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This paper presents the benefits in terms of air quality from the decommissioning of the coal-fired Liddell Power Station (LPS) in the Greater Metropolitan Region of Sydney (GMR). The impact on air quality (NO, NO2, O3 and PM2.5) are modelled using CCAM-CTM air quality model and the results show that the difference in annual average concentration is small. For NO, the maximum difference is 1 ppb, while for NO2 the value is 0.75 ppb. These are annual average decrease of NO, NO2 concentration over the GMR. The most significant decrease of NO and NO2 occurs in the Upper Hunter near the LPS. For ozone (O3), the reduction of NOx emissions from LPS decommission resulted in a slight increase of O3 over a narrow area near the facility but this increase is gradually decreasing further away from the facility. The increase in O3 is about 0.65 ppb max around LPS. For PM2.5, the annual average decreases in most of the domain. The maximum change is at LPS (about 0.19 µg/m³). [ABSTRACT FROM AUTHOR]

This paper presents two recent simulation studies conducted at NSW Department of Planning and Environment on the impact on air quality across NSW and the Greater Metropolitan Region (GMR) urban areas due to a dust storm in February 2019 and Covid 19 lock down in NSW in 2021. These studies highlight the importance of using suitable air quality models to simulate the emissions and transport of air pollutants over a region to assess the impact of events on air quality and population exposure. The WRF-Chem model is used for the large-scale dust storm event and the WRF-CMAQ is used for assessing emission changes in the GMR due to the Covid-19 lockdown on the urban air quality. Both WRF-Chem and WRF-CMAQ are regional chemical transport models and require high-end Linux-based computing resources. The advantage and disadvantage of applying each of the two models to conduct a particular air quality study will be discussed. [ABSTRACT FROM AUTHOR]

The emission of black carbon (BC) particles, which cause atmospheric warming by affecting radiation budget in the atmosphere, is the result of an incomplete combustion process of organic materials. The recent wildfire event during the summer 2019–2020 in south-eastern Australia was unprecedented in scale. The wildfires lasted for nearly 3 months over large areas of the two most populated states of New South Wales and Victoria. This study on the emission and dispersion of BC emitted from the biomass burnings of the wildfires using the Weather Research Forecast–Chemistry (WRF–Chem) model aims to determine the extent of BC spatial dispersion and ground concentration distribution and the effect of BC on air quality and radiative transfer at the top of the atmosphere, the atmosphere and on the ground. The predicted aerosol concentration and AOD are compared with the observed data using the New South Wales Department of Planning and Environment (DPE) aethalometer and air quality network and remote sensing data. The BC concentration as predicted from the WRF–Chem model, is in general, less than the observed data as measured using the aethalometer monitoring network, but the spatial pattern corresponds well, and the correlation is relatively high. The total BC emission into the atmosphere during the event and the effect on radiation budget were also estimated. This study shows that the summer 2019–2020 wildfires affect not only the air quality and health impact on the east coast of Australia but also short-term weather in the region via aerosol interactions with radiation and clouds. [ABSTRACT FROM AUTHOR]

The Upper Hunter Valley is a major coal mining area containing approximately 40% of the currently identified total coal reserves in New South Wales (NSW), Australia. Due to the ongoing increase in mining activities, PM10 (airborne particles with an aerodynamic diameter of less than 10 micrometres) pollution has become a major air quality concern in local communities. This paper summarises the spatial and temporal variability modes of PM10 pollution in the region, based on long-term multi-site monitoring data and the application of the rotated principal component analysis (RPCA) and wavelet analysis techniques. RPCA identified two distinct air quality clusters/subregions in the valley: one in the west/northwest and the other in the southeast. Wavelet analysis revealed the annual cycle to be the most persistent temporal mode of PM10 variability in both subregions, with intermittent signals also observed at time scales of around 120, 30~90, and under 30 days. How these variation modes are related to the effects of local PM10 emissions and the influence of meteorology at different time scales deserves further attention in future work. The findings will be used in air quality reporting and forecasting in NSW. The methodology and results can also be useful for air quality research in similar regions elsewhere. [ABSTRACT FROM AUTHOR]

To be sustainable in energy usage in the future, there are two aspects that need to be considered: the energy supply or generation and the consumption side, including the closely linked construction and building industries which consume a large amount of energy. Essential requirements for energy efficiency are to produce less greenhouse gas emissions and to rely more on renewable energy sources for future sustainability. Policies for mitigation of the environment impact are having effects on both the supply and demand. While the former requires more alternate sources in smart grids and improved technologies for carbon capture and storage, the latter involves the reduction of energy wastes and greenhouse gas (GHG) emissions as prerequisites to green certification within the construction and building sector. Thus, access to sustainable, affordable, and secure energy is one of the major global strategic priorities to maintain and improve public health, sustain economic growth, and mitigate the effects of climate change. Toward this goal, many countries, including Australia, are investing in clean, efficient, reliable energy systems for a prosperous and environmentally sustainable future. Hence, exploring various options to ensure energy security by diversification of energy sources is an important step in meeting the future requirements and delivering clean energy to different industry sectors. This paper discusses options to manage the use of energy sources in the power generation and construction industries. Options for mitigation of environmental impact and for achievement of sustainable energy usage, such as building design with BIM, are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Exit streams of decarbonated flue gas and carbon dioxide from monoethanolamine (MEA)-based post-combustion carbon capture (PCC) units may emit amine and its degradation products as vapor and as dissolved in fine droplets of liquid. Conventional scrubbing, cooling, adsorption and mist elimination processes used with PCC units are not sufficient to eliminate these emissions. Further attempts to eliminate these emissions could be challenging, because the available options to control them are limited. Such emissions appear to be an environmental concern and more sophisticated methods are required to capture a these emissions, if the amine based PCC process is to be widely used in coal fired power stations. Since MEA, its degradation products and various corrosion reactions in liquid phase are precursors of all gaseous emission, an ideal approach to reduce emissions would be to maintain a low concentration of degradation products in the liquid phase, which would also reduce the concentration of degradation products in fine droplets. Further improvements in process design may also eliminate vapor emissions. This paper summarizes various emission control methods, including their limitations and further scope for their improvement and use in the amine-based PCC process. [Copyright &y& Elsevier]

It has been recognized that the background ozone concentration in urban areas is changing over the years. This article aims to determine the background ozone level (BOL) using ambient air quality data measurements collected at some monitoring stations in the Sydney basin, Australia. A definition of background ozone in the context of the Sydney region is proposed. With this definition, it is possible to estimate the background ozone using ambient measurements of ozone and its precursors. The trend of the BOL is also estimated from the temporal ambient monitoring records as of early 1998-2005. These ozone level changes at different monitoring stations are assessed using the linear regression method. The results are shown to vary between different monitoring sites. This demonstrates that the local conditions at each site are important in determining as to whether an air quality management plan for reducing the ozone level to below the exceedance level is effective and achievable or not. Furthermore, the results obtained are compared with those obtained by the Clapp-Jenkin method, which is based on the relationship between oxidant and nitrogen oxides, assuming a stationary state of photochemical smog function. [ABSTRACT FROM AUTHOR]

Abstract: The photooxidation of fuel vapour was investigated in a smog chamber and simulated using three chemical mechanisms, the Master Chemical Mechanism (MCMv3.1), SAPRC-99 and the Carbon Bond chemical mechanism (CB05). Three varieties of fuel were used, unleaded petrol (ULP) and two ULP-ethanol blends which contained 5% and 10% ethanol (E5, E10). The fuel vapours were introduced into the chamber using two methods, by injecting the vapours from wholly evaporated fuel directly, and by injecting the headspace vapour from fuel equilibrated at 38 °C. The chamber experiments were simulated using the selected mechanisms and comparisons made with collected experimental data. The SAPRC-99 mechanism reproduced Δ(O3–NO) more accurately for almost all fuel types and injection modes, with negligible model error for both injection modes. The average model error for MCM simulations was −16% and for CB05 the average model error was −34%. The predictions for the CB05 mechanism varied depending on injection mode, the Δ(O3–NO) model error for wholly evaporated experiments was −44%, compared to −24% for headspace vapour experiments. The difference in aromatic content between experiments of different injection modes was likely to be the cause of the difference in model error for CB05. The model error for all headspace experiments was dependent upon the initial carbon monoxide concentrations. The results for Δ(O3–NO) were matched by the prediction of other key products, with formaldehyde predicted to within 20% by both SAPRC and the MCM. The addition of ethanol to the base SAPRC mechanism altered the predictions of Δ(O3–NO) by less than 2%. Changes observed in the concentrations of formaldehyde and acetaldehyde were consistent with the expected yields from ethanol oxidation. [ABSTRACT FROM AUTHOR]

Abstract: The updated SAPRC-07 mechanism was evaluated against data from experiments performed in the CSIRO smog chamber. The mechanism predictions have been compared to experimental results as well as predictions by SAPRC-99. Experiments were performed using either toluene or m-xylene in the presence of NOx at sub-0.1 ppmv concentrations. For the majority of m-xylene experiments, the modelled Δ(O3–NO) concentration was within 20% of observed values for both SAPRC mechanisms. However during the oxidation of toluene the production of radicals was poorly predicted, with final Δ(O3–NO) concentration under-predicted by up to 60%. The predictions of major oxidants from isoprene oxidation were in good agreement with observed values. For the NOx-limited conditions however, the ozone concentration predicted by both mechanisms were under-predicted by approximately 20% in the five experiments tested. The performance of the SAPRC-07 mechanism was also evaluated against twelve evaporated fuel experiments. Two types of evaporative mode experiments were performed: headspace evaporated fuel and wholly evaporated fuel. The major difference was a significantly higher concentration of aromatic hydrocarbons and larger alkane products in wholly evaporated fuels. For headspace evaporated fuel experiments both SAPRC mechanisms were in good agreement with experimental results. For wholly evaporated experiments the average Δ(O3–NO) model error was −25% with SAPRC-07 compared to less than −5% for SAPRC-99. Updates to the photolysis data for dicarbonyls, the light source used and the experimental conditions under which these experiments were performed are possible causes for the discrepancy between SAPRC-99 and -07 predictions for wholly evaporated experiments. [Copyright &y& Elsevier]

Dust storms and wildfires occur frequently in south-eastern Australia. Their effects on the ecology, environment and population exposure have been the focus of many studies recently. Dust storms do not emit ground-sequestered carbon, but wildfires emit significant quantities of carbon into the atmosphere. However, both natural events promote phytoplankton growth in water bodies because carbon, and other trace elements such as iron, deposit on the surface water of oceans. Carbon dioxide is reabsorbed by phytoplankton via photosynthesis. The carbon balance cycle due to dust storms and wildfires is not well known. Recent studies on the carbon emission of the 2019–2020 summer wildfires in eastern Australia indicated that this megafire event emitted approximately 715 million tonnes of CO2 (195 Tg C) into the atmosphere from burned forest areas. This study focusses on the association of dust storms and wildfires in southeastern Australia with phytoplankton growth in the Tasman Sea due to the February 2019 dust storm event and the 2019–2020 Black Summer wildfires. Central Australia and western New South Wales were the sources of the dust storm emission (11 to 16 February 2019), and the Black Summer wildfires occurred along the coast of New South Wales and Victoria (from early November 2019 to early January 2020). The WRF-Chem model is used for dust storm simulation with the AFWA (Air Force Weather Agency of the US) dust emission version of the GOCART model, and the WRF-Chem model is used for wildfire simulation with FINN (Fire Emission Inventory from NCAR) emission data. The results show the similarities and differences in the deposition of particulate matter, phytoplankton growth and carbon reabsorption patterns in the Tasman Sea from these events. A higher rate of deposition of PM2.5 on the ocean surface corresponds to a higher rate of phytoplankton growth. Using the WRF-Chem model, during the 5-day dust storm event in February 2019, approximately ~1230 tons of total dust was predicted to have been deposited in the Tasman Sea, while ~132,000 tons of PM10 was deposited in the early stage of the wildfires from 1 to 8 November 2019. [ABSTRACT FROM AUTHOR]

Soil-derived dust emissions have been widely associated with health and environmental problems and should therefore be accurately and reliably estimated and assessed. Of these emissions, the inhalable PM10 and PM2.5 are difficult to estimate. Consequently, to calculate PM10 and PM2.5 emissions from soil erosion, an approach based on an artificial neural network (ANN) model which provides a multilayered, fully connected framework that relates input parameters and outcomes was proposed in this study. Owing to the difficulty in obtaining the actual emissions of soil-derived PM10 and PM2.5 over a broad area, the PM10 and PM2.5 simulated results of the ANN model were compared with the published results simulated by the widely used wind erosion prediction system (WEPS) model. The PM10 and PM2.5 emission results, based on the WEPS, agreed well with the field data, with R2 values of 0.93 and 0.97, respectively, indicating the potential for using the WEPS results as a reference for training the ANN model. The calculated r, RMSE and MAE for the results simulated by the WEPS and ANN were 0.78, 3.37 and 2.31 for PM10 and 0.79, 1.40 and 0.91 for PM2.5, respectively, throughout Southern Xinjiang. The uncertainty of the soil-derived PM10 and PM2.5 emissions at a 95% CI was (−66–106%) and (−75–108%), respectively, in 2016. The results indicated that by using parameters that affect soil erodibility, including the soil pH, soil cation exchange capacity, soil organic content, soil calcium carbonate, wind speed, precipitation and elevation as input factors, the ANN model could simulate soil-derived particle emissions in Southern Xinjiang. The results showed that when the study domain was reduced from the entire Southern Xinjiang region to its five administrative divisions, the performance of the ANN improved, producing average correlation coefficients of 0.88 and 0.87, respectively, for PM10 and PM2.5. The performances of the ANN differed by study period, with the best result obtained during the sand period (March to May) followed by the nonheating (June to October) and heating periods (November to February). Wind speed, precipitation and soil calcium carbonate were the predominant input factors affecting particle emissions from wind erosion sources. The results of this study can be used as a reference for the wind erosion prevention and soil conservation plans in Southern Xinjiang. [ABSTRACT FROM AUTHOR]

A better understanding of background tropospheric ozone delivers multiple benefits. Robust estimates of regional background ozone are required to understand the limits of anthropogenic emissions controlling ozone reduction. Long-term estimates of background ozone assist in characterising changes in atmospheric composition and can help quantify the influence of human activity on the atmosphere. Background tropospheric ozone measurements representative of continental air masses are scarce in Australia. Here, we use k-means clustering to identify a cluster of measurements from the long-term air quality monitoring station at Oakdale, NSW, which are likely to be representative of background air. The cluster is associated with NOx-limited air masses of continental origin. From this analysis, we estimate background ozone representative of Eastern Australia. We find recent (2017–2022) mean ozone mixing ratios of 28.5 ppb and identify a statistically significant (α = 0.05) trend in the mean of +1.8 (1.0–2.8) ppb/decade. Our methods demonstrate that some long-term monitoring stations within or near urban areas can provide suitable conditions and datasets for regional Global Atmosphere Watch monitoring. [ABSTRACT FROM AUTHOR]

