Fine root decomposition and nutrient release in Toona sinensis plantation under the reconstruction mode of low-efficiency cypress forest gaps北大核心CSCD

Fine root decomposition is an important way in which nutrients are returned to plantation soil; thus, further study of this process will be helpful for understanding material cycling in forest ecosystems. We investigated a Toona sinensis plantation in the central Sichuan hilly region using litter bags containing T. sinensis fine roots to evaluate the dynamics of fine root decomposition and nutrient release for one year in forest gaps of 50 m2 (L1), 100 m2 (L2), and 150 m2 (L3). The results showed that T. sinensis fine root decomposition was fastest in the first 90 days. As time passed, the decomposition rate slowed. One year later, the residue rate was 75.44%, 73.92%, and 72.07%, respectively. The fine root decomposition rate of L3 was greater than that of L2, which was greater than that of L1. During fine root decomposition, the dynamics of the fine root nutrient concentrations changed. C, P, and K concentrations of the fine roots declined in forest gaps, while N, Ca, and Mg concentrations increased overall in the fine roots. In conclusion, forest gaps had effects on the fine root decomposition and nutrient release of T. sinensis, and different sized forest gaps produced different results. © 2018 Science Press. All rights reserved.     

Coexisting sediments and suspended particles change the sorption of lindane and ciprofloxacin in waters

The real behavior of water organic contaminants such as pesticides and pharmaceuticals is not well known because research experiments usually simplify the conditions by studying the sorption of a pure compound on a single solid. However, in natural waters, biofilms, suspended particles, and sediments are solid substances that coexist, and thus may change the contaminant fate. Therefore, we studied here the sorption of lindane and ciprofloxacin by three single-solid and three double-solid sorbents using batch experiments. We also compared the effect of dissolved organic matter (DOM) between single- and double-solid sorption systems. Results show that the sorption quantity of lindane to the double-solid system of suspended particles and sediments is lower, of 0.99 L/g, than the sum of sorption quantity in the single-solid system, of 1.39 L/g. The sorption quantity of ciprofloxacin is higher, of 2.70 L/g, than the sum of sorption quantity in the single-solid system, of 1.90 L/g. These findings are explained by changes in DOM that suppress or promote sorption. To our best knowledge, this is the first study to present evidence that coexisting river solids modify lindane and ciprofloxacin sorption.     

重金属污染场地土壤风险筛选值关键影响因子研究——以砷为例

合理确定重金属土壤筛选值是污染场地风险识别和调查评估的基础,过松或过严的标准都会增加风险评估的不确定性,甚至可能会导致风险管控措施失效或修复资金浪费,确定重金属土壤筛选值的关键影响因子是合理确定重金属土壤筛选值的前提。选择工业污染场地中检出频率高、毒性大的砷作为研究对象,通过假设工商业用地下的暴露情景,根据《污染场地风险评估技术导则》(HJ25.3—2014)得到砷筛选值计算公式,利用基于蒙特卡罗模拟的Crystal Ball模型计算公式中各参数对结果的敏感性和贡献率来确定关键影响因子,通过调研国内外砷筛选值现状,从计算模型、毒性评估及关键影响因子等方面对引起各国砷筛选值差异的原因进行了分析探讨。结果表明:工商业用地下土壤砷筛选值取值为0.84～175.7 mg·kg~(-1),均值为21.4 mg·kg~(-1),95%的置信上限为24.19 mg·kg~(-1);风险可接受水平、每日土壤摄入量(IR)、暴露频率(EF)和暴露周期(ED)对砷筛选值的贡献率依次为41.3%、-27.3%、-16.3%和-12.7%,其余因子的贡献率均小于1%;关键影响因子按贡献率绝对值从大到小分别为风险可接受水平、每日土壤摄入量(IR)、暴露频率(EF)、暴露周期(ED)。计算模型和毒性评估存在差异是国内外土壤砷筛选值差异的基础原因,当计算模型和毒性评估差异不大时,关键影响因子才是决定性因素,其影响程度与模拟计算的结果一致。建议我国完善筛选值计算模型,对砷的毒性效应和符合我国暴露人群特征的关键影响因子展开深入研究。     

Enhanced heterogeneous Fenton-like activity by Cu-doped BiFeO<Subscript>3</Subscript> perovskite for degradation of organic pollutants

Heterogeneous Fenton-like reaction has been extensively investigated to eliminate refractory organic contaminants in wastewater, but it usually shows low catalytic performance due to difficulty in reduction from Fe(III) to Fe(II). In this study, enhanced catalytic efficiency was obtained by employing Cu-doped BiFeO₃ as heterogeneous Fenton-like catalysts, which exhibited higher catalytic performance toward the activation of H₂O₂ for phenol degradation than un-doped BiFeO₃. BiFe_0.8Cu_0.2O₃ displayed the best performance, which yielded 91% removal of phenol (10 mg L^–1) in 120 min. The pseudo first-order kinetic rate constant of phenol degradation in BiFe_0.8Cu_0.2O₃ catalyzed heterogeneous Fenton-like reaction was 5 times higher than those of traditional heterogeneous Fenton-like catalysts, such as Fe₃O₄ and goethite. The phenol degradation efficiency could still reach 83% after 4 cycles, which implied the good stability of BiFe_0.8Cu_0.2O₃. The high catalytic activity of BiFe_0.8Cu_0.2O₃ was attributed to the fact that the doping Cu into BiFeO₃ could promote the generation of Fe(II) in the catalyst and then facilitate the activation of H₂O₂ to degrade the organic pollutants.

