三氯苯、二甲苯在土壤有机质中的等温吸附

采用完全混合一步平衡反应实验方法,选择三氯苯和二甲苯作为HOCs的探针,研究它们在土壤以及从土壤中分离出的胡敏酸、胡敏素等土壤有机质(SOMs)中的等温平衡吸附行为,探讨非线性吸附的机制.结果表明,憎水有机物(HOCs)在水、土壤体系中的吸附行为主要受到SOMs的控制,松散的胡敏酸表现出相对线性的吸附行为(n=0.845～0.867),而聚集的胡敏素和'黑炭'组分则表现出非线性吸附(n=0.634～0.860),并具有很强的亲和性(logKF=0.109～1.321). HOCs在土壤中的非线性吸附主要是它们在聚结的土壤有机质表面吸附的结果.

Heterogeneous electrolyte membranes enabling double-side stable interfaces for solid lithium batteries

The solid polymer electrolyte(SPE) is one of the most promising candidates for building solid lithium batteries with high energy density and safety due to its advantages of flexibility and light-weight.However,the conventional monolayered electrolytes usually exhibit unstable contacts with either high-voltage cathodes or Li-metal anodes during cell operation.Herein,heterogeneous dual-layered electrolyte membranes(HDEMs) consisting of the specific functional polymer matrixes united with the designed solid ceramic fillers are constructed to address the crucial issues of interfacial instability.The electrolyte layers composed of the high-conductivity and oxidation-resistance polyacrylonitrile(PAN) combined with Li_(0.33)La_(0.557)TiO_(3) nanofibers are in contact with the high-voltage cathodes,achieving the compatible interface between the cathodes and the electrolytes.Meanwhile,the electrolyte layers composed of the highstability and dendrite-resistance polyethylene oxide(PEO) with Li_(6.4)La_(3) Zr_(1.4)Ta_(0.6)O_(12) nanoparticles are in contact with the Li-metal anodes,aiming to suppress the dendrite growth,as well as avoid the passivation between the PAN and the Li-metal.Consequently,the solid LiNi_(0.6)Co_(0.2)Mn_(0.2)O2‖Li full cells based on the designed HDEMs show the good rate and cycling performance,i.e.the discharge capacity of 170.1 mAh g^(-1) with a capacity retention of 78.2% after 100 cycles at 0.1 C and 30℃.The results provide an effective strategy to construct the heterogeneous electrolyte membranes with double-side stable electrode/-electrolyte interfaces for the high-voltage and dendrite-free solid lithium batteries.

Characteristics and distributions of humic acids in two soil profiles of the southwest China Karst area

Characteristics and distributions of humic acid(HA) and soil organic matter(SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area. The results showed that characteristics and distribution of SOM along the two soil profiles were notably different. Total organic carbon(TOC) contents of soil samples decreased just slightly along the limestone soil profile but sharply along the yellow soil profile. TOCs of the limestone soils were significantly higher than those of the corresponding yellow soils, and C/N ratios of SOMs showed a similar variation trend to that of TOCs, indicating that SOM can be better conserved in the limestone soil than in the yellow soil. The soil humic acids were exhaustively extracted and further fractionated according to their apparent molecular weights using ultrafiltration techniques to explore underlying conservation mechanisms. The result showed that C/N ratios of HAs from different limestone soil layers were relatively stable and that large molecular HA fractions predominated the bulk HA of the top soil, indicating that HA in the limestone profile was protected while bio and chemical degradations were retarded. Combined with organic elements contents and mineral contents of two soils, weconcluded that high calcium contents in limestone soils may play a key role in SOM conservation by forming complexation compounds with HAs or/and enclosing SOMs with hypergene CaCO_3 precipitation.

Effects of Cd on reductive transformation of lepidocrocite by Shewanella oneidensis MR-1

We investigated the reduction of lepidocrocite(γ-FeOOH) by Shewanella oneidensis MR-1 in the presence and absence of Cd. The results showed that Cd^(2+) retarded microbial reduction of γ-Fe OOH and avoided formation of magnetite. The inhibitory effect on γ-Fe OOH transformation may not result from Cd^(2+) toxicity to the bacterium; it rather was probably due to competitive adsorption between Cd^(2+) and Fe^(2+) on γ-Fe OOH as its surface reduction catalyzed by adsorbed Fe^(2+) was eliminated by adsorption of Cd^(2+).

微塑料在水体中的光氧化动力学特性

环境中微塑料对动物、植物甚至人类具有潜在的毒性和生态风险,它们在环境中如何氧化降解对人们评估环境中微塑料的生态风险具有重大意义.本研究以环境中常见的微塑料聚乙烯(PE)、聚丙烯(PP)、聚苯乙烯(PS)、聚氯乙烯(PVC)为对象,用主波长为352 nm(UVA)的紫外灯作为模拟光源进行光氧化实验,探究微塑料的光氧化动力学过程及影响.结果发现:暴露在水环境中的微塑料紫外光照射后,其表面会逐渐被氧化并产生大量的含氧官能团.微塑料在海水中的羰基指数(CI)值显著高于在纯水中,且不同类型的微塑料之间存在差异.微塑料在海水中的光氧化速率显著快于纯水,速率常数与盐度呈显著正相关,这可能与海水中无机离子的光敏作用加速微塑料表面氧化反应有关.4种微塑料在不同水环境中的光氧化速率存在差异性,PP和PVC光氧化析出的TOC浓度显著高于PS.微塑料在水体中的光氧化包含两个阶段:前期发生在微塑料表面的初级光氧化反应和后期同时存在的氧化产物在水中的后续光氧化反应.本研究初步考察了微塑料的光氧化动力过程,推测了微塑料在水环境中光照氧化的动力学机制,为水环境中微塑料的风险评估提供参考.

Degradation kinetics and mechanism of aniline by heat-assisted persulfate oxidation

Oxidation of aniline by persulfate in aqueous solutions was investigated and the reaction kinetic rates under different temperature, persulfate concentration and pH conditions were examined in batch experiments. The results showed that, the aniline degradation followed pseudo first-order reaction model. Aniline degradation rate increased with increasing temperature or persulfate concentration. In the pH range of 3 to 11, a low aniline degradation rate was obtained at strong acid system （pH 3）, while a high degradation rate was achieved at strong alkalinity （pH 11）. Maximum aniline degradation occurred at pH 7 when the solution was in a weak level of acid and alkalinity （pH 5, 7 and 9）. Produced intermediates during the oxidation process were identified using liquid chromatography-mass spectrometry technology. And nitrobenzene, 4-4’-diaminodiphenyl and 1-hydroxy-1,2-diphenylhydrazine have been identified as the major intermediates of aniline oxidation by persulfate and the degradation mechanism of aniline was also tentatively proposed.

Extracellular polymeric substance induces biogenesis of vivianite under inorganic phosphate-free conditions

Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances(EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs(PFS) by Shewanella oneidensis MR-1(S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite.EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(Ⅲ). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(Ⅱ) was 107.9, 111.0,and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail.