Clay minerals alleviate lead contamination induced by soil speciation and oat translocation in neutral and saline soils

Lead (Pb) contamination in agricultural soils poses a critical environmental challenge, necessitating the development of effective remediation strategies. Clay minerals are widely employed in soil remediation owing to their natural abundance and low cost. Nevertheless, their effectiveness is highly dependent on soil pH conditions. This study evaluated the efficacy of three clay minerals (palygorskite (Pa), sepiolite (Sep), bentonite (Be)) in remediating Pb-contaminated soils under neutral and saline conditions. The addition of clay minerals reduced total Pb by 12–26% in neutral soils, compared with only 2–15% in saline counterparts. Concomitantly, Pb bioavailability was significantly reduced. Among these, Sep decreased the EX-Pb pool by 24% and enhancing the RE-Pb by 16% under neutral conditions, whereas the corresponding changes in saline soil were 9% and 10%, respectively. This differential effectiveness was attributed to a shift in the dominant environmental drivers. This reduction in Pb bioavailability led to decreased Pb uptake by crops. Furthermore, the application of clay minerals increased the Pb concentration within oat roots by −32–79% in neutral soil and by 15–82% in saline soil, while restricting the translocation of Pb to the shoots, ultimately reducing grain Pb content by 42–59% and −5–14%, respectively. Sep proved to be a stable and efficient material for immobilizing Pb and limiting its uptake by plants in contaminated soils. The study further revealed that its remediation performance was more pronounced in neutral soils than saline conditions.