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MAX-DOAS measurements and vertical profiles of glyoxal and formaldehyde in Madrid, Spain
摘要： Glyoxal (CHOCHO) and formaldehyde (HCHO) are organic trace gases that play an important role in tropospheric chemistry as oxidation products of a number of volatile organic compounds (VOCs). In this study, we report year-round daytime measurements of glyoxal and formaldehyde in the urban atmosphere of Madrid, Spain. Their vertical concentration profiles were retrieved using the Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique and a Radiative Transfer Model (RTM) that simulates solar photon paths through the atmosphere. The diurnal variations of HCHO show two distinct peaks during the day, in the early morning and late afternoon in spring and summer, while the second peak is shifted towards noon in autumn and winter, due to lower photolysis rates and more effective boundary layer accumulation of HCHO in those seasons. The HCHO surface mixing ratios range from 6 ppbv to 27 ppbv in spring-summer and from 10 ppbv to 30 ppbv in autumn-winter. Monthly hourly-averaged glyoxal surface mixing ratios in the early morning show higher values during winter, 2 ppbv, than in summer, 0.7 ppbv. We also evaluated the ratio between glyoxal and formaldehyde (RGF) surface mixing ratios, as an indicator of the nature of VOCs precursors. The RGF was also correlated with the measured NO2 -which represents a direct signal of anthropogenic emissions- along with the VOCs emission inventories in Madrid. The RGF results yielded higher ratios in spring, 0.1 - 0.13, than in winter and autumn (in the range of 0.02 to 0.07) when NO2 levels were higher.
关键词： volatile organic compounds,formaldehyde,glyoxal,MAX-DOAS,air quality
更新于2025-09-10 09:29:36
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Adsorption mechanism of typical oxygen, sulfur, and chlorine containing VOCs on TiO2 (0?0?1) surface: First principle calculations
摘要： The photocatalytic degradation of volatile organic compounds has been gaining much interest in recent years to solve the long-standing problem of indoor air pollution. For this purpose, anatase TiO2 and its derivatives are regarded as potential photocatalyst materials. Thus, we study the adsorption mechanism of selected volatile organic compounds such as formaldehyde, methyl chloride, and carbon disulfide on TiO2 (0 0 1) surface using first principle calculations to comprehend their surface interaction and catalytic degradation in depth. The study suggests that formaldehyde interacts with TiO2 (0 0 1) surface through chemical bonds that form a saddle-like structure exhibiting a high adsorption energy value (0.543 eV). It can be inferred that the fivefold coordinated Ti5c and twofold coordinated O2c atoms are the only adsorption sites on TiO2 (0 0 1) surface. However, significant variations are observed for chloride and sulfur containing groups. For instance, the methyl chloride and carbon disulfide physisorbed on the surface of TiO2 (0 0 1) without any chemical bond formation exhibits low adsorption energy values. The results are further confirmed by calculating the corresponding density of states, and electron density differences in all cases. This study provides a detailed investigation of various VOCs on the surface of TiO2 (0 0 1), which provides further insight into the construction of photocatalytic materials for the photodegradation of VOCs.
关键词： Methyl chloride,TiO2 (0 0 1) surface,Formaldehyde,VOCs,DFT
更新于2025-09-09 09:28:46
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Observing atmospheric formaldehyde (HCHO) from space: validation and intercomparison of six retrievals from four satellites (OMI, GOME2A, GOME2B, OMPS) with SEAC<sup>4</sup>RS aircraft observations over the Southeast US
摘要： Formaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs), but validation of the data has been extremely limited. Here we use highly accurate HCHO aircraft observations from the NASA SEAC4RS campaign over the Southeast US in August–September 2013 to validate and intercompare six operational and research retrievals of HCHO columns from four different satellite instruments (OMI, GOME2A, GOME2B and OMPS) and three different research groups. The GEOS-Chem chemical transport model provides a common intercomparison platform. We find that all retrievals capture the HCHO maximum over Arkansas and Louisiana, reflecting high emissions of biogenic isoprene, and are consistent in their spatial variability over the Southeast US (r=0.4–0.8 on a 0.5o×0.5o grid) as well as their day-to-day variability (r=0.5–0.8). However, all satellite retrievals are biased low in the mean by 20–51%, which would lead to corresponding bias in estimates of isoprene emissions from the satellite data. The smallest bias is for OMI-BIRA, which has the highest corrected slant columns and the lowest scattering weights in its air mass factor (AMF) calculation. Correcting the assumed HCHO vertical profiles (shape factors) used in the AMF calculation would further reduce the bias in the OMI-BIRA data. We conclude that current satellite HCHO data provide a reliable proxy for isoprene emission variability but with a low mean bias due both to the corrected slant columns and the scattering weights used in the retrievals.
关键词： SEAC4RS,OMPS,isoprene emissions,validation,satellite retrievals,HCHO,GEOS-Chem,Formaldehyde,GOME2B,OMI,GOME2A
更新于2025-09-04 15:30:14
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Perylene-Based Fluorescent Nanoprobe for Acid-Enhanced Detection of Formaldehyde in Lysosome
摘要： Formaldehyde (FA), as a reactive carbonyl species, is extremely hazardous to human health if its concentration is above normal level. In live cells, lysosome is a main organelle to generate endogenous FA. Thus, the design of facile, stable and sensitive probes for the detection of FA in lysosome is essential. Herein, a self-assembled fluorescent nanoprobe based on homoallylamino substituted perylene (P-FA) has been developed for FA detection in lysosome. P-FA can react with FA along with emission color change from blue to green. P-FA exhibited high sensitivity and selectivity to FA in DMSO solution. In aqueous solution, P-FA self-assembled into uniform sphere-like nanoparticle as a fluorescent nanoprobe. Furthermore, the reaction between the nanoprobe and FA was greatly facilitated at pH 4-5, leading to a lower detection limit (0.96 μM at pH 5) than that in DMSO. In live cells, P-FA nanoprobe achieved long-term tracking of lysosome (over 12 h). The fluorescent nanoprobe was then used for both exogenous and endogenous FA detection. Our work provides a facile and effective strategy for the detection of FA in lysosome.
