Abstract
Open cast coal mining causes complete loss of carbon sink due to the destruction of vegetation and soil structure. In order to offset the destruction and to increase sequestration of carbon, afforestation is widely used to restore these mine spoils. The current field study was conducted to assess the ecosystem status, soil quality and C pool in an 8 years old reclaimed mine spoil (RMS), compared to a reference forest (RF) site and unamended mine spoil (UMS). Biochar (BC) prepared from invasive weed Calotropis procera was applied in this 8 year RMS at 30 t ha−1 (BC30) and 60 t ha−1 (BC60) to study its impact on RMS properties and C pool. Carbon fractionation was also conducted to estimate inorganic, coal and biogenic carbon pools. The C stock of 8 year old RMS was 30.98 Mg C ha−1 and sequestered 113.69 Mg C ha−1 CO2. BC30 and BC60 improved the C-stock of RMS by 31% and 45%, respectively, and increased the recalcitrant carbon by 65% (BC30) and 67% (BC60). Spoil physio-chemical properties such as pH, cation exchange capacity, moisture content and bulk density were improved by biochar application. The total soil carbon at BC30 (36.3 g C kg−1) and BC60 (40 g C kg−1) was found to be significantly high compared to RMS (21 g C kg−1) and comparable to RF (33 g C kg−1). Thus, eco-restoration of coal mine spoil and biochar application can be effective tools for coal mine reclamation and can help in achieving the UN sustainable development goal 13 (climate action) by increasing carbon sequestration and 15 (biodiversity protection) by promoting ecosystem development.
Highlights
The UN sustainable development goal (SDG) 13 stands for climate action and promotes all activities which would ensure successful sequestration of carbon, whereas, SDG 15 safeguards and restores biodiversity protection [1,2]
The C/N ratio of 5.01 indicates that the biochar is rich in labile carbon, providing substrate for microbial action in the mine spoil, while H/C ratio of
The inorganic and biogenic carbon pool, especially the recalcitrant pool, was improved by biochar application, suggesting that biochar can be an effective mode of enhanced carbon fixation in the spoil, along with plantation activities
Summary
The UN sustainable development goal (SDG) 13 stands for climate action and promotes all activities which would ensure successful sequestration of carbon, whereas, SDG 15 safeguards and restores biodiversity protection [1,2]. Mining activities lead to complete loss of vegetation and the carbon sink in the soil and plants are lost to the atmosphere [5]. Mine spoils are carbon deficit with impoverished soil conditions that cannot support plant and microbial growth. Coal mine restoration can help restore the lost carbon sink by promoting plant growth and enriching the mine spoil, which helps sequester the atmospheric carbon [6,7]. Degraded land can be reclaimed by development of forest cover Technical reclamation such as leveling and grading of dump, reducing slope length, stabilization of slope by blanketing with coir mat along with grass-legume mixture, application of top soil, fly ash and bio-solids can be used to enhance the vegetation growth [11,12,13]
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