玉米（Zea mays）对镉积累与转运的品种差异研究

通过田间实验,研究了25个玉米（Zea mays）品种在Cd质量分数为50 mg·kg-1胁迫条件下,Cd对不同玉米品种生长的影响,以及不同玉米品种对Cd积累和转运的品种差异,以期筛选出Cd低积累玉米品种。结果表明：25个玉米品种的生物量和产量对Cd胁迫的响应,以及不同品种根、茎叶和籽粒对Cd的吸收、累积及转运能力存在显著差异（P＜0.05）。有20个品种生物量和19个品种产量下降;有2个品种籽粒的Cd质量分数超过了国家规定的食品卫生标准（≤0.1 mg·kg-1）,占供试品种的8.0%,所有品种茎叶的Cd质量分数均超过了国家规定的饲料卫生标准（≤0.5 mg·kg-1）,超标率为100%;25个玉米品种的富集系数范围为0.063~0.899、茎叶转运系数范围为0.038~0.554、籽粒转运系数范围为0.000~0.111,均小于1,其中有8个品种富集系数〉0.5,1个品种茎叶转运系数〉0.5,而所有品种的籽粒转运系数均〈0.5,说明玉米对土壤Cd仍有一定的吸收能力,但地下部向地上部转运能力以及由茎叶向籽粒的转运能力较弱;根据玉米生物量、产量、籽粒Cd含量以及对Cd的富集系数和转运系数等指标进行评价,认为云瑞8号、会单4号、路单7号3个品种可作为Cd低累积玉米品种,可在云南Cd重度污染土壤上推广种植。     

·Cl引发3种环状含有NH结构有机化合物的大气转化机制及动力学

氯自由基(·Cl)的高氧化性及其内陆来源的新发现使得·Cl在评估有机污染物的大气归趋方面起着比以往更为重要的作用。含有NH_x(x=1,2)结构的有机化合物不仅是大气中一类潜在的有机污染物,也是大气中致癌性亚硝胺的前驱体—N中心自由基的重要来源。前人研究发现,·Cl与含有NH_x(x=1,2)结构的有机化合物具有独特的相互作用且其反应具有结构依赖性。目前,大多数研究只关注链状含有NH_x(x=1,2)结构有机化合物的反应,而对于环状含有NH结构有机化合物的反应研究却很少。本研究使用量子化学和动力学模拟相结合的方法研究·Cl引发3种环状含有NH结构有机化合物(吗啉(MOR)、哌啶(PIP)和吡咯烷(PYR))的大气转化机制及动力学。结果发现,·Cl夺取3种环状含有NH结构有机化合物中N—H的H原子形成N中心自由基是最可行的反应路径。在298 K和1 atm下,计算的反应速率常数分别为5.0!10-10(MOR)、5.1!10-10(PIP)和4.9!10-10(PYR) cm~3·molecule-1·s-1,且具有正的温度依附性。结合可获得的·OH引发反应的反应速率常数,评估·Cl对MOR和PIP转化的贡献分别为·OH的2.6%～26%和6.9%～69%。上述研究结果为将来建立·Cl引发含有NH_x(x=1,2)结构有机化合物反应的结构-活性关系、全面评估含有NH_x(x=1,2)结构有机化合物的大气归趋和环境风险提供数据支持。     

过硫酸铵含铜废液预处理工艺改造

采用离子交换工艺对过硫酸铵含铜废液预处理原有工艺进行改造,改造后降低了废液预处理成本,减少二次污染,提高铜资源的回收率,达到综合利用的目的,具有很高的环境效益及经济效益。     

深埋隧道圆形基坑围护结构变形特性及控制指标探讨

基于深埋隧道超深竖井工程,对比分析了圆形与矩形基坑受力变形特征,在对国内外圆形竖井基坑典型案例统计分析的基础上,探讨圆形竖井基坑的变形抑制机理,以现有规范、工程实例为基础确定圆形竖井基坑的变形控制指标。研究结果表明:①考虑空间结构体系的圆形竖井计算的地墙内力及变形比弹性地基梁的计算结果小20%以上,而矩形基坑的计算结果仅比弹性地基梁的计算结果小0～15%;②支护结构承受轴力为主的"圆筒"效应、轴力对薄弱处的加强以及土体的"挤压"效应三者的综合作用是圆形基坑受力变形抑制的原因;③随着基坑深度增大,基坑侧墙水平位移与深度的比值显著减小;随着基坑直径增大,基坑侧墙水平位移与深度的比值变大;④建议以基坑深度35m、基坑直径40m为分界点,根据情况分别选取0.5‰、1‰、1.8‰作为对于圆形深基坑支护结构水平位移控制指标。     

RTCA与CCK-8法用于检测柴油废气颗粒物致支气管上皮细胞毒性的比较研究

运用实时无标记细胞分析系统(RTCA)和Cell Counting Kit-8(CCK-8)法分别检测柴油废气颗粒物(DEP)致支气管上皮细胞(HBE)细胞毒性,从而对2种方法进行比较研究.分别以浓度为0、3.5、7、14、28和56 mg·L-1 2种柴油废气标准参考颗粒物(Standard Reference Material 1650b,SRM 1650b;Standard Reference Material 2975,SRM 2975)对 HBE 细胞进行暴露处理,分别暴露6、12、24和48 h后,检测不同DEP致HBE细胞毒性,比较各组之间细胞存活率或标准化细胞指数(normalized cell index,NCI)值的差异,考察2种方法的优缺点.并用细胞凋亡实验检测各差异组之间的凋亡率.在相同染毒浓度及暴露时间,与SRM 1650b相比,SRM 2975对HBE细胞的毒性更强.在RTCA检测DEP致HBE细胞毒性时,低浓度DEP组的NCI值已经表现出与对照组有统计学差异(P＜0.05),而相同时间条件下,CCK-8法在更高浓度的DEP组才检测出显著的细胞活性下降(P＜0.05).且由细胞凋亡实验证实,与对照组相比,低浓度DEP组的细胞凋亡率已经有统计学差异.相对于CCK-8法,RTCA更适用于检测DEP致贴壁HBE细胞毒性.CCK-8法更适用于检测DEP致悬浮细胞的细胞毒性或与气液暴露装置联用时的贴壁/悬浮细胞毒性.     