This article discusses the use of deep learning technology to enhance air quality forecasting in New South Wales (NSW), Australia. The study analyzes historic air quality monitoring data to fill in gaps and determine background air pollution levels. The researchers applied a hybrid model, combining convolution neural networks (CNN) and long short-term memory (LSTM) neural networks, to forecast hourly ozone and PM2.5 pollution up to 72 hours ahead. The results show that the CNN-LSTM models outperformed benchmark predictions and have the potential to improve air quality forecasting in NSW. [Extracted from the article]

The need for fast responses options to manage the potential risks of exposure of population to pollutants from planned or unplanned activities is becoming critical and require a constant improvement in its management. The Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) developed by the US National Oceanic and Atmospheric Administration (NOAA), is a complete system for computing both simple air parcel trajectories and complex dispersion and deposition simulations. These simulations include tracking and forecasting the smoke from prescribed burns and wildfires, dust, volcanic ash, the release of radioactive material, and pollutants from industrial incidents. The model can also be aggregated as a decisions support tool in the different phases of emissions events management. It has been tailored to run in New South Wales with finer spatial resolution meteorological data from Bureau of Meteorology to increase the accuracy of the trajectory and dispersion modelling. This system, called 'HYSPLIT in NSW', has been successfully configured to produce operational atmospheric trajectory and dispersion forecasts twice daily since July 2019. The system provides greater certainty in predicting the transportation of smoke from wildfires and hazard reduction burns, and is able to identify areas that are likely to be affected by regional dust storms and industrial incidents. 'HYSPLIT in NSW' also supports both research applications and emergency response events that require modelling the transport and dispersion of harmful pollutants released to the atmosphere (e.g., Port Macquarie peat fire in August 2019). It is an efficient modelling tool as it does not require huge amount of computing resources. The model is often applied to support the needs from air quality regulators or local emergency managers for air parcel trajectory and dispersion forecast. [ABSTRACT FROM AUTHOR]

A crucial aspect of regional air quality modelling is the accurate characterisation of local meteorology, as this plays a significant role in the transport and chemical transformation of pollution across a region. This study explores the potential of The Weather Research and Forecasting (WRF) model as an alternative meteorological model to support near-time air quality predictions for the NSW Greater Metropolitan Region (NSW GMR). We develop an optimal WRF configuration for the NSW GMR by downscaling the latest Bureau of Meteorology (BOM) Australian Community Climate and Earth-System Simulator (ACCESS) Numerical Weather Prediction (NWP) data using a three nested domain setup with resolutions of 12km, 4km and 1 km by varying physical parameterisations including two cumulus schemes, two planetary boundary layer schemes, two microphysical schemes, two compatible shortwave and longwave radiation schemes and a standard land surface model. Thus, a set of 16 experiments were executed and evaluated on different days involving high ozone days, bushfire smoke, dust storms and heatwaves. Each simulation was initialised at 12UTC with a forecast horizon of four days, including three hourly updates of boundary conditions. All simulations were evaluated with metrics including Mean Absolute Errors (MAE) and Index of Agreement (IOA) calculated over selected stations operated by NSW Department of Planning, Industry and Environment (NSW DPIE) and BOM for surface and vertical variables (temperature (T), relative humidity (RH), wind speed (WS)) including precipitation (PRECIP) and planetary boundary layer heights (PBLH). Overall, results showed that the best configuration produced acceptable agreements at the surface for T (IOA > 0.8), RH (IOA > 0.7) and WSP (IOA > 0.6). Errors in PBLH were elevated in the mid-boundary layer but was within 100m where vertical profiles of temperature and winds were well simulated. Similarly, experiments with double moment microphysical schemes were better in simulating precipitation. Other performance metrics for the experiments conducted under different case days will also be discussed. [ABSTRACT FROM AUTHOR]

Although carbonyl compounds are a key species with atmospheric oxidation capacity, their concentrations and sources have not been sufficiently characterized in various atmospheres, especially in desert areas. In this study, atmospheric carbonyl compounds were measured from 16 May to 15 June 2018 in Tazhong in the central Taklimakan Desert, Xinjiang Uygur Autonomous Region, China. Concentrations, chemical compositions, and sources of carbonyl compounds were investigated and compared with those of different environments worldwide. The average concentration of total carbonyls during the sampling period was 11.79 ± 4.03 ppbv. Formaldehyde, acetaldehyde, and acetone were the most abundant carbonyls, with average concentrations of 6.08 ± 2.37, 1.68 ± 0.78, and 2.52 ± 0.68 ppbv, respectively. Strong correlations between formaldehyde and other carbonyls were found, indicating same or similar sources and sinks. A hybrid single-particle Lagrangian integrated trajectory was used to analyze 72 h back trajectories. The values of C1/C2 (formaldehyde to acetaldehyde, 3.22–4.59) and C2/C3 (acetaldehyde to propionaldehyde, 15.00–17.03) from different directions and distances of the trajectories were consistent with the characteristics of a remote area. Relative to various environments, the carbonyl concentration in the Tazhong desert site was lower than that in urban areas and higher than that in suburban and remote areas, implying contributions from local primary and secondary sources. The obtained data can be used to improve the source and sink estimation of carbonyls at the regional scale. [ABSTRACT FROM AUTHOR]

The atmospheric degradation of piperazine was investigated using an indoor smog chamber. Experiments were carried out in the presence of nitrogen oxides (NOx), ozone or nitric acid. Piperazine reacted rapidly under all evaluated conditions: irradiated in the presence of NOx and with ozone and nitric acid in the dark. Gas phase products from the oxidation of piperazine were identified by infrared spectroscopy, DNPH cartridges followed by HPLC analysis, and by sampling chamber gas through Tenax sorbent material followed by analysis using thermal desorption GC-ITMS (gas chromatography ion trap mass spectrometry). Eight compounds were positively identified, with a further nine compounds tentatively identified using GC–MS based on molecular weight and mass spectra. Ammonia formation was observed from piperazine oxidation, and its formation was from the subsequent reactions of photooxidation products of piperazine rather than directly from the reaction of piperazine. The nitrosamine and nitramine expected from piperazine, N -nitrosopiperazine, and N -nitropiperazine, were both identified and confirmed using 15 NO, with a tentative maximum yield of nitrosamine of less than 5% observed. Aerosol yields, relative to total piperazine reacted not including that which absorbed to the walls, were considerably high but were not able to be quantified absolutely due to unusual behaviour of the scanning mobility particle sizer instrument to aerosol containing amines. The reaction of piperazine with gas phase nitric acid gave rise to immediate formation of aerosol. [ABSTRACT FROM AUTHOR]

