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Liquid mulching film mitigates cationic heavy metals migration via enhancing soil organic matter and cation exchange capacity.
Summary
Researchers applied lignin-based and chitosan-based liquid biodegradable mulching films to cadmium- and lead-contaminated agricultural soil, finding that both films increased soil organic matter and cation exchange capacity substantially — shifting heavy metals toward stable mineral-bound fractions and reducing transfer into edible crops, with crop-specific translocation responses depending on film chemistry.
Liquid biodegradable mulching film (LBMFs) technology, an innovative agricultural technology, shows dual potential in plastic pollution reduction and heavy metal contamination control. Although their agronomic benefits are recognized, the underlying mechanisms of LBMFs in regulating heavy metal biogeochemical cycles remain inadequately understood. This study demonstrates the effectiveness of lignin-based (JH) and chitosan-based (LB) LBMFs in modifying heavy metal speciation and minimizing their uptake by crops. The results indicated that JH and LB significantly enhanced soil organic matter (SOM) by 14.29 %-27.01 % and cation exchange capacity (CEC) by 20.65 %-247.17 %, compared to soil blank control, primarily due to the enrichment of colloids derived from lignin/chitosan and the stimulation of microbial activity. Both films reduced the bioavailability of Cd and Pb by promoting their transition from mobile acid soluble/reducible (F1/F2) fractions to stable oxidizable/residual (F3/F4) fractions. In contrast, Cu and Zn speciation remained stable due to strong mineral interactions. The LBMFs also inhibited the transfer of heavy metals to edible crops. Crop-specific translocation factor (TF) variations were observed, with JH reducing pak choi TF by 32.62 %-76.09 % but increasing radish TF by 33.47 %-437.55 %, linked to lignin's root chelation and chitosan's phloem transport dynamics. Additionally, Mantel analysis confirmed bioconcentration factor (BCF)/TF reductions correlated strongly with elevated SOM (r = 0.82/0.73) and CEC (r = 0.80/0.77), governed by organo-mineral complexation and competitive cation displacement. This work positions LBMFs as valuable tools for enhancing soil health and reducing dietary risks associated with heavy metals in contaminated agricultural lands.