Soil property–driven prediction of heavy metal uptake by Anethum graveolens L. in sewage sludge–amended soils toward sustainable biomass utilization

The present study aimed to develop predictive models for the evaluation of the uptake of nine heavy metals (HMs) by the shoots and roots of Dill plants (Anethum graveolens L.). Plants were grown in soil mixed with varying concentrations of sewage sludge (0, 10, 20, and 30 g/kg) and raised for 59 days, from December 18, 2022, in the greenhouse, following the natural day-night cycle. The results indicated statistically significant (p < 0.05) differences in HM contents between roots and shoots. Specifically, Cd and Ni contents were higher in roots than in shoots, while Co and Cr were more concentrated in shoots than in roots. However, Cu, Fe, Mn, Pb, and Zn exhibited relatively uniform concentrations across both parts. The bioaccumulation factors indicated that Cd, Pb, Co, Ni, Cu, and Mn had higher values (> 1.0), with Cd and Co showing the highest BAF (~ 4.0), indicating strong accumulation, while Fe, Cr, and Zn had lower BAFs (< 1.0). Translocation factors indicated a significant transfer from roots to shoots, with Cr exhibiting the highest translocation factor (6.25), demonstrating preferential transport to aerial tissues. Prediction models (multiple linear regression) indicated that soil characteristics (pH, EC, and OM) influenced the accumulation of HMs in Dill plant tissues, although predictive performance varied markedly among metals, performing well for elements such as Mn in shoots (R² up to 0.951, model efficiency up to 0.944) but poorly for others, notably Cd in shoots (R² = 0.154), indicating reliable prediction for only a subset of the studied metals. Overall, the present study provides useful findings on the differential mechanisms of HM uptake and translocation in Dill plants and provides insights for predicting HM accumulation based on soil properties.