A new state-of-the-art indoor smog chamber facility (CAPS-ZJU) has been constructed and characterized at Zhejiang University, which is designed for chemical mechanism evaluation under well-controlled conditions. A series of characterization experiments were performed to validate the well-established experimental protocols, including temperature variation pattern, light spectrum and equivalent intensity (J NO2), injection and mixing performance, as well as gases and particle wall loss. In addition, based on some characterization experiments, the auxiliary wall mechanism has been setup and examined. Fifty chamber experiments were performed across a broad range of experimental scenarios, and we demonstrated the ability to utilize these chamber data for evaluating SAPRC chemical mechanism. It was found that the SAPRC-11 can well predict the O 3 formation and NO oxidation for almost all propene runs, with 6 hr Δ(O 3 – NO) model error of –3% ± 7%, while the final O 3 was underestimated by ~20% for isoprene experiments. As for toluene and p -xylene experiments, it was confirmed that SAPRC-11 has significant improvement on aromatic chemistry than earlier version of SAPRC-07, although the aromatic decay rate was still underestimated to some extent. The model sensitivity test has been carried out, and the most sensitive parameters identified are the initial concentrations of reactants and the light intensity as well as HONO offgasing rate and O 3 wall loss rate. All of which demonstrated that CAPS-ZJU smog chamber could derive high quality experimental data, and could provide insights on chamber studies and chemical mechanism development. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) is a major contributor to secondary aerosol in the atmosphere and can alter the kinetics of their formation. However, systematic studies related to the role of NH 3 in aerosol nucleation processes and further particle size growth under complex scenarios are lacking. In this study, we conducted 16 experiments in the CSIRO smog chamber under dry conditions using aromatic hydrocarbons (toluene, o -/ m -/ p -xylene) and different concentrations of NH 3 . The presence of NH 3 did not change the gas-phase chemistry or nucleation onset time, but slowed the nucleation rate (5%–94%) once it began. From the response of nitrogen oxides (NOx) measurement and mechanism modeling results, we hypothesised that the surface reaction between NH 3 and nitric acid played a central role in aerosol nucleation and further growth. After nucleation, the subsequently formed ammonium nitrate and organic condensation vapours may partition together into the initial growth process of new particles, thus increasing the aerosol initial growth rate (8%–90%) and size growth potentials (7%–108%), and leading to high aerosol mass formation. Further investigation implied that the initial growth and further growth rate determine the aerosol mass concentration, rather than the nucleation rate. We conclude that both the initial NOx concentration and volatile organic compound (VOC)/NOx ratio are crucial for the initial and further growth, and aerosol mass of new particles, when NH 3 levels are high. Our results provide crucial insights into the complex chemistry of VOC/NOx/NH 3 in the atmosphere, and highlight the importance of NH 3 reduction for particulate matter control. [ABSTRACT FROM AUTHOR]

The determination of background concentration of PM 2.5 is important to understand the contribution of local emission sources to total PM 2.5 concentration. The purpose of this study was to exam the performance of baseline separation techniques to estimate PM 2.5 background concentration. Five separation methods, which included recursive digital filters (Lyne-Hollick, one-parameter algorithm, and Boughton two-parameter algorithm), sliding interval and smoothed minima, were applied to one-year PM 2.5 time-series data in two heavily polluted cities, Tianjin and Jinan. To obtain the proper filter parameters and recession constants for the separation techniques, we conducted regression analysis at a background site during the emission reduction period enforced by the Government for the 2014 Asia-Pacific Economic Cooperation (APEC) meeting in Beijing. Background concentrations in Tianjin and Jinan were then estimated by applying the determined filter parameters and recession constants. The chemical mass balance (CMB) model was also applied to ascertain the effectiveness of the new approach. Our results showed that the contribution of background PM concentration to ambient pollution was at a comparable level to the contribution obtained from the previous study. The best performance was achieved using the Boughton two-parameter algorithm. The background concentrations were estimated at (27 ± 2) μg/m 3 for the whole year, (34 ± 4) μg/m 3 for the heating period (winter), (21 ± 2) μg/m 3 for the non-heating period (summer), and (25 ± 2) μg/m 3 for the sandstorm period in Tianjin. The corresponding values in Jinan were (30 ± 3) μg/m 3 , (40 ± 4) μg/m 3 , (24 ± 5) μg/m 3 , and (26 ± 2) μg/m 3 , respectively. The study revealed that these baseline separation techniques are valid for estimating levels of PM 2.5 air pollution, and that our proposed method has great potential for estimating the background level of other air pollutants. [ABSTRACT FROM AUTHOR]

Regional ozone pollution has become one of the most challenging problems in China, especially in the more economically developed and densely populated regions like Hangzhou. In this study, measurements of O 3 , CO, NO x and non-methane hydrocarbons (NMHCs), together with meteorological data, were obtained for the period July 1, 2013–August 15, 2013 at three sites in Hangzhou. These sites included an urban site (Zhaohui “ZH”), a suburban site (Xiasha “XS”) and a rural site (Qiandaohu “QDH”). During the observation period, both ZH and XS had a higher ozone level than QDH, with exceeding rates of 41.3% and 47.8%, respectively. Elevated O 3 levels in QDH were found at night, which could be explained by less prominent NO titration effect in rural area. Detailed statistical analysis of meteorological and chemical impacts on ozone formation was carried out for ZH, and higher ozone concentration was observed when the wind direction was from the east. This is possibly due to emissions of VOCs from XS, a typical chemical industrial park located in 30 km upwind area of ZH. A comprehensive comparison between three ozone episode periods and one non-episode period were made in ZH. It was concluded that elevated concentrations of precursors and temperatures, low relative humidity and wind speed and easterly-dominated wind direction contribute to urban ozone episodes in Hangzhou. VOCs reactivity analysis indicated that reactive alkenes like isoprene and isobutene contributed most to ozone formation. Three methods were applied to evaluate O 3 -VOCs-NO x sensitivity in ZH: VOCs/NO x ratio method, Smog Production Model (SPM) and Relative Incremental Reactivity (RIR). The results show that summer ozone in urban Hangzhou mostly presents VOCs-limited and transition region alternately. Our study implies that the increasing automobiles and VOCs emissions from upwind area could result in ozone pollution in urban Hangzhou, and synergistic reduction of VOCs and NO x will be more effective. [ABSTRACT FROM AUTHOR]

The formation and growth of new particles has recently been shown to have a significant influence on Chinese haze pollution, and sulfuric acid has long been recognized as a major contributor to new particle formation. In this study, four comparison groups of experiments related to SO 2 photooxidation, as well as aerosol nucleation and growth, have been conducted in the CAPS-ZJU (Complex Air Pollution Study-Zhejiang University) smog chamber. These were conducted either under SO 2 /NOx or SO 2 /toluene gas-phase environments in the absence of seed particles. During aerosol nucleation and growth process, several physical properties such as mass, size and effective density were measured simultaneously by Scanning Mobility Particle Sizer (SMPS) and Differential Mobility Analyzer-Aerosol Particle Mass Analyzer-Condensation Particle Counter (DMA-APM-CPC). The effective density of new particles decreased from 1.8 to 1.35 g/cm 3 as the particle size increased from 20 to 65 nm. The single particle mass showed good power-law relationship with mobility diameter, with an average mass-mobility exponent of 2.885. A new algorithm and a reference density of 1.38 g/cm 3 based on size-resolved single particle mass (SPM) were proposed to calculate the mass concentration of new particles. Two methods based on Log Normal and Max Concentration were applied to derive particle growth rate (GR), and data merging from both methods was implemented to decrease calculation uncertainty. Meanwhile, both continuous nucleation and inhibition of further growth in sub-20 nm size range were observed in different experiments depending on composition, and possible reasons were analyzed. The presence of NO was found to suppress nucleation and subsequent aerosol growth; while the presence of NO 2 or toluene promoted it. It was concluded that decreasing NOx (NO or NO 2 ) or increasing toluene may promote SO 2 photooxidation, nucleation and subsequent aerosol growth, all of which is significant for deeper understanding of complex air pollution in China. [ABSTRACT FROM AUTHOR]

