Iron-modified biochar inhibiting Cd uptake in rice by Cd co-deposition with Fe oxides in the rice rhizosphere.

Fe-enriched biochar has proven to be effective in reducing Cd uptake in rice plants by enhancing iron plaque formation. However, the effect of Fe on biochar, especially the biochar with high S content, for Cd immobilization in rice rhizosphere was not fully understood. To obtain eco-friendly Fe-loaded biochar at a low cost, garlic straw, bean straw, and rape straw were chosen as the feedstocks for Fe-enhanced biochar production by co-pyrolysis with Fe2O3. The resulting biochars and Fe-loaded biochars were GBC, BBC, BRE, GBC-Fe, BBC-Fe, and BRE-Fe, respectively. XRD and FTIR analyses showed that Fe was successfully loaded onto the biochar. The pristine and Fe-containing biochars were applied at rates of 0% (BC0) and 0.1% in pot experiments. Results suggested that BBC-Fe caused the highest reduction in Cd content of rice grain, and the reductions were 67.9% and 31.4%, compared with BC0 and BBC, respectively. Compared to BBC, BBC-Fe effectively reduced Cd uptake in rice roots by 47.5%. The exchangeable and acid-soluble fraction of Cd (F1-Cd) in soil with BBC-Fe treatment was 37.6% and 63.7% lower than that of BC0 and BBC, respectively. Compared to BC0, soil pH was increased by 0.53 units with BBC-Fe treatment. BBC-Fe significantly increased Fe oxides (free Fe oxides, amorphous Fe oxides, and complex Fe oxides) content in the soil as well. DGT study demonstrated that BBC-Fe could enhance the mobility of sulfate in the rhizosphere, which might be beneficial for Cd fixation in the rhizosphere. Moreover, BBC-Fe increased the relative abundance of Bacteroidota, Firmicutes, and Clostridia, which might be beneficial for Cd immobilization in the rhizosphere. This work highlights the synergistic effect of loaded Fe and biochar on Cd immobilization by enhancing Cd deposited with Fe oxides.

Cadmium uptake and transfer by Sedum plumbizincicola using EDTA, tea saponin, and citric acid as activators.

Sedum plumbizincicola (S. plumbizincicola) is known as a sufficient plant for phytoremediation of cadmium (Cd) polluted soils. This study aimed to investigate the effects of ethylene diamine tetraacetic acid (EDTA), tea saponin (TS), and citric acid (CA) on Cd uptake and translocation by S. plumbizincicola. To do so, using a pot experiment, we set four concentration levels of activators (1, 3, 5, and 10 mmol L-1) and a control (CK). Results showed that none of the applied activators had significant impact on soil pH. Except for CA-10, the concentration of available Cd in Cd polluted soils increased by 65.8-72.9% compared with CK. The EDTA-1, CA-1, and TS-5 treatments caused significant increases of 52.3, 67.2, and 38.4%, respectively, in the biomass of aerial parts of S. plumbizincicola (p < 0.05) compared with CK. Except for CA-3, activators increased Cd accumulation in the aerial parts of plants by 47-124% compared with CK. Of all activators, EDTA-3 caused the highest Cd accumulation of 6.64 g pot-1 in the aerial plant tissues followed by CA-10 (6.25 g pot-1) and TS-1 (5.48 g pot-1). Finally, our results suggested that the application of S. plumbizincicola together with different activators sufficiently reduced soil total Cd by 4.64-48.4% compared with CK. These findings suggest that appropriate application of EDTA, TS, and CA can promote phytoremediation of Cd contaminated soils by hyper-accumulators. In particular, the combined use of EDTA and S. plumbizincicola is an affordable and promising strategy for remediation of Cd contaminated soil.Novelty statement: Sedum plumbizincicola (S. plumbizincicola) is a well-known hyper-accumulator plant for remediation of cadmium (Cd) and zinc (Zn) contaminated soils. In addition, low molecular rganic acids and macromolecular chelating agents can improve the solubility and leaching of soil heavy metals. In the present work, we examined the combined effects of three activators (EDTA, tea saponin, and citric acid) with S. plumbizincicola to remediate a Cd contaminated soil in Anhui Province, East China. Our results indicated the effectiveness of these activators to increase soil available Cd, as well as improving the biomass of S. plumbizincicola and its Cd uptake. We believe that this study provides an efficient approach to increase the uptake of Cd by S. plumbizincicola, restoring Cd contaminated soils. Nevertheless, excessive activators may have adverse effects on soil aggregates and soil microorganisms. Therefore, it is necessary to control the amount of chelating agents and subsequently the deterioration of soil quality.

