Measurements of H2O2 and HCHO by Tunable Diode Laser Absorption Spectroscopy During the 1986 Carbonaceous Species Methods Comparison Study in Glendora,California

An improved, high sensitivity, tunable diode laser spectrometer system designed for tropospheric air measurements (TAMS-150) was employed during the 1986 Carbonaceous Species Methods Comparison Study at Glendora, CA. The TAMS-150 made simultaneous measurements of H₂O₂ and HCHO with a time response of 3 minutes per data point. The minimum detection limits were respectively 0.1 ppbv and 0.15 ppbv for HCHO and H₂O₂ and the estimated accuracies were ± 20% for both species. During the first 5 days of the study H₂O₂ showed little diurnal variation ranging between 0.25 and 0.5 ppbv with maximum values occurring at 15:30 PDT. During the final 4 days H₂O₂ showed stronger diurnal behavior with mixing ratios ranging from below the detection limits during some nighttime periods to as high as 1.8 ppbv during midday maxima which occurred about 15:30 PDT. HCHO showed strong diurnal behavior throughout the study with rapid changes in concentration in the early morning and evening. Mixing ratios were typically in the range 5–20 ppbv with maxima at about 10:00 and 14:00 PDT.     

Visibility and Aerosols During the 1986 Carbonaceous Species Methods Comparison Study

A modest change in synoptic meteorology occurred during the 1986 Carbonaceous Species Methods Comparison Study at Glendora, CA, resulting in a sharp change in visibility. This occurrence allowed comparisons of carbon species, soot and nonsoot, sulfates, and other aerosol components in two similar meteorological conditions with different visibilities. The results show that improvement in visibility was most strongly associated with a sharp decrease in sulfur mass median diameter, from 0.50 to 0.33 (Jim, with important contributions from nitrogen particles and volatile species such as water.     

Real-Time Measurement of Aerosol Black Carbon During the Carbonaceous Species Methods Comparison Study

During the Carbonaceous Species Methods Comparison Study, we used the aethalometer, an instrument developed at Lawrence Berkeley Laboratory that measures the concentration of aerosol black carbon [BC] in real time. Measurements were taken from August 12 to 21, 1986, with a 1-minute time base and were grouped to show 1-hour and multihour concentrations. We found concentrations generally ranging from 1 to 10 μ [BC] m^?3, usually increasing in the morning hours. We also observed short-duration (2–15 minute) peaks in the black carbon concentration that could be directly attributed to the activity of vehicles in a delivery area less than 50 m from the study site. We conclude that mobile sources were the major contributor to the short- and medium-term variability of aerosol black carbon measured at this site.     

Atmospheric Carbonaceous Species Measurement Methods Comparison Study: General Motors Results

The General Motors Research Laboratories participated in both the field sampling and round-robin portions of the Carbonaceous Species Intercomparison study that was held in Glendora, CA, during the summer of 1986. Five samplers were operated during the field study. The average particulate elemental carbon (EC) concentrations determined from the five samplers agreed to within 12%. Large differences were observed in the concentrations of particulate organic carbon (OC) determined from the five samplers. Some of the differences are attributed to losses of OC from the filters due to volatilization during the collection period. The amount of volatilization varies with the length of the sampling time and the filter face velocity. In addition, the adsorption of gas-phase organic compounds caused a significant positive interference in the determination of OC. Our OC and EC results for the round-robin samples were compared to the values obtained by the other participating laboratories. The average ratio of our results to the mean of the other laboratories was 0.97 for all the OC data and 1.23 for EC from all but the ambient wood-burning and organic aerosol samples. The ratios for the latter samples were 1.9 or greater. It is concluded that EC can be collected and analyzed with high precision; however, the accuracy of the measurements is unknown since standards for EC in atmospheric particulate do not exist.     

Measurements of Hydrogen Peroxide and Formaldehyde in Glendora,California

Gas-phase hydrogen peroxide (H₂O₂) and formaldehyde (HCHO) were measured in Glendora, CA from August 14 to 21, 1986. These measurements were part of the Carbonaceous Species Methods Comparison Study sponsored by the California Air Resources Board. Both of these species were measured using enzymatic techniques, H₂O₂ by the peroxidase catalyzed dimerization of p-hydroxyphenylacetic acid and formaldehyde by the formaldehyde dehydrogenase catalyzed reduction of NAD+ to NADH. Both H₂O₂ and HCHO showed a strong diurnal variation with the highest concentrations measured during the period of maximum photochemical activity. H₂O₂ concentrations ranged from < 0.1 ppbv at night to a maximum of 3 ppbv for the hourly average on one day. The HCHO concentrations ranged from a low of 5 ppbv a night to a maximum of 20 ppbv during the day.     

