Chaolei Yuan,Fangbai Li,Wenhua Cao,Zi Yang,Min Hu,Weimin Sun
We successfully accounted for the dynamics of cadmium (Cd) solubility in paddy soil that contained a realistically low total Cd concentration (0.36 mg kg −1 ) after submergence and redrying by monitoring multiple chemical and microbial soil properties. The addition of rice straw promoted greater microbial iron reduction and induced a greater increase in soil pH after submergence, compared to the control and treatments with added gypsum or hematite. Consequently, dissolved Cd decreased to under the detection limit in one week in the straw-amended treatment but remained high even after eight weeks in the other three treatments. The Cd solubility strongly correlated with soil pH and was unlikely to decrease due to Cd precipitation in secondary iron minerals. After five weeks of redrying, the dissolved Cd content was still the lowest, and the putative iron-reducing bacteria Geobacter remained the most abundant in the straw-amended soil. The results suggest that the addition of organic matter can efficiently immobilize soil Cd at an environmentally realistic concentration by stimulating the microbial reduction of native oxidized soil components after submergence, while adding extra iron oxide or sulfate alone is not effective because it does not eliminate the limitation imposed by electron donors on microbial reduction.
Song Guo,Shao-hua Luo,Xiaolong Li,Zihan Wang,Xian Zhang,Xuefei Lei,Sheng-xue Yan
This investigation focused on the contribution of various silane blends, used as coupling agents, to the ultimate performance of dental nanocomposite dimethacrylate photocurable resins . Initially, the surface of silica nanospheres was silanized with three different silane coupling agents : γ-MPS, APTES , and OTMS, with the grafting rate serving as the index. Fourier Transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) verified the modification of nanosilica . Through orthogonal test experiments on the three silane coupling agents, the optimal modifier concentration, temperature, and time were determined. Subsequently, 15 wt% organomodified SiO 2 nanospheres were incorporated into Bis-GMA/TEGDMA (70/30 by wt%) based resins via a photocuring process. Scanning electron microscopy (SEM) findings revealed a relatively vague interface between inorganic fillers and resins in the polymer composite , especially when reactive silanes like γ-MPS and their corresponding blends were used. The combination of SiO 2 and γ-MPS functional silane blend provided the highest flexural properties and the lowest solubility after storing the nanocomposite in water for 1 week at 37 °C. With these methods, composite resins containing 15 wt% MPS-SiO 2 nanospheres in a Bis-GMA/TEGDMA (70/30 by wt%) mixture exhibited the best comprehensive properties, making them a promising choice for achieving long-term durable restorations in clinical therapies.
危险品化学品经营许可证（带存储）