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Abstract

Surface mining can decrease carbon (C) but reclamation can improve soil quality and promote plant growth while restoring the terrestrial C sink. The objective of this study was to determine the effects of biosolids on the C storage capacity of mine tailings over time. Changes in C, nitrogen (N) and plant production over a 13 year period at a deactivated tailings site at Highland Valley Copper mine situated in interior British Columbia, were evaluated. Soil and biomass samples were taken in 2011 and compared to data from a study originally established in 1998. A randomized block design was used and the treatments included a control (no biosolids) and biosolids at application rates of 150 and 250 Mg ha⁻¹. Data was compiled in a chronosequence (representing years 0, 1, 2, and 13 years of reclamation) and analyzed. Biosolids increased total C, N and plant biomass while lowering the C:N ratio. Tailings C concentrations ranged from 1.4% for the control up to 17.2% for the 250 Mg ha⁻¹ treatment. Depending on the biosolid application rate, tailings sequestered up to 14 Mg C ha⁻¹ yr⁻¹ during the 13 years of reclamation. The results show that the use of biosolids during reclamation can improve the C sequestering capacity of mine tailings, which is beneficial to the restoration of the terrestrial C sink and the global C cycle.