Examination of in-cloud sulfate chemistry using a different model initialization In the original publication, the family name of the 3rd author was mispelled. Boro Jakimosvki should be Boro Jakimovski

The challenges of air quality modelling when crossing multiple spatial scales Abstract Multiscale air quality assessment implies understanding the interaction among atmospheric processes and scales. In this perspective, the use of air quality models has a fundamental role and the way they address these interactions is very important for the quality of results. However, in multiscale air quality modelling, the relationship between models, simulation domains and resolutions remains a challenging research issue. This paper presents a state-of-the-art review on multiscale air quality modelling applications from the regional to the street level, identifying which models are used, the methodological principles and the required input datasets. Based on the findings, an analysis of the current limitations associated with the integration of different models and multiple spatial scales in a single modelling system is presented and discussed. Lastly, taking as support the reviewed contents, a set of guidelines for strengthening the synergy among scales and harmonizing different types of models within a system is proposed. Unsuitable or non-existent urban canopy parametrizations (UCP), limited grid resolutions, discarded microscale impacts on upper domains, inadequate input data and simplified chemistry are some important aspects contributing to large uncertainties when analyzing multiscale air quality results. To overcome these shortcomings in current multiscale modelling systems, more research aimed at improving the modelling performance is required, focusing on (i) UCP coupled to mesoscale models, (ii) developing modelling systems with two-way nesting capability to boost feedbacks among domains and (iii) promoting the use, improvement and development of multiscale online modelling systems, in order to have a comprehensive multiscale understanding of all atmospheric processes that govern the transport, dispersion, transformation and deposition of air pollutants.

Macao air quality forecast using statistical methods Abstract The levels of air pollution in Macao often exceeded the levels recommended by WHO. In order for the population to take precautionary measures and avoid further health risks under high pollutant exposure, it is important to develop a reliable air quality forecast. Statistical models based on linear multiple regression (MR) and classification and regression trees (CART) analysis were developed successfully, for Macao, to predict the next day concentrations of NO2, PM10, PM2.5, and O3. All the developed models were statistically significantly valid with a 95% confidence level with high coefficients of determination (from 0.78 to 0.93) for all pollutants. The models utilized meteorological and air quality variables based on 5 years of historical data, from 2013 to 2017. Data from 2013 to 2016 were used to develop the statistical models and data from 2017 was used for validation purposes. A wide range of meteorological and air quality variables was identified, and only some were selected as significant independent variables. Meteorological variables were selected from an extensive list of variables, including geopotential height, relative humidity, atmospheric stability, and air temperature at different vertical levels. Air quality variables translate the resilience of the recent past concentrations of each pollutant and usually are maximum and/or the average of latest 24-h levels. The models were applied in forecasting the next day average daily concentrations for NO2 and PM and maximum hourly O3 levels for five air quality monitoring stations. The results are expected to be an operational air quality forecast for Macao.

Investigation of factors affecting the gaseous and particulate matter emissions from diesel vehicles Abstract This study presents a detailed investigation of diesel vehicle emissions utilizing chassis dynamometer testing. The recruited vehicle fleet consists of 15 in-use diesel vehicles, spanning a wide range of emission standards, engine sizes, weight, model year, etc. The real-time emission concentrations of nitrogen oxides (NOx), total hydrocarbons (THC), carbon monoxide (CO) and carbon dioxide (CO2), and the mass of particulate matter (PM) collected on filters are measured and used to calculate the vehicle emission factors (EFs) under various driving conditions. Results show that in general EFs of NOx, CO, THC, and PM of the recruited fleet span a wide range of values (NOx 0.80 ± 0.34 to 60.28 ± 2.94 g kg−1; THC 0.10 ± 0.04 to 5.28 ± 1.28 g kg−1; CO below detection limits to 24.01 ± 8.48 g kg−1; PM below detection limits to 2.47 ± 1.22 g kg−1). Further data analysis shows that the implementation of a higher emission standard has a significant effect on reducing the emission of pollutants, except for NOx. Driving conditions are also important factors affecting the EFs. Besides, statistical analysis shows a significant correlation between EFs of NOx with the testing weight and the maximum engine power of the vehicle. Further investigation is recommended to explore the effect of maintenance of the vehicles to the vehicular emission.

Leaves of common urban tree species ( Aesculus hippocastanum , Acer platanoides , Betula pendula and Tilia cordata ) as a measure of particle and particle-bound pollution: a 4-year study Abstract Magnetic biomonitoring using tree leaves has been proven as a proxy for airborne particle matter (PM) pollution. Since the leaf entrapment of PM is species-specific, in this study, four tree species common in urban areas of Europe and wider (Aesculus hippocastanum, Acer platanoides, Betula pendula and Tilia cordata) were investigated to evaluate which biomonitor enables consistent ‘signal’ to particle and particle-bound toxic elements. The tree leaves were sampled in the central urban and suburban parks in Belgrade (Serbia) in May and September from 2011 until 2014. Magnetic PM fractions in the samples were quantified by saturation isothermal remanent magnetization (SIRM) while the concentrations of Al, Cr, Cu, Fe, Ni, Pb and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Magnetic and elemental measurements were considered in relation to regulatory PM10 data. Median leaf SIRM values of T. cordata, A. hippocastanum and A. platanoides (174, 140 and 123 × 10−5 × A m2 kg−1, respectively) implied the considerable magnetic enhancement contrary to B. pendula (68 × 10−5 × A m2 kg−1). However, B. pendula leaves showed the significant correlation between SIRM and PM10 values (r = 0.75) and SIRM and element concentrations and significant spatio-temporal differences in SIRM/element content between the studied parks/years. These results recommend B. pendula as a valuable biomonitor of PM and the associated elements. Nevertheless, both the results (high SIRM values, the significant correlation between SIRM and PM10—r = 0.71) and literature findings (abundance, adaptability, PM removal efficiency) favour A. platanoides over B. pendula in magnetic particle biomonitoring.

Impact of air-conditioning system disinfection on microbial contamination of passenger cars Abstract An automobile air-conditioning (AC) system can be a source of microbiological contamination in a driver’s car. The aim of this study was to assess the level of microbial contamination before and after servicing of the automobile AC system, based on qualitative and quantitative analyses of bacteria and fungi isolated from the air, and to check the efficiency of different AC system cleaning methods in the removal of microbial contaminants. The study was carried out in 35 randomly selected cars, equipped with AC systems. In each car tested, viable bioaerosol samples were taken using a single-stage MAS impactor before and after servicing the AC systems. Four methods were used to disinfect the air-conditioning installations in the vehicles examined: ozonisation, application of chemical disinfectant using ultrasounds, manual application of chemical disinfectant foam and simultaneous ozonisation and application of chemical disinfectant foam. The bacterial and fungal concentrations in air samples before AC servicing in cars were between 7.5 × 101 cfu/m3 and 2.0 × 103 cfu/m3 and 4.0 × 101 cfu/m3 and 5.0 × 102 cfu/m3, respectively. Regardless of the disinfection method, after the AC service, a decrease in microbial concentrations was observed. The highest disinfection efficiency was observed for two methods: ozonisation combined with manual application of the chemical disinfectant into the air-conditioning system and spraying of the chemical disinfectant using ultrasounds. On the basis of the results obtained, it can be concluded that air-conditioning systems in cars should be regularly disinfected to eliminate microbiological contaminants, which may be the cause of adverse health effects on humans.

Evaluation of thermal climatic region areas in terms of building density in urban management and planning for Burdur, Turkey Abstract The main aim of this research is to investigate the bioclimatic conditions of Burdur city center in different terrain areas by taking measurements at 20 different points in the same time zone over the city. In order to investigate the bioclimatic comfort properties of Burdur City by taking into consideration the number of floors in Burdur city center, on 17 February 2018 between 16.00 and 16.30 h, temperature and relative humidity measurements were made with two Benetech GM8910 devices from 20 different locations with different characteristics. In addition to the parameters taken from 20 points, the physiological equivalent temperature (PET) index which includes the human energy balance was used. Thermal detection values of 20 stations were calculated. Multiple linear regression models were used for spatial distribution of the obtained values. According to the analysis, urban high building density areas have higher PET values in most of the day than in other terrestrial areas. Between these areas and open areas was a difference of 0.4–1.2 °C, between parks 2.2–3 °C, between locations 1.4–2.2 °C, and between rural areas 1.7–2.5 °C per day. There are mean PET differences.

