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Widespread lead (Pb) contamination of agricultural soils is a global issue stemming from human activities. The remediation of Pb-contaminated soils used for agricultural purposes is critically important to safeguard food crop safety. Despite the modulating effects of sulfur (S) on plant responses to toxic heavy metals, the ecological, physiological, and molecular mechanisms driving such modulation in the Pb hyperaccumulator Arabis alpina L. remain unclear. Here, we investigated the effects of five S concentrations (0, 50, 100, 150, and 200 mg kg -1 ) on A. alpina grown in Pb-contaminated soil from a lead-zinc mining area. Under S50 (i.e., 50 mg kg -1 ) and S100 treatments, the Pb concentration in both shoots and roots of A. alpina significantly decreased compared to the control (S0). Specifically, the S50 treatment significantly enhanced Pb accumulation, plant biomass, and plant height, indicating that low S applications facilitate Pb accumulation from the soil and alleviate Pb toxicity. Additionally, S50, S100, and S150 treatments significantly improved photosynthetic rate, stomatal conductance, and intercellular CO 2 concentration in A. alpina. Transcriptomic analysis showed that S50 and S100 treatments increased the expression of the LHCA, LHCB, psa, and psb genes, which had a significant impact on photosynthetic efficiency. S50 and S100 boosted glutathione (GSH) levels in A. alpina roots, and the increased expression of GST gene enhanced tolerance to environmental stress. In summary, these results suggest that an appropriate supply of S (S50 and S100) not only alleviates Pb toxicity by enhancing plant biomass, height, photosynthetic features, and sulfur metabolites but also stimulates Pb accumulation in the hyperaccumulator A. alpina. Our study elucidated the specific concentrations of sulfur that optimally enhance both Pb accumulation and stress tolerance in the hyperaccumulator A. alpina, providing novel insights into the practical application of sulfur in phytoremediation strategies and advancing our understanding of the underlying molecular mechanisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The effects of sepiolite and biochar on the contents of available nutrients (N, P, and K); the chemical forms and available contents of Cd and Pb in soils; the biomass and growth of maize; and the contents of nutrients, Cd, and Pb in maize were studied in situ in Cd- and Pb-polluted farmlands around the Lanping Pb-Zn mine in Yunnan Province, China. Results demonstrated that sepiolite did not influence the contents of available nutrients in soils, although it significantly increased the pH value and decreased available Cd (CaCl 2 -extractable and exchangeable) contents and exchangeable and reducible Pb. Moreover, sepiolite increased the biomass in the aboveground part of maize, resulting in the reduction of Cd contents in maize plants and grains by 25.6-47.5%. Meanwhile, the biochar increased the contents of available nutrients in soils and decreased the contents of exchangeable Pb in soils and biomass in the aboveground part of maize plants and grains; decreased the Cd contents in maize stems and grains by 26.7% and 24.6%, respectively; and decreased the Pb content in roots by 16.2%. However, neither sepiolite nor biochar had considerable influence on the Pb content in maize grains. According to a correlation analysis, soil pH has extremely significant negative correlations with available Cd content in soils, which in turn have extremely significant positive correlation with the Cd content in maize plants and grains. These results revealed that sepiolite increases soil pH and decreases Cd bioavailability in farmland soils around the Pb-Zn mine. Furthermore, biochar increases the contents of available nutrients in farmland soils and the maize yield. Sepiolite and biochar both decrease the contents and transfer coefficients of Cd in maize plants and grains and are, thus, applicable to the immobilization remediation of Cd-polluted farmlands.

Sulfur plays a vital role in the phytoremediation of lead-contaminated soil. The effects of different sulfur forms (S Na2S, and Na2SO4) on lead (Pb) absorption in hyperaccumulator Arabis alpina L. var. parviflora Franch were studied in a soil pot experiment. The subcellular sulfur and lead enrichment characteristics in A. alpina were studied by adding sulfur in different forms and concentrations (0, 75, and 150 mg·kg−1) to Pb-contaminated soil. The results show that the root and shoot biomass increased by 1.94 times under Na2S and Na2SO4 treatment, and the root–shoot ratio of A. alpina increased 1.62 times under the three forms of sulfur treatments, compared with the control. Sulfur content in cell walls and soluble fractions of the root and shoot of A. alpina significantly increased 3.35~5.75 times and decreased 5.85 and 9.28 times in the organelles under 150 mg·kg−1 Na2SO4 treatment. Meanwhile, Pb content in the root and shoot cell walls of A. alpina significantly increased by 3.54 and 2.75 times, respectively. Pb content in the shoot soluble fraction increased by 3.46 times, while it significantly reduced by 3.78 times in the shoot organelle. Pb content in the root organelle and soluble fraction decreased by 2.72 and 2.46 times. Different forms and concentrations of sulfur had no regularity in the effect of Pb and sulfur content in the subcellular components of A. alpina, but the bioconcentration and translocation factors of A. alpina increased compared with the control. Under different concentrations of Na2SO4, there was a significant positive correlation between the contents of sulfur and Pb in the subcellular components of the root of A. alpina (p < 0.05). These results indicate that sulfur application can enhance the Pb resistance of A. alpina by strengthening the cell wall fixation and vacuolar compartmentalization. [ABSTRACT FROM AUTHOR]

Five profiles located in the peri-urban market garden of Yunnan Province, China were investigated for the distribution and sequential extraction fractions (SEF) of Pb, Cd, Cu and Zn, and mobility in relation to soil properties. SEF heavy metals included acetic acid extractable (A-fraction), hydroxylamine hydrochloride extractable (B-fraction) and hydrogen peroxide and ammonium acetate extractable fractions (C + D-fraction). The results showed that: (1) Total Pb and Zn contents decreased with soil depth. The accumulation of different fractions of Pb and Zn was due to accumulation of organic carbon and Fe–Mn oxides. (2) Total Cd content increased with soil depth with the ratio of A to C horizons (RAC) < 1.0. Cd was relatively mobile within the A horizon. C + D-Cd contents were consistent with organic carbon accumulation. (3) Total Cu content in profiles 2 and 3 decreased with depth, while in other profiles it increased. A-Cu contents in the B horizon in profiles 1, 2 and 3 were higher than in the A and C horizons, and decreased with depth in profiles 4 and 5 in the transition unit. B-Cu content increased with depth, whereas C + D-Cu contents decreased. The mobility and redistribution of heavy metals in soil profiles were influenced by clay content, organic carbon and Fe–Mn oxides. [ABSTRACT FROM PUBLISHER]