Raman spectroscopy of diesel and gasoline engine-out soot using different laser power

We studied engine-out soot samples collected from a heavy-duty direct-injection diesel engine and port-fuel injection gasoline spark-ignition engine. The two types of soot samples were characterized using Raman spectroscopy with different laser powers. A Matlab program using least-square-method with trust-region-reflective algorithm was developed for curve fitting. A DOE (design of experiments) method was used to avoid local convergence. The method was used for two-band fitting and three-band fitting. The fitting results were used to determine the intensity ratio of D (for “Defect” or “Disorder”) and G (for “Graphite”) Raman bands. It is found that high laser power may cause oxidation of soot sample, which gives higher D/G intensity ratio. Diesel soot has consistently higher amorphous/graphitic carbon ratio, and thus higher oxidation reactivity, compared to gasoline soot, which is reflected by the higher D/G intensity ratio in Raman spectra measured under the same laser power.     

泥沙沉降对水体中溶解性有机物光谱学特性的影响

以沈阳市新开河为研究对象,考察了泥沙沉降过程中,沉降时间、泥沙含量、pH、盐度对水体中溶解性有机物(DOM)的含量和光谱学特性的影响.结果表明,泥沙沉降条件下,水体中DOC随泥沙沉降时间的增长而先增大后减小,随泥沙含量的增加而先减小后增大,随pH的增大而增大,随盐度的增大而减小.随着pH的增大,水体中DOM的芳香性增强;随着盐度的增大,水体中DOM的芳香性降低.随着泥沙沉降时间的增长,DOM中各类荧光物质的含量先增加后减少;随着泥沙含量的增加,DOM中类腐殖酸和类富里酸荧光物质的含量增加,而类溶解性微生物代谢产物荧光物质和类芳香族蛋白质荧光物质的含量降低.在泥沙沉降过程中,下层水体中DOC、在波长为254 nm处的紫外吸光度(UV-254),以及DOM中荧光物质含量的变化量高于上层水体.     

Selective elimination of chromophoric and fluorescent dissolved organic matter in a full-scale municipal wastewater treatment plant

Effluent organic matter (EfOM) from municipal wastewater treatment plants potentially has a detrimental effect on both aquatic organisms and humans. This study evaluated the removal and transformation of chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) in a full-scale wastewater treatment plant under different seasons. The results showed that bio-treatment was found to be more efficient in removing bulk DOM (in terms of dissolved organic carbon, DOC) than CDOM and FDOM, which was contrary to the disinfection process. CDOM and FDOM were selectively removed at various stages during the treatment. Typically, the low molecular weight (MW) fractions of CDOM and protein-like FDOM were more efficiently removed during bio-treatment process, whereas the humic-like FDOM exhibited comparable decreases in both bio-treatment and disinfection processes. Overall, the performance of the WWTP was weak in terms of CDOM and FDOM removal, resulting in enrichment of CDOM and FDOM in effluent. Moreover, the total removal of the bulk DOM (P < 0.05) and the protein-like FDOM (P < 0.05) displayed a significant seasonal variation, with higher removal efficiencies in summer, whereas removal of CDOM and the humic-like FDOM showed little differences between summer and winter. In all, the results provide useful information for understanding the fate and transformation of DOM, illustrating that sub-fractions of DOM could be selectively removed depending on treatment processes and seasonality.     

亚热带河口陆基养虾塘水体CDOM三维荧光光谱平行因子分析

利用三维荧光光谱平行因子分析(EEMs-PARAFAC)技术,对我国亚热带地区闽江、木兰溪、九龙江河口滨海陆基养虾塘水体的有色溶解性有机质(CDOM)进行了组分及来源分析.研究表明从养虾塘水体CDOM荧光光谱中解析出4个有效PARAFAC荧光组分,包括2种类蛋白质物质和2种类腐殖酸物质,其中类蛋白质组分是河口陆基养虾塘水体中CDOM的主要组成部分.水体的荧光指数FI和自生源指标BIX表明河口区滨海陆基养虾塘水体中CDOM的强自生来源贡献.而腐殖化指标HIX表明养殖塘水体具有弱腐殖化特征.类蛋白质组分与类腐殖质组分之间可能具有相同的来源属性和地化行为,盐度与CDOM呈现极显著负相关,而DOC与CDOM中类腐殖质组分(C2、C3)呈现显著正相关.本研究为进一步揭示养虾塘水体CDOM的光化学性质提供了科学依据.     

模拟酸雨淋溶条件下紫壤淋出液中溶解性有机质的三维荧光特性

运用三维荧光技术分析了模拟酸雨淋溶紫壤淋出液中溶解性有机质（dissolved organic matter,DOM）的组分与酸度及淋溶量的关系.研究结果表明,模拟酸雨淋溶紫壤淋出液中DOM荧光峰主要为类胡敏酸和类富里酸,荧光峰的中心位于Ex/Em=305—370 nm/420—450 nm和Ex/Em=260—270...     

