skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Distinguishing 'new' from 'old' organic carbon in reclaimed coal mine sites using thermogravimetry: II. Field validation

Abstract

Thermogravimetry was used under laboratory conditions to differentiate 'new' and 'old' organic carbon (c) by using grass litter, coal, and limestone to represent the different C fractions. Thermogravimetric and derivative thermogravimetry curves showed pyrolysis peaks at distinctively different temperatures, with the peak for litter occurring at 270 to 395{sup o}C, for coal at 415 to 520 {sup o}C, and for limestone at 700 to 785{sup o}C. To validate this method in a field setting, we studied four reforested coal mine sites in Kentucky representing a chronosequence since reclamation: 0 and 2 years located at Bent Mountain and 3 and 8 years located at the Starfire mine. A nonmined mature (approximate to 80 years old) stand at Robinson Forest, Kentucky, was selected as a reference location. Results indicated a general peak increase in the 270 to 395{sup o}C region with increased time, signifying an increase in the 'new' organic matter (OM) fraction. For the Bent Mountain site, the OM fraction increased from 0.03 to 0.095% between years 0 and 2, whereas the Starfire site showed an increase from 0.095 to 1.47% between years 3 and 8. This equates to a C sequestration rate of 2.92 Mg ha{sup -1} yr{sup -1} formore » 'new' OM in the upper 10-cm layer during the 8 years of reclamation on eastern Kentucky reclaimed coal mine sites. Results suggest that stable isotopes and elemental data can be used as proxy tools for qualifying soil organic C (SOC) changes over time on the reclaimed coal mine sites but cannot be used to determine the exact SOC accumulation rate. However, results suggested that the thermogravimetric and derivative thermogravimetry methods can be used to quantify SOC accumulation and has the potential to be a more reliable, cost-effective, and rapid means to determine the new organic C fraction in mixed geological material, especially in areas dominated by coal and carbonate materials.« less

Authors:
; ; ; ;  [1]
  1. University of Kentucky, Lexington, KY (United States). Dept. of Forestry
Publication Date:
OSTI Identifier:
20905908
Resource Type:
Journal Article
Resource Relation:
Journal Name: Soil Science; Journal Volume: 172; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; SOILS; CARBON; LAND RECLAMATION; COAL MINING; THERMAL GRAVIMETRIC ANALYSIS; COAL; LIMESTONE; GRAMINEAE; TREES; REVEGETATION; CARBON SEQUESTRATION; SOIL CHEMISTRY; CARBONATES; BIOLOGICAL ACCUMULATION; BUILDUP

