Microplastics (MPs) increase the effective state of heavy metals (HMs) in soil and seriously threaten the yield and quality of peanuts (Arachis Hypogea L.). Kaolinite (KL) has the potential to ameliorate MP- and HM- contaminated soils, but the mechanism of action between them is not well understood. Therefore, 60-day experiments were conducted, where KL (1 %, 2 %) and MPs (0.1 %, 1 %) were individually or jointly mixed into soils with different cadmium (Cd) concentrations (0.5, 2.5, and 5.0 mg·kg^-1) to cultivate peanuts in a greenhouse. Finally, soil-bioavailable Cd, peanut dry weight, peanut Cd concentrations, the pH, cation exchange capacity (CEC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were determined. It was shown that MPs negatively affected the peanut dry weight and increased the content of soil-bioavailable Cd and Cd concentration in peanut. In the MP- and Cd-contaminated soils, KL mitigated the negative influence of MPs by increasing the dry weight of peanuts by 8.40 %-40.59 %, decreasing the soil-bioavailable Cd by 23.70-35.74 %, and significantly decreasing peanut Cd concentrations by 9.65-30.86 %. The presence of MPs decreased soil pH (7.69-7.87) and the CEC (20.96-23.95 cmol·L^-1) and increased the soil DOC (1.84-2.26 mg·kg^-1). KL significantly increased soil pH (7.79-8.03) and the CEC (24.96-28.28 cmol·L^-1) and mitigated the adverse influence of MPs on the pH and CEC of Cd-contaminated soils. A regression path analysis (RPA) evidenced that KL decreased Cd accumulation in plants by changing the properties of soil contaminated with MPs and Cd. The research results revealed the mechanism of KL on peanut growth and Cd absorption in MP- and Cd-contaminated soil. The results of this study provide a foundation to improve the quality of MP- and HM-contaminated soils and realize safe peanut production.

The impact of microplastics (MPs) as emerging pollutants on plant heavy metal toxicity has been extensively reported in vegetable–soil systems over recent years. However, little attention has been given to cultivar variations between degradable and non-degradable MPs. This study investigated the effects of degradable polylactic acid (PLA) and nondegradable polypropylene (PP) MPs on plant growth and biomarker (malonaldehyde (MDA) and antioxidant enzymes) performance in Cd-contaminated arable soil. The results show that both types of MPs significantly impacted plant biomass and biomarker contents across all three Cd levels. The degree of impact was significantly sensitive to both the type and dose of MPs, as they reduced the soil pH and cation exchange capacity (CEC) while increasing soil dissolved organic carbon (DOC), microbial biomass carbon, and nitrogen. PP exhibited greater root growth inhibition and phytotoxicity at higher doses of 1% and 5% compared to PLA. Specifically, the highest MDA contents were 1.44 and 2.20 mmol mg⁻¹ protein for shoots and roots, respectively, in the 5% PLA treatment under a 10.1 mg kg⁻¹ Cd level, which were 1.22 and 1.18 times higher than those in corresponding treatments of 5% PP. Overall, PLA had less significant effects on plant phytotoxicity, Cd availability, and soil properties compared to PP. Regression pathway analysis indicated that MPs increased shoot Cd uptake by altering both soil physical–chemical and microbial characteristics. Among the soil variables, pH, CEC, and Cd bioavailability were found to play vital roles. Yet, no single variable acts alone in the mechanism for plant Cd uptake. PLAs are suggested to replace conventional non-biodegradable plastics to control environmental MP pollution, particularly in agricultural systems with higher Cd contamination. However, the long-term effects of the by-products generated during the biodegradation process require further investigation.

Excessive cadmium (Cd) causes toxic effects on crops. The effects of chitosan (CTS) with different molecular weight (Mw) (5 kDa, 3kDa, and 1 kDa) on the growth and biochemical parameters, as well as Cd concentrations in Cd-treated wheat plants were examined in a pot experiment. The results demonstrated that foliar spraying with CTS significantly improve the wheat growth, reduce malondialdehyde (MDA) content in leaves and decrease Cd concentrations in roots and shoots of wheat seeding under Cd stress. The alleviation of Cd toxicity by CTS is probably related with the activity of antioxidant enzymes, osmotic adjustment matter and root morphology. The application of CTS enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in Cd-stressed wheat seedling leaves by 6.6%–13.1%, 17.2%–33.0%, and 19.6%–25.5%, respectively. Besides, exogenously applied CTS also increased the soluble protein and soluble sugar contents by 17.6%–33.8% and 30.1%–36.1% in the leaves of wheat under Cd stress. Furthermore, CTS with a molecular weight of 1 kDa was the most effective in mitigating Cd toxicity in wheat seedlings, which indicates that the activity of CTS is depend on its molecular weight. It can be concluded that the use of foliar spraying, especially with 1 kDa CTS, could have potential in reducing the damage of Cd stress.

This study investigated the effects of fully biodegradable poly(butylene adipate-co-terephthalate) (PBAT) mulch films with different thicknesses on soil hydrothermal conditions, soil fertility indicators, soil enzyme activities, and peanut growth and yield in a three-year field experiment. Three PBAT thicknesses (0.006, 0.008, and 0.010 mm) were compared with 0.010 mm polyethylene (PE) mulch and a bare soil control (CK). The effects of PBAT mulch films with different thicknesses on peanut yield, agronomic traits, photosynthetic characteristics, soil fertility indicators, and soil enzyme activities were systematically evaluated. PBAT008 showed the most favorable overall balance among the tested treatments. Compared with PE, PBAT008 significantly increased pod yield by 6.87–13.69% and 100-pod weight by 10.36–18.94%, whereas PE tended to reduce pod yield by 5.55–5.95% relative to CK. PBAT008 also promoted biomass accumulation and increased photosynthetic pigment content. Although PE showed the strongest water-retention capacity, PBAT008 maintained moderate soil moisture and suitable soil temperatures during pod formation. PBAT treatments improved soil organic matter, dissolved organic carbon, available phosphorus, and soil enzyme activities more effectively than PE. Path analysis identified available phosphorus, stem weight, and soil temperature as the strongest positive drivers of pod yield. Overall, PBAT008 enhanced peanut yield by achieving a coordinated improvement in soil hydrothermal conditions, soil fertility, and crop physiological performance, suggesting that an appropriate PBAT mulch thickness may provide an agronomically viable biodegradable alternative to PE mulch in peanut production.