Electro-catalytic activity of CeOx modified graphite felt for carbamazepine degradation via E-peroxone process

•CeO_x/GF-EP process had the better degradation efficiency than GF-EP process. •CeO_x/GF-EP process had the flexible application in the pH range from 5.0 to 9.0. •CeO_x could enhance surface hydrophilicity and reduce the charge-transfer resistance. •The interfacial electron transfer process was revealed. E-peroxone (EP) was one of the most attractive AOPs for removing refractory organic compounds from water, but the high energy consumption for in situ generating H₂O₂ and its low reaction efficiency for activating O₃ under acidic conditions made the obstacles for its practical application. In this study, cerium oxide was loaded on the surface of graphite felt (GF) by the hydrothermal method to construct the efficient electrode (CeO_x/GF) for mineralizing carbamazepine (CBZ) via EP process. CeO_x/GF was an efficient cathode, which led to 69.4% TOC removal in CeO_x/GF-EP process with current intensity of 10 mA in 60 min. Moreover, CeO_x/GF had the flexible application in the pH range from 5.0 to 9.0, TOC removal had no obvious decline with decrease of pH. Comparative characterizations showed that CeO_x could enhance surface hydrophilicity and reduce the charge-transfer resistance of GF. About 5.4 mg/L H₂O₂ generated in CeO_x/GF-EP process, which was 2.1 times as that in GF-EP process. The greater ozone utility was also found in CeO_x/GF-EP process. More O₃ was activated into hydroxyl radicals, which accounted for the mineralization of CBZ. An interfacial electron transfer process was revealed, which involved the function of oxygen vacancies and Ce³⁺/Ce⁴⁺ redox cycle. CeO_x/GF had the good recycling property in fifth times’ use.     

·Cl引发萘的大气氧化机制及动力学

氯自由基(·Cl)内陆来源的新发现增强了其对转化大气有机污染物的贡献,因此,需要更深入地研究·Cl引发有机污染物的转化机制和动力学.萘(Nap)是一种重要的化学品,也是城市大气浓度最高的多环芳烃,前人针对羟基自由基(·OH)引发Nap的大气氧化开展了研究.然而,目前对于·Cl引发Nap的大气氧化机制还不清楚.本研究通过量子化学计算(ωB97XD/6-311++G(3 df,2pd)//ωB97XD/6-31 +G(d,p))和动力学模拟相结合的方法研究了·Cl引发Nap的大气氧化机制与动力学,发现·Cl主要加成到Nap分子的C5位置,形成加成中间体·C10H8Cl(R1).随后,O2加成到R1的C2和C6位置生成过氧自由基(RO2·)R1-2OO-s/a和R1-6OO-s/a(s/a=syn/anti,syn表示O2加成方向和·C1加成方向相同,anti表示O2加成方向和·C1加成方向相反).这4种RO2·的环化、氢迁移和氯迁移反应均很难(能垒＞20 kcal· mol-1)发生.因此,在低NO浓度条件下,RO2·主要和HO2·反应生成氢过氧化合物(QOOH)和烷氧自由基(RO ·)R1-2O-s/a和R1-6O-s/a;在高NO浓度条件下,RO2·将主要与NO反应生成RO· (R1-2O-s/a和R1-6O-s/a)和有机硝酸酯(C10 H8 ClNO3).生成的RO·进一步通过单分子环化反应生成双环产物R1-21O-s/a和R1-61O-s/a.重要的是,生成的有机氢过氧化合物和有机硝酸酯的水生毒性比其母体化合物Nap更强,表明·Cl引发Nap反应增加了Nap释放的环境风险.揭示的机制对理解大气Nap化学及Nap释放导致的环境风险具有重要意义.     

Isolation,identification, and the degradation characteristics of a BDE-47 degrading strain北大核心CSCD

In an effort to remove BDE-47 residues from the environment, a bacterial strain that is capable of utilizing BDE-47 as the sole carbon source was isolated and screened from soil collected from an e-waste recycling area in Tianjin to analyze the degradation properties. The strain was preliminarily identified as Enterobacter sp. according to a 16S rDNA gene sequence analysis. The strain degraded 35.8% of 525 μg/L of BDE-47 in 35 d when the initial concentration of bacteria was 7.1 × 105 cells/ mL. The product of the biodegradation of BDE-47 was BDE-28. The biodegradation of BDE-47 fit well with first-order kinetics, and its degradation kinetics was ln Ct = - 0.104t + 6.22. With the addition of an electron acceptor, such as Fe3+, SO4 2- and NO3 -, the BDE-47 degradation rate was significantly increased to 49.8%, 59.1%, and 67.3%, respectively. The above results revealed that the strain could degrade BDE-47, which is of importance in the application of environmental bioremediation of BDE-47. © 2018 Science Press. All rights reserved.     

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.