Abstract
Contamination of paddy soils with potentially toxic elements (PTEs) has become a severe environmental issue. Application of functionalized biochar for rice cultivation has been proposed as an effective means to reduce environmental risks of these PTEs in paddy soils. This work was undertaken to seek the positive effects of a rice husk-derived silicon (Si)-rich biochar (Si-BC) and a pig carcass-derived phosphorus (P)-rich biochar (P-BC), as well as their Fe-modified biochars (Fe-Si-BC and Fe-P-BC) on the enzyme activity and PTE availability in an As-Cd-Pb-contaminated soil. A rice cultivation pot trial was conducted using these functionalized biochars as soil amendments for the alleviation of PTE accumulation in rice plants. Results showed that Si-BC decreased the concentrations of As in rice grain and straw by 59.4 % and 61.4 %, respectively, while Fe-Si-BC significantly (P < 0.05) enhanced plant growth, increasing grain yield (by 38.6 %). Fe-Si-BC significantly (P < 0.05) elevated Cd and Pb accumulation in rice plants. P-BC enhanced the activities of dehydrogenase, catalase, and urease, and reduced grain-Pb and straw-Pb by 49.3 % and 43.2 %, respectively. However, Fe-P-BC reduced plant-As in rice grain and straw by 12.2 % and 51.2 %, respectively, but increased plant-Cd and plant-Pb. Thus, Fe-modified Si- and P-rich biochars could remediate paddy soils contaminated with As, and enhance the yield and quality of rice. Application of pristine P-rich biochar could also be a promising strategy to remediate the Pb-contaminated paddy soils and limit Pb accumulation in rice.
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Novel renewable dual-functionalized biochars, Fe-modified Si- and P-rich biochars, were used to simultaneously immobilize hazardous PTEs (e.g., As, Cd, and Pb) in a paddy soil, promote rice growth, and thus regulate rice yield and quality in a paddy soil under intermittently flooding conditions. We found that the Fe-modified Si- and P-rich biochars could increase rice yield and quality when As is the concern. When Pb is the concern, the raw P-rich biochar could be a promising amendment. However, none of the tested functionalized biochars could reach an appropriate effectiveness on a simultaneous mitigation of multi-PTEs in the paddy soil.
•Si-rich biochar could limit As accumulation in rice plant and promote rice growth.•Fe-Si-rich biochar reduced As uptake, but elevated environmental risk of Cd and Pb.•P-rich biochar reduced Pb in rice without affecting grain-As and -Cd and rice yield.•Fe-P-rich biochar reduced uptake of As, but increased uptake of Cd and Pb by rice.`