Mobility, bioavailability and pH-dependent leaching of cadmium, zinc and lead in a contaminated soil amended with biochar

• Published in: Chemosphere (Oxford) 2013-09, Vol.92 (11), p.1450-1457
• Main Authors: Houben, David, Evrard, Laurent, Sonnet, Philippe
• Format: Article
• Language: English
• Subjects: Amendment; Applied sciences; Bioavailability; Biochar; Biological and physicochemical properties of pollutants. Interaction in the soil; Biological Availability; cadmium; Cadmium - chemistry; Cadmium - pharmacokinetics; Charcoal - chemistry; Exact sciences and technology; Heavy metal; Hydrogen-Ion Concentration; Immobilization; Kinetics; leaching; lead; Lead - chemistry; Lead - pharmacokinetics; Lolium - metabolism; Lolium multiflorum; Metals, Heavy - chemistry; Metals, Heavy - pharmacokinetics; Motion; neutralization; polluted soils; Pollution; shoots; Soil and sediments pollution; soil pH; Soil Pollutants - chemistry; Soil Pollutants - pharmacokinetics; sowing; zinc; Zinc - chemistry; Zinc - pharmacokinetics
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2013.03.055

•Biochar application to soils reduces the mobility and the bioavailability of metals.•Biochar-induced immobilization of metals in soil is mainly due to a liming effect.•Aging reactions can decrease metal mobility over time in biochar amended soils.•Biochar incorporation does not affect the metal release at acidic pH.•Biochar incorporation increases the acid neutralizing capacity of the soil. The effect of biochar application on the fate of Cd, Zn and Pb was investigated in a contaminated soil amended with three different rates of biochar (1%, 5% and 10%; w/w). In an incubation experiment, the 0.01M CaCl2-extractability of metals after 1h of incubation significantly decreased with increasing rate of biochar application. This effect was mostly attributed to the raise in soil pH. In the presence of 5% and 10% of biochar, the metal extractability continued to decrease over the next 56days, likely due to aging reactions. In a pot experiment, the metal concentration in shoots of ryegrass (Lolium multiflorum Lam.) harvested at 28 and 56days after sowing decreased with increasing rate of biochar application. Using a pH-dependent leaching test, we found that the metal release at a defined pH was not affected by the presence of biochar. However, because the acid neutralizing capacity (ANC) increased with increasing rate of biochar application, the time required to reach a hazardous pH can be predicted to be longer after biochar application. It is concluded that the application of biochar for in situ metal immobilization can be feasible provided soil pH is monitored over time.