Surveillance efficiency evaluation of air quality monitoring networks for air pollution episodes in industrial parks: Pollution detection and source identification Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Zihan Huang, Qi Yu, Weichun Ma, Limin Chen Abstract Both air pollution detection and source identification for air pollution episodes are highly desirable for detecting and controlling industrial air pollution. Surveillance of air pollution episodes in industrial parks is the focus of this article. The surveillance in this study consists of air pollution detection and subsequent source identification. The Gaussian puff model is applied to simulate the dispersion of air pollution, and the source area analysis method is used to reconstruct unknown source terms. A case study involving hydrogen sulfide emissions in a typical chemical industrial park is presented. The long-term efficiencies of both pollution detection and source identification of a developing planning of boundary-type air quality monitoring network (AQMN) are evaluated. Five typical scenarios are identified for the evaluation. Moreover, several key factors for the surveillance efficiency variation (i.e., meteorological conditions, monitor number and distance between sources) are discussed. The efficiency of pollution detection increases with the number of monitors. The efficiency of source identification increases with the number of monitors and the distance between sources.

Opportunities and challenges for filling the air quality data gap in low- and middle-income countries Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Robert W. Pinder, Jacqueline M. Klopp, Gary Kleiman, Gayle S.W. Hagler, Yewande Awe, Sara Terry Abstract Given the millions of people suffering from air pollution, filling the air quality monitoring gap in low- and middle-income countries has been recognized as a global challenge. To meet this challenge and make it work will require private enterprise, multiple levels of government, international organizations, academia and civil society to work together toward the common goal of characterizing, understanding better, and then reducing, the air pollution that causes sickness and preventable death for millions of people each year in lowand middle-income countries around the world. This article offers concrete next steps on how to make progress toward increasing air quality monitoring using a combination of emerging technologies, adaptation to country-specific conditions, and building capacity towards the development of lasting institutions.

Influence of air pollution to incident photosynthetically active radiation during clear sky conditions in Ostrava, Czech Republic Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Marie Opálková, Michal Burda, Martin Navrátil, Vladimír Špunda Abstract This research paper focuses on with the effects of air pollutants PM10, NOx, and SO2 on the blue (400–510 nm), green (510–600 nm), and red (600–700 nm) spectral regions of photosynthetically active radiation (PAR). The measurements of solar radiation incident on a horizontal surface were taken at two locations in the city of Ostrava (Czech Republic) that differed in the source of air pollution. Linear regression models, with two explanatory variables (solar elevation angle and logarithm of individual pollutant concentration), were used as statistical tools for revealing the effect of air pollutants on incident solar radiation. The effect of air pollution on the Blue/PAR spectral ratio was ambiguous. There was a significant decrease in the Green/PAR spectral ratio, whereas there was a significant enhancement in the Red/PAR spectral ratio caused by the increasing air pollutant concentrations. The effects of air pollutants on these spectral ratios were significant from a statistical point of view with p-values smaller than 0.05, but the magnitude of the effect that the air pollutants had on the Blue/PAR and Red/PAR was small. In comparison to the above mentioned, the pollutants had a dominating effect on the Green/PAR spectral ratio. Pollution did not induce homogenous reduction of all PAR spectral regions, instead each pollutant had a specific effect on the contributions of blue, green, and red spectral regions to PAR irradiance. Possible causes of these effects are discussed.

