Influence of Modified Biochar on Soil Fluoride and Cadmium Speciation and Their Bioavailability to Tea Seedling (Camellia Sinensis L.)

ABSTRACTABSTRACTBiochar is widely used as a good soil amendment, while knowledge of modified biochar application in tea garden soils contaminated by fluoride (F) and cadmium (Cd) is insufficient. The tea seedling (Camellia sinensis L.) growth assay was performed to evaluate interaction of soil Cd and F and the improving effect of aluminum trichloride-modified corn stalk biochar (Al-BC) on their speciation, phytoaccumulation and phytotoxicity. Results showed that soil F speciation ratio sequence was as follows: residual > exchangeable > organic-bound > water-soluble > Fe/Mn oxide-bound. Soil exchangeable Cd was the largest Cd speciation (>35.6%), probably due to the low pH values in the acid tea gardens. Root F contents showed a strong significant relationship with soluble F contents (r = 0.92, P < .01) and similarly root Cd highly connected with exchangeable Cd (r = 0.86, P < .01). Seedling height, fresh and dry weight, root surface area, length, and photosynthetic pigment showed different sensitivities to F or Cd oxidative stress and toxicity effects, and only root F contents significantly inversely correlated with them (r = 0.74–0.80, P < .01). The interaction of Cd and F, could influence their speciation distribution and antagonized each other in root accumulation. Meanwhile, joint simulation models showed that antagonistic effects were observed in the F and Cd mixture soils for most cases at Enshi. Biochar application reduced bioavailable F and Cd contents, and thus decreased F and Cd accumulation in tea roots and obviously alleviated toxicity effects. For instance, biochar application significantly reduced root F contents, which had 33.2% to 62.2% declines at Enshi and 39.7% to 77.2% declines at Huanggang. Meanwhile, the soil properties were improved as biochar added, with an increase in soil pH, EC, CEC and organic matter. Overall, Al-modified biochar was beneficial environmental materials for reducing both F and Cd bioavailability.KEYWORDS: BioavailabilityBiocharCadmiumFluorideTea garden soil Disclosure statementNo potential conflict of interest was reported by the authors.CRediT authorship contribution statementXin Li: Methodology, Investigation, Visualization, Writing – original draft. Yili Qi: Methodology, Investigation, Visualization. Xiaoqing Zhang: Methodology, Validation, Formal analysis, Data curation, Writing – original draft, Funding acquisition. Zhihua Chen: Methodology, review & editing. Wangsheng Chen: Methodology, Project administration. Bo Zhao: Writing – review & editing, Project administration. Dajun Ren: Methodology, Writing – review & editing. Shuqin Zhang: Writing – review & editing, Project administration.Availability of data and materialsThe authors confirm that all data gathered or analyzed during this study are included in this published. articleSupplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/15320383.2023.2228415Additional informationFundingAuthors thank to the financial support by the National Natural Science Foundation of China (51906182), the Department of Education of Hubei Province (19ZD014, T2020002) and Hubei Technological Innovation Special Fund of the Department of Science and Technology of Hubei Province (2020ZYYD019)