Impact of using paper mill sludge for surface-mine reclamation on runoff water quality and plant growth
Paper mills generate large amounts of solid waste consisting of fibrous cellulose, clay, and lime. Paper mill sludge (PMS) can improve reclamation of surface-coal mines where low pH and organic-carbon levels in the spoil cover material can inhibit revegetation. When applied at high rates, however, PMS may adversely impact the quality of surface runoff. Therefore, we applied PMS at 0, 224, and 672 dry Mg ha–1 to 22.1 x 4.6-m plots at a recently mined site and monitored runoff for a total of 13 mo. The zero-rate plots served as controls and received standard reclamation consisting of mulching with hay and fertilization at planting. Compared to the control plots, PMS reduced runoff fourfold to sixfold and decreased erosion from 47 Mg ha–1 to <1 Mg ha–1. Most of the reduction occurred in the 2.5 mo before the plots were planted. Flow-weighted average dissolved oxygen concentrations in runoff from plots at the 224 and 672 Mg ha–1 rates, however, were much lower (0.4 vs. 8.2 mg L–1) and chemical oxygen demand (COD) was much higher for the 672 Mg ha–1 rate plots than the control plots during the pre-plant period (7229 vs. 880 mg L–1). There were few noteworthy differences in water quality among treatments post-planting, but plant dry-matter yields were greater for the PMS plots than for the controls. The 672 Mg ha–1 rate did not increase COD or nutrient loads compared to the 224 Mg ha–1 rate and may have more persistent beneficial effects by increasing soil organic carbon levels and pH to a greater extent.