Causal Analysis Between Rice Growth and Cadmium Accumulation and Transfer under Arbuscular Mycorrhizal Inoculation

Cadmium(Cd)contamination in rice has been a serious threat to human health.To investigate the effects of arbuscular mycorrhizal fungi(AMF)on the Cd translocation in rice,a controlled pot experiment was conducted.The results indicated that AMF significantly increased rice biomass,with an increase of up to 40.0%,particularly in root biomass by up to 68.4%.Notably,the number of prominent rice individuals also increased,and their plasticity was enhanced following AMF inoculation.AMF led to an increase in the net photosynthetic rate and antioxidant enzyme activity of rice.In the AMF treatment group,the Cd concentration in the rice roots was significantly higher(19.1%‒68.0%)compared with that in the control group.Conversely,the Cd concentration in the rice seeds was lower in the AMF treatment group,indicating that AMF facilitated the sequestration of Cd in rice roots and reduced Cd accumulation in the seeds.Path coefficients varied across different treatments,suggesting that AMF inoculation reduced the direct impact of soil Cd concentration on the total Cd accumulation in seeds.The translocation of Cd was consistently associated with simultaneous growth dilution and compensatory accumulation as a result of mycorrhizal effects.Our study quantitatively analyzed this process through path analysis and clarified the causal relationship between rice growth and Cd transfer under the influence of AMF.

Mine tailings as a raw material in alkali activation: A review

The mining industry produces billions of tons of mine tailings annually.However,because of their lack of economic value,most of the tailings are discarded near the mining sites,typically under water.The primary environmental concerns of mine tailings are related to their heavy metal and sulfidic mineral content.Oxidation of sulfidic minerals can produce acid mine drainage that leaches heavy metals into the surrounding water.The management of tailing dams requires expensive construction and careful control,and there is the need for stable,sustainable,and economically viable management technologies.Alkali activation as a solidification/stabilization technology offers an attractive way to deal with mine tailings.Alkali activated materials are hardened,concrete-like structures that can be formed from raw materials that are rich in aluminum and silicon,which fortunately,are the main elements in mining residues.Furthermore,alkali activation can immobilize harmful heavy metals within the structure.This review describes the research on alkali activated mine tailings.The reactivity and chemistry of different minerals are discussed.Since many mine tailings are poorly reactive under alkaline conditions,different pretreatment methods and their effects on the mineralogy are reviewed.Possible applications for these materials are also discussed.

Hardening Properties of Foamed Concrete with Circulating Fluidized Bed Boiler Ash, Blast Furnace Slag, and Desulfurization Gypsum as the Binder

Recently, a large amount of circulating fluidized bed boiler ash (CFBA) and desulfurization gypsum (DSG) has been produced, and it is essential to develop technology to utilize them. These materials have CaO and SO3, which are considered to be a stimulant for blast furnace slag (BFS). This study presents an experimental investigation of the compressive strength and heavy metal ions immobilization properties of cement-free materials comprising CFBA, BFS, and DSG. The feasibility of manufacturing foamed concrete using these materials was examined, and field test of foamed concrete was conducted. Experimentally, the flow, compressive strength, and heavy metal ions concentration were evaluated via inductively coupled plasma atomic emission spectroscopy (ICP-AES) of the paste and foamed concrete. The experimental investigation revealed the self-healing hardening ability of fluidized bed boiler ash. In addition, the compressive strength was increased with the increasing replacement rates of BFS and DSG in the CFBA paste, and the compressive strength of 14.6 - 17.2 MPa was recorded over 28 days of curing. From the result obtained, the feasibility of manufacturing foamed concrete with a foam volume of 120 L, incorporating the aforementioned materials, is confirmed. It was also found that after 28 days of age, a 7.9-MPa compressive strength of the foamed concrete was attained, and heavy metal ions elution in this foamed concrete was also significantly reduced. Therefore, CFBA, BFS, and DSG could be used as a binder for the foamed concrete.

The preparation of paddy soil amendment using granite and marble waste: Performance and mechanisms

The wastes generated from themining and processing of granite and marble stone are generally regarded as useless.However,these waste materials were used as the soil amendments for the first time.The functional groups,crystalline structure andmicro-morphology of granite and marble wastes amendments(GMWA)were different from the original wastes demonstrated by X-ray diffractometer(XRD),Fourier transform infrared spectrometer(FTIR)and Scanning electron microscope-energy dispersive spectrometer(SEM-EDS)analyses.With the addition of the amendments,the cation exchange capacity,electrical conductivity and nutrient availability of the soil increased,and the extractable heavy metals of the soil reduced significantly.Under the condition of the addition of 3%amendments,7.0%,99.9%,99.7%and 70.5%of Cu,Pb,Zn and Cd in exchangeable fractions in soil were transformed to the more stable Fe-Mn oxides-or carbonates-bounded fractions.Tessier method and correlation analysis showed that the reduction of extractable metals in the acidic paddy soil can be attributed to the adsorption of available SiO_(2),the co-precipitation induced by the elevated pH value,the complexation induced by Fe-Mn oxides and the cation exchange induced by mineral nutrients.This study provides a new strategy for resource recovery of waste stones and remediation of heavy metal-contaminated soil.

Combined effects of adsorption and photocatalysis by hybrid TiO_2/ZnO-calcium alginate beads for the removal of copper

The use of nanosized titanium dioxide（TiO2） and zinc oxide（ZnO） in the suspension form during treatment makes the recovering and recycling of photocatalysts difficult.Hence,supported photocatalysts are preferred for practical water treatment applications.This study was conducted to investigate the efficiency of calcium alginate（CaAlg） beads that were immobilized with hybrid photocatalysts,TiO2/ZnO to form TiO2/ZnO-CaAlg.These immobilized beads,with three different mass ratios of TiO2：ZnO（1：1,1：2,and 2：1） were used to remove Cu（Ⅱ） in aqueous solutions in the presence of ultraviolet light.These beads were subjected to three cycles of photocatalytic treatment with different initial Cu（Ⅱ） concentrations（10-80 ppm）.EDX spectra have confirmed the inclusion of Ti and Zn on the surface of the CaAlg beads.Meanwhile,the surface morphology of the beads as determined using SEM,has indicated differences of before and after the photocatalytic treatment of Cu（Ⅱ）.Among all three,the equivalent mass ratio TiO2/ZnO-CaAlg beads have shown the best performance in removing Cu（Ⅱ） during all three recycling experiments.Those TiO2/ZnO-CaAlg beads have also shown consistent removal of Cu,ranging from 7.14-52.0 ppm（first cycle） for initial concentrations of10-80 ppm.In comparison,bare CaAlg was only able to remove 6.9-48 ppm of similar initial Cu concentrations.Thus,the potential use of TiO2/ZnO-CaAlg beads as environmentally friendly composite material can be further extended for heavy metal removal from contaminated water.