This study investigated particulate and gaseous emission factors (EFs) from an ocean-going cargo vessel operating under different real-world conditions. EFs were determined for criteria gaseous (including NO, NO2, CO, CO2, SO2) and particulate pollutants (including PM2.5 and PM2.5 components, such as organic carbon, elemental carbon, BC, water-soluble inorganic ions and metal elements). The results showed that the gaseous emissions were dominated by CO2 and NO, the EFs of which were ranging from 489 g/kWh to 1040 g/kWh, and 11.2 g/kWh to 29.1 g/kWh, respectively. And the EFs of PM2.5 were ranging from 0.13 g/kWh to 1.12 g/kWh. Vanadium, silicon, calcium and nickel were the main contributors to the presence of inorganic metal elements. Marine diesel oil (MDO) and heavy fuel oil (HFO) were used in the cargo vessels sailing along the coastline and in the ocean, respectively. When using MDO instead of HFO, the SO2, NOX and PM2.5 emissions were reduced by 5%, 90% and 60%, respectively. There seemed no obvious effect of the fuel type on the CO2 emission. Besides, the CO2 and SO2 emissions of HFO were linearly correlated with PM2.5. Moreover, the energy efficiency management system (EEMS) was used to estimate the relationship between emissions and engine working conditions. Effective thermal efficiency (ηet) was calculated based on combustion status. CO and BC decreased with increasing ηet for both HFO and MDO, while NO increased with increasing ηet. These results could provide important data support for the use of certification values for emissions inventories.

Volatile organic compounds (VOCs) of motor vehicles contribute greatly to ground-level ozone formation, especially in the megacity regions. While the variations of tailpipe VOC emissions along with the vehicle technologies and road conditions are rarely investigated systematically. Thus, on-road tailpipe VOC emissions from in-use vehicles, including light-duty gasoline vehicles (LDGV), light-duty diesel trucks (LDDT), heavy-duty diesel truck (HDDT) and liquefied petroleum gas-electric hybrid bus (LPGB), were sampled with a combined portable emission measurement system (PEMS). A total of 102 individual VOC species were quantified by a gas chromatography mass spectrometry detector (GC-MSD), and the maximum incremental reactivity (MIR) scale was used to calculate the ozone formation potentials (OFPs). Results showed that aromatics and alkanes were the major VOC groups regardless of the vehicle type, accounting for 68.1–98.0%. For the LDGV, i-pentane, acetone, and propane were the top three VOC species. Naphthalene, dodecane and n-undecane were main VOC constituents in the diesel exhaust. Acetone was the most abundant VOC species for the LPGB, followed by i-pentane, i-butane and n-butane. Road conditions had a significant impact on the VOC emission factors. Specifically, emission factors on urban roads were 3.3–7.0 times those on the highway. The OFPs were 70.7, 128.1, 2189.4 and 124.7 mg O3/km for the LDGV, LDDT, HDDT and LPGB, respectively; aromatics were the main contributors, occupying 49.6–93.4% of the total OFPs. Results indicated that emission factors and dominant species of VOCs were strongly affected by vehicle technologies and road conditions, but aromatics were the major group for both VOC composition and OFPs.

Black carbon (BC) is a major component in atmospheric particulate matter (PM), which causes adverse health impacts and contributes significantly to climate change. Without widespread and accurate BC measurements, it remains difficult to track incomplete combustion sources and reduce BC emissions. Currently commercial BC sensors remain too costly to be deployed widely. In this work, a fast, cost-effective, and easily accessible method based on a smartphone camera was used to quantify color information of PM collected on filters to estimate BC and elemental carbon (EC) loadings. A robust RGB (red, green, blue)-based linear interaction model was built and validated using 1,878 PM samples collected in three different regions with collocated BC and EC measurements. After applying image correction methods, this model shows a good predictability with an R-squared (R2) of 0.904 with state-of-the-art BC measurement techniques, and a coefficient of variation of the root mean square error (CV(RMSE)) of 25.3% despite the complex sources and different reference measurement techniques. This work validates the viabilities of using smartphones to quantify BC or EC loading on PM filters with a unified model and track incomplete combustion sources.

This study investigates the impact of Arctic Oscillation (AO) abnormalities on the haze days in China for 57 winters from 1961 to 2017. The results reveal that that AO abnormalities mainly affected meteorological conditions and haze pollution in northern and central China, while their impact on the southeast coastal and Guangdong-Guangxi regions is not significant. During years with an abnormally high AO index (AOI) in winter, the number of haze days increased in northern and central China, especially in the Shanxi–Shandong–Hebei–Beijing–Tianjin and Hubei–Hunan–Henan–Jiangxi regions, while the number of haze days decreased during years of abnormally low AOI. When in the years of abnormally high AOI, the weakening of the East Asian trough caused the decrease of the meridional circulation and the increase of zonal winds compared with normal years. Furthermore, the weakening of the Siberian high pressure and the enhancement of the westerly circulation affected several meteorological factors, including the boundary layer height, surface temperature, wind speeds, and precipitations. These changes effectively inhibited the development of low-level vertical motion and the vertical diffusion of pollutants in the air, leading to the accumulation of haze pollution. The situation was the opposite for low AOI years, but the impact on the meteorological conditions was relatively weak compared to that during high AOI years. The impacts of the regional characteristics of AO abnormalities on the haze days are also investigated in this study.

In this paper, by means of thermo-gravimetric analysis(TGA), the desorption kinetics of CO2 absorbed in two kinds of rich amine solutions, MDEA (3.25mol/L) and MDEA+DEA(3.25mol/L-0.3mol/L), were investigated under different heating rates(2.5℃/min, 5℃/min, 10℃/min and 20℃/min). The thermal analysis kinetics was applied to analyze the TG-DTG curves of two rich amine solutions so as to research CO2 desorption kinetics. In addition, the CO2 desorption kinetics parameters have been calculated with model-free method Flynn-Wall-Ozawa (FWO) and model-fitting method Coats-Redfern (CR). The results indicated that CO2 desorption process could be divided into two stages. The CO2 and H2O were released with non-uniform speed in the first stage and MDEA or DEA with higher boiling points were evaporated in the second stage. For MDEA solution the average activation energy E was 50.36kJ/mol, the pre-exponential factor A was 1.68×107, and the most probable integral mechanism function was Gα=α3/2. For MDEA+DEA solution the average activation energy E was 59.68kJ/mol, the pre-exponential factor A was 2.22×107, and the most probable integral mechanism function was Gα=[(1+α)1/3−1]2. The technical feasibility of CO2 desorption performance in rich amine solutions with thermo-gravimetric analysis method was demonstrated.

Background Short-term exposure to ambient air pollution (AAP) has been widely linked to asthma morbidity such as outpatient and emergency visits and hospitalization. Up to date, however, the acute effects of AAP exposure on asthma mortality remained largely unknown possibly due to the rare occurrence of asthma deaths. Objectives This study aimed to investigate whether the death risks from asthma are triggered by short-term AAP exposures in a Chinese urban population who suffered poor air quality. Methods 1385 asthma death cases were identified from the total 61.3 thousand death records in two urban districts in Wuhan, central China, 2003–2013. We performed a time-stratified case-crossover design and conditional logistic regression models were applied to assess short-term associations of air pollutants (particulate matter with aerodynamic diameter ≤10 μm [PM10], sulfur dioxide [SO2], and nitrogen dioxide [NO2]) along different exposure days with asthma mortality. Results A total of 1385 case days and 4668 control days were investigated during the study period. Daily mean concentrations of PM10, SO2, and NO2 were 116.6 μg/m3, 53.4 μg/m3, and 60.7 μg/m3, respectively. A 10 μg/m3 rise in exposure to SO2 and NO2 at 2 days prior to death (lag 2 days), was associated with increased asthma death risks of 2.9% (odds ratio [OR] = 1.029, 95% confidence interval [CI]: 1.006, 1.053) and 4.3% (OR = 1.043, 95% CI: 1.012, 1.076), respectively. No evident PM10-asthma associations were identified in all subpopulations except for those aged 85 + years (OR = 1.022, 95% CI: 1.001 to 1.044). In our stratified analyses, significant effects of SO2 and NO2 were only observed in female, the older elderly, 7+ years-educated and unmarried persons, as well as those died outside the hospital and in cold season. We observed some evidence for effect modification by age, with p-values of 0.032 for PM10 and 0.051 for SO2, suggesting higher vulnerability to air pollution among the older asthma cases. Conclusions This study provided suggestive evidence for the short-term association between air pollution exposure and asthma death in highly polluted urban areas. Several days’ high-level exposures to air pollutants, particularly SO2 and NO2, may elevate risks of asthma death. Our findings highlighted the potential health benefits from intervention and preventive actions targeted to reducing AAP exposure among asthma patients.

