Maximum Hourly Concentrations Research Articles

Wintertime ozone surges: The critical role of alkene ozonolysis

Ozone (O3) pollution is usually linked to warm weather and strong solar radiation, making it uncommon in cold winters. However, an unusual occurrence of four high O3 episode days (with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv) was recorded in January 2018 in Lanzhou city, China. During these episodes, the average daytime concentration of total non-methane volatile organic compounds (TVOCs) reached 153.4 ± 19.0 ppbv, with alkenes—largely emitted from the local petrochemical industry—comprising 82.3 ± 13.1 ppbv. Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O3 pollution. We find that the typically low temperatures (−1.7 ± 1.3 °C) and weak solar radiation (263.6 ± 60.7 W m-2) of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals. Instead, the ozonolysis of alkenes generated Criegee intermediates, which rapidly decomposed into substantial ROx radicals (OH, HO2, and RO2) without sunlight. This radical production led to the oxidation of VOCs, with alkene ozonolysis ultimately contributing to 89.6 ± 8.7% of the O3 formation during these episodes. This mechanism did not activate at night due to the depletion of O3 by the NO titration effect. Furthermore, the findings indicate that a reduction of alkenes by 28.6% or NOx by 27.7% in the early afternoon could significantly mitigate wintertime O3 pollution. Overall, this study unravels the unique mechanism of alkene-induced winter O3 pollution and offers a reference for winter O3 reduction strategies in the petrochemical industrial regions.

Seasonal variation characteristics of atmospheric peroxyacetyl nitrate (PAN) and its source apportionment in a megacity in southern China

Owing to its biotoxicity and inductive effect on photochemical pollution, atmospheric peroxyacetyl nitrate (PAN), which is a typical product of atmospheric photochemical reactions, has attracted much research attention. However, to the best of our knowledge, few comprehensive studies have been conducted on the seasonal variation and key influencing factors of PAN concentrations in southern China. In this study, PAN, ozone (O3), precursor volatile organic compound (VOC), and other pollutant concentrations were measured online for 1 year (from October 2021 to September 2022) in Shenzhen, a megacity in the Greater Bay Area of China. The average concentrations of PAN and peroxypropionyl nitrate (PPN) were 0.54 and 0.08 parts per billion (ppb), and the maximum hourly concentrations reached 10.32 and 1.01 ppb, respectively. The results of the generalized additive model (GAM) showed that the atmospheric oxidation capacity and precursor concentration were the most important factors affecting the PAN concentration. According to the steady-state model, the average cumulative contribution to the peroxyacetyl (PA) radical formation rate by six major carbonyl compounds was calculated at 4.2 × 106 molecules cm−3 s−1, and acetaldehyde (63.0 %) and acetone (13.9 %) contributed the most. Furthermore, the photochemical-age-based parameterization method was used to analyze the source contributions of carbonyl compounds and PA radicals. The results showed that although the primary anthropogenic (40.2 %), biogenic (27.8 %), and secondary anthropogenic (16.4 %) sources were the most important contributors of PA radicals, the biogenic and secondary anthropogenic source contributions both increased considerably in summer, and the cumulative proportion of both sources reached ~70 % in July. In addition, a comparison of PAN pollution processes in different seasons revealed that in summer and winter, the PAN concentration was predominantly limited by precursors and meteorological parameters, such as light intensity, respectively.

Low sensitivity of Pinus mugo to surface ozone pollution in the subalpine zone of continental Europe.

