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ABSTRACT
Pyrogenic carbon (PyC), including soil native PyC and engineered PyC (biochars), is increasingly being recognized for its potential role as a low-cost immobilizer of contaminants in soils. Published reviews on the role of soil native PyC as a sorbent in soils have so far focused mainly on organic contaminants and paid little or no attention to inorganic contaminants. Further, a comprehensive review on the production of both natural PyC and engineered PyC (biochars), mechanisms involved, and factors influencing their role as soil contaminant immobilizer is so far not available. The objective of this review is thus to systematically summarize the sources, formation, and properties of PyC, including its quantification in soils, followed by their roles in the immobilization of both organic and inorganic contaminants in soils. Effectiveness of PyC on bioavailability, leaching, and degradation of soil contaminants was summarized. Notably, the mechanisms and factors (for the first time) influencing the immobilization processes for soil contaminants were also extensively elucidated. This review helps better understand and design PyC for soil contaminant immobilization.
Abbreviations
| ADE | = | Amazonian dark earth |
| AOM | = | Amorphous organic matter |
| BC | = | Black carbon |
| BPCAs | = | Benzenepolycarboxylic acids |
| CEC | = | Cation exchange capacity |
| CG | = | Carbonaceous geosorbents |
| CTO-375 | = | Chemo-thermal oxidation method |
| COM | = | Carbonized organic matter (of biochars) |
| DOC | = | Dissolved organic carbon |
| EDA | = | Electron-donor-acceptor |
| HA | = | Humic acid |
| HOCs | = | Hydrophobic organic contaminants |
| NPOM | = | Non-PyC organic matter (of soils) |
| NOM | = | Non-carbonized organic matter (of biochars) |
| PAHs | = | Polycyclic aromatic hydrocarbons |
| PCBs | = | Polychlorinated biphenyls |
| PyC | = | Pyrogenic carbon |
| SOM | = | Soil organic matter |
| TOC | = | Total organic carbon |
Acknowledgments
The authors would like to acknowledge the financial support from CRC CARE (Cooperative Research Centre for Contamination Assessment and Remediation of the Environment).