Combined calcium-copper materials based on calcium zirconate (CaO/CuO/CaZrO3) for Calcium-Copper Chemical Looping (Ca-Cu Looping) have been synthesized using a scalable wet chemical method and characterized by powder X-ray diffraction (PXRD) with Rietveld refinement, temperature-programmed reduction (H2-TPR) and oxidation (O2-TPO), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and 45–50 cycles in a thermogravimetric analyser (TGA) representing realistic Ca-Cu Looping conditions. A material at 50 wt% active CuO loading and a CuO/CaO weight ratio of 2 deactivated due to copper migration and agglomeration, while materials with 40 wt% active CuO loading were stable throughout TGA cycles at CuO/CaO ratios of 2 and 10. 40 wt% CuO loaded combined CaO/CuO/CaZrO3 materials are promising candidates for Ca-Cu Looping with a demonstrated tuneable and stable CuO/CaO ratio (≥ 2 [wt/wt]) that could lead to process intensification. The maximum CuO loading for the investigated materials is likely found in the range of [40, 50) wt%, subject to the constraints of Ca-Cu Looping relevant CuO/CaO ratios (≥ 2 [wt/wt]) and the performed TGA testing.

We analyze four general architectures for electrochemically mediated carbon dioxide capture systems, in each of which the electrophilicity of a redox active absorbent or absorbent blocking species is manipulated to influence the system's affinity for CO2. It is shown that the open circuit potentials of these architectures converge given the appropriate reference - namely a state in which no CO2 is present in the stream. The resulting difference between the open circuit potential of a stream and of that same stream lacking CO2 is referred to as the deviation potential. In the context of this deviation potential, four system process configurations are analyzed. The most efficient process configuration for all four electrochemical architectures is one that employs both a cathodic absorption taking place simultaneously with the reduction process and an anodic desorption that occurs along with the oxidation of the redox active species; decoupled electrochemical reactions and absorption/desorption steps incur significant energetic penalties.

Prescribed burning is a prominent source of PM2.5 in the southeastern U.S. An air quality forecasting system called HiRes2 currently serves most areas in the southeastern U.S. to forecast PM2.5 concentrations one day in advance, including the impact of forecast prescribed burning activity. The output prescribed fire impact from the HiRes2 forecasting system is the combined impact of all the fires in the domain. When there are many fires close to each other, it is difficult to distinguish the ones that are more likely to lead to air quality issues. A novel source apportionment method, Dispersive Apportionment of Source Impacts (DASI), has been developed and applied to split the combined prescribed fire impact obtained from a chemical transport model (CTM) by using simulated fields from a dispersion model. Comparisons of apportioned fire impacts with single burn impacts simulated directly by the CTM show that DASI works well with large and small fires that do not have too much interaction with other fires. Individual fire impacts obtained by splitting the combined fire impacts from CTMs could help local land and air quality managers to evaluate which burns should be allowed or restricted based on their individual impacts on air quality and public health in areas of concern.

Background Ambient air pollution and cigarette smoking are two significant risk factors for mortality; however, less is known about their interaction. Objectives We aimed to assess effect modification of cigarette smoking on the association between short-term exposure to air pollution and mortality in the Chinese Elderly Health Service Cohort in Hong Kong. Methods We included 16,290 Chinese elders aged 65 years or older who died between 1 July 1998 and 31 December 2011. Smoking history was collected through face-to-face interviews by registered nurses or doctors using a standardized structured questionnaire when they were recruited into the cohort. We used a time-stratified case-crossover approach to estimate the percent excess risk (ER%) of all-natural mortality per 10 μg/m3 increase in fine particulate matter (PM2.5), respirable particulate matter (PM10), and nitrogen dioxide (NO2) among current-, ex-, and never-smokers, and to estimate the additional percent excess risk (ΔER%) for current- and ex-smokers relative to never-smokers. We performed secondary analysis to assess whether the estimated additional risks varied by personal characteristics. Results There were a greater ER % associated with air pollutants among current- and ex-smokers relative to never-smokers. We found ΔER% per 10 μg/m3 increase in air pollutants was statistically significant for PM2.5 among ex-smokers [2.63% (95% CI: 0.39%, 4.88%) at 1 day prior to death (lag1)], and PM10 among current-smokers [2.21% (95% CI: 0.08%, 4.33%) at lag1] and ex-smokers [1.96% (95% CI: 0.26%, 3.65%) at lag1]. The increased risks associated with cigarette smoking were more pronounced among males, overweight or obese elders, elders with three or more comorbidities, or elders received primary or lower education. Conclusion Ever-smokers were more susceptible to excess mortality risk associated with daily air pollution, especially for males, overweight or obese elders, and those with poor health conditions or received lower educational attainment. Tobacco control can reduce the health burdens attributable to air pollution.

Modern dust plays essential roles in marine and climate processes, which bring continental material to the ocean and sensitivity in marine ecosystems. However, the atmospheric dust deposition process has rarely been studied in the South China Sea (SCS). Here, we present 51 atmospheric dust samples, collected along the SCS, to investigate the grain size distribution, depositional flux, and features revealed by scanning electron microscopy, combined with 5-day back trajectories to indicate the present-day dust deposition process for the first time. The grain size distribution and depositional flux of aerosol samples illustrate the seasonal trend, coarser particle and higher flux mass in winter than summer, reflected in average grain size (5.75 μm during winter and 3.62 μm from summer) and 1.4 times depositional flux in former than that in summer, both are related to the transport pathway and power of the East Asian monsoon. Modeled 5-day back trajectories of dust samples suggest a southwesterly transport pathway in summer and the Southeast Asian monsoon as a possible source of the dust loading, while the northeast winds drove the aeolian dust transport during the winter monsoon from the Asian continent. Meanwhile, westerly circulation conveys the fine particles (∼0.63 μm) as the stable terrigenous component into the SCS, deposited through the entire dust deposition process from the atmosphere and water to the surface sediment. Furthermore, the surface of quartz particles from atmospheric dust shows the unique structure in the aeolian environment as a reference to distinguish the different continental components in the sediments. This study provides new insights into the present-day dust deposition process in the SCS, significantly extending the current understanding of the relationship between atmospheric dust and the marginal sea.

Serious haze pollution (e.g., PM2.5, particulate matter with aerodynamic diameters less than 2.5 μm) and increased ground-level ozone are severe air quality issues in China. In Beijing-Tianjin-Hebei and the surrounding areas (denoted as BTH&SA), although recently the particulate matter pollution appeared to be under control due to stringent pollution mitigation measures, ozone pollution rebounded rapidly, especially during summers. Thus, the exploration of strategies for efficiently lowering both ground-level ozone and PM2.5 concentrations is urgently needed. In this study, we target on the precursors contributing to both ozone and PM2.5 formation (i.e., NOx and volatile organic compounds (VOCs)) and adopt a Combined Empirical Kinetics Modeling Approach (CEKMA) to synthetically evaluate the cost-effective mitigation strategies for air quality control. We find that over the BTH&SA region, the choice of mitigation strategy in the initial stage (e.g., within 20% reductions on NOx or VOCs emissions) is critical because NOx-focused strategies may exacerbate O3 pollution. In addition, equally reducing NOx and VOCs emissions may have the least benefit for air pollution improvement. From a long-term perspective, we suggest reducing VOCs emissions by ∼60% and NOx emissions by ∼20% in the first stage, thereby avoiding the potential increase in ambient O3. Then in the second stage, the remaining VOCs and NOx emissions should be phased out to reach a deep mitigation of PM2.5 and O3. With those steps, both PM2.5 and ozone can be mitigated efficiently over the BTH&SA region.