China has implemented two national clean air actions in 2013–2017 and 2018–2020, respectively, with the aim of reducing primary emissions and hence improving air quality at a national level. It is important to examine the effectiveness of such emission reductions and assess the resulting changes in air quality. However, such evaluation is difficult as meteorological factors can amplify, or obscure the changes of air pollutants, in addition to the emission reduction. In this study, we applied the random forest machine learning technique to decouple meteorological influences from emissions changes, and examined the deweathered trends of air pollutants in 12 Chinese mega-cities during 2013–2020. The observed concentrations of all criteria pollutants except O 3 showed significant declines from 2013 to 2020, with PM 2.5 annual decline rates of 6–9% in most cities. In contrast, O 3 concentrations increased with annual growth rates of 1–9%. Compared with the observed results, all the pollutants showed smoothed but similar variation in trend and annual rate-of-change after weather normalization. The response of O 3 to NO 2 concentrations indicated significant regional differences in photochemical regimes, and the differences between observed and deweathered results provided implications for volatile organic compound emission reductions in O 3 pollution mitigation. We further evaluated the effectiveness of first and second clean air actions by removing the meteorological influence. We found that the meteorology can make negative or positive contribution in reducing pollutant concentrations from emission reduction, depending on type of pollutants, locations, and time period. Among the 12 mega-cities, only Beijing showed a positive meteorological contribution in amplifying reductions in main pollutants except O 3 during both clean air action periods. Considering the large and variable impact of meteorological effects in changing air quality, we suggest that similar deweathered analysis is needed as a routine policy evaluation tool on a regional basis. [Display omitted] • We used a random forest method to remove meteorological effect for air quality data. • The deweathered results show smoothed but similar variation in annual trends. • The meteorology can play positive or negative role depending on specific conditions. • Beijing shows positive meteorology in reducing pollutants for two clean air actions. [ABSTRACT FROM AUTHOR]

The planetary boundary layer height (PBLH) is one of the key factors in influencing the dispersion of the air pollutants in the troposphere and, hence, the air pollutant concentration on ground level. For this reason, accurate air pollutant concentration depends on the performance of PBLH prediction. Recently, ceilometers, a lidar instrument to measure cloud base height, have been used by atmospheric scientists and air pollution control authorities to determine the mixing level height (MLH) in improving forecasting and understanding the evolution of aerosol layers above ground at a site. In this study, ceilometer data at an urban (Lidcombe) and a rural (Merriwa) location in New South Wales, Australia, were used to investigate the relationship of air pollutant surface concentrations and surface meteorological variables with MLH, to validate the PBLH prediction from two air quality models (CCAM-CTM and WRF-CMAQ), as well as to understand the aerosol transport from sources to the receptor point at Merriwa for the three case studies where high PM10 concentration was detected in each of the three days. The results showed that surface ozone and temperature had a positive correlation with MLH, while relative humidity had negative correlation. For other pollutants (PM10, PM2.5, NO2), no clear results were obtained, and the correlation depended on the site and regional emission characteristics. The results also showed that the PBLH prediction by the two air quality models corresponded reasonably well with the observed ceilometer data and the cause and source of high PM10 concentration at Merriwa can be found by using ceilometer MLH data to corroborate back trajectory analysis of the transport of aerosols to the receptor point at Merriwa. Of the three case studies, one had aerosol sources from the north and north west of Merriwa in remote NSW, where windblown dust is the main source, and the other two had sources from the south and south east of Merriwa, where anthropogenic sources dominate. [ABSTRACT FROM AUTHOR]

A measurement program designed to evaluate health impacts or benefits of using ethanol blend petrol examined exhaust and evaporative emissions from 21 vehicles representative of the current Australian light duty petrol (gasoline) vehicle fleet using a composite urban emissions drive cycle. The fuels used were unleaded petrol (ULP), ULP blended with either 5% ethanol (E5) or 10% ethanol (E10). The resulting data were combined with inventory data for Sydney to determine the expected fleet emissions for different uptakes of ethanol blended fuel. Fleet ethanol compatibility was estimated to be 60% for 2006, and for the air quality modelling it was assumed that in 2011 over 95% of the fleet would be ethanol compatible. Secondary organic aerosol (SOA) formation from ULP, E5 and E10 emissions was studied under controlled conditions by the use of a smog chamber. This was combined with meteorological data from Sydney for February 2004 and the emission data (both measured and inventory data) to model pollutant concentrations in Sydney's airshed for 2006 and 2011. These concentrations were combined with the population distribution to evaluate population exposure to the pollutant. There is a health benefit to the Sydney population arising from a move from ULP to ethanol blends in spark-ignition vehicles. Potential health cost savings for Urban Australia (Sydney, Melbourne, Brisbane and Perth) are estimated to be A$39 million (in 2007 dollars) for a 50% uptake (by ethanol compatible vehicles) of E10 in 2006 and $42 million per annum for a 100% take up of E10 in 2011. Over 97% of the estimated health savings are due to reduced emissions of PM2.5 and consequent reduced impacts on mortality and morbidity (e.g., asthma, cardiovascular disease). Despite more petrol-driven vehicles predicted for 2011, the quantified health impact differential between ULP and ethanol fuelled vehicles drops from 2006 to 2011. This is because modern petrol vehicles, with lower emissions than their older counterparts, will make up a higher proportion of the fleet in the future. Hence the beneficial effects of reductions in particulate matter become less significant as the fleet as a whole produces lower emissions. [ABSTRACT FROM AUTHOR]

Zibo, a highly industrialized cluster city in the central area of the North China Plain (NCP), has suffered from serious ozone pollution in recent years. In this study, a comprehensive field campaign was conducted during July 2019 at three representative and diversified areas in Zibo, including two suburban sites (Tianzhen (TZ) and Xindian (XD)) and one urban site (Beijiao (BJ)). The O 3 variation patterns were overall similar among the three sites, while its precursors (i.e. volatile organic compounds (VOCs) and nitrogen oxides (NO x)) showed distinct site-to-site differences. A 0-D box model incorporating the latest Master Chemical Mechanism (MCMv3.3.1) was applied using observations as constraints, and NO x -limited, VOC-limited and transitional regimes were generally identified for TZ, BJ and XD respectively, particularly during high-O 3 episodes. We believe that such large variability of O 3 -precursor relationship found in Zibo may exist widely in many other cities, which challenges the current O 3 pollution control. It was further concluded that both high in-situ O 3 production rate (daytime peak 21–27 ppbv h−1) and O 3 transported from residual layer are responsible for the high ground-level O 3. Detailed mechanism modelling with many scenarios suggested that a synergic reduction plan for NO x and VOC would be the most feasible and effective option to achieve O 3 -attainment levels. It is suggested that the minimum reduction in NO x should be by more than 40% (TZ), 60% (BJ) and 20% (XD), while anthropogenic VOC should simultaneously be cut more than 60% (TZ), 40% (BJ) and 60% (XD). Our fundamental chemical mechanism modelling provided an improved understanding of O 3 -precursor relationship, and the derived policy-relevant guidance can assist the local government like Zibo to deal with O 3 challenge. These results could also provide insights for regional O 3 control across the North China Plain. • The characteristics of O 3 and its precursors were investigated during 2019 summertime in Zibo. • 0-D box model showed a large variability of O 3 -precursor relationship in spatial-temporal scales over Zibo. • Both strong local photochemistry and residual layer transport contributed to high ground-level O 3. • A synergic reduction plan for NO x and VOC was developed to achieve O 3 -attainment levels. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) is an important base gas in the atmosphere and has received extensive research interest due to its role on secondary aerosol formation. However, the effects of NH 3 on the photochemical smog oxidants formation including ozone and secondary aerosol did not attract much attention. In this study, a set of smog chamber experiments was conducted under toluene/NOx photo-oxidation base condition and adding NH 3 in the following photochemical regimes referred as hydrocarbon, NOx-limited and transitional regimes. Dedicated instruments including gas analysers, scanning mobility particle sizer (SMPS), aerosol mass spectrometry (HR-ToF-AMS) were used to measure the gaseous compounds, aerosol mass concentration and chemical composition. It was found that the presence of NH 3 did not affect the O 3 formation rate. However, the particle number concentration increased dramatically after NH 3 was injected in any photochemical regimes. This effect has been mainly attributed to the rapid formation of organic ammonium and ammonium nitrate. The mass spectra of organic aerosols from AMS showed that the most abundant fragments were at m/z 28, 29, 43 and 44, which became higher after the addition of NH 3 in the transition and NOx-limited regimes, indicating that NH 3 could enhance the formation of the compounds containing carbonyl and carboxylic acid functional groups. Compared to hydrocarbon-limited regime, higher atomic nitrogen-to-carbon (N:C) ratios were observed when NH 3 were injected into transition and NOx-limited regimes, and this is mainly due to more organic nitrate formation. Four factors, which were assigned to inorganic nitrate aerosols, carboxylic acid compounds, carbonyl compounds and N-containing organic compounds (NOC), were identified and interpreted by applying the positive matrix factorization (PMF) to the AMS dataset. These results provide new insights into the complex chemistry of toluene/NOx/NH 3 during different O 3 formation regimes, and imply the benefit of controlling NH 3 to mitigate PM 2.5 when O 3 formation is under VOC-limited regime. [Display omitted] • How NH 3 affects particle formation in different photochemical regimes was investigated. • NH 3 does not affect O 3 formation but affect particle formation and composition. • Higher O:C and N:C were observed after NH 3 injection in NOx-limited regime. • Four factors contributing to the secondary aerosols were identified by PMF analysis. [ABSTRACT FROM AUTHOR]

