This study investigated the enhancing effects of soil treatment with ethylene diamine tetraacetic acid (EDTA) and oxalic acid (OA) on the remediation of Cr(VI) contaminated soil by Datura stramonium L. A greenhouse pot experiment was conducted, where Cr(VI) contaminated soil was treated with 100 mg/kg Cr(VI) and varying concentrations of EDTA (5 and 10 mmol/kg) and OA (5 and 10 mmol/kg). The effects of these soil treatments on biomass, chlorophyll content, antioxidant enzyme activities, and Cr(VI) enrichment and translocation efficiency of D. stramonium were evaluated. The results showed that added OA to soil significantly increased the biomass and chlorophyll content of D. stramonium. The addition of 10 mmol/kg of OA to soil increased the plant biomass by 67.16 % and chlorophyll b content by 40.01 %. In addition, OA soil treatment significantly enhanced the activities of superoxide dismutase (SOD) by 6.36 %, peroxidase (POD) by 163.13 %, catalase (CAT) by 36.92 %, and ascorbate peroxidase (APX) by 32.12 %, which effectively alleviated the oxidative stress induced by Cr(VI). In contrast, soil treatment with a high concentration of EDTA (10 mmol/kg) significantly reduced plant biomass and chlorophyll content, although it increased the biological concentration factor (BCF) of the stem and leaf, as well as the translocation factor (TF). In conclusion, appropriate amounts of EDTA and OA added to soil can enhance the phytoremediation efficiency of D. stramonium grown in Cr(VI) contaminated soil, with OA added to soil being more effective than addition of EDTA. This study revealed the potential mechanisms of chelating agents EDTA and OA in enhancing the phytoremediation of Cr(VI) contaminated soil by D. stramonium, providing a scientific basis for further optimization of phytoremediation techniques.

Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 x 10-6 cm2/s-9.5 x 10-6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 x 10-8 to 4.13 x 10-7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills.

Chromium (Cr) poses a high ecological risk, however the toxic mechanisms of Cr in different valence states to soil organisms at cellular and molecular levels are not exactly. In this study, the Eisenia fetida coelomocytes and Cu/ Zn-superoxide dismutase (Cu/Zn-SOD) were chosen as the target subjects to investigate the effects and mechanisms of cellular toxicity induced by Cr(VI) and Cr(III). Results indicated that Cr(VI) and Cr(III) significantly reduced the coelomocytes viability. The level of reactive oxygen species (ROS) was markedly increased after Cr (VI) exposure, which finally reduced antioxidant defense abilities, and induced lipid peroxidation and cellular membrane damage in earthworm coelomocytes. However, Cr(III) induced lower levels of oxidative stress and cellular damage with respect to Cr(VI). From a molecular perspective, the binding of both Cr(VI) and Cr(III) with Cu/Zn-SOD resulted in protein backbone loosening and reduced beta-Sheet content. The Cu/Zn-SOD showed fluorescence enhancement with Cr(III), whereas Cr(VI) had no obvious effect. The activity of Cu/Zn-SOD continued to decrease with the exposure of Cr. Molecular docking indicated that Cr(III) interacted more readily with the active center of Cu/Zn-SOD. Our results illustrate that oxidative stress induced by Cr(VI) and Cr (III) plays an important role in the cytotoxic differences of Eisenia fetida coelomocytes and the binding of Cr with Cu/Zn-SOD can also affect the normal structures and functions of antioxidant defense-associated protein.