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In the present work, we conducted experiments of secondary organic aerosol (SOA) formation from urban cooking and vehicular sources to characterize the mass spectral features of primary organic aerosol (POA) and SOA using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Our results showed that the cooking styles have a greater impact on aged COA (cooking organic aerosol) mass spectra than oxidation conditions. However, the oxidation conditions affect the aged HOA (hydrocarbon-like OA) spectra more significantly than vehicle operating conditions. In our study, we use mass spectra similarity analysis and positive matrix factorization (PMF) analysis to establish the POA and SOA mass spectra of these two sources. These mass spectra are used as source constraints in a multilinear engine (ME-2) model to apportion the OA (organic aerosol) sources in the atmosphere. Compared with the traditional ambient PMF results, the improved ME-2 model can better quantify the contribution of POA and SOA from cooking and vehicular sources. Our work, for the first time, establishes the vehicle and cooking SOA source profiles, and can be further used in the OA source apportionment in the ambient atmosphere.

In the present work, we conducted experiments of secondary organic aerosol (SOA) formation from urban lifestyle sources (cooking and vehicle) to characterize the mass spectral features of primary organic aerosol (POA) and SOA using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Our results showed that the cooking styles have greater impact on aged COA mass spectra than oxidation condition. However, the oxidation conditions affect the aged HOA spectra more significantly than vehicle operation conditions. In our study, we use mass spectra similarity analysis and positive matrix factorization (PMF) analysis to establish the POA and SOA mass spectra of these two typical lifestyle sources. These mass spectra are used as source constraints in a multilinear engine (ME-2) model to apportion the OA sources in the atmosphere. Comparing with the traditional ambient PMF results, the improved ME-2 model can better quantify the contribution of POA and SOA from life-style sources. Our work, for the first time, establishes the vehicle and cooking SOA source profiles, and can be further used in the OA source apportionment in the ambient atmosphere.

Both vehicle exhaust and cooking emission are closely related to the daily life of city dwellers, which are considered as major sources of urban secondary organic aerosol (SOA). Here, we defined the SOA derived from vehicle exhaust and cooking emission as Urban Lifestyle SOA, and simulated their formation using a Gothenburg potential aerosol mass reactor (Go: PAM). After samples had been aged under 0.3–5.5 days of equivalent photochemical age, these two urban lifestyle SOA showed markedly distinct features in SOA mass growth potentials, oxidation pathways and mass spectra. The SOA / POA mass ratios of vehicle groups (107) were 44 times larger than those of cooking groups (2.38) at about 2 days of equivalent photochemical age. It reveals that organics from vehicle may undergo the alcohol/peroxide and carboxylic acid oxidation pathway to produce abundant less/more oxidized oxygenated OA (LO-OOA and MO-OOA), and only a few primary hydrocarbon-like organic aerosol (HOA) remains unaged. In contrast, organics from cooking may undergo the alcohol/peroxide oxidation pathway to produce moderate LO-OOA, and comparable primary cooking organic aerosol (COA) remains unaged. Our findings provide an insight into atmospheric contributions and chemical evolutions for urban lifestyle SOA, which would greatly influence the air quality and health risk assessments in urban areas.

Relation extraction between medical concepts from electronic medical records has pervasive applications as well as significance. However, previous researches utilizing machine learning algorithms judge the semantic types of medical concept pair mentions independently. In fact, different concept pair mentions in the same context are of dependencies which can provide beneficial evidences for identifying their relation types. To the best of our knowledge, only one study has considered such dependencies in discharge summaries. However, its hard constraints are not applied effectively to the History of Present Illness (HPI) in electronic Medical Records. According to the writing characteristics of HPI records, we generalize two regularities of dependencies among concept pairs mentioned in an HPI record to enhance the performance of relation extraction. We incorporate the two soft constraints corresponding to the regularities and the posterior probabilities returned by a local classifier into a joint inference process which applies Integer Quadratic Programming method to carry out collective classification for all concept pair mentions in an HPI record. We implement four local classification models including support vector machine, logistics regression, random forest and piecewise convolutional neural networks to examine the performance of our approach. A series of experimental results demonstrate that our collective classification method has made a principal improvement and outperforms the other state-of-the-art methods.

There are vast resources of oil shale in the Chang-7 section of the Upper Triasic Yanchang Formation, Ordos Basin, China. They would provide secure access to transportation fuels, if utilized in an effective, economic and environmental manner. A Chang-7 oil shale sample containing pyrite has been pyrolysed in a thermogravimetric analyzer at constant heating rates of 5, 10, 20℃/min up to 1150℃ with nitrogen as purge gas. Meanwhile, the pyrolysis-gas chromatograph-mass spectrometry experiments were performed on parallel samples of Chang-7 oil shale sample at 20℃/min in the four temperature sections, ranging from 100 to 700℃ to understand the decomposition mechanism. The initial decomposition temperature and the final decomposition temperature of hydrocarbonaceous material were about 367℃ and 521℃ (average values), respectively, which raised with the increase of heating rate. The decomposition of pyrite began to take place over 500℃, and the pyrolysates involving sulfur compounds are harmful to the environment and corrode the equipment. Thus, we recommended that the final temperature of Chang-7 oil shale pyrolysis was best not to exceed 550℃ considering the heating rate to avoid environmental pollution and damage of the instruments. Chang-7 oil shale exhibited a single stage decomposition in the range of about 367–521℃, representing the rearrangement of kerogen molecules in the temperature range of 100–350℃. The activation energies of kerogen decomposition were calculated using Coats–Redfern method at different heating rate. We found that both activation energy and pre-exponential factor increased with an increasing heating rate. Finally, the DTA curves of Chang-7 oil shale verified the reliability of the calculated activation energies.

The correct understanding of shale pore characteristics is the foundation of shale gas exploration and development. Comminution is an essential sample pretreatment in many measurements of shale pore characteristics, but little is known about the influence of comminution on shale pore characteristics. This study utilizes low-pressure nitrogen adsorption and helium porosity measurements to investigate the evolution of shale pore characteristics during comminution. The results show that reducing the proportion of inaccessible pores and improving the gas diffusion efficiency are the main effects of comminution on the shale pore characteristics, resulting in an increase in measured porosity. The recommended analytical shale particle size for low-pressure nitrogen adsorption and helium porosity measurements is below 80 and 20 mesh, respectively. The proportion of inaccessible pores in shale investigated in this study ranges from 13.11 to 45.89% and shows a negative correlation with thermal maturity and a positive correlation with clay content. This suggests an improvement of organic pore accessibility during thermal evolution and a high content of inaccessible pores in clay minerals.

The organic acid is important in forming secondary pores and enhancing total porosity of the clastic rock. But there is little study to investigate the effect of organic acid on the porosity distribution of clastic rock from deep reservoirs. The changes in porosity, permeability, and porosity distribution of the dissolved medium-grained lithic arkose, from Yanchang Formation in Ordos Basin, were examined by nuclear magnetic resonance (NMR). The results show that porosity and permeability of rock increase with the time of exposure of the rock to the organic acid solution and it increases rapidly in the early period, then slightly increases to a saturation level. Besides, organic acid mainly changes the frequency and the shapes of T2 distribution in NMR analysis, and this study suggests that organic acid has more effect on rocks with larger pore throat than those with smaller pore throat.

The thermal stability of organic acids has a close relationship with the formation mechanism of secondary pores in deep reservoirs. Experiments were conducted to investigate the thermal stability of oxalic acid under high pressure and the influence of K-feldspar on oxalic acid decomposition. The experiment temperatures were set in the range of 130-330°C and each experiment was performed for 72h under 60MPa. Results show that both temperature and K-feldspar have significant influence on the decomposition of oxalic acid. The oxalic acid decomposed slowly at temperatures less than 180°C, and most of the oxalic acid decomposed at temperatures between 180°C and 230°C. Besides, the decarboxylation reaction proceeded more slowly in the presence of K-feldspar than the mineral-free experiments, which is most likely attributed to the increasing pH caused by dissolution. In addition, because the decomposition rate of oxalic acid was low, the K-feldspar dissolution was not affected at temperatures lower than 230°C.

Non-methane hydrocarbons (NMHCs) play a critical role in the photochemical production of ozone (O3) and organic aerosols. Obtaining an accurate understanding on temporal trends of NMHC emissions is essential for predicting air quality changes and evaluating the effectiveness of current control measures. In this study, we evaluated temporal trends of anthropogenic NMHC emissions during August in Beijing based on ambient measurements during selected summer periods at an urban site in Beijing from 2002 to 2013. In the contrast to the results from the most recent inventory (Multi-resolution Emission Inventory for China, MEIC), which reported that anthropogenic NMHC emissions during August increased by 28% from 2004 to 2012, whereas mixing ratios of NMHCs measured at this urban site decreased by 37% during the same time period. A positive matrix factorization (PMF) model was applied to these NMHC measurements for source apportionment. The results showed that the relative contributions of vehicular exhaust and gasoline evaporation to measured NMHC concentrations decreased by 66% during August from 2004 to 2012, comparable to the relative decline of 67% for transportation-related NMHC emissions reported by the MEIC inventory. This finding indicates that the implementation of stricter emissions standards for new vehicles and specific control measures for in-use vehicles has been effective for reducing transportation-related NMHC emissions. In addition, the PMF results suggested that there were no significant temporal changes in NMHC concentrations from solvent use and industry during August from 2004 to 2012, in contrast with the rapid rate of increase (8.8% yr−1) reported by the MEIC inventory. To re-evaluate the NMHC emissions trends for solvent use and industry, annual variations in NMHC / NOx ratios were compared between ambient measurements at the PKU site and the MEIC inventory. In contrast to the significant rise in NMHC / NOx ratios from the MEIC inventory, the measured NMHC / NOx ratios declined by 14% during August from 2005 to 2012. The inferred NMHC / NOx ratios based on PMF results exhibited a comparable decline of 11% to measured ratios. These results indicate that the increase rate for NMHC emissions from solvent use and industry in Beijing might be overestimated in the current inventory; therefore, additional research is necessary to verify the NMHC emission trends for this source.