[Sustained Effects of Remediation Materials on Soil Copper Remediation Under Oil-Rice Rotation].

In this study, a continuous rape-rice rotation plot experiment was conducted over three years. Repair materials were continuously applied in the first two years, and no repair materials were applied in the second year. The repair effects of hydroxyapatite, lime, biochar, bio-organic fertilizer, and nano-materials on copper contaminated soil and the enrichment of copper in different parts of rape and rice were investigated. The results show that hydroxyapatite, lime, and nanomaterials can significantly increase soil pH, and different restoration materials can effectively inhibit the movement of soil copper. The effective copper treatment with lime restoration soil had the largest decrease. The four seasons of continuous application of restoration materials were 38.9%, 34.9%, 27.88%, and 29.04%, respectively, and the subsequent effect of lime passivation of effective copper was better than other restoration materials. The application of the repair material significantly reduced the copper content in edible parts of rape and rice. In the four seasons of application of the repair material, the maximum copper content in edible parts of different crops decreased by 46.03%, 22.2%, 29.44%, and 31.71%, respectively. Due to the application effect of the repair material, the copper content in the edible part of the two season crops, without the repair material, did not exceed the national food safety limit. With the use of different repair materials, the yields of rapeseed and rice were improved. This test can provide some theoretical basis and technical support for soil improvement in copper-contaminated areas.

Adsorption of Cd(II) in water by mesoporous ceramic functional nanomaterials.

Mesoporous ceramic functional nanomaterials (MCFN) is a self-assembled environmental adsorbent with a monolayer molecular which is widely used in the treatment of industrial wastewater and contaminated soil. This work aimed to study the relationship between the adsorption behaviour of Cd(II) by MCFN and contact time, initial concentration, MCFN dosage, pH, oscillation rate and temperature through a batch adsorption method. The adsorption kinetic and isotherm behaviours were well described by the pseudo-second-order and Langmuir models. The batch characterization technique revealed that MCFN had several oxygen-containing functional groups. Using Langmuir model, the maximum adsorption capacity of MCFN for Cd(II) was 97.09 mg g-1 at pH 6, 25°C, dosage of 0.2 g and contact time of 180 min. Thermodynamic study indicated that the present adsorption process was feasible, spontaneous and exothermic at the temperature range of 25-55°C. The results of this study provide an important enlightenment for Cd removal or preconcentration of porous ceramic nanomaterial adsorbents for environmental applications.

Rapid Detection Methods for Asphalt Pavement Thicknesses and Defects by a Vehicle-Mounted Ground Penetrating Radar (GPR) System.

The thickness estimation of the top surface layer and surface layer, as well as the detection of road defects, are of great importance to the quality conditions of asphalt pavement. Although ground penetrating radar (GPR) methods have been widely used in non-destructive detection of pavements, the thickness estimation of the thin top surface layer is still a difficult problem due to the limitations of GPR resolution and the similar permittivity of asphalt sub-layers. Besides, the detection of some road defects, including inadequate compaction and delamination at interfaces, require further practical study. In this paper, a newly-developed vehicle-mounted GPR detection system is introduced. We used a horizontal high-pass filter and a modified layer localization method to extract the underground layers. Besides, according to lab experiments and simulation analysis, we proposed theoretical methods for detecting the degree of compaction and delamination at the interface, respectively. Moreover, a field test was carried out and the estimated results showed a satisfactory accuracy of the system and methods.