A combination of bottom-up and top-down approaches for calculating of air emission for developing countries: a case of Ho Chi Minh City, Vietnam Abstract A comprehensive emission inventory (EI) was conducted in Ho Chi Minh City (HCMC), the largest city of Vietnam rapid urbanization rate. In 2017, HCMC had 8.6 million inhabitants with a total of nine millions of private vehicles, 19 manufacturing and industrial zones, 30 industrial clusters, and numerous other factories and enterprises. All those sources could contribute to the high levels of emissions which caused the potentially negative impact on human health and environment. The aims of this study were (i) application bottom-up and top-down approaches to conduct a complete air emission inventory, (ii) development of spatial distribution of air emission, and (iii) estimation of emission forecast for HCMC by 2025 and 2030. A combination of bottom-up and top-down approaches was employed to conduct air pollution EI, in which EMISENS model was utilized to generate the EI for road traffic sources. The results showed that the motorcycles were the main reasons of emission in HCMC, contributing 90% of CO, 68% of non-methane volatile organic compounds (NMVOC), 63% of CH4, 41% of SO2, 29% of NOx, and 18% of patriculate matter (PM2.5). The emission forecasts for HCMC by 2025 and 2030 also were calculated based on the data of strategies and plans for socioeconomic development of HCMC. The results showed that the emissions of pollutants will increase around 30 to 50% by the year 2025 and from 40 to 65% by the year 2030. If the local government does not have any plan for the reduction of emissions (scenario of socioeconomic development as usual), the emissions will increase significantly.

Modeling study on the spatial variation of the sensitivity of photochemical ozone concentrations and population exposure to VOC emission reductions in Japan Abstract Despite ozone precursor emission reduction efforts in most polluted areas worldwide, photochemical ozone remains among the most concerning air pollutants in some regions, possibly because of spatial heterogeneity of ozone sensitivity to individual precursors. However, regional differences in ozone sensitivity to volatile organic compounds (VOCs), a major precursor, have not been quantitatively shown. Therefore, this study estimated the spatial variations in the efficacy of VOC emission reductions to mitigate photochemical ozone concentrations and population exposure (as related to ozone-related health problems) over Japan, and to inform policy makers pursuing effective ozone reduction strategies in polluted regions. Using air quality simulations, we found that the abovementioned efficacy differed substantially, up to 10-fold, among 20 × 20-km areas in which VOCs had been reduced. Using the above-calculated spatial distribution of the efficacy and data on emission source locations of several industries, upstream industries (e.g., petroleum and coal products) showed greater reduction efficacies than downstream industries (e.g., plastic products). By comparing the calculated ozone sensitivity to VOCs with the ozone–NOx–VOC sensitivity derived from space-based observations of the HCHO/NO2 column ratio from the Ozone Monitoring Instrument, the general spatial trends in ozone sensitivity to VOC emission reductions were verified qualitatively. Thus, regional countermeasures should be considered rather than the existing uniform nationwide measures in Japan. Moreover, to prioritize VOC emission reductions by industry, considering the reactivity or ozone formation potential of each emitted VOC exclusively, as is currently done, is insufficient, the emission locations of each industry should also be considered.

A conceptual model to understand the soluble and insoluble Cr species in deliquesced particles Abstract Trivalent chromium is a trace nutrient essential to human beings while hexavalent chromium is a known carcinogen and was among the 18 core hazardous air pollutants defined in 2004 by the US EPA. A new conceptual model of Cr speciation in deliquesced particles (pH 4) has been developed. The model provides new information on the soluble and insoluble forms of Cr in atmospheric PM. The dominant form of Cr(VI) in the solution was found to be Cr2O72−. CrO42− was produced by the dissolution of Na2CrO4(s) and K2CrO4(s) available in the solid core, but a considerable portion of the CrO42− precipitated as (NH4)2CrO4(s), CaCrO4(s), BaCrO4(s), and PbCrO4(s). Cr(OH)3 was found to be soluble, and the insoluble form of Cr(III) was Cr2(SO4)3. Conversion of Cr(VI) to Cr(III) was higher than the conversion of Cr(III) to Cr(VI). The simulation results agree with the field measurements near Cr industries.