Dissolve Inorganic Carbon (DIC) and Stable Carbon Isotope Evolution in a Tailings Pile
Hendratta Ali and Eliot Atekwana
Boone Pickens School of Geology, Oklahoma State University 105 Noble Research Center, Stillwater, OK 74078
The Old Lead Belt of SE Missouri (USA) was the nation's major source of lead for close to
100 years. As a result mine spoils estimated at more than 254 billion kg are disposed of in
more than 6 major tailings piles that cover more than 12 sq km within the Big and Flat River
watersheds. Sediments of mine tailings, groundwater below mine spoils, soil
water, surface
water and
soil
gas from tailings were analyzed for physical parameters, major ions and
carbon isotope ratios of DIC and carbon dioxide. Surface water was collected from lakes
surrounding the tailings, groundwater from wells between 4.6 and 30.5m deep,
soil
water
and
soil
gas from lysimeters and gas samplers between 0.5 and 3m. Results show that in
ground-,
soil
- and surface water, pH ranged from 6.3 to 8.1, alkalinity from 60 to 513 mg/l
and DIC range from 0.6 to 4.9 mM/l for groundwater, 3.4, to 8.5 mM/l for
soil
water, 1.3 mM/l
in lake water and 2.7 and 3.3 mM/l at tailings seeps.
Soil
carbon dioxide ranged between 0.4
and 21.9 mM C. The isotope ratios of DIC was -9.0 per mil for tailing seeps, -8.4 to -9.3 per
mil for lake water, -2.9 to -12.5 for groundwater, -3.5 to -5.8 per mil for
soil
water and -1.4 for
tailings sediments. The stable carbon isotope ratio of carbon dioxide from
soil
gas was -11.4
to -16.4 per mil and background
soil
gas (without mine spoils) -22.1 per mil. The results of
this study show that mine tailings can generate high DIC in ground and
soil
water that degas
as carbon dioxide to the unsaturated
soil
zone. Isotope values intermediate between tailings
sediment and background
soil
carbon agree with input of heavier carbon from tailings
carbonate into ground,
soil
and surface water DIC.
AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas