EFFECTS OF BIOCHAR AND MARBLE MUD ON MINE WASTE PROPERTIES TO RECLAIM TAILING PONDS

The effects of biochar addition in improving soil physical properties are not clearly understood in mining tailings. The objective of this study was to determine the effects of three different types of biochars, in addition to marble mud (MM) and their mixtures, on the structural stability and water retention of mine wastes in Cartagena, Spain. Biochars were produced at 500 degrees C from pig manure (PM), cotton (Gossipium hirsutum L.) crop residues (CR) and municipal solid waste (MSW). Biochars were added to the mine waste (MW) along with MM and a control (no amendments added). These mixtures were incubated in cores for 90 days (25 degrees C). PM and CR mixed with MM decreased soil bulk density (from 0.98 g cm(-3) to 0.89 and 0.84 g cm(-3), respectively). Amendments had no significant effect on total porosity whereas they increased gas diffusion by 100%, except for MSW. MM improved the plant available water from 0.59 to 2.56 cm as its combination with biochars, extremely relevant in water scarce climates. The micropores were likely replaced by mesopores when application of PM, CR, MM, and biochars + MM and they improved water retention. Total carbon (TC) and total nitrogen (TN) increased by using biochars and MM and no significant effects were assessed on aggregates. In general, MM mixed with PM and CR derived biochar improved the structural stability and exhibited a strong impact in reclaiming physical quality on mine tailings. Copyright (C) 2016 John Wiley & Sons, Ltd.