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201.
Multi-walled carbon nanotubes (MWNTs) oxidized with sulfuric acid, nitric acid, and the mixture of sulfuric and nitric acids were characterized by thermogravimetric analysis (TGA), Raman spectroscopy, elemental analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The TGA data showed that the MWNTs were more resistant to oxidation than C60 or activated carbon fibers. Catalyst particles could be removed by the oxidants containing sulfuric acid, and thus indicative of the tip opening of MWNTs. The sulfuric acid had a propensity to create defect sites and introduce the surface oxides at those defects that already exist or be newly generated on MWNTs. However, the acid mixture could open the caps of MWNTs but preserve the structure homogeneity. The treatment with nitric acid gave rise to the highest bulk oxygen content in MWNTs, while the most abundant surface oxides were provided by sulfuric acid oxidation. In addition, nitric acid exhibited the best ability to transform the phenolic groups into carboxyl groups. 相似文献
202.
A 3,3′-benzidine/β-cyclodextrin fluorescence derivative (BCDFD) was prepared and characterized by means of elemental analysis and 1H NMR. An inclusion complex was formed between BCDFD and the pesticide dithianon based on the internal cavity of β-cyclodextrin (β-CD), and the binding constant (KS ) of the inclusion complex was investigated. The inclusion complex could be applied for the determination of dithianon residues. Based on this, a sensitive method for the determination of dithianon was established. The linear dynamic range was from 0.63 to 12.5?mg?L?1 with a correlation coefficient of 0.9927. The limit of detection for an aqueous solution of standard and the relative standard deviation (RSD) were 10.6?µg?L?1 and 0.76%, respectively. The proposed method has been successfully applied for the determination of dithianon residues in water and fruit samples with satisfactory results, and recoveries in the range of 96.0–108% were obtained. The method is rapid, direct, economical, and sensitive for dithianon analysis. 相似文献
203.
Fluvalinate was applied on chickpea crop at (i) 0.056, (ii) 0.112 and (iii) 0.56 kg a.i. ha‐1 to evaluate its rate of dissipation. Two major degradation products of fluvalinate formed on the crop were identified and characterised as phenoxybenzoic acid and 2‐[2‐chloro‐4‐(trifluoromethyl)anilino]‐3‐methylbutanoic acid. They were estimated in day‐5 and day‐10 samples of chickpea crop as their methyl esters by gas liquid chromatography. 相似文献
204.
以沈阳市新开河底泥为研究对象,考察了河流底泥中溶解性有机物(DOM)的释放途径,并分析了时间、温度、pH值、底泥粒径、盐度和上覆水体中溶解性有机碳(DOC)浓度对河流底泥DOM释放的影响.此外,还研究了底泥释放对上覆水体中DOM的光谱学特性的影响.结果表明,对底泥DOM释放影响程度最高的是间隙水的混合作用,其次是底泥表层静态释放,而悬浮颗粒释放对底泥DOM释放的影响程度较小.底泥DOM的释放量随温度,pH值,底泥粒径,盐度的增大而增大.上覆水体DOC浓度较高时,DOM由上覆水体向底泥迁移.扰动作用能够影响底泥DOM的迁移.类富里酸荧光物质和类芳香族蛋白质荧光物质是底泥DOM中的主要荧光物质.河流底泥DOM向上覆水体释放的主要是激发波长分别为280~300nm和320~380nm的荧光物质.并且,扰动作用促进了荧光物质由底泥向上覆水体的释放. 相似文献
205.
Chuan Lin Renzhi Hu Pinhua Xie Shengrong Lou Guoxian Zhang Jinzhao Tong Jianguo Liu Wenqing Liu 《环境科学学报(英文版)》2022,34(4):376-390
Comprehensive observations of the nocturnal atmospheric oxidation of NO3 and N2O5 were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO3 precursors were observed, and the nocturnal production rate of NO3 was determined to be 1.7 ± 1.2 ppbv/hr. However, the nighttime NO3 and N2O5 concentrations were relatively low, with maximum values of 17.7 and 304.7 pptv, respectively, illustrating the rapid loss of NO3 and N2O5. It was found that NO3 dominated the nighttime atmospheric oxidation, accounting for 50.7%, while O3 and OH only contributed 34.1% and 15.2%, respectively. For the reactions of NO3 with volatile organic compounds (VOCs), styrene was found to account for 60.3%, highlighting its dominant role in the NO3 reactivity. In general, the contributions of the reactions between NO3 and VOCs and the N2O5 uptake to NO3 loss were found to be about 39.5% and 60.5%, respectively, indicating that N2O5 uptake also played an important role in the loss of NO3 and N2O5, especially under the high humidity conditions in China. The formation of nitrate at night mainly originated from N2O5 uptake, and the maximum production rate of NO3− reached 6.5 ppbv/hr. The average NOx consumption rate via NO3 and N2O5 chemistry was found to be 0.4 ppbv/h, accounting for 47.9% of the total NOx removal. The predominant roles of NO3 and N2O5 in nitrate formation and NOx removal in the YRD region was highlighted in this study. 相似文献
206.