工作场所空气中磷酸的测定方法研究和比较

通过改进钼酸胺分光光度法来测定工作场所空气中的磷酸,将样品洗脱后,在酸性溶液中,与钼酸铵生成磷钼酸,用抗坏血酸原剂,生成磷钼蓝,在700nm波长下进行测定。该方法线性关系好,检出限低,准确度和精密度高,使用安全方便。     

广州大气颗粒物与酸沉降的关系研究

本文研究了大气颗粒物的酸度和酸缓冲能力,实验证实广州大气颗粒物中存在着游离的硫酸,其水溶性离子中SO4^2-及NO3^-占很大的比例。颗粒物中的碱性成分含量大于酸性成分,对酸性降水有一定的缓冲能力。气溶胶中细颗粒物的酸性大于粗颗粒物,且酸缓冲能力远低于粗颗粒物。     

Changes of Molecular Glycerophospholipid Species in Plasma and Red Blood Cells During Docosahexaenoic Acid Supplementation

Docosahexaenoic acid (DHA) status is related to health and disease risk. DHA status is mainly determined by dietary DHA intake, since endogenous synthesis of DHA is limited. We aimed to investigate the changes of different molecular glycerophospholipid species containing DHA in plasma and red blood cells (RBC) in response to increased DHA intake. Thirteen healthy adults had their diet supplemented with 510 mg DHA/day for 29 days. Fasted blood samples were taken at 11 time points and glycerophospholipid species were analyzed by liquid chromatography mass spectrometry. In plasma, percentages of glycerophospholipid species containing DHA increased significantly by 64–104 % relative to baseline values during supplementation, but the relative distribution between species was not markedly altered. In RBC, phosphatidylcholine (PtdCho) species containing DHA increased to a similar extent as in plasma, while phosphatidylethanolamine and phosphatidylserine species with DHA increased by only 12–25 %, respectively, which was significantly different compared to PtdCho species (p < 0.01). Despite the high increase, the contribution of DHA PtdCho species to total DHA remained minor (14 % after supplementation). In conclusion, DHA supplementation does not alter the relative distribution of DHA among glycerophospholipid species in plasma. A majority of PtdCho species are rapidly exchanged between plasma lipoproteins and RBC membrane lipids, while there is a minor exchange of phosphatidylethanolamine and phosphatidylserine species.     

Dispersive XAFS Study on Cu and Mo Species in Zeolites During the Catalyst Preparation

A time-resolved energy dispersive XAFS (DXAFS) technique is applied to elucidate the local structure of catalyst precursors and active species during the preparation of catalysts. The structure of ion-exchanged copper species in ZSM-5 zeolite during temperature-programmed reduction and the structure of molybdenum carbonyl species in NaY zeolite during temperature-programmed decarbonylation were investigated by the DXAFS technique. The way of the analysis of XAFS data during the dynamic processes is also discussed. The XANES spectra were analyzed to determine the ratio of different species involved in the system as a function of temperature as well as the curve-fitting analysis of the time-resolved EXAFS. The detailed analysis of the XANES and EXAFS shed light on the structural changes during the dynamic processes. In Cu-ZSM-5, a stepwise reduction process of Cu species and the subsequent growth of Cu particles during the reduction were elucidated. In Mo–NaY, the formation of Mo subcarbonyl monomer species as an intermediate of molybdenum oxycarbide dimer species was observed. This paper demonstrates that the DXAFS technique is useful to study the chemistry of catalyst preparation and can provide vital information that cannot be obtained by other techniques.     

PR方程与SRK方程在计算水露点中的比较与应用

水露点是天然气管道输送安全的一个重要指标。介绍了PR方程与SRK方程,利用两个方程的不同混合法则及相平衡计算,通过编写程序,计算出在相同条件下,不同方程之间计算出的水露点的差异,得出利用PR方程计算出的水露点较SRK方程计算的结果偏低。     

给水排水专业物理化学课教学方法研究

物理化学课是给水排水专业的重要专业基础课,是一门理论性很强的学科。作者对物理化学课的教学方法进行了研究,运用了三种教学方法:(1)启发式教学法;(2)举例说明法;(3)理论联系实际法;以使学生系统地掌握物理化学基本原理及其在给水排水专业领域中的应用。     

肉桂酸制备工艺研究及在有机化学实验教学中的应用

实验教学中肉桂酸的制备通常采用Perkin反应由苯甲醛和乙酸酐为原料制得,其在基础化学实验教学中占有比较重要的一环。然而在教学实践中,现有的制备方法耗时长且学生很难得到产品。讨论了反应温度、反应时间、反应物摩尔比和催化剂用量对肉桂酸产率的影响,确定了最佳反应条件。将此反应条件应用到教学实践中,反应效率明显提高,实验教学时间明显缩短,且每一组同学都能得到纯度较高的产品。     

