quartz sand for the non-buffered systems: • Couples: NH4+ / NO3- and HS- / SO42- • Couples with trace metal media • Nitrogen Couple stability with trace metal and Phosphorus buffer

  9. Infrared Digital Orthoquad Sp 2003 water soil

  10. Future Plans • Testing under varied pe, DOC conditions while recording mV, pH and determining HgT and less often MeHg • quartz sand with HgS • soil • soil with HgS

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