Application of temperature dependent ozone absorption cross-sections in total ozone retrieval at Kunming and Hohenpeissenberg stations Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Haoyue Wang, Suying Chai, Xiao Tang, Bin Zhou, Jianchun Bian, Xiangdong Zheng, Holger Vömel, Ke Yu, Weiguo Wang Abstract We analyzed the temperature dependence of ozone absorption cross-sections in four data sets: the quadratic temperature data based on measurements of Bass and Paur (BPQ); data measured with the SCIAMACHY satellite spectrometer (SAC); data derived by Daumont, Brion, and Malicet (DBM); and data determined by Serdyuchenko et al. from the University of Bremen (SER). The ozone effective absorption coefficients of the Dobson and Brewer instruments at Kunming in the low-latitude stations and Hohenpeissenberg in the middle-latitude stations were calculated. The test of the total ozone column (TOC) from different ozone absorption cross-section data sets shows that in the Dobson and Brewer retrieval algorithms, the effect of temperature on the Brewer instrument is smaller than that for the Dobson instrument. The temperature sensitivity of the two instruments to the SAC is −0.005%°C−1 and 0.102%°C−1, respectively, indicating that the differences in the temperature sensitivity result in differences in the TOC measurements between the two instruments, as well as in systematic seasonal differences. Using BPQ, DBM and SER to retrieve TOC will increase the overall deviation of the two instruments by 2.5%, −2.77% and −1.89%, respectively. The consistency of the TOC retrieval in the two instruments is the best when using the SAC, which shows a deviation of only 0.03%. The systematic seasonal deviation can also be effectively improved. In addition, this work makes up for the lack of relevant research in low-latitude areas. The rangeability of the monthly mean value of the instrument system deviation at a low-latitude station is about one-half of that at the mid-latitude station (Kunming: 0.2%–1.1%, Hohenpeissenberg: 0.2%–2.0%). This is because the vertical distribution of the ozone and temperature varies in different latitudes, the seasonal variation in the middle and high latitudes is significant, and the effective temperature of ozone (Teff) in low latitudes changes little. Graphical abstract

High time-resolution measurement of light scattering hygroscopic growth factor in Beijing: A novel method for high relative humidity conditions Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Pusheng Zhao, Jing Ding, Xiang Du, Jie Su Abstract The light scattering hygroscopic growth factor (f(RH)), which quantifies the hygroscopicity of polydisperse ambient aerosols at continuous relative humidity (RH) levels, is usually measured by a humidified nephelometer system. The hygroscopicity of aerosol will change evidently under high RH conditions (>90%). However, in previous studies, only the aerosol hygroscopicity below 90% RH was generally obtained and discussed due to the difficulty in creating a stable high RH and measuring it accurately. In view of these conditions, an improved high-resolution humidified nephelometer system was established to observe the f(RH) of PM2.5 for a wide RH range between 30 and 96% in an urban area of Beijing during three seasons (winter, summer, and autumn) in 2017. Two sensors were used to calculate the humidified RHs, which made the uncertainty in the f(RH) at a high RH much lower than that in previous studies (lower than 10% for the maximum value). It was found that the f(80%) at 525 nm of PM2.5 was evidently higher under polluted conditions and highly correlated with the fractions of all of the water-soluble ions. A two-parameter fitting equation was selected to fit the observed f(RH) data. The f(RH) data under polluted conditions were more uniform with higher fitting R2values during the summer and autumn. The hygroscopicity of aerosols has probably increased compared with that in the previous study conducted in the NCP. The fitted curves of the seasonal f(RH) data showed a significant dependence on the wavelength and increased with increasing wavelength. The hygroscopicity of PM2.5 for RH > 90% was definitely lower than that for 80% < RH ≤ 90%. The hygroscopic growth of aerosols under high RH conditions can probably be overestimated by only using f(RH) data below a RH of 90%.

