Biogeochemistry Biogeochemistry and Natural and Natural Attenuation of Attenuation of Acid- -Mine Mine Acid Drainage at Davis Drainage at Davis Richard F. Yuretich Pyrite Mine, Pyrite Mine, David Ahlfeld Rowe MA Rowe MA Sarina Ergas Allan Feldman Klaus Nüsslein UMass Amherst
Davis Mine • Town of Rowe, MA • Remains of an abandoned pyrite mine • Small area – Ore body: 15 ha – AMD area: 3-4 ha
Davis Mine Shaft #1 Acidic Mine Effluent 100 m
Geology of Davis Mine • Located in northwestern Massachusetts. • Sulfide mineralization primarily (Fe)-Cu-Zn, low Pb and As. • Scattered sulfide ore bodies along NE-SW trend. • Hydrothermal origin related to arc volcanism
Davis Mine, Rowe, MA • Pyrite extracted from 1886 until 1910. Shaft #1 • Collapsed because of poor mining practices .
Davis Mine, Rowe, MA Shaft #1 • Leaching acidity, iron, sulfate, and other metals into nearby brook
Pristine vs. Impacted Water pH Cond Na Fe Zn Cl SO4 SiO2 Normal 5.7 20 2.2 0.27 0.08 2.61 8.12 5.14 Effluent 3.19 134 5.75 22.5 4.51 5.32 178.5 26.7
Initial Monitoring Network • Mine effluent drains from Shaft #1 into Davis Mine Brook. • Three sampling points along effluent stream.
Well #2 Mine Shaft Site 1
Well #8 Site 2
Well #13
pH, SO 4 in Mine Effluent 3.20 250 3.17 3.15 Site #1 Site #2 200 Site #3 Concentration (mg/l ) 3.10 3.07 150 3.05 3.00 100 2.97 2.95 50 2.90 2.85 0 SO 4 pH
Trace Elements in Mine Effluent 40.00 Fe, Zn highest at mine entrance 35.00 33.80 Precipitates via oxidation downstream 30.00 Augmented by groundwater from tailings Concentration (mg/l) 25.00 23.57 Site #1 Site #2 20.00 Site #3 14.36 15.00 Mn, Al, (Cu) increase downstream 10.00 4.89 4.59 5.00 4.07 3.83 2.88 2.26 1.27 0.97 0.79 0.65 0.59 0.51 0.00 Fe Mn Al Cu Zn
Present Study • Impacts upon Davis Mine Brook downstream from effluent • Biogeochemistry of natural attenuation
Davis Mine Brook: A4 to B4
Davis Mine Brook: Well 2 and Power Lines
pH, SO 4 in Davis Mine Brook 30 6.00 Mine Effluent Input 25 5.50 Mine Effluent Input 20 Concentration mg/l 5.00 pH 15 4.50 10 4.00 5 0 3.50 A4 B1 B2 B3 B4 W 2 P. L. S. X A4 B1 B2 B3 B4 W 2 P. L.S. X Downstream Downstream
Trace Elements: Davis Mine Brook Zn, Al, most 2.50 persistent trace elements 2.00 Fe disappears more rapidly Stream Xing B1 downstream Concentration (mg/l) 1.50 B2 B3 Dilution by B4 tributary has Near Well 2 Power Lines greatest effect 1.00 Stream Xing Brook “macrobiota- 0.50 free” for ~5 km 0.00 Fe Mn Zn Cu Al
Groundwater • Hand-augur wells 1994-95 • Multi-level monitoring wells installed April, 2003 • Geochemical and hydrological modeling • Assessment of rates and mechanisms of natural remediation • Documentation of sulfate and iron- reducing bacteria
Groundwater Wells Shallow wells 1994-95 Multilevel wells Installed April, 2003
• Acidification of groundwater locally intense • Extreme values found in old tailings piles • Ambient groundwater from unimpacted areas helps restrict the AMD zone
• Iron “hot zone” confined to small area of groundwater. • Greater extension to S down Davis Mine Brook. • Reflects the more complicated redox and solubility behavior of Fe.
• Sulfate shows extensive area of elevated concentration. • Reduction only possible removal mechanism
Down Gradient Trends • Three 1994-95 shallow wells ~1m deep
Trace Elements in Groundwater 45.00 Fe, Al, Cu increase down gradient 40.65 40.00 Mn, Zn highest in Well #8, where 35.00 hydraulic conductivity is lowest 32.44 30.00 Concentration (mg/l) Well #2 25.00 Well #8 Well #13 20.00 15.00 12.35 9.17 10.00 6.83 6.76 6.55 5.00 3.36 2.14 2.05 1.82 1.76 1.30 0.53 0.46 0.00 Fe Mn Al Cu Zn
Considerations • Low pH limits ability of oxyhydroxides to absorb Zn, Cu • H 2 S odor noticeable is some areas = active sulfate reduction by anaerobic microorganisms? • CuS has lower solubility than ZnS, so Cu would be scavenged preferentially on sulfide precipitates
Secular Variations in Groundwater 16 14 12 Concentration (mg/l) 10 Well #2 Zn in Groundwater Well #8 8 Well #13 6 4 2 0 3/7/94 4/26/94 6/15/94 8/4/94 9/23/94 11/12/9 1/1/95 2/20/95 4/11/95 4
Secular Variations in Groundwater 10 9 8 Cu in Groundwater 7 Concentration (mg/l) 6 Well #2 Well #8 5 Well #13 4 3 2 1 0 3/7/94 4/26/94 6/15/94 8/4/94 9/23/94 11/12/94 1/1/95 2/20/95 4/11/95
Secular Variations in Groundwater 18.00 Zn/Cu Ratio in Groundwater 16.00 14.00 Concentration Ratio 12.00 Well #2 10.00 Well #8 Well #13 8.00 6.00 4.00 2.00 0.00 3/7/94 4/26/94 6/15/94 8/4/94 9/23/94 11/12/94 1/1/95 2/20/95 4/11/95
Natural Remediation? • Active microbial sulfate reduction promotes preferential removal of dissolved Cu on precipitated sulfides. • High Zn/Cu ratios in groundwater point towards this process. • Seasonal patterns reflect variations in microbial activity.
Additional evidence of sulfate reduction 1000 y = 0.6907x + 15.37 800 R 2 = 0.2083 Sulfate (mg / l) 600 400 200 0 0 100 200 300 400 500 600 ORP (mV)
Cultivating Reducing Bacteria
Sulfate-reducing bacteria are present in this environment
Ongoing Investigation Ongoing Investigation • Continued field monitoring Continued field monitoring • • Column studies to model geochemistry Column studies to model geochemistry • • DNA identification DNA identification • • Enrichment cultures and community ID Enrichment cultures and community ID • • Benefits of research to K12 teachers Benefits of research to K12 teachers • Ongoing research supported by the National Science Foundation “Biocomplexity in the Environment” Program CHE-0221791
Thanks to the Team! Thanks to the Team! • Jessica Bloom Jessica Bloom • • Liam • Liam Bevan Bevan • Melissa Russell Melissa Russell • Ongoing research supported by the National Science Foundation “Biocomplexity in the • Mercedita Mercedita Monserrate Monserrate • Environment” Program CHE-0221791 • Krissy • Krissy Forloney Forloney • Phil Dixon Phil Dixon • • Cristine Cristine Barreto Barreto • • Jason Jean • Jason Jean • Janice Wing Janice Wing • • Jaime Harrison Jaime Harrison • • Melinda Solomon • Melinda Solomon
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