Organic matter degradation in paper sludge amendments over gold mine tailings Christine Cousins a , Glenn H. Penner b , Bruce Liu b , Peter Beckett c , Graeme Spiers a, * a Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada P3E 2C6 b Department of Chemistry, University of Guelph, Ontario, Canada N1G 2W1 c Department of Biology, Laurentian University, Sudbury, Ontario, Canada P3E 2C6 article info Article history: Available online 17 September 2009 abstract The long-term stability of paper sludge amendments as covers for reclaimed mine waste storage facilities must be assessed by the mining industry. This study examines a 6 yr old sequence of paper sludge amendments applied over wastes from historic Au mines located in Northern Ontario, Canada. As paper sludge is mostly comprised of C-rich organic compounds, elemental quantification, 13 C cross polarization/ magic angle spinning nuclear magnetic resonance ( 13 C CP/MAS NMR) spectroscopy, and Fourier trans- form infrared (FTIR) spectroscopy were used to examine the minimal changes in the C content and spe- ciation observed of the amendments over time. These results suggest that paper sludge covers are suitable for use in medium to long-term mining reclamation strategies. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The long-term management of tailings and waste rock is of pri- mary concern in mine closure strategies. Tailings and waste rock can produce metalliferous mine drainage and nuisance dust, both having adverse environmental impacts. Furthermore, these mining wastes are generally deficient in plant nutrients and have a low water-holding capacity (Bradshaw and Chadwick, 1980; Stjernman Forsberg and Ledin, 2003), which discourages the natural estab- lishment of vegetation. To prevent contamination of adjacent ecosystems, the mining industry is currently investigating the use of organic residual materials as dry covers for tailings and waste rock disposal areas. Organic residual covers can maintain a high degree of saturation (Bussiere et al., 2004), using O 2 in their bio-degradation pathways (Markewitz et al., 2004; Panarotto et al., 2005), limiting the influx of O 2 to underlying waste materials, potentially significantly reducing acidification and mobilization of metals. Furthermore, or- ganic amendments can act as a growth medium for the re-estab- lishment of vegetation (Beauchamp et al., 2006). Some organic cover materials currently being considered for reclamation pur- poses are by-products of other industries, such as: municipal solid waste compost, sewage sludge, wood chips and paper sludge (Kuyucak, 2006). Rising costs of landfilling and considerable annual production makes paper sludge an economically attractive covering option where available. Paper sludge, a by-product of the pulp and paper industry, is commonly a mixture of kaolinite clay, CaCO 3 , cellulose, hemi-cellulose and lignin (Boni et al., 2004). Due to a high organic matter content, water retention capacity, and appropriate bulk density for plant establishment, paper sludge covers have the po- tential to alleviate many of the detrimental qualities of mining wastes that inhibit successful re-vegetation. However, there is significant concern about the rate of organic matter degradation in these cover materials. The organic residuals, which make up the majority of the constituents of paper sludge, must be resistant enough to degradation to maintain the required cover thickness for dust suppression and mine drainage prevention until a carbon-neutral or -accumulative vegetative cover is established. As paper sludge is primarily composed of organic matter, changes in the stability may be reflected in changes in the amendment’s C content. Comparing total C to N ratios, indicating N mineralization, has long been considered an indicator of early organic matter decomposition; however, late-stage decay is often monitored through changes in lignin content (Rowell et al., 2001; Chen et al., 2004). Carbon-13 cross polarization/magic angle spinning ( 13 C CP/ MAS) nuclear magnetic resonance (NMR) spectroscopy has increasingly been applied to the study of organic matter decompo- sition. Types of organic matter analyzed by 13 C CP/MAS NMR in- clude: humic acids (Schnitzer and Preston, 1986; Smejkalova et al., 2008), leaf litter (Preston and Trofymow, 2000; Prescott et al., 2004), wood degradation products (Haw et al., 1984; Preston et al., 1998), paper-making by-products (Marche et al., 2003), soil organic matter (Schnitzer et al., 2006; Fontaine et al., 2007; Salati et al., 2008; Sequaris et al., 2008), or soil amendment materials (Bellamy et al., 1995; Benoit and Preston, 2000; Folley and Cooper- band, 2002). Carbon-13 CP/MAS NMR has also been used to assess 0883-2927/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2009.09.009 * Corresponding author. Fax: +1 705 675 4828. E-mail address: gspiers@mirarco.org (G. Spiers). Applied Geochemistry 24 (2009) 2293–2300 Contents lists available at ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem