Effects of biochar amendments on speciation and bioavailability of heavy metals in coal-mine-contaminated soil

ABSTRACT

An incubation experiment was executed on applying biochar as a soil remediation amendment to discuss an effect of the various addition rates on the speciation and bioavailability of heavy metals in mining-contaminated soil. The result showed that the content of Cd in soil was 9.51 times higher than the Huainan soil background values. The contents of Cu, Zn and As were 2.97, 1.60 and 1.42 times the background values, respectively, and the total contents of all heavy metals were higher than the standard values of soil environment quality GB15618-1995 set by the China Ministry of Environmental Protection. Speciation analysis indicated that Cu and Cd were mainly associated with the reducible fraction, while Zn and As were dominated by the residual fraction. After biochar was added to contaminated soil, the residual fractions of heavy metals increased, while the acid-soluble fractions reduced. According to the results of CaCl₂ extraction experiment, CaCl₂-extractable concentrations of Cu, Zn, As, and Cd were observed with a biochar dosage rate of 10%, which were 57.26%, 51.37%, 6.94% and 42.04% lower than those of control soil samples, respectively, but there were no obvious changes of CaCl₂-extractable As.

KEYWORDS:

• heavy metals
• biochar
• contaminated soil
• speciation
• bioavailability

Acknowledgments

The authors would like to thank the anonymous reviewers for their helpful comments that improved the quality of the article.

Additional information

Funding

This work was financially supported by the National Science and Technology Support Program in China (NO.2015BAL01B01), President Youth Innovation Fund of Anhui Academy of Agricultural Science (NO.16B1326) and Innovative Talent Program of Anhui Academy of Agricultural Science (NO.16R13).