Assessment of indoor volatile organic compounds in Head Start child care facilities Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Danh C. Vu, Thi L. Ho, Phuc H. Vo, Mohamed Bayati, Alexandra N. Davis, Zehra Gulseven, Gustavo Carlo, Francisco Palermo, Jane A. McElroy, Susan C. Nagel, Chung-Ho Lin Abstract Exposure to volatile organic compounds (VOCs) in child care environments has raised a public concern. This study aimed to characterize indoor VOCs in four facilities of Head Start programs in Kansas city, Missouri, investigate seasonal and spatial variations in VOC levels, and assess health risks associated with children's VOC exposure. In total, 49 VOCs including aromatic and aliphatic hydrocarbons, aldehydes, glycol ethers, esters and chlorinated hydrocarbons were identified and quantified in the facilities. Significant differences were noted for the VOC concentrations among the facilities. Toluene was the most abundant aromatic hydrocarbon detected in all the air samples, with a narrow median concentration range of 2.17–3.07 μg/m3. 2-(2-Methoxyethoxy)ethanol never reported in prior research was detected in only one facility in this study, with the median (range) concentration of 0.83 (<LOD, 5.64) μg/m3. The VOC concentrations in ground-floor classrooms differed significantly from those in basement classrooms. The VOC profiles varied substantially between fall and winter. Identified emission sources of VOCs included vehicle-related emission, solvent-related emission, building materials, personal care products and household products. Through health risk assessment, potential carcinogenic compounds (i.e., benzene, ethylbenzene, naphthalene, 1,4-dichlorobenzene, tetrachloroethylene and trichloroethylene) were of concern as the total cancer risk exceeded 10−6. Future research on children's chronic exposure to these pollutants needs to further assess their possible additive and/or synergistic effects on children's health and development.

Quantification of secondary particle loading during a heavy air pollution event in Beijing: A simplified method based on coal emission indicators Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Jie Ouyang, Li-Juan Song, Ling-Ling Ma, Min Luo, Xiong-Xin Dai, Jin-Tao Zhang, Dian-Dou Xu Abstract Secondary aerosol (SA) is considered to be an increasingly dangerous air pollutant. However, quantification of SA has suffered from considerable uncertainty due to its poorly understood formation mechanism. In this study, a simplified approach based on characterizing coal combustion emission indicators polonium-210 (210Po), selenium (Se) and arsenic (As) was used to estimate SA loading (increment) during a heavy air pollution event in December 2016 in Beijing. Due to the insignificant input and output of air pollutants as well as the assumption of non-local emissions during this heavy air pollution event, a steady-state method of severe air pollution has been proposed to estimate SA increment (the sum of newly formed secondary inorganic aerosols and secondary organic aerosols) during this typical air pollution event. Corresponding algorithm of the method was developed depending on the characteristics of coal combustion related pollutants (210Po, Se, and As). The results indicated that the median contribution of newly formed SA to total suspended particulates (TSP) during this heavy air pollution event was 42.4% (interquartile range [IQR]: 36.6%–48.8%), which quantitatively confirms the dominant contribution of substantial enhancement of SA to heavy air pollution. Although further verification is needed, this steady-state method of evaluating severe air pollution has potential for quantification of the SA increment. Graphical abstract

A large eddy simulation of the dispersion of traffic emissions by moving vehicles at an intersection Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Huw Woodward, Marc Stettler, Dimitrios Pavlidis, Elsa Aristodemou, Helen ApSimon, Christopher Pain Abstract Traffic induced flow within urban areas can have a significant effect on pollution dispersion, particularly for traffic emissions. Traffic movement results in increased turbulence within the street and the dispersion of pollutants by vehicles as they move through the street. In order to accurately model urban air quality and perform meaningful exposure analysis at the microscale, these effects cannot be ignored. In this paper we introduce a method to simulate traffic induced dispersion at high resolution. The computational fluid dynamics software, Fluidity, is used to model the moving vehicles through a domain consisting of an idealised intersection. A multi-fluid method is used where vehicles are represented as a second fluid which displaces the air as it moves through the domain. The vehicle model is coupled with an instantaneous emissions model which calculates the emission rate of each vehicle at each time step. A comparison is made with a second Fluidity model which simulates the traffic emissions as a line source and does not include moving vehicles. The method is used to demonstrate how moving vehicles can have a significant effect on street level concentration fields and how large vehicles such as buses can also cause acute high concentration events at the roadside which can contribute significantly to overall exposure.

