Soil heavy metal pollution is a global environmental challenge, posing significant threats to eco-environment, agricultural development, and human health. In recent years, advanced and effective remediation strategies for heavy metal-contaminated soils have developed rapidly, and a systematical summarization of this progress is important. In this review paper, first, the anthropogenic sources of heavy metals in agricultural soils, including atmospheric deposition, animal manure, mineral fertilizers, and pesticides, are summarized. Second, the accumulation of heavy metals in crops as influenced by the plant characteristics and soil factors is analyzed. Then, the reducing strategies, including low-metal cultivar selection/breeding, physiological blocking, water management, and soil amendment are evaluated. Finally, the phytoremediation in terms of remediation efficiency and applicability is discussed. Therefore, this review provides helpful guidance for better selection and development of the control/remediation technologies for heavy metal-contaminated agricultural soils.

Selenium (Se) is an essential trace element for human and animal health, and toward an understanding of the uptake and translocation of Se in plants is important from the perspective of Se biofortification. In this study, we conducted hydroponic experiments to investigate the mechanisms of organic Se [selenomethionine (SeMet) and selenomethionine-oxide (SeOMet)] uptake, translocation, and the interactions between SeMet and SeOMet in rice. We also investigated differences in the dynamics of organic and inorganic Se uptake by rice roots. Concentration-dependent kinetic results revealed that SeMet uptake during a 1 h exposure was 3.19–16.0 times higher than that of three other Se chemical forms, with uptake capacity (V_max) values ordered as follows: SeMet>SeOMet>selenite>selenate. Furthermore, time-dependent kinetic analysis revealed that SeMet uptake by roots and content in shoots were initially clearly higher than those of SeOMet, although the differences gradually diminished with prolonged exposure time; while no significant difference was found in the transfer factor of Se from rice roots to shoots between SeMet and SeOMet. Root uptake of SeOMet was significantly inhibited by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) (30.4%), AgNO₃ (41.8%), and tetraethylammonium chloride (TEACl) (45.6%), indicating that SeOMet uptake is a metabolically active process, and that it could be mediated via aquaporins and K⁺ channels. Contrarily, SeMet uptake was insensitive to CCCP, although markedly inhibited by AgNO₃ (93.1%), indicating that rice absorbs SeMet primarily via aquaporins. Furthermore, Se uptake and translocation in rice treated simultaneously with both SeMet and SeOMet were considerably lower than those in rice treated with SeMet treatment alone and notably lower than the theoretical quantity, indicating interactions between SeMet and SeOMet. Our findings provide important insights into the mechanisms underlying the uptake and translocation of organic Se within plants.

Wheat (Triticum aestivum L.) is a staple food worldwide, and agronomic biofortification with selenium (Se) and zinc (Zn) is a simple and effective way to increase nutrient intake. This study aimed to evaluate the combined effects of Zn and Se on the biofortification of wheat grain. Zinc sulfate (ZnSO₄·H₂O, 1.74, 2.61 and 3.48 kg Zn hm⁻²) and sodium selenite (Na₂SeO₃, 15 and 30 g Se hm⁻²) were sprayed individually or simultaneously at key stages of wheat growth (the jointing, booting, and filling stage) under field conditions. On the basis of soil Zn application, the foliar application of Zn or Se alone greatly increased grain Zn by 12.07–71.88% (up to 41.66–64.30 mg kg⁻¹), and grain Se content by 131.81–527.21% (up to 0.21–0.50 mg kg⁻¹), while the soil application of Zn had little effect on grain Zn. Compared with the foliar application of Zn or Se alone, the co-application of Se increased the grain Zn content by 1.74–16.15%, while the co-application of Zn significantly reduced grain Se content by 25.43–86.34% and the effect was more pronounced with an increase in Zn dosage. Moreover, positive correlations were found between Zn and copper (Cu) in grains, and wheat grains could provide adequate dietary intakes of manganese (Mn), Cu, and molybdenum (Mo) for humans. In summary, the soil application of 11 kg Zn hm⁻² combined with the foliar application of 2.61 kg Zn hm⁻² and 30 g Se·hm⁻² is a feasible Zn-Se co-enrichment strategy, which would provide the recommended nutrient intake (RNI) of 113.63–124.72% (female) and 68.18–74.84% (male) of Zn and 81.30–95.85% of Se.