ABSTRACT
This study evaluated the effects of combining Aspergillus niger and fluorapatite (FAp) as a remediation strategy on cadmium (Cd) immobilization in contaminated soil. Soil Cd speciation, immobilization efficiency, soil microbial abundance, and soil enzyme activities were used as parameters to evaluate the effectiveness of the amendment. European community Bureau of reference (BCR) sequential extraction was used to determine fractions or speciation of the heavy metal in the soil. At 50 mg/kg Cd contamination level, the concentration of acid-soluble species was significantly the lowest at 19.54 mg/kg under the combination amendment. The concentrations (mg/kg) of acid-soluble species under separate applications of FAp and the fungus were 22.05 and 25.34, respectively. At 50 mg/kg contamination, residual fraction or species immobilized under the combination amendment was 5.74 mg/kg, while that immobilized under applications of FAp and the fungus separately were 2.79 mg/kg and 1.46 mg/kg, respectively. At 25 mg/kg contamination level, the residual fraction immobilized under the combination amendment was 8.42 mg/kg, while that of applications of FAp and the fungus separately were 4.28 mg/kg and 1.27 mg/kg, respectively. The higher populations of soil microorganisms and the improved enzyme activities observed under the combination amendment also indicate that combining the fungus with FAp reduced Cd bioavailability and toxicity effectively, and restored soil biological activities.
Acknowledgments
Authors appreciate the Federal Scholarship Board of the Ministry of Education, Federal Republic of Nigeria and the Chinese Scholarship Council (CSC) for the award of scholarships for Doctorate Degree studies and funding of this research in China (CSC No. 2017GBJ001327).
Disclosure statement
No potential conflict of interest was reported by the author(s).