Field experiments was conducted to evaluate the effectiveness of sepiolite (S), sepiolite + fungi residues (SFR) and sepiolite + vermicompost (SVC) on in situ immobilization remediation of Cd contaminated soils. The results showed that treatments of S, SFR and SVC decreased soil Cd availability by 15.2-47.8%, 17.5-44.9% and 13.2-44.9%, respectively, when compared with the control groups. Moreover, the content of Cd in edible parts of Lactuca sativa L., Cichorium endivia L. and Brassica campestris L. was experienced a decrease of 15.9-41.9%, 1.6-38.0% and 29.0-37.4% reduction, respectively, under the amended soil. The improvement of soil fertility was obtained under addition of SVC and SFR, while the amounts of available P, K, organic matter, microbial carbon, microbial nitrogen and dehydrogenase activity were increased by 9.6-68.2%, 1.2-28.3%, 37.5-70.5%, 4.1-121.0%, 220-640% and 6.8-56.8%, respectively, in contrast to CK. Moreover, high-throughput sequencing analysis showed that the combined treated soils got higher values of alpha diversity indices, Chao1, ACE and Shannon. The number of dominant phyla (Proteobacteria, Acidobacteria, Gemmatimonadetes, Crenarchaeota) and genera (Aquicella, Lysobacter, Candidatus Nitrososphaera, Sphingopyxis, Mesorhizobium) were enhanced. Therefore, the use of sepiolite and organic amendments could be an adequate strategy to immobilization remediation of Cd-contaminated soils.

Arsenic (As) contamination poses a significant global environmental and health concern. Crayfish shell biochar (CSBC) has shown considerable potential for remediating As-contaminated soil. However, the effect of CSBC on As mobility in acid and alkaline aerobic soils, and its underlying mechanism remains unclear. This study investigated the variation in As availability, dissolved organic matter (DOM), microbial community, and As metabolism genes in CSBC-amended soil. Results indicated that CSBC application decreased the available As content in alkaline soil (4.5–9.9%), but increased it in acid soil (19.6–26.8%). The increase in soil pH and DOM humification degree, along with the decrease in DOM molecular weight, contributed to enhanced As mobility in CSBC-amended acid soil. Additionally, CSBC application stimulated microbial membrane transport and signal transport function in acid soil. Furthermore, it increased the relative abundance of Bradyrhizobium, Sphingomonas, Streptomyces, and Ktedonobacter, which harbor As(V) reduction (arsC and arrB) and As(III) efflux (ACR3) genes, thereby promoting As mobility in acid soil. In alkaline soil, the CSBC provided additional bonding sites for As to mitigate its environmental risk. This study provides new insights into the critical role of biochar in influencing As fate in aerobic soil.