F油田降压开采过程中沥青质沉淀规律

沥青沉降是影响原油生产的一个重要因素,针对其沉淀机理和规律进行分析研究对于控制沥青沉淀,提高原油采收率有重要的意义.研究了依靠自然能量开采的F油田原油的沥青沉淀析出规律和沥青沉淀量变化规律.沥青沉淀析出实验研究表明随着压力的降低,沥青沉淀现象的发生对应有一个临界压力(AOP).当压力低于AOP高于泡点压力时,沥青沉淀随压力降低而增加,当压力高于AOP时不会发生沥青沉淀;不同温度也会对沥青的沉淀造成影响,与储层相比井筒靠近井口附近发生沥青沉淀的概率更高;沥青的沉淀量实验研究表明,沉淀量随压力先降低后增加,在近似饱和压力处沉淀量最大.     

天然水中腐殖酸的分离测定方法比较

比较研究了天然湖水中腐殖酸含量的3种分离/测定方法,即紫外-可见分光光度法、氧化法和XAD大孔树脂吸附-TOC联用法的优缺点和适用性,并对分离出的天然腐殖酸进行了紫外光谱等光学性能的表征。结果表明,3种方法的准确度和精密度都较好,紫外-可见分光光度法最为简便、快捷,氧化法适合对不同来源的水体腐殖酸进行定量分析,树脂吸附-TOC联用法提取的有机物更符合腐殖酸的化学特征,最为准确。天然腐殖酸的光学指标说明树脂吸附法可以分离得到大部分紫外吸收物质,其性质更接近于腐殖酸,并且较高的SUVA值和E4/E6值说明天然腐殖酸具有芳香度高、相对分子质量大的特点。     

不同分析方法测定水中丁基黄原酸的比较

探讨了铜试剂亚铜分光光度法、紫外分光光度法、吹扫捕集/气相色谱-质谱法3种分析方法对测定水中丁基黄原酸的影响,从样品采集和保存、方法原理和干扰、方法检出限和标准曲线、精密度和加标回收率、实际样品分析结果等方面,比较了3种分析方法的优缺点及适用范围.结果表明:采集未知样品时,应保持样品的弱碱性,并尽快地分析.由于丁基黄原...     

Mandibular Gland Chemistry of Grass-cutting Ants: Species, Caste, and Colony Variation

The compositions of the alarm pheromones of two species of grass-cutting ant, Atta bisphaerica and A. capiguara, were examined, and caste and colony variations quantified. The pheromones of A. bisphaerica and A. capiguara were remarkably similar and were composed of a complex mixture of volatiles in which 4-methyl-3-heptanone and 2-heptanone were the most abundant compounds. Small but consistent intraspecific differences were found between the worker castes and between individual colonies. The results support the view that alarm pheromones are rarely species specific. The possible importance of intercolony variation is discussed.     

高氯酸提取土壤中形态铁及其直接测定的研究

利用1 mol/L高氯酸提取果园土壤中的Fe(Ⅱ),建立了在1 mol/L高氯酸体系下,Fe(Ⅱ)与邻菲啉显色反应(5ε10=1.1×104L/(mol.cm)的分光光度法。具有快速、灵敏、提取与测定体系一致的优点。吸光度与浓度在0.063~8.0μg/mL范围内具有良好的线性,检出限为29 ng/mL,相对标准偏差≤2.11%,平均回收率为97.5%。该法用于测定土壤中形态铁的提取与测定,均获得满意结果。     

Variations in Solution Chemistry During the Low-Temperature Formation of Hydroxyapatite

Both the kinetics and the microstructure of monolithic hydroxyapatite formed by a low-temperature dissolution and precipitation reaction strongly depend on the conditions in solution during the reaction. The relationships between the molar ratio of the particulate reactants (dicalcium phosphate and tetracalcium phosphate), the solution chemistry, and the rates of formation of hydroxyapatite are examined. During reaction, steady-state solution conditions are rapidly achieved. However, the steady states attained are not those associated with the metastable invariant point involving the reactants. Rather, the steady-state condition varies depending on the molar ratio of the reactants. The ultimate product of the reactions investigated is calcium-deficient hydroxyapatite. Hydroxyapatite formation occurs in two stages: initial formation of nearly stoichiometric hydroxyapatite followed by its conversion to calcium-deficient material. Microstructural evidence indicates that the formation of hydroxyapatite occurs in association with dicalcium phosphate, eventually causing the dissolution of the hydroxyapatite reactant to become diffusionally controlled. Effects of common ions, sodium chloride and magnesium chloride, on the chemistry of the aqueous phase and on microstructural development are investigated.