The Use of Biochar as a Soil Amendment to Reduce Potentially Toxic Metals (PTMs) Phytoavailability

Abstract

The contamination of potentially toxic metals (PTMs) is widespread in the world and has negatively affected plants, humans, soil health, and environmental quality. Some metals are essential plant nutrients but they are also toxic to vegetation and aquatic live when present in high concentrations, such as Cu, Mn and Zn. Others (e.g., Pb, Cd, Cr, and As) are potential toxic metals for all organisms, and are not needed (or are toxic) for plant growth. This chapter summarizes the use of readily available biochars (BCs) to reduce PTMs phytoavailability in soils thus improving crop yields and to minimize its impact on the environment. The physicochemical and morphological properties of BCs as affected by feedstock sources and pyrolysis temperatures are discussed. The effectiveness of biochar rates on plant growth and metal fractions are also highlighted. Biochar has the potential to be used as a viable bioproduct for the remediation of contaminated soils since it reduces the phytoavailability of PTMs pollutants. Biochars produced from different feedstocks and at different pyrolysis temperatures present highly heterogeneous physicochemical and morphological properties, which can affect the effectiveness in the remediation of PTMs contaminated soils. Therefore, potential technologies need to be developed and research gaps still need to be overcome to optimize the use of BCs as a feasible alternative for remediation of metal contaminated soils.

Biochar supplementation regulates growth and heavy metal accumulation in tomato grown in contaminated soils

“…The maximum effect on the heavy metal concentration was observed when biochar was applied at the B3 (9%), followed by B1 (3%) and B2 (6%) (Table 1). In agreement with our results, many previous studies have reported that biochar application significantly increases the immobilization of heavy metals in soils as well as reduces their bioavailability for plant uptake (Kim et al 2015; Dang et al 2015; Liu et al 2020; Antonangelo & Zhang, 2020). These studies have demonstrated that the biochar interacts with the heavy metals in the soil, thus the ions of heavy metals are adsorbed on the pore surfaces, and transformed into the carbonate, hydroxide, and phosphate precipitates.…”

Recent advances in biochar engineering for soil contaminated with complex chemical mixtures: Remediation strategies and future perspectives

“…But challenges remain in terms of practicality, effectiveness, cost and sustainability at large-scale field application at commercial levels. Large-scale field trials are essential before implementation of operational scale remediation projects Antonangelo and Zhang, 2020). One of the key challenges associated with large-scale filed trials is to achieve comparable or better remediation results compared to smallscale experiments considering the prevailing real-world environmental parameters.…”

Sustainable Use of Biochar in Environmental Management

“…The greatest concern of organic contaminants such as pesticides, herbicides, polycyclic aromatic hydrocarbons, dyes, and antibiotics have been a concern due to its toxicity and accumulative properties [38]. In the soil medium, biochar has been used for heavy metal sequestration [39,40]. In this process, heavy metals are immobilised not removed and maybe converted into hydroxide, carbonate, and phosphate precipitates [40].…”

“…Properties of biochar such carbonaceous materials, degree of aromatization, elemental composition, pH, pore structure, surface chemistry, etc., plays vital roles in its ability to adsorb organic pollutants [41]. Biochar therefore reduces CO 2 emissions into the atmosphere [39]. The indiscriminate exploitation of natural resources and the rapid growth of environmental destruction resulting from anthropogenic activities have already posed a burden on efforts to sustain natural environment.…”

“…The indiscriminate exploitation of natural resources and the rapid growth of environmental destruction resulting from anthropogenic activities have already posed a burden on efforts to sustain natural environment. Biochar's uses also includes the neutralisation of acidic soils and this is because of its calcium and magnesium carbonate contents [39] and ability to elevate pH [40]. Reducing acidity may however negatively affect acid loving worms and fungi in the soil environment [42].…”