High altitudes have been exposed to enhanced levels of surface ozone (O3) concentrations over recent decades compared to the pre-industrial era. The responses of vegetation to this toxic pollutant are species-specific and depend on the climate conditions. In this paper, we explored the reaction of Pinus mugo (P. mugo) to O3-induced stress in the continental climate of an ozone-rich mountain area in the High Tatra Mountains (Western Carpathians). The effects of O3 doses modelled by a deposition model, O3 concentrations and other factors on P. mugo were identified from (a) satellite-based data via NDVI (normalised differenced vegetation index) over 2000-2020 and (b) visible injury on needle samples gathered from P. mugo individuals at ground-truth sites in 2019 and 2020. Analysing the NDVI trend, we observed non-significant changes (p > 0.05) in the greenness of P. mugo despite growing in an environment with the average seasonal O3 concentration around 51.6 ppbv, the maximum hourly concentrations more than 90 ppbv and increasing trend of O3 doses by 0.1mmolm-2 PLA (plant leaf area) year-1. The visible O3 injury of samples collected at study sites was low (mean injury observed on 1-10% of needles' surface), and the symptoms of injury caused by other biotic and abiotic factors prevailed over those caused by O3. In addition, the correlation analyses between NDVI and the climatic factors indicated a significant (p < 0.05) and positive relationship with photosynthetic active radiation (R = 0.45) in July, and with stomatal conductance (R = 0.52) and temperature factor (R = 0.43) in August. Therefore, we concluded that the positive effect of climate conditions, which support the growth processes of P. mugo, may suppress the negative effect of the mean O3 doses of 17.8mmolm-2 PLA accumulated over the growing season.

Assessment of temporal shifting of PM2.5, lockdown effect, and influences of seasonal meteorological factors over the fastest-growing megacity, Dhaka

Dhaka is subjected to high pollution levels throughout the year, holding some relatively high amounts of pollution readings, making its air unhealthy to breathe. The study examined hourly, shifting, seasonal fluctuations in particulate matter (PM2.5), the effects of seasonal meteorological variables, and the lockdown effect over the megacity of Dhaka from 2019 to 2021 using data from AirNow. The results indicate the daily average PM2.5 concentration between 2019 and 2021 was 112.49 µg/m3, about four times higher than the WHO limit and two times higher than the Bangladesh standard. Daily PM2.5 concentrations was high during morning and evening pick-up hours, reaching a maximum hourly concentration of 472.9 µg/m3 in February 2020. The maximum average PM2.5 concentration was 211.23 µg/m3 in March 2021 (winter season), and the lowest average was 27.58 µg/m3 in August 2020 (rainy season). The Pearson correlation coefficient (r) between the PM2.5 and meteorological variables were inverse with rainfall (− 0.62), temperature (− 0.73), humidity (− 0.82), but positive with wind (0.09). Daily average Air Quality Index (AQI) concentrations improved from 108.53 to 67.99 µg/m3 during the lockdown period. Finally, the study recommended many mitigation strategies that might assist accountable authorities in lowering the number of life-threatening components in the air.

An evaluation of CO, CO2, and SO2 emissions during continuous and non-continuous operation in a gas refinery using the AERMOD.

Air quality modeling can be considered as a useful tool to predict air quality in the future and determine the control strategies of emissions abatement. In this study, the AERMOD dispersion model has been applied as a tool for the analysis of the values of pollutant emissions from the flares of the Maroon gas refinery located in the suburb of Ahvaz, Iran. First, the values of pollutant emissions from the refinery's flares were investigated by measurement and using the emission factors during cold and warm seasons of 2018. The gas burns continuously in two flares and the other 11 flares are used in emergency situations and only their spark plugs are lit. The type of compounds and their molar, volumetric, and weight percentages were determined by gas chromatography (GC) injection. By entering data such as emission rate, flare characteristics, and topographic and meteorological data of the study area into the AERMOD model, dispersion of pollutants was predicted by using the AERMOD model in the region with an area of 2500 km2. The statistical evaluation showed that the maximum 8-h concentration of CO in the cold season was 133441 μg/m3 which was higher than the standard and reached 9755 μg/m3 in the warm season that was close to the standard. The maximum hourly concentration of SO2 was in the cold season with 215 μg/m3 that was higher than the standard value, occurred in a local scale of 50 km2. This can be attributed to the high concentration of SO2 wet deposition. According to the direction of the wind from the northwest, pollutant emissions can lead to adverse health effects on the population of refinery employees, residents around the refinery, and occupants of passing vehicles. The concentration of pollutants generated due to the high volume of heavier compounds in the gas in the winter season was higher than that of the warm season. Comparison of maximum concentrations of the predicted results with the national and international standards showed that SO2 and CO concentration is higher than standard values. In total, according to the evaluation of the predictions made, the performance of the AERMOD model was acceptable in the prediction of pollutant concentrations in the study area.

