Carboxymethyl chitosan-assisted enzyme-induced carbonate precipitation for efficient cadmium stabilization in contaminated soil

Abstract

Cadmium (Cd) contamination in industrially polluted soils poses persistent environmental risks because of its high mobility and toxicity. In this study, a carboxymethyl chitosan (CMCS)-assisted enzyme-induced carbonate precipitation (EICP) strategy was developed to increase Cd stabilization while maintaining enzymatic activity under high Cd stress. Batch experiments optimized CMCS and urea dosages at 4 g/kg soil, achieving a > 90% reduction in extractable Cd and effectively preserving urease activity. Long-term incubation and column leaching tests further demonstrated that EICP induced a pronounced transformation of Cd from labile fractions to carbonate-associated fractions, resulting in markedly reduced Cd release under both acidic (pH 3.2) and elevated hydraulic loading conditions. Mineralogical and structural characterization provided direct evidence for in situ carbonate precipitation and concomitant improvements in soil aggregate stability. Pot experiments using Pennisetum purpureum as a model plant revealed significant increases in plant biomass and soil nitrogen availability after EICP treatment. High-throughput sequencing analyses indicated that EICP moderated deterministic community assembly processes and promoted higher microbial diversity and network connectivity. Although microbial network robustness remained comparable across treatments, Cd contamination substantially increased network vulnerability, which was effectively alleviated after EICP remediation. Overall, CMCS-assisted EICP enables effective and durable Cd stabilization while simultaneously improving soil physicochemical properties and microbial community organization, highlighting its potential as an eco-compatible remediation approach for Cd-contaminated industrial soils.

Graphical abstract

Keywords

Cadmium stabilization / Enzyme-induced carbonate precipitation (EICP) / Carboxymethyl chitosan (CMCS) / Soil quality improvement / Microbial community organization

Highlight

	● CMCS-assisted EICP was developed for effective Cd stabilization in soils.
	● Optimized EICP reduced Cd mobility while maintaining high urease activity.
	● EICP promoted Cd mineral transformation and improved soil properties.
	● EICP enhanced Pennisetum purpureum growth and soil nutrient availability.
	● EICP moderated microbial assembly processes and network vulnerability.

References

[1] Ahenkorah I , Rahman M , Karim R , Beecham S . (2021). Enzyme induced calcium carbonate precipitation and its engineering application: a systematic review and meta-analysis. Construction and Building Materials, 308: 125000

[2] Ahenkorah I , Rahman M , Karim R , Beecham S . (2023). Unconfined compressive strength of MICP and EICP treated sands subjected to cycles of wetting-drying, freezing-thawing and elevated temperature: experimental and EPR modelling. Journal of Rock Mechanics and Geotechnical Engineering, 15(5): 1226–1247

[3] Chang Y X , Lin L H , Shen J L , Lin Z , Deng X Y , Sun W M , Wu X Y , Wang Y F , Li Y Q , Xu Z M . (2025). Enhanced nitrogen fixation and Cd passivation in rhizosphere soil by biochar-loaded nitrogen-fixing bacteria: chemisorption and microbial mechanism. Journal of Hazardous Materials, 481: 136588

[4] Chen Y B , Wang Q Y , Bian Y , Zhan L T , Gao Y F , Guo H W , Wang Y Z , Gao Y Q . (2024). Effects of enzyme-induced carbonate precipitation (EICP) with different urease sources on the zinc remediation. Journal of Hazardous Materials, 480: 136321

[5] Han Y , Tang Z W , Sun J Z , Xing X Y , Zhang M N , Cheng J L . (2019). Heavy metals in soil contaminated through e-waste processing activities in a recycling area: implications for risk management. Process Safety and Environmental Protection, 125: 189–196

[6] Hao Y , Cai Z Y , Ma C X , White J C , Cao Y N , Chang Z F , Xu X X , Han L F , Jia W L , Zhao J . et al. (2023). Root exposure of graphitic carbon nitride (g-C₃N₄) modulates metabolite profile and endophytic bacterial community to alleviate cadmium- and arsenate-induced phytotoxicity to rice (Oryza sativa L.). ACS Nano, 17(20): 19724–19739