207.
发射光谱法同时测定卷烟及晒烟中的有害微量元素 总被引:1,自引:0,他引:1
本文提出了同时测定卷烟和晒烟中有害元素Pb,Cd,Sn.V,Cr和Ni的原子发射光谱分析新方法。采用深孔电极粉末光谱法,优选了最佳的实验条件和仪器参数,考查了基体组分的影响。一次摄谱能同时测定以上六个元素。各元素的回收率在85.4—113%范围内,相对标准偏差在3.6—7.0%之间,用本法分析了6个实际样品,结果满意。方法可靠、适用。 相似文献
208.
The photooxidation of a nonwoven polyethylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy. The infrared spectroscopic data indicated that hydroperoxide, alcohol, aldehyde, ketone, carboxylic acid, and anhydride groups were formed as the products of the photooxidation of the polyethylene fabric and that the relative amount of carboxyl among all carbonyls increased as the photooxidation progressed. The distribution of the photooxidation products was inhomogeneous between the two surfaces of the fabric. The highest degree of photooxidation occurred on the surface of the fabric facing the UV radiation source, whereas the lowest degree of photooxidation was on the back surface of the fabric. We also found that the polyethylene nonwoven fabric showed a slower photooxidation rate than the polypropylene nonwoven fabric. The UV radiation at 254 nm caused photooxidation of polyethylene. No photooxidation was observed in the fabric exposed to the UV radiation at 350 nm under the same conditions. 相似文献
209.
Edward D. Ramsey Qiubai Sun Zhiqiang Zhang Wei Guo Jing Y. Liu Xiu H. Wu 《环境科学学报(英文版)》2010,22(9):1462-1468
A direct aqueous supercritical fluid extraction (SFE) system using carbon dioxide provides a sustainable means by which a vast
range of industries may continue to depend on well established infrared (IR) techniques to determine oil-in-water. The SFE-IR method
provides an environmentally friendly substitute for current national standard IR reference methods for measuring oil-in-water that rely
on using increasingly restricted ozone depleting solvents whose manufacture is being phased out in accordance with international law.
The SFE-IR analysis of a 500 mL water sample can be accomplished in 15 min. A rapid on-line SFE-IR calibration method has been
implemented. With this calibration method, SFE-IR accuracy for determining diesel oil in 500 mL spiked water samples using single
wave number measurement was 86.0%–98.8% with precision (RSD) ranging from 2.5%–7.0%. Using a general purpose calculation
which involves measuring infrared absorbance values at three di erent wave numbers, SFE-IR method accuracy for determining
diesel oil in 500 mL spiked water samples was 83.7%–92.2% with RSD 1.0%–9.3%. Data is presented that indicates current long
established national standard IR reference methods involving three wave number calculations should be reviewed since, without careful
consideration, the inclusion of calculated aromatic hydrocarbon species contributions to final oil-in-water concentration values may
provide less accurate results. 相似文献
210.
厌氧-缺氧-好氧处理出水中溶解性有机物组分的特征分析 总被引:1,自引:0,他引:1
本研究利用XAD-8大孔树脂对某城市污水处理厂的厌氧-缺氧-好氧(A2O)工艺出水中的溶解性有机物进行了组分分离,分析了各组分的溶解性有机碳(Dissolved organic carbon,DOC)、紫外-可见光谱和遗传毒性.结果表明,污水中亲水性物质和疏水酸性物质的DOC含量分别占总DOC含量的65%和24%.亲水性物质组分中的芳香族化合物含量显著高于其它组分,但是单位质量的亲水性物质、疏水酸性物质和疏水碱性物质中的芳香族化合物含量相近.污水具有一定的遗传毒性,主要遗传毒性物质为亲水性物质和疏水酸性物质,而疏水碱性物质和疏水中性物质则未检出遗传毒性. 相似文献