The role of precursors' concentrations and meteorological conditions on the emerging ozone pollution problem in China has received wide attention, especially after the releasing of the Air Pollution Prevention Control and Action Plan (APPC) since 2013. With the decreasing trend of PM 2.5 nationwide, the effect of the strict control measures on increasing ozone variation has less been studied due to the challenge of complexity of nonlinear relationship among a number of factors on ozone formation. This paper evaluated the influence of both ozone precursors and meteorology on maximum daily average 8 h (MDA8) ozone at two urban sites and one rural site in Hebei province, China, from 2013 to 2017, by using a combined application of Kolmogorov-Zurbenko (KZ) filter and artificial neural network (ANN) model. Results showed that R2 was 0.80 between the measured and the simulated MDA8 ozone concentration when using meteorological factors and precursors' concentrations as input variables for ANN model. However, ANN model has limitation in estimating O 3 concentration peaks. The values of threat score (TS), probability of detection (POD) and false alarm rate (FAR) for MDA8 ozone concentration were 39%, 44% and 21%, respectively, throughout three studied sites in Hebei province. The annual average percentage change of precursor-related ozone was 0.67% from 2014 to 2017. Temperature, atmospheric pressure and boundary layer height were shown to account for 64% of the variability in long-term ozone levels. Ozone variation in Hebei province was reproduced mainly by meteorological parameters, and the contribution from precursors' concentration was smaller during the years when the APPC was implemented. [Display omitted] • Ozone level was estimated based on precursors' level and meteorological factors. • The ambient ozone concentration estimated by ANN model was acceptable. • Meteorology dominates the ozone variation in 2013–2017 in Hebei province. [ABSTRACT FROM AUTHOR]

Southern Xinjiang located in the far northwest of China is experiencing serious particulate matter (PM) pollution. The wind erosion has been recognized as a great contributor of PM 10 and PM 2.5 concentrations in southern Xinjiang. In this study we developed a method that used the Wind Erosion Prediction System (WEPS) to establish the PM 10 and PM 2.5 emission inventories from the wind erosion source in southern Xinjiang with a 10 km × 10 km spatial resolution and a temporal resolution of one month. The PM 10 and PM 2.5 emission inventories from wind erosion sources were provided as input to the Models3/SMOKE (Sparse Matrix Operator Kernel Emission). The Community Multi-scale Air Quality (CMAQ) model was employed to simulate PM 10 and PM 2.5 concentrations from wind erosion source and the results were compared with the monitoring data to verify the emission inventories. The total PM 10 and PM 2.5 emissions were 12 × 106 t and 4 × 106 t, respectively, and the emission per unit area were 14.6 t/km2 and 4.9 t/km2, respectively, in southern Xinjiang in 2016. The PM 10 and PM 2.5 emissions per unit area were highest in Kashi being 19.1 t/km2 and 9.1 t/km2, respectively. The total emissions peaked at 5.4 × 106 t/km2 in PM 10 and 1.4 × 106 t/km2 in PM 2.5 in Bazhou. The PM 10 and PM 2.5 emissions were highest in spring, followed by summer, winter and autumn. The Normalized Mean Error (NME) between the predicted monthly average PM 10 and PM 2.5 concentrations from wind erosion source and the results from multiplying the monitoring data by the source apportionment results of PM 10 and PM 2.5 were 25.3% and 26.1%, respectively, which indicated that the accuracies of the PM 10 and PM 2.5 emission inventories from wind erosion source in southern Xinjiang were satisfactory. • PMs emission inventories of wind erosion source were established using WEPS model. • PMs emission inventories of wind erosion source were verified based on CMAQ. • The ratios of PM 2.5 to PM 10 emissions were derived from the wind tunnel experiment. [ABSTRACT FROM AUTHOR]

Dust storms originating from Central Australia and western New South Wales frequently cause high particle concentrations at many sites across New South Wales, both inland and along the coast. This study focussed on a dust storm event in February 2019 which affected air quality across the state as detected at many ambient monitoring stations in the Department of Planning, Industry and Environment (DPIE) air quality monitoring network. The WRF-Chem (Weather Research and Forecast Model—Chemistry) model is used to study the formation, dispersion and transport of dust across the state of New South Wales (NSW, Australia). Wildfires also happened in northern NSW at the same time of the dust storm in February 2019, and their emissions are taken into account in the WRF-Chem model by using Fire Inventory from NCAR (FINN) as emission input. The model performance is evaluated and is shown to predict fairly accurate the PM2.5 and PM10 concentration as compared to observation. The predicted PM2.5 concentration over New South Wales during 5 days from 11 to 15 February 2019 is then used to estimate the impact of the February 2019 dust storm event on three health endpoints, namely mortality, respiratory and cardiac disease hospitalisation rates. The results show that even though as the daily average of PM2.5 over some parts of the state, especially in western and north western NSW near the centre of the dust storm and wild fires, are very high (over 900 µg/m3), the population exposure is low due to the sparse population. Generally, the health impact is similar in order of magnitude to that caused by biomass burning events from wildfires or from hazardous reduction burnings (HRBs) near populous centres such as in Sydney in May 2016. One notable difference is the higher respiratory disease hospitalisation for this dust event (161) compared to the fire event (24). [ABSTRACT FROM AUTHOR]

