Selenate reduced wheat grain cadmium accumulation by inhibiting cadmium absorption and increasing root cadmium retention.

Selenium (Se) fertilizer has been recently used to reduce cadmium (Cd) accumulation in plant. A pot culture was performed to analyze Cd uptake, translocation, and distribution in wheat plants during the reproductive growth period in a Cd-contaminated soil after selenate was applied to the soil, and a hydroponic culture was carried out to investigate the effects of selenate application on Cd2+ influx, subcellular Cd distribution, and Cd accumulation in wheat seedlings. Results showed that selenate application had no significant effect on DTPA-Cd and Cd fraction in soil. The application of selenate greatly inhibited the whole-plant Cd absorption by 14%-23%. In addition, selenate prompted the retention of Cd in root by increasing the Cd distribution in the vacuole, which reduced the root-to-shoot Cd translocation by 18%-53%. The application of selenate increased the Cd concentration in nodes, inhibited Cd remobilization from nutritive organs to grain, and ultimately reduced Cd accumulation in wheat grain. Further, heading to grain filling was the key growth stage for exogenous selenate to regulate grain Cd accumulation. In summary, soil selenate application is an effective method to reduce grain Cd concentration in wheat, which provided scientific basis for remediation of Cd-contaminated soil.

Mercapto-palygorskite efficiently immobilizes cadmium in alkaline soil and reduces its accumulation in wheat plants: A field study.

Cadmium (Cd) contamination in wheat fields has become a major environmental issue in many regions of the world. Mercapto-palygorskite (MPAL) is a high-performance amendment that can effectively immobilize Cd in alkaline wheat soil. However, MAPL as an in-situ Cd immobilization strategy for alkaline wheat soil remains to be evaluated on a field-scale and the underlying mechanisms requires further evaluation. Here, MPAL were used as soil amendment to evaluate their immobilization efficiency on Cd-contaminated alkaline soil in the field experiments. The field experiments showed that MPAL application significantly reduced wheat grain Cd concentration from 0.183 mg/kg to 0.056 mg/kg, with Cd concentration in wheat grain treated with MPAL all falling below the limit value of 0.1 mg/kg as defined in China's food safety standard (GB 2762-2022). The maximal immobilization efficiency of MPAL on soil Cd figured out by diethylenetriaminepentaacetic acid (DTPA) extraction was 61.5%. The mechanisms involved in Cd immobilization by MPAL were mainly related to the enhanced sorption of Cd onto Fe oxides, and the removal of amorphous or free Fe oxides from soil had a substantial impact on Cd immobilization efficiency by MPAL. Furthermore, the antagonistic effect between Mn and Cd uptake may also contribute to the reduction of wheat Cd accumulation after MPAL application. The current research can provide theoretical and technical support for the large-scale application of MPAL in Cd-contaminated wheat fields.

Microstructure characteristics of aggregates and Cd immobilization performance under a 3-year sepiolite amendment: A field study.

Sepiolite is an efficient mineral for the immobilization of Cd in contaminated soils. Here, we conducted a 3-year field experiment to investigate the effect of sepiolite on soil aggregation and porosity, Cd availability, and organic carbon content in the bulk and aggregate soils and Cd accumulation by leafy vegetables. The sepiolite-treated soils showed a 15.4%-53.4% and 5.5%-63.0% reduction in available Cd content in the bulk soil and different particle-size aggregates, respectively. Moreover, the Cd concentrations in the edible parts of Brassica campestris, Lactuca sativa L., and Lactuca sativa var. ramosa Hort. decreased by 5.9%-26.2%, 22.8%-30.1%, and 14.4%-19.1%, respectively, compared with those of the control groups. Treatments with 0.5%-1.5% sepiolite resulted in a significant increase (P < 0.05) in the proportion of 0.25-5.0 mm aggregates, and the increase in the mean weight diameter and geometric mean weight of the soil aggregates indicated that sepiolite treatments enhanced soil aggregate stability. Furthermore, three-dimensional X-ray computed tomography imaging showed that sepiolite treatments resulted in an increase in the total area, average size, and pore perimeter of aggregates, with the maximum values being 1.63-, 1.41-, and 1.401-fold higher than those of the corresponding control groups, respectively. The highest values of soil organic carbon and particulate organic carbon were obtained in 1.5% sepiolite-treated soils and were 2.07- and 1.91-fold higher than those of the control groups, respectively. Additionally, the level of organic carbon functional groups in the bulk soil and different particle-size aggregates generally increased with increasing sepiolite application. Overall, sepiolite, as a soil amendment, not only reduced toxic element bioavailability and uptake by plants but also enhanced soil structure and function.

Effect of different pyrolysis temperatures on physico-chemical characteristics and lead(ii) removal of biochar derived from chicken manure.

Biochar derived from chicken manure, as an effective metal adsorbent, was prepared through a pyrolysis method at different pyrolytic temperatures (200, 400, 600, and 800 °C). The physicochemical characteristics of chicken manure biochar (CMB) and its lead (Pb2+) adsorption mechanisms were studied by batch adsorption experiments, DTA/TGA, XRD, SEM-EDS, FTIR and an analysis of the composition of their mineral ash. Results showed that the best-fit for the Pb2+ adsorption data was achieved using a Langmuir isotherm and a pseudo-second-order model. The maximum adsorption capacities of Pb2+ increased with increasing of pyrolytic temperatures of the CMB, being 180.21, 200.80, 239.59, and 242.57 mg g-1, respectively, for CMB-200, CMB-400, CMB-600 and CMB-200. Although Pb2+ adsorption on CMB revealed that adsorption was controlled by multiple mechanisms, (e.g. surface complexation, ion exchange, surface precipitation, electrostatic attraction, physical adsorption, and co-precipitation), the ion exchange and surface precipitation played a dominant role in Pb2+ sorption. Using CMB for the removal of Pb from water is proposed as an effective, environmentally protective, novel approach.