Interactions between the spatiotemporal distribution of pollutants and the structure of the atmospheric boundary layer were studied using data obtained by GPS (Global Positioning System) sounding balloons in an intensive observation period from December 2018 to January 2019 at the Dezhou experimental station in the North China Plain. Under haze weather conditions, negligible variation or a slight increase in temperature, higher relative humidity (RH) and lower wind speed with uncertain wind direction are common characteristics. The concentration distribution of particulate matter ≤2.5 μm (PM2.5) has a close relationship with the inversion layer, which contributes to the accumulation of PM2.5 in the lower atmosphere. The reduction of pollutants suspended in the upper layer during haze periods is closely related to low-level jets and intermittent turbulence. Higher RH values are also favourable for the formation of heavy haze, and the value of PM2.5 increases with an increase in humidity. During hazy days, the heat fluxes and turbulent kinetic energy (TKE) are much smaller than those during clear days. The values of the average maxima of net radiation, sensible heat flux, and latent heat flux are 154, 76, and 15 W/m2, respectively, and the value of TKE is approximately 0.67 m2/s2. The decrease in atmospheric boundary layer height (ABLH) is caused by weaker turbulent transfer during haze episodes. The ABLH is approximately 400 m during the daytime and 240 m at night. The power function relationship is shown by a negative correlation between the ABLH and surface PM2.5 concentration in the convective boundary layer.

With Tibetan Plateau higher than 4 km to the west, the location of Sichuan Basin is unique all around the world and provides a good platform to study air pollution in the urban agglomerations over the complex terrain. To fill in the blanks on vertical distributions of PM1 (the particles smaller than 1 μm) and carbonaceous aerosols within the basin, by means of high topographic relief, PM1 were off-line sampled during 20 January to 2 February 2018 at eight sites with increasing altitudes from the basin to southeastern margins of the Tibetan Plateau. The regional potential sources for each site were revealed by HYbrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The lowest carbonaceous aerosol levels occurred at Lixian, while the highest OC (organic carbon) (EC, elemental carbon) was at Hongyuan (the altitude of 3500 m) (Ande, a rural site) due to more primary emissions. The pollutants inside the basin can be transported the altitudes from 2 km to 3 km by vertical dispersion, but they cannot be dispersed to higher altitudes. The vertical stratification of the pollutants was obvious and easily formed “high-low-high” pattern from Sichuan Basin to southeastern Tibetan Plateau, especially during highly polluted episodes. The regional potential sources significantly varied as the increased altitudes. Regional pollution was significant inside the basin. The sources at the altitudes from 2 km to 3 km originated from southeastern margins of the Plateau and surrounding cities, while those at higher altitudes were transported from southeastern margins of the Plateau. The impact of basic meteorological variables (temperature, wind speed and vapor pressure) on carbonaceous aerosols was opposite between the basin and Plateau sites. This study was essential to understanding formation mechanisms of severe pollution episodes and thus to making control measures for the urban agglomerations inside the mountainous terrain.

A record-breaking episode of highly concentrated particulate matter (PM) with diameters ≤ 2.5 μm (PM2.5) and ≤10 μm (PM10) occurred in South Korea during the period January 11–15, 2019: the hourly PM2.5 (PM10) in Seoul was 188 μg m−3 (262 μg m−3) on January 14. At the Baengnyeong and Socheongcho stations, located in the Yellow Sea between China and Korea, the hourly PM2.5 concentration reached up to 155 μg m−3 and 119.8 μg m−3, respectively, 16−19-h prior to this episode. This and the fact that the maximum PM10 concentration at Baengnyeong was 199 μg m−3 indicated a westerly transport of air pollutants. Satellite observations and 72-h back trajectory analysis clearly indicate that air pollutants from China flowed into Korea via the westerlies. According to contribution analysis using particulate matter source apportionment technology in the Comprehensive Air-quality Model with extension, air pollutants originating from northeastern China including Hebei and Shandong provinces were largely linked to the present record-breaking high concentration event in Seoul. This study will elucidate the mechanism of transboundary transport of air pollutants and help East Asian countries cooperate on air quality management.

Oxy-combustion typically consists of burning coal with a combination of oxygen and a large amount of recycled flue gas (60–70%) to obtain a similar heat flux profile to that of air-fired systems. As the cost of electricity from first-generation oxy-combustion is relatively high, several new oxy-combustion process concepts have been proposed in recent years, and within these, the proposed amount of flue gas recycle (FGR) has varied from near-zero to 80%. To better understand the fundamental impact of FGR on the efficiency of oxy-combustion systems, a thermodynamic approach is used herein. Second-law losses associated with flue gas recycle are found to be significant and highly non-linear with recycle ratio. A difference in efficiency of up to 10 %-points can be realized, with a maximum efficiency occurring at zero FGR. Furthermore, due to the non-linear relation of plant efficiency with recycle ratio, processes with low recycle (< ∼33%) experience only a small efficiency penalty, compared to no recycle. Additionally, fan power requirements also scale non-linearly with recycle ratio, resulting in significantly lower FGR fan power requirements for low recycle processes as well. These results suggest that for systems employing cold recycle, FGR should be kept below 33%. Due to the recent interest in developing pressurized oxy-combustion (POC) for efficient, low-cost carbon capture, the impact of flue gas recycle on POC systems is also presented, with a discussion on the valorization strategies for the latent heat of flue gas moisture recovery.

A 30-kWth moving-bed chemical looping system has been developed at the Industrial Technology Research Institute of Taiwan. In this system, methane is supplied as a fuel to a reducer, and steam enters an oxidizer to produce hydrogen under ambient pressure. An iron-based oxygen carrier is used and pneumatically transported in the system. In this study, a hydrogen production test was performed on the system, while the methane flow rate was 40 L/min according to the capacity requirement of a 30-kWth system, and the oxygen carrier circulation rate was 2100 g/min for 40-wt% Fe2O3 content. The concentration of carbon dioxide produced in the reducer was 95 %, and the concentration of hydrogen produced in the oxidizer reached 90 %. Partially oxidized oxygen carriers then reacted with air in the combustor, leading to a temperature increase of approximately 120°C. The oxygen carriers in the reducer were reduced to Fe, and the integrating conversion rate was 61.5 %. In the oxidizer, the oxygen carrier contained Fe3O4, and the integrated conversion rate was 22.2 %. 75 % of the oxygen carriers in the combustor exhibited a conversion rate of 5.3 %, indicating a nearly complete oxidation state. By conducting the hydrogen production test while effectively removing small particles of worn oxygen carriers from the system, the moving-bed chemical looping system was evaluated for the circulation and reaction of oxygen carriers. The system development experience will be used for system scale-up design.

It has been suggested that non-aqueous solvents containing amines may provide alternatives to aqueous alkanolamine solvents due to the potentially lower energy requirement for the regeneration of the amine. This paper presents experimental data on the solubility of CO2 and heat of absorption in the organic solvent N-methyl-2-pyrrolidone (NMP) and mixtures of 2-amino-2-methyl-1-propanol (AMP) in NMP. The solubility of CO2 was found to be very low at temperatures above 70 °C, the temperature at which the AMP/NMP solvent can be regenerated. The solubility of CO2 was higher at lower temperatures, particularly when precipitation of the AMP carbamate occurred. The heat of absorption in the AMP/NMP solvent decreased with increasing temperature, from approximately 90 kJ/mol CO2 at 40 °C and low loadings, to approximately 40 kJ/mol CO2 and 65 kJ/mol CO2, at 88 °C and low loadings, for the 15 wt% and 25 wt% AMP in NMP solvents, respectively. The results obtained complement our previous studies, together providing comprehensive data on the vapor–liquid equilibrium and the heat of absorption of CO2, which can be used to model the system.