Because ambient ozone (O 3) has fine spatial scale variability in addition to a large scale regional distribution, accurate exposure predictions for population health studies need to also capture fine spatial scale differences in exposure. To address these needs, we developed a 3-year average land use regression (LUR) and combined LUR and Bayesian maximum entropy (BME) by incorporating a national area variability LUR model for China from 2015 to 2017 along with data that take into account incompleteness of O 3 monitoring data into a BME framework. Spatio-temporal kriging models that either included or did not include "soft" data were used for comparison. The final LUR model included five predictor variables: road length within a 1000 m buffer, temperature, wind speed, industrial land area within a 3000 m buffer and altitude. The 1-year predicted O 3 concentrations based on the ratio method moderately agreed with the measured concentration, and the regression R2 values were 0.53, 0.57 and 0.59 in the year of 2015, 2016 and 2017, respectively. The LUR/BME model performed better (R2 = 0.80, root mean squared error [RMSE] = 23.5 μg/m3) than the ordinary spatio-temporal kriging model that either included "soft" data (R2 = 0.57, RMSE = 49.2 μg/m3) or did not include the "soft" data (R2 = 0.52, RMSE = 58.5 μg/m3). We have demonstrated that a hybrid LUR/BME model can provide accurate predictions of O 3 concentrations with high spatio-temporal resolution at the national scale in mainland China. Unlabelled Image • A 3-year average LUR model was developed to predict the annual O 3 concentration. • A combined LUR/BME model was developed to predict the daily O 3 concentration. • LUR/BME model outperformed ordinary spatio-temporal kriging model. [ABSTRACT FROM AUTHOR]

A field campaign was carried out during May–September of 2018 at three sites in Hangzhou, representing residential (ZH), industrial (XS), and natural (HZHP) areas, respectively. The characteristics of precursors to ozone (O 3) - volatile organic compounds (VOCs) and nitrogen (NOx) - revealed observably diversities among the three sites. A 0-D atmospheric box model contained the Master Chemical Mechanism (MCMv3.3.1) was implemented to study the O 3 -precursor sensitivity and O 3 in-situ photochemical processing. The discussion of relative incremental reactivity (RIR) showed that O 3 production at HZHP was mostly limited by both VOCs and NOx, while ZH and XS were generally identified as VOC-limited regime. More specifically, ethene, m -xylene, and toluene had the largest contributing to O 3 production in Hangzhou. The simulated mixing ratios of hydroxyl radical (OH) were within same level among ZH, XS and HZHP, while the simulated mixing ratios of hydroperoxyl radical (HO 2) at HZHP were much higher than the other two sites, indicating the different cyclic processes between OH and HO 2 among the three sites. Modellings for various emission reduction scenarios were conducted, and the results implied that different strategies were needed for different areas in order to efficiently reduce O 3 pollution. For example, the abatement ratio of anthropogenic VOCs (AVOCs) to NOx mixing ratios should be higher than 1.6 and 2.5 at ZH and XS, respectively, while we should target on reducing NOx instead of AVOCs at HZHP. The obtained results provide policy relevant guidance on understanding the photochemical pollution through fundamental chemical mechanism, and can assist local governments (Hangzhou) in taking effective control strategies to deal with O 3 pollution. • 0-D box model with MCMv3.3.1 was applied to investigate the summertime O 3 formation mechanism at three sites of Hangzhou. • The photochemical regimes of the three sites were identified through relative incremental reactivity (RIR) analysis. • Ethene, toluene, and m -xylene were identified as the most sensitive anthropogenic VOC species to O 3 formation in Hangzhou. • Modellings for reduction scenarios were conducted, and different ozone control strategies were developed for each area. [ABSTRACT FROM AUTHOR]

The secondary aerosol formation mechanism in the presence of ammonia (NH 3), is poorly understood, especially under high relative humidity (RH) conditions. In this study, a total of seven experiments were conducted from toluene/NOx photo-oxidation in the presence/absence of NH 3 under dry (~7% RH) and wet (>60% RH) conditions in a ~3 m3 smog chamber. A series of instruments including gas analysers, scanning mobility particle sizer (SMPS), aerosol mass spectrometry (HR-ToF-AMS) etc. were applied to measure the NOx and O 3 concentrations, the mass concentration and chemical composition of secondary aerosol. It was found that NH 3 could enhance the mass loading of secondary aerosol, especially under wet condition. However, the presence of NH 3 or increasing RH did not have a significant influence on SOA yield. The organic aerosol mass spectrum from AMS showed that the most abundant fragment was at m / z = 44, which was mainly from the fragmentation of carboxylic acids. Compared to the absence of NH 3 , the fraction of fragment at m / z = 44 and O:C was higher in the presence of NH 3 , regardless of dry or wet conditions. The highest O:C value of 0.71–0.75 was observed in the presence of NH 3 under wet condition, suggesting there could be a synergetic effect between the high RH and the presence of NH 3 , which jointly contributed to the photochemical aging process of SOA. The N:C increased in the presence of NH 3 under both dry and wet conditions, which might be attributed to the carboxylates and organic nitrates formed from the reaction between NH 3 and carboxylic acids. The results implied that SOA modelling should consider the role of NH 3 and water vapour, which might fill the gap of O:C between laboratory studies and field measurements. Unlabelled Image • NH 3 significantly enhanced SOA formation from toluene/NOx photo-oxidation under high RH condition. • High RH and NH 3 could jointly accelerate the photochemical aging process of SOA. • Both the addition and replacement of carboxylic functional group contributed to the formation of carboxylic acids. • NH 3 could react with the carboxylic acids formed from toluene, generating carboxylates and other organic nitrates. [ABSTRACT FROM AUTHOR]

Biomass burnings either due to Hazards Reduction Burnings (HRBs) in late autumn and early winter or bushfires during summer periods in various part of the world (e.g., CA, USA or New South Wales, Australia) emit large amount of gaseous pollutants and aerosols. The emissions, under favourable meteorological conditions, can cause elevated atmospheric particulate concentrations in metropolitan areas and beyond. One of the pollutants of concern is black carbon (BC), which is a component of aerosol particles. BC is harmful to health and acts as a radiative forcing agent in increasing the global warming due to its light absorption properties. Remote sensing data from satellites have becoming increasingly available for research, and these provide rich datasets available on global and local scale as well as in situ aethalometer measurements allow researchers to study the emission and dispersion pattern of BC from anthropogenic and natural sources. The Department of Planning, Industry and Environment (DPIE) in New South Wales (NSW) has installed recently from 2014 to 2019 a total of nine aethalometers to measure BC in its state-wide air quality network to determine the source contribution of BC and PM2.5 (particulate Matter less than 2.5 μm in diameter) in ambient air from biomass burning and anthropogenic combustion sources. This study analysed the characteristics of spatial and temporal patterns of black carbon (BC) in New South Wales and in the Greater Metropolitan Region (GMR) of Sydney, Australia, by using these data sources as well as the trajectory HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) modelling tool to determine the source of high BC concentration detected at these sites. The emission characteristics of BC in relation to PM2.5 is dependent on the emission source and is analysed using regression analysis of BC with PM2.5 time series at the receptor site for winter and summer periods. The results show that, during the winter, correlation between BC and PM2.5 is found at nearly all sites while little or no correlation is detected during the summer period. Traffic vehicle emission is the main BC emission source identified in the urban areas but was less so in the regional sites where biomass burnings/wood heating is the dominant source in winter. The BC diurnal patterns at all sites were strongly influenced by meteorology. [ABSTRACT FROM AUTHOR]

