Elsevier

Pedosphere

Volume 32, Issue 6, December 2022, Pages 866-875
Pedosphere

Effective alleviation of Cd stress to microbial communities in mining reclamation soils by thiourea-modified biochar amendment

https://doi.org/10.1016/j.pedsph.2022.06.017Get rights and content

ABSTRACT

Reclaimed soils in mining area usually display low fertility and present Cd stress. The amendment of modified biochar effectively fixes Cd in soils, enhances soil fertility, and reduces Cd stress in soil microorganisms. However, the effect of thiourea-modified biochar (TBC) on microbial adaptability to Cd stress in mining reclamation soils is still unclear. The present work studied the Cd immobilization and microbial community changes in a mining reclamation soil displaying extreme Cd contamination under TBC amendment. The results indicated that the amendment of TBC significantly enhanced (P < 0.05) soil pH, the content of available phosphorus (AP), and the activities of urease and polyphenol oxidase by 1.3%, 463.4%, 54.4%, and 84.0%, respectively, compared to the control without amendment. The amount of toxicity characteristic leaching procedure-extracable Cd decreased (P < 0.05) by 68.0% in the TBC-amended soil compared with the unamended soil. The structure of soil microbiota was reorganized and the alpha diversity index was increased in the TBC treatment. The TBC amendment increased the relative abundances of Proteobacteria, Bacteroidota, and Zoopagomycota, which were strongly associated (P < 0.01) with higher soil pH and AP. Structural equation model results demonstrated that Cd immobilization was directly influenced by soil pH, AP, and urease, and indirectly affected by bacterial structure in the TBC treatment. The TBC amendment can effectively improve the structural composition of soil bacteria under Cd stress and enhance the pathways of decreasing soil Cd availability as well. The results might facilitate the development of in-situ remediation programs in Cd-contaminated soils in the future.

Section snippets

INTRODUCTION

Mining activities, industrial production, and excessive use of agricultural chemicals have resulted in the accumulation of different contaminants in the environment that severely threaten environmental quality and public health (Chen L J et al., 2019; Wang et al., 2020). Cadmium (Cd), a nonessential element, can be accumulated through the food chain and greatly threaten human health (Huang et al., 2017; Zeng et al., 2019). Cadmium compounds are highly toxic, highly mobile, and not biodegradable

Soil and biochar

Topsoil (0–20 cm) samples were collected from the reclaimed soil in Liuxin Mine Land, Xuzhou City, Jiangsu Province, China (34°23′43″ N, 117°07′29″ E). Detailed information was provided by Zhu Y F et al. (2020b). After removing stone fragments and animal and plant residues, soil samples were placed into sterile sealed bags and transported to the lab. After aging for 30 d at room temperature, soil was air-dried at room temperature and screened using a 2-mm mesh for further analysis. Biochar (BC)

Effect of biochar amendment on soil physicochemical pro- perties, TCLP-Cd, and enzyme activity

There were no significant differences in the effects of BC and TBC on soil properties and enzyme activities (Table II). Compared with CK, soil pH, SOM, and AP under BC treatment increased by 0.6%, 56.3%, and 761.2%, respectively, and TBC increased pH, EC, and AP by 1.3%, 45.8%, and 463.4%, respectively. By contrary, the content of NO3−-N decreased by 41.3% and 56.7% in the BC- and TBC-amended soils, respectively, and TCLP-Cd decreased by 35.13% and 68.05%, respectively. Compared with CK, BC and

Effect of biochar amendment on soil properties and available Cd in soil

The present investigation showed that biochar amendment significantly enhanced soil pH and soil nutrient content, significantly decreased soil TCLP-Cd, and improved soil microbial quantity as well as enzyme activity. The possible reason might be that the oxygen-containing functional groups (e.g., hydroxyl, carboxyl, and carbonyl), which can be formed during the process of pyrolysis, bind Cd through surface complexation or precipitation (Bashir et al., 2020; Liu et al., 2020). In addition, the

CONCLUSIONS

The TBC amendment investigated in the present study represents a potential in-situ soil restoration technique. The TBC application was important for the reduction of Cd bioavailability and TBC increased soil pH value and AP content, as well as the activities of UA and PO. Under TBC, bacterial diversity significantly increased and bacterial and fungal community structure changed. The SEM results showed that the TBC amendment influenced Cd immobilization by directly increasing soil pH, AP, and

ACKNOWLEDGEMENTS

This work was supported by the National Natural Science Foundation of China (Nos. 41807515, 51974313, and 51974314) and the Jiangsu Provincial Natural Science Foundation of China (No. BK20180641). We would also like to thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.

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