The aerosol change over the Tibetan Plateau (TP) is poorly understood due to the scarcity of aerosol measurements over the TP. The aerosol optical properties were measured with a CE-318 sun photometer from January to December in 2017 at the Litang station (30.00°N, 100.16°E, 3950.5 m a.s.l.) over the eastern edge of the TP to characterize the variations in the aerosol optical properties and assess the applicability of MODIS AOD products at the eastern edge of TP. The analyses show that the annual mean aerosol optical depth at 440 nm (AOD440nm) is 0.08 ± 0.03. The mean annual Angström exponent between 440 and 870 nm (AE440–870nm) is 0.72 ± 0.23. The monthly-averaged AOD440nm exhibits a maximum (0.11 ± 0.04) in July and minimum (0.05 ± 0.02) in January, while the monthly mean AE440–870nm shows a maximum (1.08 ± 0.19) in July and minimum (0.48 ± 0.32) in February. The findings based on measured AOD440nm and AE440–870nm indicate low AOD, dominated by coarse particles in winter and fine particles in summer over the eastern TP edge. Three datasets of MODIS AOD products with 3 km spatial resolution as well as with 10 km spatial resolution based on Dark Target (DT) and Deep Blue (DB) algorithms are validated using the ground-based measurements over the eastern edge of the TP. Although the validations show a low accuracy of MODIS AOD products of the three datasets over this TP region, the MODIS AOD products based on the DB algorithm with 10 km resolution could be used in the atmospheric environment over the eastern edge of the TP based on the best match between AOD data and ground-based measurements, the lowest retrieval error, and the largest percentage falling within the expected error envelope.

Pollution weather may cause serious damages to human life and property. Meteorological conditions like large-scale circulation can affect the formation and dissipation of pollution weather. We apply the hierarchical clustering method to classify circulation patterns based on the National Centers for Environmental Prediction (NCEP) Final Operational Global Analysis (FNL) sea level pressure (SLP) daily data and investigate their features during the formation and dissipation process of the defined 31 continuous pollution weather (CPW) cases in the Sichuan Basin using the meteorological data from 104 surface observation stations during 2007–2017. We find that the Sichuan Basin during the formation process is controlled by the large scale high-pressure circulation at sea level, and the SLP can be divided into high-pressure front type FC1 (32%) with the high pressure located in the west of the Basin, weak high-pressure type FC2 (35%) with the weak high pressure located in the Basin, and uniform pressure field type FC3 (33%) with the near homogeneous pressure distributed in the Basin. The Sichuan Basin during the dissipation process is dominated by the low-pressure circulation at sea level, and the SLP can be classified as low-pressure type DC1 (35%) with the low pressure centralize in the Basin, low-pressure front type DC2 (38%) with the low pressure center in the west of the Basin, and low-pressure bottom type DC3 (27%) with the low pressure in the north of the Basin. Besides, the wind, relative humidity, geopotential height and temperature data are used to explore the formation and dissipation mechanisms of the CPW. The wind speed and temperature are lower during the formation phase of the CPW compared to those from the dissipation phase. Furthermore, we estimate the effects of the CPW on pollutants based on the air quality index and Particulate Matter (PM10 and PM2.5) concentration from environmental protection monitoring data during 2013–2017. The FC2 type shows the strongest enhancement of pollutants (36%), and the DC3 circumstance generates the most efficient scavenging mechanism to dispel pollutants (−57%).

Ozone is one of remaining air quality issues in Japan. Effective strategies are required to reduce ozone at the ground level. Regional chemical transport models are useful in investigating relationships between precursor emissions and ambient concentrations of secondary pollutants including ozone. Model performance on ozone concentrations over urban areas in Japan were thoroughly evaluated in model inter-comparisons conducted in Japan's study for reference air quality modeling (J-STREAM). Specifically, 33 models with different configurations including the Community Multiscale Air Quality Modeling System (CMAQ), the Comprehensive Air Quality Model with Extensions (CAMx), and the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) participated. They realized inter-comparisons with an unprecedented number of different model configurations. All the participating models overestimated ozone concentrations by 22 ± 4.6 ppb over urban areas in Japan during the summer. Spatial and temporal variations in model performance suggest the influence of background ozone concentrations. Based on differences in the participating model configurations, halogen chemistry and deposition, dry deposition velocity, precursor emissions in other countries, and vertical transport were identified as the key factors influencing simulated background ozone concentrations. Specific sensitivity analyses were conducted to evaluate the effects of the key influencing factors. Halogen chemistry and deposition implemented in recent versions of CMAQ caused more than 10 ppb reduction of simulated ozone over the ocean surrounding Japan, while the original dry deposition schemes used in CAMx and WRF-Chem, without any effect of halogen, can also cause larger dry deposition. Horizontal and downward transport of ozone kept in a residual layer over the continent can spread the effect of precursor emissions in other countries to downwind regions, including Japan. Differences in vertical transport can alter the spatial extent of their effects. It is essential to improve the influence of the aforementioned key factors to realize better model performance on ozone concentrations over urban areas, not only in Japan, but all over the world.

Open biomass burning is one of the largest sources of aerosols and reactive trace gases into the atmosphere, having a significant effect on earth's radiative budget and air quality. Biomass burning degrades air quality by increasing both particulate matter and ozone levels. Unlike aerosols, ozone is not directly emitted in fires but it is frequently formed in ageing plumes. This is not surprising, as many of the reactive trace gases emitted in biomass burning including nitrogen oxides, carbon monoxide and volatile organic compounds, act as precursors for ozone formation. Geographically, Africa is the most significant source region of biomass burning emissions. Here, we report rapid ozone formation in daytime savanna and grassland fire plumes observed in South Africa. We observed higher ozone production in more flaming cases for plumes fresher than 1.5h. However, in plumes aged >1.5h combustion characteristics have no effect, but ozone production is positively correlated with nitrogen oxides. Furthermore, the plumes with highest ozone production also had the strongest secondary aerosol formation during plume ageing. Additionally, we report emission factors of nitric oxide and sulphur dioxide for southern African savanna and grassland fires. SO2 emission factor was on average 1.1 g kg−1, which is two to three times higher than previous observations for savanna and grassland. On the other hand, the average NO emission factor (2.6 g kg−1) agrees well with previous observations.

Fine particulate matter (PM2.5) concentration that exceeds standards is causing poor air quality in most Chinese cities. Meteorological conditions are an important factor affecting PM2.5 concentration, but few quantitative studies have been conducted on the effects of long-term and large-scale changes in meteorological factors on PM2.5 pollution. In this study, a Weather Research and Forecasting/Community Multiscale Air Quality (WRF/CMAQ) modeling system was applied to study the spatial and temporal distributions of the impact of meteorological conditions on PM2.5 pollution in China from 2000 to 2017. During the study period, Me-PM2.5 decreased in general (P = 0.0018) in nationwide, and showed significant spatiotemporal variations. There was an overall increasing trend for Beijing, Fujian, Shaanxi, Gansu, and Qinghai provinces (P < 0.05) as the meteorological conditions deteriorated, and there was an overall negative trend for nine provinces (P < 0.05) which indicated meteorological conditions were causing a decrease in concentrations. Substantial differences in the impact of meteorological changes on PM2.5 pollution were observed across the provinces, with FMe-PM2.5 (fluctuating range of Me-PM2.5) between 9.3% and 55.1%. In addition, the best, typical, and worst meteorological years were selected based on Me-PM2.5; these should be considered when setting air quality goals and pollution control plans.

This experimental study explored the impacts of some codissolved inorganic ions (in particular, sulfate, nitrate and chloride) on the photo-bleaching kinetics of the aqueous solutions of brown carbon (BrC) extracted from rice-straw smoldering aerosol. All the aqueous BrC solutions showed two distinct phases of decreasing mass absorption coefficient (MAC) with irradiation time, where the first phase (0–1h) was 2.4–5.3 times faster than the second phase (1–3h). Interestingly, the photo-bleaching process was slowed down for both phases when SO42− (0–1h: 0.196±0.02 h−1; 1–3h: 0.045±0.01 h−1), NO3− (0–1h: 0.158±0.004 h−1; 1–3h: 0.066±0.007 h−1) and Cl− (0–1h: 0.169±0.007 h−1; 1–3h: 0.032±0.006 h−1) salt solutions were added separately to the BrC extracts (0–1h: 0.27±0.04 h−1; 1–3h: 0.067±0.01 h−1). Alternatively, the corresponding lifetimes of the light-absorbing organic species were enhanced in the salt-added BrC solutions. In addition, the magnitudes of the fluorescence quantum yields were measured to be of the order of 10−3−10−2, implying that most of the absorbed solar energy would convert into heat rather than fluorescing back into the atmosphere. The findings of this study are suggestive of possible increase in heating of BrC containing atmospheric aqueous bodies like cloud-water, resulting in water evaporation and hence reduced precipitation (semi-direct effect).

A road simulator was used to generate wear particles from the interaction between two tyre brands and a composite pavement. Particle size distributions were monitored using a scanning mobility particle sizer and an aerosol particle sizer. Continuous measurements of particle mass concentrations were also made. Collection of inhalable particles (PM10) was conducted using a high-volume sampler equipped with quartz filters, which were then analysed for organic and elemental carbon, organic constituents and elemental composition. Tyre fragments chopped into tiny chips were also subjected to detailed organic and elemental speciation. The number concentration was dominated by particles <0.5 μm, whereas most of the mass was found in particles >0.5 μm. The emission factor from wear between pavements and tyres was of the order of 2 mg km−1 veh−1. Organic carbon represented about 10% of the PM10 mass, encompassing multiple aliphatic compounds (n-alkanes, alkenes, hopanes, and steranes), PAHs, thiazols, n-alkanols, polyols, some fragrant compounds, sugars, triterpenoids, sterols, phenolic constituents, phthalate plasticisers and several types of acids, among others. The relationship between airborne particulate organic constituents and organic matter in tyre debris is discussed. The detection of compounds that have been extensively used as biomass burning tracers (e.g. retene, dehydroabietic acid and levoglucosan) in both the shredded tiny tyre chips and the wear particles from the interaction between tyres and pavement puts into question their uniqueness as markers of wood combustion. Trace and major elements accounted for about 5% of the mass of the tyre fragments but represented 15–18% of the PM10 from wear, denoting the contribution of mineral elements from the pavement. Sulphur and zinc were abundant constituents in all samples.

Previous research has shown the significant transboundary air pollution (TAP) in China. Despite its adverse environmental and human health impacts, the characteristics and mechanisms of TAP have yet to be fully understood. This study comprehensively analyzed intensive ground and upper levels measurements along with the atmospheric modeling approach to determine the driving meteorological conditions to the formation and evolution of a persistent severe PM2.5 pollution episode in Central-East China (CEC, 112°E −118°E, 30°N −34°N) starting from 18:00 on Dec. 3 to 18:00 on Dec. 5, 2017, which had obvious characteristics of TAP and explosive increases in PM2.5 concentration. We assessed and quantified contributions of local and nonlocal emissions to PM2.5 in the region and different cities during the episode and determined the altitude level at which TAP occurred. Results show that PM2.5 concentration in most cities in CEC region experienced two major increases: the first increase was due to the change in wind direction from south to north, transporting pollutants from north China to CEC; the second increase was driven by several important meteorological factors, including warm/cold advection at different altitudes, large-scale subsidence, and radiative cooling, jointly resulting in a deep (reaching around 800 m) and strong elevated temperature inversion with a significant reduction in mixing layer thickness and thus causing a rapid increase in PM2.5 concentration in CEC region. On average, TAP accounted for 42% of total PM2.5 concentration in the region during the event, in which the TAP impact varied by cities, ranging from ∼26% to ∼70%. Our findings demonstrate the synergetic effect of TAP and large-scale subsidence, providing a critical reference for air pollution forecast and assessment in the eastern China.

Precipitation chemistry and atmospheric nitrogen (N) deposition are of great concern worldwide due to their close relationships with air quality and impacts on ecosystems. However, evaluation of the chemical composition of precipitation and N deposition flux in rural areas of Beijing has received little attention to date. This paper presents the chemical constituents, possible sources and wet deposition fluxes of water-soluble ions (NH4+, NO3−, SO42−, Cl−, Na+, K+, Ca2+, Mg2+) in precipitation samples collected during 2017–2018 at a rural site located at northwest of Beijing city; meanwhile, dry deposition of reactive N species (gaseous ammonia, nitrogen dioxide, nitric acid, and particulate (p) NH4+ and NO3−) were also quantified. During this 2-year period, the volume-weighted mean (VWM) pH of precipitation was 6.73, and all samples had pH values above 6.0. The VWM electric conductivity of precipitation and the mean sum of all measured ions was 43.8 μS cm−1 and 591.9 μeq L−1, respectively, indicating a significant impact of atmospheric pollution. Ca2+ and NH4+ were the dominant neutralizing species for precipitation acidity. Positive matrix factorization analysis further confirmed five sources for water-soluble ions, including sea salt aging, secondary formation, agriculture, crust, and biomass burning. The annual mean wet N deposition was 4.6, 3.4 and 8.0 kg N ha−1 yr−1 for NH4+, NO3− and total inorganic N, respectively. The total dry N deposition was dominated by gaseous ammonia (11.5 kg N ha−1 yr−1). The total N deposition (wet plus dry) was 27.7 kg N ha−1 yr−1, where dry deposition contributed to 75% and wet deposition 25% of the total. The simulations from the GEOS-Chem model indicate that agricultural (fertilizer use and livestock) and nonagricultural sources (industry, power plant, and transportation) are both important contributors to total N deposition. These results could be useful in evaluating/developing emission control policies to protect the eco-environment in Beijing.

In this study, we use the level-1.5 and level-2.0 aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) Version 3 dataset at 12 sites in China to evaluate the MODIS Collection 6.1 (C6.1) AOD products retrieved using three distinct algorithms: Dark Target (DT), Deep Blue (DB), and DTB merged from DT and DB from Terra and Aqua. The performance of the three algorithms is evaluated. Based on these evaluations, a simple and efficient AOD retrieval algorithm at a high spatial resolution of 1.0 km for China is proposed. AODs at this spatial resolution over China are then retrieved using the methods of DT and DB, respectively. The evaluation results showed that: (1) there is little difference in the AOD products derived from Terra and Aqua. The differences in the determination coefficient (R2) between the two platforms at most sites are less than 0.05. (2) There are relatively large differences in AODs between the AERONET level-1.5 dataset and MODIS dataset while these differences are mostly filtered out by the quality assurance process of the AERONET level-2.0 dataset. The statistical tests indicate that the MODIS DTB AOD product is generally better than those from the other two algorithms. Using the new algorithm developed in this study, the AODs at a high spatial resolution of 1 km in the whole of China are determined and the results are compared with the MODIS DTB product. The results show that the AODs determined using the new method agree reasonably well with those of the MODIS DTB dataset though the new results have slightly negative biases in the wintertime. However, these negative biases may not be a negative sign due to the fact that the MODIS AODs are subject to a positive bias relative to the AERONET AODs.

BioSampler is now being widely used for bioaerosol sampling. However, the sampling efficiency in wide size range especially for nanoparticles as well as the size-dependent retention efficiency have not been well evaluated until now. Through literature review, theoretic analysis and experiments, this paper reviews the sampling process, collection mechanism and sampling performance of commercial BioSampler including pressure drop as a function of sampling flow rate, the mass loss rate and temperature of the collection fluid as a function of sampling time, the variation of retention efficiency with time, and the sampling efficiency in wide size range from nanometers to microns. The effects of low pressure and high relative humidity on determination of sampling efficiency in literature were carefully analyzed. To compensate the collection fluid loss and extract the insoluble/dissolved sample for further analysis, Continuous-Extraction BioSampler (CEBS) is proposed. The retention efficiency for particles of different sizes as well as the collection efficiency were determined and found to be identical with commercial BioSampler when no steam was introduced into CEBS. Finally, the combination uses of CEBS and Inductively-Coupled-Plasma Mass Spectrometer (ICP-MS) was developed. Exponentially Modified Gaussian (EMG) Model was derived and verified to describe the temporal concentration of the dissolved component originating from individual soluble droplet. Using internal standard calibration method and EMG fitting of signal curve, the target element amount in individual droplet could be determined accurately. For continuously-collected soluble droplet with duration of minutes, the observed signal curve can be described by EMG model and the fitted value of area varies linearly with the sample amount introduced. This paper not only provides comprehensive performance evaluation of commercial BioSampler, but also demonstrates that the proposed CEBS-ICPMS is capable of monitoring environmental coarse aerosol with time resolution of ∼17 min.

The recent AVHRR aerosol products expended from MODIS Deep Blue (DB) algorithm provide an unprecedented long-term data record over land that dates back to 1980s. Unlike previous studies focused on performance of AVHRR retrievals, here we present a critical view into the influence of retrieval frequency on consistency of AVHRR Aerosol Optical Depth (AOD) with other satellite DB products, and application potential in characterizing the dramatic aerosol loading in China. Despite the good consistency of collocated AVHRR, SeaWiFS, and MODIS DB AOD, their different retrieval frequency leads to distinct distribution of annual or seasonal AOD. In particular, the over-strict cloud screening of AVHRR with fewer bands tends to filter out high-AOD and clean bright surface, with the overall AOD frequency only half of MODIS's. Retrieval frequency and selection criterion of AOD quality can determine representativity and consistency of conventional averaged satellite AOD, uncertainties of which should be considered according to specific application purpose. The time series variation of AVHRR AOD shows that early 1990s is a key time point when frequent haze pollution appears and increases in eastern China. By contrast, aerosol loading in 1995–1999 has reached similar level as in 2000s with notable hotspot of high-AOD (∼0.8–0.9) and slight changes. Our results shows that full record of AVHRR aerosol products with corresponding improvement can greatly renew the understanding of aerosols in China.

This work performed a systematic investigation on the aqueous hydroxyl radical (OH) - induced photochemical oxidation of three modestly-soluble precursors from biomass combustion including 4-methylsyringol (DMP), eugenol (Eug), and 2,4,6-trimethylphenol (TRMP) under both simulated sunlight and ultraviolet (UV) light irradiations. An Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was used to monitor the bulk chemical and elemental compositions of aqueous secondary organic aerosol (aqSOA) formed. AqSOA mass yields varied in ranges of 80–190% and 0–200% under sunlight and UV light conditions, respectively. AqSOA oxygen-to-carbon (O/C) ratio and carbon oxidation state increased steadily under sunlight + OH condition, but increased then decreased under UV + OH condition. Organic acids including malic acid, glycolic acid, formic acid and oxalic acid were formed, and their total accounted for ∼12% of SOA mass. The UV–vis spectral change suggested formation of light-absorbing organics. Reaction pathways were proposed by combining gas chromatography-mass spectrometry (GC-MS) and SP-AMS results. Under sunlight + OH condition, oligomerization, functionalization, and fragmentation processes all involved in aqSOA evolution, with more contribution from functionalization via hydroxylation and oxygenation reactions. Reaction mechanism of UV + OH oxidation was initially dominated by functionalization then by fragmentation, indicating by the decrease of total organic carbon (TOC) contents, formation of small organic acids and low-molecular-weight products. Our work highlight that combination of SP-AMS with GC-MS is a powerful method for laboratory investigation of aqueous-phase reactions.

An almost continuous 13,000 h long-term testing under real operating conditions was conducted at the post combustion capture pilot plant in the Niederaussem lignite-fired power plant, with a 30 wt% aqueous monoethanolamine (MEA) solvent solution. The capture plant at Niederaussem shows lower solvent consumption and emissions in comparison to other testing facilities, which are also part of the ALIGN-CCUS project (capture plant at Technology Centre Mongstad (NOR), pilot rig at Tiller (NOR), PACT facilities at Sheffield (UK)). One of the key activities of the ALIGN-CCUS project is to investigate how the time-dependent degradation products and trace components that might act as catalysts for degradation develop over long-term operation, as well as which countermeasures against degradation could be applied. Particularly, it was tested if critical threshold values for the iron ion concentration from literature could be confirmed. Therefore, partial solvent inventory replacement by “Bleed and Feed” and solvent reclaiming based on ion exchange were applied. Dedicated test campaigns on the dynamic behaviour of the capture plant were also carried out and MEA emissions under transient conditions were investigated. Important results are: (i) the confirmation of the non-linear degradation behaviour of MEA; (ii) a different degradation behaviour of MEA in comparison to shorter testing campaigns at other pilot plants regarding the main degradation product acetate; (iii) no critical threshold concentration of iron in the solvent was detected; (iv) very low emissions of MEA < 3 mg/m³ and <10 mg/m³ even under transient operating conditions could be reached; and (v) no aerosol formation occurred.

Increasing trends in summer-time temperature maxima (Tmax) over India, show consequent increases in the intensity and frequency of heatwave events in recent years. Heat waves have been largely attributed to large-scale meteorological blocking, characterized by subsidence, clear skies and low soil moisture, in observational studies, or greenhouse gas enhancements in model studies. While radiative effects of absorbing aerosols are acknowledged, the association of absorbing aerosols with temperature maxima has not been investigated comprehensively. In the current study, statistical tools (such as correlation and Granger causality) were applied to long term (1979–2013) satellite and ground based observations to evaluate influence of absorbing aerosols on Tmax in north-west India (Tmax-NW). Regional absorbing aerosol index (AAI) in the north-west (AAI-NW) and central-India (AAI-CI) showed co-variability with Tmax-NW, implying connections to both local and non-local absorbing aerosols. The effects persisted on seasonal and heatwave event scales, becoming stronger on heatwave days with presence of enhanced AAI loadings. Causal effects of AAI-NW and AAI-CI were identified on Tmax-NW with a lag of 1–11 days, across multiple years, thereby establishing the influence of absorbing aerosols on heatwave events. The absence of confounding effects of surface pressure on these links suggests that, even during heat wave events linked to atmospheric blocking, absorbing aerosols can further enhance temperature maxima and related heat-wave intensity.

Observations from the Ozone Monitoring Instrument (OMI), onboard the NASA's Earth Observing System (EOS) Aura satellite, reveal a large SO2 “hotspot” over Morbi, Gujarat, India, while the available emissions inventories do not report any major sources in this region. There are no industries that are typically associated with the elevated SO2 such as large power plants, smelters, or oil refineries in the Morbi region. Our analysis shows that the elevated SO2 source is attributed to the ceramic industries in an area of ∼7 × 7 km2 near the city. OMI-estimated SO2 emissions from the Morbi ceramic industries have been near or above 100 kt y−1 since 2009, which are similar to emission levels from larger Indian oil refineries (such as Essar and Jamnagar) and power stations (such as Mundra Thermal Power Station and Ultra Mega Power Plant) located in Gujarat, India. According to OMI measurements, the SO2 emissions from the Morbi ceramic industries are presently five times higher than they were in 2005. This study demonstrates that in the absence of any other information about SO2 emissions from the ceramic industry, these satellite-based estimates can fill the gap in emission inventories in a timely fashion.

Land use regression (LUR) modeling has been applied to study the spatiotemporal patterns of air pollution, which when combined with human space-time activity, is important in understanding the health effects of air pollution. However, most of these studies focus either on the temporal or the spatial domain and do not consider the variability in both space and time. A temporally aggregated model does not reflect the temporal variability caused by traffic and atmospheric conditions and leads to inaccurate estimation of personal exposure. Besides, most studies focus on a single air pollutant (e.g., O3, NO2, or NO). These pollutants have a strong interaction due to photochemical processes. For studying relations between spatial and temporal patterns in these pollutants it is preferable to use a uniform data source and modelling approach which makes comparison of pollution surfaces between pollutants more reliable as they are produced with the same methodology. We developed temporal land use regression models of O3, NO2 and NO to study the co-variability of these pollutants and the relations with typical weather conditions over the year. We use hourly concentrations from the measurement network of the Dutch National Institute for Public Health and the Environment and aggregate them by hour, for weekday/weekend and month, and fit a regression model for each hour of the day. 70 candidate predictors that are known to have a strong relationship with combustion-related emissions are evaluated in the LUR modelling process. For all pollutants, the optimal LUR was identified with 4 predictors and the temporal variability was determined by the explained variance of each temporal model. Our temporal models for O3, NO2, and NO strongly reflect the photochemical processes in space and time. O3 shows a high background value throughout the day and only dips in the (close) vicinity of roads. The diminishing rate is affected by traffic intensity. The NO2 LUR is validated against NO2 measurements from the Traffic-Related Air pollution and Children's respiratory HEalth and Allergies (TRACHEA) study, resulting in an R2 of 0.61.

Mitigation of CO2 emissions in the industrial sector is one of the main climate challenges for the coming decades. This work, carried out within the STEPWISE H2020 project, performs a preliminary techno-economic assessment of the Sorption Enhanced Water Gas Shift (SEWGS) technology when integrated into the iron and steel plant to mitigate CO2 emissions. The SEWGS separates the CO2 from the iron and steel off-gases with residual energy content (i.e. Blast Furnace Gas, Basic Oxygen Furnace Gas and Coke Oven Gas) and the produced H2 is sent to the power generation section to produce the electricity required by the steel plant, while the CO2 is compressed and transported for storage. Detailed mass and energy balances are performed together with a SEWGS cost estimation to assess the energy penalty and additional costs related to CO2 capture. Results demonstrates the potential of SEWGS to capture over 80 % of CO2 in the off-gases, which results in entire plant CO2 emission reduction of 40 % with a Specific Energy Consumptions for CO2 Avoided (SPECCA) around 1.9 MJ/kgCO2. SEWGS outperforms a commercial amine scrubbing technology which has a SPECCA of 2.5 MJ/kgCO2 and only 20 % of CO2 avoided. The cost of CO2 avoided calculated on the basis of a fully integrated steel plant is around 33 €/tCO2 compared to 38 €/tCO2 of the amine technology.

Inhalable particulate matter (size <2.5 μm: PM2.5) inside commuting and tourist buses moving through the city of Barcelona, Spain, was chemically analysed. The analyses show PM dominated by organic carbon (mostly 10–20 μg/m3) and elemental carbon (mostly 3–6 μg/m3; OC/EC = 3.4), followed by SO42, Fe, Ca, K, Al2O3, Mg, and Na, with calculated mineral content being around one third that of total carbon. Elemental carbon levels are higher inside diesel buses than those powered by natural gas or electricity, and higher in the upper floor of open-top double decker tourist buses than in the lower floor. Overall, major element concentrations inside the buses are typically 2–8 times higher than 24 h-averaged urban background levels, although some metallic trace elements, notably Cu and Sb, are exceptionally enriched due to the presence of brake particles, especially on routes involving higher gradients and therefore more brake use. In contrast, Cu and Sb concentrations in electric buses are unexceptional, presumably because these buses rely more on regenerative braking and are hermetically sealed when moving. Seasonal differences reveal PM to be more mineral in winter (Al2O3 1.3 μg/m3 vs. summer average of 0.3 μg/m3), with summer enrichment in Na, Mg, P, V, Ni and SO42− being attributed to marine aerosols contaminated by port emissions. Source apportionment calculations identify 6 main factors: road dust resuspension, metalliferous (brake wear and metallurgy), local urban dust, secondary sulphate and shipping (6%), vehicle exhaust (19%), and an indoor source (46%) interpreted as likely related to the textile fibres and skin flakes of bus occupants. Volatile Organic Compounds measured inside all buses except one were dominated by 2-Methylpentane (14–36 μg/m3), Toluene (10–30 μg/m3), Xylene isomers (10–28 μg/m3, with m- » o- > p-Xylene) and n-Pentane (5–15 μg/m3). ƩBTEX concentrations were <70 μg/m3, with Toluene being commonest, followed by m-Xylene, with p-Xylene, o-Xylene and Ethylbenzene each below 7 μg/m3 and Benzene concentrations always less than the EU limit value of 5 μg/m3. The VOCs mixture is similar to that recently reported from inside Barcelona taxis (although inside the larger volume bus VOC concentrations are lower than in the taxis) and is interpreted as providing a chemical fingerprint characterising traffic-contaminated ambient air in the city road environment. The notable exception to the VOC content was a brand new hybrid diesel bus still offgassing volatiles to such an extent that Ʃ(alkane + alkene + aromatic) indoor concentrations exceeded 800 μg/m3, with ƩBTEX ten times higher than normal.

Coupled fluid-flow and geomechanical analysis of caprock integrity has gained a lot of attention among scientists and researchers investigating the long-term performance of geologic carbon storage systems. Reactivation of pre-existing fractures within the caprock or re-opening of faults can create permeable pathways which can influence the seal integrity. Stability of the caprock during and after injection of super-critical CO2, and the impact of pre-existing fractures in the presence or absence of one or multiple faults have been investigated in this study. The impact of the wellbore orientation and the injection rate are among other key factors in understanding the structural trapping mechanisms within such geological formations. In this study, we numerically investigated the impact of each of these factors. This study revealed the interplay between joints and faults and how different leakage pathways are formed and under which scenario they play a dominant role in terms of CO2 leakage. This study also highlights the role of one versus multiple faults in the domain and the importance of the fault hydrological property in forming leakage pathway.

Simultaneous field measurements of ozone (O3) and its precursors were conducted at an urban site (Zi Yang, ZY) and a suburban site (Huang Pi, HP) in August 2018 in Wuhan, China. The observation results revealed that the mean levels of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO) and non-methane hydrocarbons (NMHCs) were higher at ZY than those detected at HP, while the opposite trend was observed for O3 levels. Compared to non-O3 episode days, higher levels of O3 and its precursors (i.e. NMHCs, NO and CO) were observed on O3 episode days at both ZY and HP. A chemical box model was used to investigate the O3 photochemistry on O3 episode days and non-O3 episode days at ZY and HP, and the O3 production was found to be dominated by the reaction of HO2 + NO at the two sites. In terms of O3 destruction, OH + NO2 was the major contributor at ZY, while the highest contribution at HP was from the reaction of O(1D) + H2O. The net O3 production rates increased significantly from non-O3 episode days to O3 episode days at both ZY and HP, indicating increased O3 accumulation on O3 episode days. In addition, the model simulation indicated that O3 formation was controlled by volatile organic compounds (VOCs) at ZY, whereas O3 formation was cooperative controlled by VOCs and NO at HP. Overall, these findings can provide valuable information on formulating and implementing O3 control strategies in urban and suburban areas in China.

Recently, NASA's Multiangle Imaging SpectroRadiometer (MISR) team released the Version 23 (V23) 4.4-km Aerosol Optical Depth (AOD) product, which has better spatial resolution than V22 at 17.6 km. However, its quality has not been validated in China. Here, V23 products for different spatiotemporal domains are obtained for validation against Aerosol Robotic NETwork (AERONET) AOD measurements for 29 sites from 2008 to 2017. Based on the national daily mean, V23 AOD yields a correlation coefficient (R) of 0.902 with AERONET; 59.45% of retrievals fall within the expected error (=EE; ±0.05 or ±0.2×AOD). A mean error (ME) of −0.0605 with 24.11% of retrievals falling below the EE indicates that MISR data are still underestimated at high AODs. The sample numbers and accuracies of spatially averaged 17.6-km and 50-km data are greatly improved relative to V22. The seasonal mean of V23 retrievals = EE in fall and winter are highest, followed by those in summer and spring; the validation results at 17.6 km are generally better than those at 50 km. By region, V23 retrievals = EE in the Beijing–Tianjin–Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions are 68.87%, 61.43%, and 73.13% respectively, while that of Taiwan is below 60% (55.75%). No V22 records exist in PRD, and V23 products over other regions in all seasons perform well; V22 retrievals in summer are also recommended. Compared with Terra/MODIS 3-km AOD in 2016, the V23 product has a slightly higher R value (0.925) with AERONET than MODIS (0.909). The MISR AOD bias is lower, and MODIS AOD is overestimated relative to the ground truth; both present consistent seasonality characteristics (spring > winter > summer > autumn), with the maximum in March and minimum in August. To investigate the spatiotemporal characteristics over long-term AOD, MISR V23 4.4-km AOD can be used in combination with other observation data.

Arctic aerosol-climate interactions are controlled by multiple factors including sources, processes and removal mechanisms of particles. The Arctic is mostly ocean, surrounded by mostly land, and our understanding of Arctic aerosol processes is incomplete due to scarce measurements carried out in sea ice regions. In particular, it is currently not known if these particular regions are sources of aerosols of primary or secondary origin. We present new results from ship-based measurements illustrating that marine new particle production and growth events occur in open ocean and melting sea ice regions in the Chukchi and East Siberian Seas. We report two new particle formation events during which a recently formed nucleation mode (<15 nm diameter) is detected and is observed to slowly grow into an Aitken mode (0.1–3.8 nm h−1). Our results suggest that new particle formation occurs in the marine boundary layer contributing to the Arctic aerosol population in the study region for the first time studied and herein reported.