The effect of human activities on the characteristics and variations of indoor air pollutants is poorly understood, in particular for the classroom environment due to the limited reports at present. In this study, an observational campaign (17 days) was carried out in two selected classrooms (one equipped with air purifier) in a primary school of Hangzhou, China. Highly time-resolved particulate matter (PM) and black carbon (BC) were measured using Aerodynamic Particle Sizer (APS) and Aethalometer, and the diurnal variations of PM 2.5 , PM 10 , PM 20 and BC were characterized in detail. It was found that the student activities occurred throughout the daytime and could result in rapid changes in air pollutants. For example, the daytime student activities (e.g., chasing and running) strongly enhanced the PM level and changed PM diurnal pattern, in particular for coarse particles (2.5–10 μm) with short-term spikes at intervals, which was not observed under vacant conditions. The indoor BC did not show clear diurnal patterns, regardless of working days and weekends. Through absorption exponent analysis, it was inferred that the source of indoor BC was stable at most of the time, and possibly related to traffic emission. Besides, three volatile organic compounds (VOCs) samples were collected from the two classrooms, and the laboratory analysis results showed that oxygenated VOCs was a major contributor to indoor VOCs. Through inter-comparison analysis of indoor and outdoor samples, it was further found that the VOC profile of classrooms has a similar pattern with outdoor environments. Finally, the most abundant VOC species of classroom environment were identified, and their potential sources were estimated. • Variations and characteristics of PM, BC and VOCs were characterized in classroom environment. • Student activities were identified as a major source of classroom PM under occupied conditions. • The source of indoor BC was stable at most of the time. • The VOC profile of classroom environment showed similar pattern with outdoor air. [ABSTRACT FROM AUTHOR]

In order to study the characteristics of pollutants in the remote background site of Tibetan Plateau, volatile organic compounds (VOCs), NO, NO 2 , SO 2 , CO, O 3 and meteorological parameters (temperature, relative humidity, rainfall, horizontal wind speed and direction) were measured in the autumn of 2013 at Menyuan station (37.59°N, 101.29°E, 3250 m a.s.l.), which is a newly established background site located in the Tibetan Plateau. The significantly lower average concentrations of NO, NO 2 , SO 2 and CO were observed, indicating the distinct background characteristics at Menyuan. The O 3 diurnal variation pattern and correlation analyses revealed the influence of in situ photochemical reactions and vertical mixing during the daytime and the long-range and vertically downslope transport from the upper troposphere or lower stratosphere during the nighttime. A total of 30 VOCs samples were collected and 66 VOCs species were analyzed. The oxygenated VOCs (OVOCs) were the most abundant components and high levels of acetone, acetaldehyde, nonanal, hexachloro-1,3-butadiene, 1,2-dichloroethane and CCl 4 were observed. The L OH and OFP analysis confirmed that OVOCs and aromatics were the most active substances, and the VOCs had relatively stable chemical compositions and low photochemical potential. The long-range transport air masses from the southeast of Menyuan station passed by some polluted areas, such as Xining, and could result in the elevated NO x , CO and SO 2 concentrations at Menyuan. Therefore, this work enriches the understanding of O 3 cycles and transport influence in the Tibetan Plateau. • The relatively high O 3 concentrations were observed in the Tibetan Plateau. • Air masses from southeast have positive contributions to NO x , CO, SO 2 and O 3 concentrations. • The O 3 were influenced by both in situ photochemical production and vertical mixing during the day. • VOCs at Menyuan have relatively stable chemical compositions and low photochemical potential. [ABSTRACT FROM AUTHOR]

• NO x /SO x removal was integrated into NH 3 -based CO 2 capture in coal power station. • The combined NO x /SO x /CO 2 removal reduced capital cost by 23.3% in NH 3 process. • The combined NO x /SO x /CO 2 removal reduced CO 2 -avoided cost by 17.8% in NH 3 process. • The combined process has significant cost advantage over separated process. Traditional method of removing gas pollutants from a coal-fired power station involves a series of separate processes, which include selective catalytic reduction for NO x treatment, flue gas desulfurisation for SO x removal, and post-combustion CO 2 capture. Each of these individual processes involves significant capital investment. To reduce costs, we propose an alternative approach to simultaneously remove these three pollutants by incorporating NO x /SO x treatment into an aqueous NH 3 -based CO 2 capture process. In our advanced process design, NO x /SO x pollutants are effectively scrubbed by sodium chlorite (NaClO 2) oxidizing reagent, with the resultant acidic solution efficiently reducing NH 3 emissions from CO 2 absorber to <1 ppmv. An advanced, NH 3 -based flash stripper is used to achieve high capture energy performance, and flue gas heat integration is employed to further reduce the regeneration energy to 2.17 GJ/tonne CO 2. Techno-economic evaluation revealed that our NH 3 -based combined NO x /SO x /CO 2 removal process has great advantages in capital and energy saving, resulting in a CO 2 -avoided cost of $46.2/tonne, which is significantly lower than the cost of the conventional, monoethanolamine-based process ($79.1/tonne CO 2) and the base NH 3 process ($56.2/tonne CO 2). This simultaneous NO x /SO x /CO 2 capture technology provides an alternative approach to advancing multi-pollutant emission control and CO 2 -capture technology, leading to the development of a cost-effective clean coal technology. [ABSTRACT FROM AUTHOR]

As atmospheric fresh soot particles age, they become coated with other chemical species. This transforms their physicochemical properties and affects their optical characteristics, which is of great importance to air quality, the environment and climate change. One of the predominantly occurring states of soot particles in the ambient environment is the core-shell mixing state. In this study, we used the core-shell model to calculate the optical absorption, scattering and extinction efficiency, absorption proportion and absorption exponent of coated soot particles. We then investigated the effects of different core sizes (D0), incident wavelengths (λ), coating materials and coating thicknesses on these optical characteristics. Absorption efficiency and absorption proportion of soot particles decreased as the coating became thicker, at core sizes of D0 = 20, 50 and 100 nm and λ = 405, 532 and 781 nm, regardless of the type of coating material. As the coating thickness increased, the absorption exponent (β) of inorganic-coated soot particles tended to rise and then fall, while the β value of organic-coated soot particles kept increasing. Our results advance our scientific understanding of the interaction of optical properties with chemical composition, mixing state, and aging processes of soot particles in the atmosphere. [ABSTRACT FROM AUTHOR]

A field sampling campaign of volatile organic compounds (VOCs) was conducted during ozone polluted days at three sites of botanic gardens (HP), industrial areas (XS), and traffic residential mixed areas (ZH) in Hangzhou. The sampling was performed using stainless steel canisters from 6:00 to 20:00 synchronously with a time interval of 2 h on 17 May, 26 June, 20 July, 24 August, and 26 September 2018. A total of 107 species of VOCs for each sample were quantified using two standard gases with a pre-concentrator coupled by GC/MS. The Positive Matrix Factorization (PMF) model was used to identify the major VOC sources and assess their contribution to VOC concentrations. The effects of VOCs on O3 formation were investigated, based on propylene-equivalent concentrations (Prop-E), ozone formation potential (OFP), and Smog Production Model (SPM). It was found that the concentration of ozone during the sampling days tended to be highest in the downwind area while the concentrations of VOCs and NO2 in HP were rather low. The most reactive species were isoprene, ethylene, m-xylene, toluene, and propylene. The average total VOC volume mixing ratios in HP, XS, and ZH were 32.00, 36.63, and 50.34 ppbv, respectively. Bimodal profiles of propane and n-butane were exhibited in ZH while unimodal diurnal variation of isoprene was performed in HP. Liquefied petroleum gas/natural gas (LPG/NG) usage, aged background, and secondary source were identified as the major contributors to total VOCs in Hangzhou, accounting for 19.65%, 15.53%, and 18.93%, respectively. [ABSTRACT FROM AUTHOR]