关键词： Weak Acidity,Perylene,Formaldehyde Detection,Lysosome,Fluorescent Nanoprobe
更新于2025-09-04 15:30:14
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Smithsonian Astrophysical Observatory Ozone Mapping and Profiler Suite (SAO OMPS) formaldehyde retrieval
摘要： This paper presents our new formaldehyde (H2CO) retrievals, obtained from spectra recorded by the nadir instrument of the Ozone Mapping and Profiler Suite (OMPS) flown on board NASA’s Suomi National Polar-orbiting Partnership (SUOMI-NPP) satellite. Our algorithm is similar to the one currently in place for the production of NASA’s Ozone Monitoring Instrument (OMI) operational H2CO product. We are now able to produce a set of long-term data from two different instruments that share a similar concept and a similar retrieval approach. The ongoing overlap period between OMI and OMPS offers a perfect opportunity to study the consistency between both data sets. The different spatial and spectral resolution of the instruments is a source of discrepancy in the retrievals despite the similarity of the physic assumptions of the algorithm. We have concluded that the reduced spectral resolution of OMPS in comparison with OMI is not a significant obstacle in obtaining good-quality retrievals. Indeed, the improved signal-to-noise ratio of OMPS with respect to OMI helps to reduce the noise of the retrievals performed using OMPS spectra. However, the size of OMPS spatial pixels imposes a limitation in the capability to distinguish particular features of H2CO that are discernible with OMI. With root mean square (RMS) residuals ～ 5×10?4 for individual pixels we estimate the detection limit to be about 7.5 × 1015 molecules cm?2. Total vertical column density (VCD) errors for individual pixels range between 40 % for pixels with high concentrations to 100 % or more for pixels with concentrations at or below the detection limit. We compare different OMI products (SAO OMI v3.0.2 and BIRA OMI v14) with our OMPS product using 1 year of data, between September 2012 and September 2013. The seasonality of the retrieved slant columns is captured similarly by all products but there are discrepancies in the values of the VCDs. The mean biases among the two OMI products and our OMPS product are 23 % between OMI SAO and OMPS SAO and 28 % between OMI BIRA and OMPS SAO for eight selected regions.
关键词： formaldehyde,OMPS,H2CO,retrieval,AMFs,vertical column density,air mass factors,spectral fitting,OMI,VCD
更新于2025-09-04 15:30:14
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Synthesis, Characterization and Photocatalysis of Mesoporous TiO2
摘要： The mesoporous TiO2 nanoparticulate has been prepared by evaporation induced self-assembly method using EO-PO type polyether P123 as a template. The small angle X-ray diffraction, wide angle X-ray diffraction, high-resolution transmission electron microscopy and N2 isothermal adsorption-desorption are used to study the microstructure and morphology of the as-synthesized mesoporous TiO2. The results demonstrate that the mesoporous TiO2 belongs to anatase and the size is 20-30 nm. The sample is prepared using P123 as a template with average pore size distribution of 11.54 nm, specific surface area of 84.83 m2/g and pore volume of 0.234 cm3/g. The as-synthesized mesoporous TiO2 exhibits remarkably high photocatalytic activity of 93.6 % in decomposing formaldehyde under ultraviolet light irradiations for 90 min. This work provides a basic experimental process for the preparation of mesoporous TiO2, which will possess a broad prospect in terms of the applications in improving indoor air quality.
关键词： Photocatalysis,Evaporation induced self-assembly,Mesoporous TiO2,Formaldehyde
更新于2025-09-04 15:30:14
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Advanced oxidation of formaldehyde in aqueous solution using the chemical-less UVC/VUV process: Kinetics and mechanism evaluation
摘要： This study was conducted to evaluate the degradation of high concentrations of formaldehyde in the chemical-less UVC/VUV photo-reactor. 99.5% degradation and 94% chemical oxygen demand (COD) removal of 200 mg/L formaldehyde was achieved in the UVC/VUV photo-reactor at reaction time of 60 min and solution pH of 7. The effect of water anions such as carbonate, bicarbonate, nitrate, chloride, sulfate and phosphate was examined on degradation and COD removal of formaldehyde; nitrate and carbonate exhibited the highest inhibitory effects on the process. Besides, treatment of formaldehyde-contaminated tap water was also investigated and formaldehyde removal was decreased from 99.5% is aqueous solution to 86.2% in tap water. The findings of radical scavenging tests revealed that hydroxyl radical was the most predominant oxidizing agent contributed in degradation of formaldehyde. It is concluded therefore that the UVC/VUV process as a unique chemical-less process efficient for advanced degradation of high concentrations of formaldehyde.
关键词： Hydroxyl radical,COD removal,Vacuum UV,Formaldehyde degradation,Advanced photo-oxidation
更新于2025-09-04 15:30:14