Mitigating combined cadmium and microplastics toxicity in rice through nano-zinc modified biochar

Background Cadmium (Cd) and microplastics (MPs) are gradually increasing in soils, posing a serious threat to humans and crop production. Biochar is a important amendment used worldwide for the remediation of contaminated soils. The role of biochar in mitigating combined Cd and MPs toxicity is rarely studied. Thus, we studied the impact of nano-zinc modified biochar (NZMB) on rice growth, functioning, and productivity in Cd and MPs-co-contaminated soil. Methods The study has different treatments: control, Cd contaminated soil (20 mg kg -1 ), MPs contaminated soil (1%), Cd + MPs contaminated soil, NZMB (2%), Cd contaminated soil (20 mg kg -1 ) + NZMB (2%), MPs contaminated soil (1%) + NZMB (2%) and Cd + MPs contaminated soil + NZMB (2%). Results It was observed that Cd and MPs reduced rice yield (-81%) by impairing chlorophyll synthesis, leaf water contents (-91%), soil nutrient availability, and increasing Cd availability. Biochar application increased the antioxidants activities, osmolyte synthesis, soil organic carbon (+26%), soil pH (18%), nitrogen (+61%), phosphorus (+50%) and potassium availability (40%) and reduced soil Cd availability (-31%), roots Cd (-52%) and shoot Cd (-28%), led to increase in yield in Cd + MPs contaminated soil. Further, NZMB also enhanced the gene expression related to proline ( OsP5CS ), sucrose ( OsSPS1 ), and antioxidants, while decreased expression of gene associated with Cd uptake ( OsNRAMP1 and OsHMA3 ), all of which contributed to an increase in rice yield. Conclusion This study highlights that NZMB can mitigate the combined Cd and MPs toxicity by decreasing Cd uptake and improving plant functioning. Therefore, these findings will help to develop eco-friendly measures for remediating multi-contaminated soils.