Biochar application to hardrock mine tailings: Soil quality, microbial activity, and toxic element sorption
•Historic mine sites remain unvegetated due to toxic elements and acidity.•We examine how biochar additions may ameliorate toxic soil conditions.•Biochar increased pH and organic matter content, and decreased bulk density.•Sorption of toxic elements varied by initial metal content of mine material.•...
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| Published in: | Applied geochemistry Vol. 43; pp. 35 - 48 |
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| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Kidlington
Elsevier Ltd
01-04-2014
Elsevier |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | •Historic mine sites remain unvegetated due to toxic elements and acidity.•We examine how biochar additions may ameliorate toxic soil conditions.•Biochar increased pH and organic matter content, and decreased bulk density.•Sorption of toxic elements varied by initial metal content of mine material.•From one mine material, biochar caused an increase in Cd and Zn mobility.
Waste rock piles from historic mining activities remain unvegetated as a result of metal toxicity and high acidity. Biochar has been proposed as a low-cost remediation strategy to increase soil pH and reduce leaching of toxic elements, and improve plant establishment. In this laboratory column study, biochar made from beetle-killed pine wood was assessed for utility as a soil amendment by mixing soil material from two mine sites collected near Silverton, Colorado, USA with four application rates of biochar (0%, 10%, 20%, 30% vol:vol). Columns were leached seven times over 65days and leachate pH and concentration of toxic elements and base cations were measured at each leaching. Nutrient availability and soil physical and biological parameters were determined following the incubation period. We investigated the hypotheses that biochar incorporation into acidic mine materials will (1) reduce toxic element concentrations in leaching solution, (2) improve soil parameters (i.e. increase nutrient and water holding capacity and pH, and decrease compaction), and (3) increase microbial populations and activity. Biochar directly increased soil pH (from 3.33 to 3.63 and from 4.07 to 4.77 in the two materials) and organic matter content, and decreased bulk density and extractable salt content in both mine materials, and increased nitrate availability in one material. No changes in microbial population or activity were detected in either mine material upon biochar application. In leachate solution, biochar increased base cations from both materials and reduced the concentrations of Al, Cd, Cu, Pb, and Zn in leachate solution from one material. However, in the material with greater toxic element content, biochar did not reduce concentrations of any measured dissolved toxic elements in leachate and resulted in a potentially detrimental release of Cd and Zn into solution at concentrations above that of the pure mine material. The length of time of effectiveness and specific sorption by biochar is variable by element and the toxic element concentration and acidity of the initial mine material. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0883-2927 1872-9134 |
| DOI: | 10.1016/j.apgeochem.2014.02.003 |