We performed MAX-DOAS measurements during the PRIDE-PRD2006 campaign in the Pearl River Delta region (PRD), China, for 4 weeks in July 2006 at a site located 60 km north of Guangzhou. The vertical distributions of NO2, HCHO, and CHOCHO were independently retrieved by an automated iteration method. The NO2 mixing ratios measured by MAX-DOAS showed reasonable agreement with the simultaneous, ground based in-situ data. The tropospheric NO2 vertical column densities (VCDs) observed by OMI on board EOS-Aura satellite were higher than with those by MAX-DOAS. The 3-D chemical transport model CMAQ overestimated the NO2 VCDs as well as the surface concentrations by about 65%. From this observation, a reduction of NOx emission strength in CMAQ seems to be necessary in order to well reproduce the NO2 observations. The average mixing ratios of HCHO and CHOCHO were 7 ppb and 0.4 ppb, respectively, higher than in other rural or semirural environments. The high ratio of 0.062 between CHOCHO and HCHO corresponds to the high VOCs reactivity and high HOx turnover rate consistent with other observations during the campaign.

In order to characterize the features of particulate pollution in the Pearl River Delta (PRD) in the summer, continuous measurements of particle number size distributions and chemical compositions were simultaneously performed at Guangzhou urban site (GZ) and Back-garden downwind regional site (BG) in July 2006. Particle number concentration from 20 nm to 10 μm at BG was (1.7±0.8)×104 cm−3, about 40% lower than that at GZ, (2.9±1.1)×104 cm−3. The total particle volume concentration at BG was 94±34 μm3 cm−3, similar to that at GZ, 96±43 μm3 cm−3. More 20–100 nm particles, significantly affected by the traffic emissions, were observed at GZ, while 100–660 nm particle number concentrations were similar at both sites as they are more regional. PM2.5 values were similar at GZ (69±43 μg m−3) and BG (69±58 μg m−3) with R2 of 0.71 for the daily average PM2.5 at these two sites, indicating the fine particulate pollution in the PRD region to be regional. Two kinds of pollution episodes, the accumulation pollution episode and the regional transport pollution episode, were observed. Fine particles over 100 nm dominated both number and volume concentrations of total particles during the late periods of these pollution episodes. Accumulation and secondary transformation are the main reasons for the nighttime accumulation pollution episode. SO42−, NO3− accounted for about 60% in 100–660 nm particle mass and PM2.5 increase. When south or southeast wind prevailed in the PRD region, regional transport of pollutants took place. Regional transport contributed about 30% to fine particulate pollution at BG during a regional transport case. Secondary transformation played an important role during regional transport, causing higher increase rates of secondary ions in PM1.0 than other species and shifting the peaks of sulfate and ammonium mass size distributions to larger sizes. SO42−, NO3−, and NH4+ accounted for about 70% and 40% of PM1.0 and PM2.5, respectively.

The formation of Secondary organic aerosol (SOA) was simulated with the Secondary ORGanic Aerosol Model (SORGAM) by a classical gas-particle partitioning concept, using the two-product model approach, which is widely used in chemical transport models. In this study, we extensively updated SORGAM including three major modifications: firstly, we derived temperature dependence functions of the SOA yields for aromatics and biogenic VOCs, based on recent chamber studies within a sophisticated mathematic optimization framework; secondly, we implemented the SOA formation pathways from photo oxidation (OH initiated) of isoprene; thirdly, we implemented the SOA formation channel from NO3-initiated oxidation of reactive biogenic hydrocarbons (isoprene and monoterpenes). The temperature dependence functions of the SOA yields were validated against available chamber experiments. Moreover, the whole updated SORGAM module was validated against ambient SOA observations represented by the summed oxygenated organic aerosol (OOA) concentrations abstracted from Aerosol Mass Spectrometer (AMS) measurements at a rural site near Rotterdam, the Netherlands, performed during the IMPACT campaign in May 2008. In this case, we embedded both the original and the updated SORGAM module into the EURopean Air pollution and Dispersion-Inverse Model (EURAD-IM), which showed general good agreements with the observed meteorological parameters and several secondary products such as O3, sulfate and nitrate. With the updated SORGAM module, the EURAD-IM model also captured the observed SOA concentrations reasonably well especially those during nighttime. In contrast, the EURAD-IM model before update underestimated the observations by a factor of up to 5. The large improvements of the modeled SOA concentrations by updated SORGAM were attributed to the mentioned three modifications. Embedding the temperature dependence functions of the SOA yields, including the new pathways from isoprene photo oxidations, and switching on the SOA formation from NO3 initiated biogenic VOCs oxidations contributed to this enhancement by 10%, 22% and 47%, respectively. However, the EURAD-IM model with updated SORGAM still clearly underestimated the afternoon SOA observations up to a factor of two. More work such as to improve the simulated OH concentrations under high VOCs and low NOx concentrations, further including the SOA formation from semi-volatile organic compounds, the correct aging process of aerosols, oligomerization process and the influence on the biogenic SOA by the anthropogenic SOA, are still required to fill the gap.