Characteristics and sources of volatile organic compounds (VOCs) in Shanghai during summer: Implications of regional transport Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Yuehui Liu, Hongli Wang, Shengao Jing, Yaqin Gao, Yarong Peng, Shengrong Lou, Tiantao Cheng, Shikang Tao, Li Li, Yingjie Li, Dandan Huang, Qian Wang, Jingyu An Abstract Intensive field measurements were carried out in urban Shanghai between 20th and 30th of May 2017, and the VOC characteristics and sources were investigated with a focus on the relative contributions of local emissions and regional transport, as well as on the potential source regions. The VOC characteristics and sources largely depended on the meteorological conditions, especially wind direction and wind speed. Generally, two kinds of episodes were associated with regional transport. In one scenario, pollutants were transported from areas upwind (north-to-northwest) of Shanghai, specifically the Suzhou-Wuxi-Changzhou and Nantong city clusters and were characterized by combustion emissions and aged air masses. In the other scenario, pollutants were transported from areas upwind (south-to-southeast) of Shanghai, specifically Ningbo-Zhoushan port, and were characterized by industrial emissions and aged air masses. Additionally, an episode associated with air masses from the clean area over the sea provided an opportunity to study the local emissions of VOCs in Shanghai. Vehicle exhaust and chemical industries, especially solvent usage, contributed a majority of the VOCs in urban Shanghai in summer, together accounting for more than 55%. The aromatic fraction of the PAMS in Shanghai was significantly higher than that in other regions in China. Regional transport and secondary formation were also important sources of VOCs, and their contribution ranged from ~15% to ~25% depending on the meteorological conditions, with an hourly maximum contribution as high as 67%. Fuel evaporation, especially leakage emissions, should be addressed in Shanghai. The present study highlights the fact that joint control of VOCs in conjunction with surrounding cities is critical for Shanghai. Graphical abstract

Numerical assessment of PM2.5 and O3 air quality in Continental Southeast Asia: Impacts of potential future climate change Publication date: 15 October 2019 Source: Atmospheric Environment, Volume 215 Author(s): Giang Tran Huong Nguyen, Hikari Shimadera, Katsushige Uranishi, Tomohito Matsuo, Akira Kondo Abstract Changing climate will impact future air quality. In this study, an online coupled meteorology and chemistry WRF-CMAQ model was applied to simulate such impacts on future O3 and PM2.5 air quality over Continental Southeast Asia. Simulations were conducted for present (2006–2015) and future (2046–2055) years under two climate scenarios, RCP4.5 and RCP8.5. Future climate projections were obtained by implementing a downscaling dynamical method based on pseudo global warming technique. In order to estimate the impacts of climate change alone, anthropogenic and biomass burning emissions were held constant at present level while biogenic emissions varying with climate were used. The model results indicated a future regional meteorology characterized by a warmer and more humid atmosphere, increased precipitation, and more stagnant condition. Affected by climate change, NOx and NMVOCs biogenic emissions increase which contribute to the increasing effects on O3 and PM2.5 precursors concentrations. Subsequently, the changes in meteorology and biogenic emission affect air quality. These influence on ground level O3 and PM2.5 are different between the two climate scenarios. Under RCP4.5 scenario, future atmosphere appears to be reduced in O3 and PM2.5 concentrations, suggesting a potential “climate benefit” for air quality. At four target countries, namely Cambodia, Laos, Thailand, and Vietnam, O3 concentration decreases by −0.76 ppb (−2.40%), PM2.5 concentration decreases by −0.95 μg/m3 (−4.32%) on average for the entire year. However, climate change worsen O3 and PM2.5 air pollution under RCP8.5 scenario. O3 concentration increases by +0.26 ppb (+0.84%), PM2.5 concentration increases by +0.92 μg/m3 (+4.20%) on average for the entire year. Significant increases were generally located in northern Vietnam (for O3) and southern Vietnam (for PM2.5) during the dry season. The analysis suggests that the decrease in O3 concentration is due to the dominancy of the negative effect of water vapor increase and the increase in O3 concentration is affected largely by the temperature increase, stagnant condition, and biogenic emission increase. The responses of PM2.5 to climate change depend on the physical and chemical characteristics of each PM2.5species. The major climate change effect on PM2.5 is the physical effect, rather than the chemical effect.