Influence of biochar on trace element uptake, toxicity and detoxification in plants and associated health risks: A critical review

Abstract

Environmental contamination by toxic trace elements is a global issue faced by soil-plant-human systems. Biochar has gained substantial attention as a soil amendment to reduce toxic trace element impacts on plant and human health due to biochar’s capacity to influence trace element biogeochemistry. This review focuses on the key roles of biochar with respect to trace element interactions, mobility and phytoavailability in soil-plant systems. In addition to direct interactions, various biochar types can impact soil physicochemical properties and subsequently trace element biogeochemical behavior. A critical literature review revealed increasing and/or decreasing trends with respect to biochar-induced variation in soil physicochemical characteristics and soil-plant trace element transfer. Data analysis revealed that biochar-mediated an overall decrease in the phyto-uptake of As, Cd, Cu, Ni, Pb, and Zn by 48%, 40%, 38%, 44%, 28%, and 22%, respectively. This article also discusses the possible biochar-mediated alleviations of human health hazards (41% less cancer risk) due to consuming trace elements-contaminated foods. Likewise, for the first time, the effect of soil biochar application on plant physiological and morphological attributes, as well as activation of tolerance mechanisms (enzymatic and non-enzymatic) is critically discussed.

Highlights

• Literature review revealed biochar applications increased soil trace element sorption and decreased phyto-uptake.

• Plant uptake of trace element depends on soil and biochar properties as well as trace element and plant type.

• Biochar-mediated trace element phytoavailability reductions cause lower toxicity in plant-human systems.

• Biochar alters plant detoxification and tolerance mechanisms directly or indirectly.

Keywords:

• Biochar
• oxidative stress
• soil-plant transfer
• toxicity
• health risk
• trace element

Acknowledgements

The authors are thankful to Higher Education Commission (Project Nos. 6425/Punjab/NRPU/R&D/HEC/2016 and 6396/Punjab/NRPU/R&D/HEC/2016), Pakistan for providing financial support. Drs Nabeel Khan Niazi and Irshad Bibi are thankful to the University of Agriculture Faisalabad.