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Metal Leaching in Mine Tailings: Short‐Term Impact of Biochar and Wood Ash Amendments
Author(s) -
Beauchemin Suzanne,
Clemente Joyce S.,
MacKin Ted,
Tisch Bryan,
Lastra Rolando,
Smith Derek,
Kwong John
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.04.0195
Subject(s) - biochar , tailings , leaching (pedology) , wood ash , leachate , amendment , environmental chemistry , chemistry , toxicity characteristic leaching procedure , pyrolysis , pulp and paper industry , waste management , environmental science , soil water , heavy metals , soil science , organic chemistry , political science , law , engineering
Biochar is perceived as a promising amendment to reclaim degraded, metal‐contaminated lands. The objective of this study was to compare the potential of biochar and wood ash amendments to reduce metal(loid) leaching in mine tailings. A 2‐mo leaching experiment was conducted in duplicate on acidic and alkaline tailings, each mixed with 5 wt.% of one of the following amendments: three wood‐derived, fast‐pyrolysis biochars (OC > 57 wt.%) and two wood ash materials (organic carbon [OC] ≤ 16 wt.%); a control test with no carbon input was also added. The columns were leached with water after 1, 2, 4, 8, 16, 32, and 64 d, and the leachates were monitored for dissolved metals, OC, and pH. For the acidic and alkaline tailings, the most significant impact on metal mobility was observed with wood ash materials due to their greater neutralization potential (>15% CaCO 3 eq.) compared with biochar (≤3.3% CaCO 3 eq.). An increase of 1 pH unit in the wood ash–treated alkaline tailings led to an undesirable mobilization of As and Se. The addition of biochar did not significantly reduce the leaching of the main contaminants (Cu and Ni in the acidic tailings and As in the alkaline tailings) over 2 mo. The Se attenuation noted in some biochar‐treated acid tailings may be mainly due to a slight alkaline effect rather than Se removal by biochar, given the low capacity for the fresh biochars to retain Se under acidic conditions (pH 4.5). The increased loss of dissolved OC in the biochar‐amended systems was of short duration and was not associated with metal(loid) mobilization.