Haze is a phenomenon caused by suspension of fine particulate matters in the air that leads to impaired visibility. In the meteorological practice, a haze day is determined using the observation of visibility and relative humidity, after screening the special weather days of rain, snow, dust, fog and others. While in the environmental monitoring practice and relevant studies, the term haze is also commonly used and a haze day is determined using the reading of particulate matters (PM). This has actually caused two different kinds of haze day, i.e., meteorological haze days (MHDs) and environmental haze days (EHDs), each with different definition and standard. Our analysis shows that although MHDs and EHDs overlap, the proportion of MHDs in EHDS is 43% in Beijing, 44% in Shanghai, and 46% in Guangzhou. Meanwhile, there are large percentage of MHDs that are not EHDs, about 21% in Beijing, 42% in Shanghai and 67% in Guangzhou. Therefore, an explicit distinction of the two haze definitions should be made in the study of PM pollution variation and cause in China, which will have important applications in addressing air pollution, formulating environmental policy, and dealing with health effect of haze in China.

CO2 leakage through damaged wellbore cement sheaths is a major risk of geologic CO2 storage (GCS), as conventional wellbore cement is brittle and can be damaged due to acid attack and downhole stresses during CO2 injection. Here we examine a novel fiber-reinforced engineered cementitious composite (ECC) proposed as a substitute to conventional wellbore cement due to its superior ductility and intrinsic crack width control. ECC and conventional wellbore cement coupons were exposed to water in equilibrium with CO2 at 50 °C and 10 MPa. The samples were retrieved after several days and their mechanical performance was evaluated using a four-point bending test, microhardness, and compressive strength analyses. Optical microscopy and mercury intrusion porosimetry were used to characterize the progression of the carbonation front and pore structures of the specimens. Control experiments were conducted under the same temperature and pressure conditions but with a N2 headspace to isolate the impact of CO2. It was found that carbonation increased the ultimate flexural strength of ECC but decreased its ductility. However, the ductility of carbonated ECC remained higher than that of conventional wellbore cements that exhibited brittle failure under all test conditions. Additionally, ECC exhibited minimal material loss and continued resistance to deformation in comparison to conventional wellbore cements. This suggests that while the exposure of ECC to CO2 will alter its mechanical properties, altered ECC will continue to exhibit mechanical performance superior to conventional wellbore cement, and therefore shows promise as a highly durable wellbore cementing material for GCS applications.

Particulate matter (PM) pollution poses a huge public health threat, and exposure to haze pollution for short or long periods of time cause health problems. In this study, 16S rDNA and ITS high-throughput sequencing were used to analyze the microbial components of fine particulate matter (PM2.5) collected between December 20th and December 27th of 2016 during a severe haze in Tai'an, China. Although most inhalable microorganisms are not pathogenic to humans, we detected the presence of some types of bacteria that cause respiratory inflammation (such as Pseudomonas and Corynebacterium), allergic reactions (such as Alternaria), and lung inflammation (such as Nesterenkonia). Acute and chronic haze PM2.5 exposure experiments were conducted using BALB/c mice to gain insight about the harm these microbes may have on human health. Results indicate that acute exposure to haze PM2.5 can cause pathological lung damage, decrease the expressions of oxidative stress indicators T-AOC, SOD, and GSH-PX, increase the expression of MDA, and induce apoptosis. Furthermore, chronic exposure was found to cause more damage. Toll-like receptors can be used identify molecular patterns associated with microbial pathogens. The expression of TLR2 and TLR4 were increased in both single- and repeated-exposure groups, but they were significantly increased in the repeated-exposure group (P < 0.05). The role of biological components in PM in mediating inflammation and pathological damage should not be neglected.

Centrifugal Fluid Separation technology, in particular Supersonic Gas Separation (SGS), is one of the potential technologies considered for offshore CO2 capture. SGS has advantages in terms of CAPEX, hydrocarbon losses, footprint, tonnage and power requirement compared to conventional solutions such as membrane. Even though the technology has been developed since 1989, the applications are limited to mainly dehydration and hydrocarbon dew pointing. For CO2 separation from natural gas, substantial development works are needed prior to the field application as there are a lot of uncertainties in the feed conditions to be tackled. In particular, the stringent requirements of cryogenic temperature, high pressure and inlet CO2 composition of its feed require a robust feed conditioning process plant. For a relatively new technology such as SGS for CO2 removal application, it is crucial to investigate and assess the variations of feed and process conditions i.e. temperature, pressure and gas compositions prior to being applied at actual field, as these will impact the CO2 separation performance inside the separator. Hence, this paper investigates the control strategies for the SGS feed conditioning plant subjected to ±15 % disturbances in temperature and pressure, and ±5 mol% variations in feed CO2 composition. Results show that effective disturbances elimination in the first flash separator of the feed conditioning plant is crucial in minimizing the impact to the SGS operation. A comparative study reveals that standard PID controller performs significantly better in disturbance rejection than Model Predictive Control.

Carbon dioxide capture and storage combined with enhanced deep saline water recovery (CCS-EWR) is a potential approach to mitigate climate change. However, its investment has been a dilemma due to high costs and various uncertainties. In this study, a trinomial tree modelling-based real options approach is constructed to assess the investment in CCS-EWR retrofitting for direct coal liquefaction in China from the investor perspective. In this approach, the uncertainties in CO2 prices, capital subsidies, water resource fees, the residual lifetime of direct coal liquefaction plants, electricity prices, CO2 and freshwater transport distance, and the amount of certified emission reductions (CERs) are considered. The results show that the critical CER price for CCS-EWR retrofits is 7.15 Chinese yuan per ton (CNY/ton) higher than that (141.95 CNY/ton) for CCS retrofits. However, the exemption from water resource fees for freshwater recovered from saline water and a subsidy of 26% of the capital cost are sufficient to eliminate the negative impact of enhanced deep saline water recovery (EWR) on the investment economy of CCS-EWR. In addition, when the residual lifetime is less than 14 years, CCS-EWR projects are still unable to achieve profitability, even with flexible management and decision making; therefore, investors should abandon CCS-EWR investments. On the whole, the investment feasibility for CCS-EWR technology is not optimistic despite access to preferential policies from the government. It is necessary to establish a carbon market with a high and stable CER price.

Primary organic aerosol (POA) in diesel exhaust is semi-volatile and partitions mass between the gas and particle phases. POA volatility is not well understood for alternative fuels, varying engine loads, and for engines that feature modern emissions controls. In this study, we performed filter-based measurements of diesel exhaust from a modern-day non-road diesel engine for two different fuels (conventional diesel and soy-based biodiesel), two different engine loads (idle and 50% load), and with and without an emissions control device. Filters were analyzed offline to determine the POA volatility in two different ways: positive artifact on quartz filters at varying dilution ratios and speciation of alkanes. The POA volatility determined from our data suggests that POA mass emissions from diesel exhaust may be reduced by a factor of five with dilution to atmospherically relevant concentrations. These results are generally consistent with previous literature on POA volatility from non-road diesel engines but not with that from on-road diesel vehicles. POA volatility may hence need to be treated separately for non- and on-road sources in atmospheric models. Surprisingly, the POA volatility did not appear to vary under different combinations of fuel, engine load, and emissions control experiments performed, suggesting that POA might be dominated by unburned lubricating oil and its oxidation products. The POA volatility estimated from the speciation of alkanes was found to agree well with that determined from the dilution experiments. A kinetic model was used to calculate the gas/particle partitioning of POA in the dilution system. The modeling suggests that residence times in the dilution tunnel need to be on the order of minutes to allow the POA in the diluted exhaust to achieve gas/particle equilibrium. The use of short residence times (less than tens of seconds), similar to those used in conventional dilution systems, may bias the measurement of POA mass emissions in such systems and is of particular concern for emissions from cleaner, more modern combustion sources. The precise magnitude and direction of the bias depends on the exhaust temperature before dilution, tailpipe seed concentrations, dilution ratio, and residence times in the dilution tunnel. We recommend that kinetic models such as those used in this work be used, instead of using equilibrium assumptions, to inform the design and operation of the dilution tunnels as well to interpret the POA volatility from measurements made with those dilution tunnels.