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Complexation of iron by salicylic acid and its effect on atrazine photodegradation in aqueous solution

The photodegradation of atrazine and the photochemical formation of Fe(II) and H₂O₂ in aqueous solutions containing salicylic acid and Fe(III) were studied under simulated sunlight irradiation. Atrazine photolysis followed first-order reaction kinetics, and the rate constant (k) corresponding to the solution of Fe(III)-salicylic acid complex (Fe(III)-SA) was only 0.0153 h^?1, roughly one eighth of the k observed in the Fe(III) alone solution (0.115 h^?1). Compared with Fe(III) solution, the presence of salicylic acid significantly enhanced the formation of Fe(II) but greatly decreased H₂O₂ generation, and their subsequent product, hydroxyl radical (˙OH), was much less, accounting for the low rate of atrazine photodegradation in Fe(III)-SA solution. The interaction of Fe(III) with salicylic acid was analyzed using Fourier-transform infrared (FTIR) spectroscopy and UV-visible absorption, indicating that Fe(III)-salicylic acid complex could be formed by ligand exchange between the hydrogen ions in salicylic acid and Fe(III) ions.     

基于生物膜模型的脉冲生物滤池硝化效果模拟

针对脉冲生物滤池的硝化功能,依据物料衡算方程、Fick第一定律构建生物膜传质子模型以及简化的ASM3模型,建立生物膜反应子模型。以Matlab软件为平台编程,模拟在沿脉冲生物滤池水流方向上基质浓度,并依据实测值和参数灵敏度进行分步校正。实测和模拟结果均表明:COD、NH+4-N、NO-2-N的去除主要集中在脉冲生物滤池的中上部、中部、下部,COD和氨氮去除率分别为45%、50%。当改变有机负荷和布水周期时,氨氮去除率随有机负荷的增大而减小,随布水周期的增大而增大。     

大区域环境噪声评价模型NEM的构建及应用

提出一种适用于大区域噪声评价的模型——NEM模型,该模型综合考虑暴露人群和声环境功能区差异,并根据城市声环境质量标准及噪声对人体健康的影响程度进行了分级表征。文章运用该模型对广州市噪声状况进行评价,同时将评价结果分别与NPI法和NII法的评价结果进行对比。对比结果表明:NEM模型用于大区域环境噪声评价科学合理,结论可靠。     

The influence of chlorinated aromatics' structure on their adsorption characteristics on activated carbon to tackle chemical spills in drinking water source

This study focused on evaluating the efficiency of powdered activated carbon (PAC) adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC’s capacities for five chlorobenzenes and three chlorophenols at drinking water contamination levels were studied in order to determine the influence of different functional groups on the adsorption behavior. The results showed that PAC adsorption could be used as an effective emergency drinking water treatment process to remove these compounds. The adsorption kinetics took 30 min to achieve nearly equilibrium and could be described by both pseudo first-order and pseudo second-order models. A mathematic relationship was developed between the pseudo first-order adsorption rate constant, k₁, and the solutes’ properties including lgK_ow, polarizability and molecular weight. The Freundlich isotherm equation could well describe the adsorption equilibrium behaviors of chlorinated aromatics with r² from 0.920 to 0.999. The H-bond donor/acceptor group, hydrophobicity, solubility and molecular volume were identified as important solute properties that affect the PAC adsorption capacity. These results could assist water professionals in removing chlorinated aromatics during emergency drinking water treatment.     

新型膦磺酸阻垢缓蚀剂SEDMP的性能评定

对自制的新型膦磺酸阻垢缓蚀剂SEDMP对CaCO3和Ca3(PO4)2的阻垢性能进行评定。在SEDMP加入量为4 mg/L、浓缩至水溶液中Ca2+质量浓度为500 mg/L时,SEDMP对CaCO3的阻垢率为90.6%,对CaCO3的阻垢效果大大优于其他有机膦类阻垢剂。当SEDMP加入量为10 mg/L时,对Ca3(PO4)2的阻垢率为96.0%。SEDMP作为缓蚀剂单独使用时具有一定的缓蚀效果,与磺酸盐共聚物、锌盐复配后效果更佳。SEDMP与常用杀菌剂同时使用时仍可保持良好的对CaCO3的阻垢性能,且不影响杀菌剂的杀菌率。     

Clean Preparation Process of Chitosan Oligomers in Gly Series Ionic Liquids Homogeneous System

Chitosan oligomers because of its water solubility has some special physiological functions, such as binding lipid, affecting the mitogenic response, restraining the growth of tumors, and was widely used in cosmetics and health. H₂O₂/Gly (Glycine) series ionic liquids system, a new solvable-catalytic system, was an efficient clean process for preparation of chitosan oligomers. The effects of the anions of Gly series ionic liquids on the solubility and degradation for chitosan were investigated, and the results showed that [Gly]Cl aqueous solution was of good solubility and assistant degradation for chitosan. In additional, the mechanism for oxidative degradation of chitosan in ionic liquids (ILs) was studied. The effect on the property of chitosan oligomers catalyzed by H₂O₂, in two different kinds of solvents (HAc and [Gly]Cl) were compared. It was found that the performance of moisture absorption and retention of chitosan oligomers using ionic liquid aqueous solution as solvent was better than that using HAc aqueous solution as solvent, and even superior to that of hyaluronic acid. Furthermore, [Gly]Cl could be easily separated from the product and reused with only slight loss. It could provide an efficient and environmental friendly method for the preparation of chitosan oligomers in H₂O₂/ILs system.