[7] Hou D Y , Al-Tabbaa A , O’Connor D , Hu Q , Zhu Y G , Wang L W , Kirkwood N , Ok Y S , Tsang D C W , Bolan N S . et al. (2023). Sustainable remediation and redevelopment of brownfield sites. Nature Reviews Earth & Environment, 4(4): 271–286

[8] Hu X S , Yu C H , Shi J S , He B H , Wang X R , Ma Z Z . (2024). Biomineralization mechanism and remediation of Cu, Pb and Zn by indigenous ureolytic bacteria B. intermedia TSBOI. Journal of Cleaner Production, 436: 140508

[9] Latif D O , Diana W , Daga W , Apriyono A . (2026). A PRISMA-guided systematic review of MICP and EICP in clayey soils: mineralogy-aware mechanisms, injection control, and multi-scale performance synthesis. Results in Engineering, 29: 109337

[10] Li M , Liu J , Cao D , Chen X Y , Shi J X , Hu W Z , Xiao C Q , Fang Y . (2025). Heavy metal pollution simplifies microbial networks and enhances modularity during tailings primary succession: divergent assembly dynamics for bacterial and fungal communities. Frontiers in Microbiology, 16: 1566627

[11] Li M M , Yao J , Sunahara G , Duran R , Liu B , Cao Y , Li H , Pang W C , Liu H Q , Jiang S . et al. (2023). Assembly processes of bacterial and fungal communities in metal(loid)s smelter soil. Journal of Hazardous Materials, 451: 131153

[12] Li W L , Zhang Y H , Achal V . (2022). Mechanisms of cadmium retention on enzyme-induced carbonate precipitation (EICP) of Ca/Mg: nucleation, chemisorption, and co-precipitation. Journal of Environmental Chemical Engineering, 10(3): 107507

[13] Liang Y X , Gao B , Zhang X F , Yi H F , Li J J , Zhang W Y . (2025). Combined addition of γ-PGA and DCD facilitates phytoremediation of heavy metals and carbon sequestration: a field experiment. Journal of Environmental Management, 379: 124746

[14] Liu J L , Yao J , Li R F , Liu H Q , Zhu J J , Sunahara G , Duran R . (2024a). Unraveling assemblage of microbial community dwelling in Dabaoshan As/Pb/Zn mine-impacted area: a typical mountain mining area of South China. Science of the Total Environment, 912: 168850

[15] Liu S , Quan L , Yang M , Wang D , Wang Y Z . (2024b). Regulation of cellulase production via calcium signaling in Trichoderma reesei under PEG8000 stress. Applied Microbiology and Biotechnology, 108(1): 178

[16] Ma X N , Zhai T F , Bao X L , Wu Z H , Yang Y X , Yin R , Cai C , Liu G . (2025). Salinity-driven trade-offs between nitrogen removal and microbiome dynamics in Fe-C-CWs toward saline aquaculture tailwater management. Water Research, 287: 124519

[17] Mao W , Shen X W , Zhang L X , Liu Y , Liu Z H , Guan Y T . (2024). A review on Bi₂WO₆-based photocatalysts synthesis, modification, and applications in environmental remediation, life medical, and clean energy. Frontiers of Environmental Science & Engineering, 18(7): 86

[18] Ning D L , Yuan M T , Wu L W , Zhang Y , Guo X , Zhou X S , Yang Y F , Arkin A P , Firestone M K , Zhou J Z . (2020). A quantitative framework reveals ecological drivers of grassland microbial community assembly in response to warming. Nature Communications, 11(1): 4717

[19] Qi X , Xiao S Q , Chen X M , Ali I , Gou J L , Wang D , Zhu B , Zhu W K , Shang R , Han M W . (2022). Biochar-based microbial agent reduces U and Cd accumulation in vegetables and improves rhizosphere microecology. Journal of Hazardous Materials, 436: 129147

[20] Qin D Y , Zhang C , Qin F Z , Weng H , Luo H Z , Huang C , Wu B B , Chu C H . (2026). Sunlight-driven production of hydroxyl radical from manganese minerals. Environmental Science & Technology, 60(8): 6276–6286

[21] Qiu J C , Bai J H , Wang Y M , Zhai Y J , Zhang X H , Xu Y H , Wang Y Q . (2024). Cadmium contamination decreased bacterial network complexity and stability in coastal reclamation areas. Journal of Hazardous Materials, 476: 134896

[22] Ribeiro E S , De Farias B S , Junior T R S C , De Almeida Pinto L A , Diaz P S . (2021). Chitosan–based nanofibers for enzyme immobilization. International Journal of Biological Macro-molecules, 183: 1959–1970

[23] Robinson M L , Strauss S Y . (2020). Generalists are more specialized in low-resource habitats, increasing stability of ecological network structure. Proceedings of the National Academy of Sciences of the United States of America, 117(4): 2043–2048

[24] Táncsics A , Banerjee S , Soares A , Bedics A , Kriszt B . (2023). Combined omics approach reveals key differences between aerobic and microaerobic xylene-degrading enrichment bacterial communities: Rhodoferax: a hitherto unknown player emerges from the microbial dark matter. Environmental Science & Technology, 57(7): 2846–2855

[25] Tessier A , Campbell P G C , Bisson M . (1979). Sequential extraction procedure for the speciation of particulate trace metals. Analytical Chemistry, 51(7): 844–851

[26] Wang L , Cheng W C , Xue Z F , Zhang B , Lv X J . (2023). Immobilizing of lead and copper using chitosan-assisted enzyme-induced carbonate precipitation. Environmental Pollution, 319: 120947

[27] Wang T , Chen E T , He J Z , Xu J M , Liu X M . (2025). Rhizosphere alkalization and microbial sulfur pathways drive Cd detoxification and Se enrichment in geogenically contaminated soil. Journal of Hazardous Materials, 499: 140251

[28] Wang Z , Su J F , Ali A , Yang W S , Zhang R J , Li Y F , Zhang L F , Li J W . (2022). Chitosan and carboxymethyl chitosan mimic biomineralization and promote microbially induced calcium precipitation. Carbohydrate Polymers, 287: 119335

[29] Yan K , Wang H Z , Lan Z , Zhou J H , Fu H Z , Wu L S , Xu J M . (2022). Heavy metal pollution in the soil of contaminated sites in China: research status and pollution assessment over the past two decades. Journal of Cleaner Production, 373: 133780

[30] Yang W J , Chen Y X , Deng X , Tu P F , Tan K F , Liu Z Y , Zeng Q R , Yang Y . (2025). Screening and rotating winter and summer crops to effectively remediate Cd-contaminated agricultural land and ensure safe production. Frontiers of Environmental Science & Engineering, 19(3): 38

[31] Yang Z B , Guo W Q , Cheng Z , Wang G Y , Xian J R , Yang Y X , Liu L X , Xu X X . (2022). Possibility of using combined compost–attapulgite for remediation of Cd contaminated soil. Journal of Cleaner Production, 368: 133216

[32] Yuan M M , Guo X , Wu L W , Zhang Y , Xiao N J , Ning D L , Shi Z , Zhou X S , Wu L Y , Yang Y F . et al. (2021). Climate warming enhances microbial network complexity and stability. Nature Climate Change, 11(4): 343–348

[33] Zhang C W , Du C B , Liang B , Yi F , Li J S , Sun Q , Zhang X G . (2025). Carboxymethyl chitosan-mediated biomineralization for the bio-solidification of graphite tailings with different particle sizes: strength, leaching, and mechanism. Construction and Building Materials, 492: 142948

[34] Zhang L X , Guan Y T . (2022). Microbial investigations of new hydrogel-biochar composites as soil amendments for simultaneous nitrogen-use improvement and heavy metal immobilization. Journal of Hazardous Materials, 424: 127154

[35] Zhang Y , Li M Y , Su A X , Lv X F , Qiu Y L , Xu Y . (2023). Co-planting improves the phytoremediation efficiency of combined phenanthrene and copper co-contaminated soils. Journal of Cleaner Production, 382: 135380

[36] Zhou Y , Lv L , Yu Z , Zhang J , Wang B , Yang R D , Chen M , Wu P , Wang S S . (2024). Synergistic effect between biochar and sulfidized nano-sized zero-valent iron enhanced cadmium immobilization in a contaminated paddy soil. Biochar, 6(1): 55

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