Citation Formats

Maharaj, S., Barton, C.D., Karathanasis, T.A.D., Rowe, H.D., and Rimmer, S.M. Distinguishing 'new' from 'old' organic carbon in reclaimed coal mine sites using thermogravimetry: II. Field validation. United States: N. p., 2007. Web. doi:10.1097/SS.0b013e3180314702.
Maharaj, S., Barton, C.D., Karathanasis, T.A.D., Rowe, H.D., & Rimmer, S.M. Distinguishing 'new' from 'old' organic carbon in reclaimed coal mine sites using thermogravimetry: II. Field validation. United States. doi:10.1097/SS.0b013e3180314702.
Maharaj, S., Barton, C.D., Karathanasis, T.A.D., Rowe, H.D., and Rimmer, S.M. Sun . "Distinguishing 'new' from 'old' organic carbon in reclaimed coal mine sites using thermogravimetry: II. Field validation". United States. doi:10.1097/SS.0b013e3180314702.
@article{osti_20905908,
title = {Distinguishing 'new' from 'old' organic carbon in reclaimed coal mine sites using thermogravimetry: II. Field validation},
author = {Maharaj, S. and Barton, C.D. and Karathanasis, T.A.D. and Rowe, H.D. and Rimmer, S.M.},
abstractNote = {Thermogravimetry was used under laboratory conditions to differentiate 'new' and 'old' organic carbon (c) by using grass litter, coal, and limestone to represent the different C fractions. Thermogravimetric and derivative thermogravimetry curves showed pyrolysis peaks at distinctively different temperatures, with the peak for litter occurring at 270 to 395{sup o}C, for coal at 415 to 520 {sup o}C, and for limestone at 700 to 785{sup o}C. To validate this method in a field setting, we studied four reforested coal mine sites in Kentucky representing a chronosequence since reclamation: 0 and 2 years located at Bent Mountain and 3 and 8 years located at the Starfire mine. A nonmined mature (approximate to 80 years old) stand at Robinson Forest, Kentucky, was selected as a reference location. Results indicated a general peak increase in the 270 to 395{sup o}C region with increased time, signifying an increase in the 'new' organic matter (OM) fraction. For the Bent Mountain site, the OM fraction increased from 0.03 to 0.095% between years 0 and 2, whereas the Starfire site showed an increase from 0.095 to 1.47% between years 3 and 8. This equates to a C sequestration rate of 2.92 Mg ha{sup -1} yr{sup -1} for 'new' OM in the upper 10-cm layer during the 8 years of reclamation on eastern Kentucky reclaimed coal mine sites. Results suggest that stable isotopes and elemental data can be used as proxy tools for qualifying soil organic C (SOC) changes over time on the reclaimed coal mine sites but cannot be used to determine the exact SOC accumulation rate. However, results suggested that the thermogravimetric and derivative thermogravimetry methods can be used to quantify SOC accumulation and has the potential to be a more reliable, cost-effective, and rapid means to determine the new organic C fraction in mixed geological material, especially in areas dominated by coal and carbonate materials.},
doi = {10.1097/SS.0b013e3180314702},
journal = {Soil Science},
number = 4,
volume = 172,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • Reclaimed coal mine sites represent a potential terrestrial carbon (c) sink. However, there is currently no cost-effective, rapid, and reliable method to quantify soil organic matter accumulation in soils containing appreciable quantities of coal and carbonate media. The derivative thermogravimetry method was evaluated as a potential analytical tool for differentiating C in spoils that may contain both recently derived and ancient ('old') C fractions. Grass litter and coal were used to represent 'new' and 'old' organic C, respectively, and limestone to represent the carbonate fraction. Derivative thermogravimetry curves showed pyrolysis peaks at distinctively different temperatures: grass litter, 270 to 395{supmore » o}C; coal, 415 to 520{sup o}C; limestone, 700 to 785{sup o}C. Recoveries from mixtures of these three components at the 95% confidence interval were found to be 94.49% {+-} 4.23% (coal), 93.67% {+-} 2.11% (litter), and 108.88% {+-} 2.88% (limestone). Petrographic analysis was used to validate derivative thermogravimetry findings. The results indicate that organic petrography can be a useful approximation of 'new' organic C, but particle density differences and time constraints might limit it. Thermogravimetry appears to be the superior of the two methods as it proved to be a more cost-effective, rapid, and direct method for differentiating and quantifying C.« less
  • Terrestrial systems represent a significant potential carbon (C) sink to help mitigate or offset greenhouse gas emissions. Nearly 3.2 Mha are permitted for mining activities in the United States, which are required to be reclaimed with vegetative cover. While site-specific studies have assessed C accumulation on reclaimed mine sites, regional analyses to estimate potential C increases have not been conducted. For this analysis, potential C sequestration is analyzed on 567000 ha of mine land in a seven-state region reclaimed to cropland, pasture, or forest. Carbon accumulation is estimated for cropland, pasture, and forest soils, forest litter layer, and aboveground biomassmore » by estimating average annual rates of C accumulation from site-specific and general C sequestration studies. The average annual rate of C storage is highest when mine land is reclaimed to forest, where the potential sequestration is 0.7 to 2.2 Tg yr{sup -1}. The C from soils, litter layer, and biomass from mine lands reclaimed to forest represents 0.3 to 1.0% of the 1990 CO{sub 2} emissions from the study region (919 Tg CO{sub 2}). To achieve the greenhouse gas (GHG) emission reduction goal of 7% below the 1990 level as proposed by the Kyoto Treaty requires CO{sub 2} emissions in the study area to be reduced by just over 64 Tg CO{sub 2}. The potential carbon storage in mine sites reclaimed to forest could account for 4 to 12.5% of these required reductions.« less
  • The Surface Mining Control and Reclamation Act of 1977 requires that coal mine sites in the United States be reclaimed to establish vegetative cover that is diverse, native, and capable of plant succession. However, there is a question as to whether vegetation established on coal mine sites reclaimed with biosolids is diverse and capable of plant succession. The influx of nutrients with the addition of biosolids leads to long-term dominance by early-successional species, most notably grasses, and consequently, a low establishment of woody and volunteer species. Additionally, many grass species commonly planted in reclamation have aggressive growth habits that leadmore » to their dominance in coal mine plant communities. The establishment and growth of selected grass mixes was evaluated to determine whether alternative grass mixes would be less competitive with woody and volunteer species as compared to commonly used grass mixes. Percent vegetative cover, species richness, and the survival of direct-seeded woody species were assessed for each treatment grass mixture. It was found that Poa compress and a mixture of P. compress, Panicum virgatum, and Trifolium repens provided adequate coverage while still allowing the highest species richness and survival of woody species. Use of these species mixtures in coal mine reclamation with biosolids in the eastern United States would likely lead to establishment of a more species-rich plant community with a greater woody species component while still providing erosion control and site protection.« less
  • Plantings on northwestern New Mexico raw mine spoils from 1973, examined for establishment (1975) and survival (1979), showed 75% survival of fourwing saltbush (Atriplex canescens (Pursh) Nutt.), each plant occupying 2.32 m/sup 2/ (1.52 x 1.52 m). Alkali sacaton (Sporobolus airoides (Torr.) Torr.) cover was 4% and had a density of 0.05 plant per m/sup 2/.
  • Acid mine drainage from reclaimed coal strip mines is simulated by use of a comprehensive model described in an earlier paper. The simulated concentrations of key components are well within the ranges of measured values from reclaimed mines. In systems without iron-oxidizing bacteria the simulations indicate that oxygen is the only important oxidizer of pyrite. The oxidation of ferrous to ferric iron by purely chemical means is too slow to affect the overall oxidation rate of pyrite and is not important in these systems. For the typical physical parameters used here the diffusion rate of oxygen is the primary factormore » controlling the rate of pyrite oxidation. The pyrite oxidation rate is decreased by decreased air-filled porosity, by increased tortuosity of the oxygen diffusion path, by increased size of the spoil fragments, and by burying the pyritic material at deeper depths. Where oxygen resupply is not limiting the results indicate that iron-oxidizing bacteria can greatly increase the rate of pyrite oxidation. Whether or not bacteria are important in these zones depends primarily on the pH of the spoil solution. In the optimal pH range, between reduced bacterial efficiency and reduced ferric iron solubility (2.0 less than or equal to pH less than or equal to 3.0), the pyrite oxidation rate is accelerated by bacterially produced ferric iron. The extent and type of chemical reactions between H/sup +/, produced by pyrite oxidation, and the spoil matrix appears to be crucial in establishing the pH of the spoil solution.« less