河口区有色溶解有机物(CDOM)三维荧光光谱的影响因素

结合在厦门湾九龙江口的现场调查与实验室分析,对目前河口区CDOM三维荧光光谱(excitation-emission matrix spectroscopy,EEMS)分析的一些影响因素(主要是离子强度、浓度效应、不同孔径滤膜过滤)进行了探讨.结果表明,CDOM的EEMS与样品中离子强度关系不大,说明在河口区河海水混合过程中,仅仅由于水体盐度的变化不会造成CDOM光学特征的明显变化.河端CDOM的荧光强度随物理稀释倍数的增大成相应比例的减小,稀释对EEMS的影响仅仅体现在荧光强度上,显示河口区的CDOM样品不存在荧光淬灭效应.九龙江口河流端样品中共含有类腐殖质(C、A)及类蛋白质(T1、T2)4种荧光团,随着混合样品中海水体积分数的增大,样品荧光强度逐渐降低,代表海洋来源的类腐殖质荧光峰M逐渐显露,T1峰逐渐高于A峰.这说明从河端至外海CDOM的组成结构发生了一系列的变化,来源上逐渐完成了以陆源为主到海源为主的转变;性质上逐渐完成了以类腐殖质荧光团为主到类蛋白质荧光团为主的转变.在中、高盐度区,0.2μm的Millipore聚碳酸酯滤膜可以很好地去除水体散射对EEMS的干扰,EEMS(0.2μm)比EEMS(0.7μm)更为规则,各峰的显示更加清晰.不同荧光基团的划分更加容易.无论高、中、低盐度站位,0.7μm滤膜过滤的样品,其CDOM荧光强度都要略高于0.2μm滤膜过滤的样品,2种不同孔径滤膜过滤对CDOM荧光测定带来的差异不可忽略.     

Correction model for CO detection in the coal combustion loss process in mines based on GWO-SVM

Accurate detection of CO gas is crucial to the prevention of coal combustion. Tuneable diode laser absorption spectroscopy (TDLAS) is a reliable method for CO detection during coal combustion. The influences of temperature and pressure cause changes in the line strength and linewidth of the index gases’ absorption spectra, leading to sizable measurement errors. To correct the distortion of the CO absorption spectrum caused by temperature and pressure fluctuation, a compensation model based on the grey wolf optimizer–support vector machine (GWO–SVM) was proposed. The results were compared with those of the single SVM, the back propagation neural network (BPNN), and multiple regression analysis (MRA). MRA was revealed to result in the lowest accuracy, which indicated that MRA is not ideal for compensation in TDLAS. The hyperparameter selection of the SVM had the disadvantages of randomness and blindness, which led to instability and large errors. The BPNN achieved better correction in the training stage, but severe overfitting occurred in the testing stage. The modified results revealed that the GWO–SVM model had higher accuracy and stability than the other models. It effectively inhibited the effects of temperature and pressure on the measured concentration and greatly improved the measurement accuracy. The equipment is thus suitable for CO gas detection with the aim to preventing coal combustion loss, and it can be further applied to loss prevention in other process fields.     

恒能量同步荧光光谱法测定水体中多环芳烃

建立了胶束溶液中多环芳烃混合物同时测定的恒能量同步荧光分析法,方法简便快速,无需对混合物进行分离,就可实现11种组分的同时鉴别和定量测定,方法的检出限在1.3×10-11～4×10-9g/mL,标准偏差为1.03～1.73,方法应用于分析河水样、污水样中的多环芳烃的效果良好,回收率分别为77.88%～120.13%、6...     

粉煤灰对废水中的石油样品的吸附去除

用紫外分光光度法分析经粉煤灰处理后含油废水中的油样含量。考察了pH值,粉煤灰使用量,接触时间,废水中油样的初始浓度,温度等因素对粉煤灰除油率的影响。结果表明：用石油醚溶解的油样紫外光最佳吸收波长为272．5nm;中性条件下,粉煤灰对废水中的油样有较好的去除率;粉煤灰使用量增大、接触时间增加、温度升高有利于粉煤灰对油样的吸附去除;废水中油样含量越高,粉煤灰对其去除率越低。     

7A04铝合金在周浸试验中的腐蚀行为研究

采用周期浸泡的腐蚀试验方法,并通过电化学阻抗谱(EIS)、扫描电子显微镜(SEM)等检测技术,研究了7A04铝合金的腐蚀行为和腐蚀机理.结果表明,7A04铝合金的腐蚀动力学符合幂函数规律,其腐蚀历程为由点蚀经短暂的晶间腐蚀后快速发展为剥蚀,EIS由高中频3个容抗弧和低频收缩的感抗弧组成.