Assessment of atmospheric pollutant dispersion from mobile sources in Antarctica: a case study of Vecherny Oasis

ABSTRACT The first results of high spatial resolution modeling of the dispersion of atmospheric pollutant emissions from mobile sources in Antarctica are presented. Options for assessing the impacts of vehicles on air quality in Antarctica are discussed using the Belarusian Antarctic Station at Vecherny Oasis, Enderby Land, as an example. Sources of input data and collection and processing of these data are described. Surface air concentrations of nitrogen dioxide (NO2), and concentrations and dry atmospheric deposition levels of respirable suspended particulate matter (PM10) are estimated for different averaging periods and scenarios of the volume and spatial allocation of emission. Nowadays, the number of vehicles in the oasis is small. However, by the estimates, the maximum hourly concentrations of PM10 and NO2 at certain locations and under certain conditions could reach perceptible share of the air quality guideline value. Some other Antarctic stations have significant vehicle population, and assessment of their air impacts will be especially important. Suggestions for improvements of the quantitative assessment of impacts of mobile emission sources in Antarctica are proposed.

Compliance and port air quality features with respect to ship fuel switching regulation: a field observation campaign, SEISO-Bohai

Abstract. Since 1 January 2017, ships berthed at the core ports of three designated “domestic emission control areas” (DECAs) in China should be using fuel with a sulfur content less than or equal to 0.5 %. In order to evaluate the impacts of fuel switching, a measurement campaign (SEISO-Bohai) was conducted from 28 December 2016 to 15 January 2017 at Jingtang Harbor, an area within the seventh busiest port in the world. This campaign included meteorological monitoring, pollutant monitoring, aerosol sampling and fuel sampling. During the campaign, 16 ship plumes were captured by the on-shore measurement site, and 4 plumes indicated the usage of high-SF (SF refers to the sulfur content of marine fuels). The average reduction of the mean ΔNOx∕ΔSO2 ratio from high-sulfur plumes (3.26) before 1 January to low-sulfur plumes (12.97) after 1 January shows a direct SO2 emission reduction of 75 %, consistent with the sulfur content reduction (79 %). The average concentrations of PM2.5 (particulate matter with a diameter less than 2.5 µm), NOx, SO2, O3 and CO during campaign were 147.85 µg m−3, 146.93, 21.91, 29.68 ppb and 2.21 ppm, respectively, among which NOx reached a maximum hourly concentration of 692.6 ppb, and SO2 reached a maximum hourly concentration of 165.5 ppb. The mean concentrations of carbonaceous and dominant ionic species in particles were 6.52 (EC – elemental carbon), 23.10 (OC – organic carbon), 22.04 (SO42-), 25.95 (NO3-) and 13.55 (NH4+) µg m−3. Although the carbonaceous species in particles were not significantly affected by fuel switching, the gas and particle pollutants in the ambient air exhibited clear and effective improvements due to the implementation of low-sulfur fuel. Comparison with the prevailing atmospheric conditions and a wind map of SO2 variation concluded a prompt SO2 reduction of 70 % in ambient air after fuel switching. Given the high humidity at the study site, this SO2 reduction will abate the concentration of secondary aerosols and improve the acidity of particulate matter. Based on the enrichment factors of elements in PM2.5, vanadium was identified as a marker of residual fuel ship emissions, decreasing significantly by 97.1 % from 309.9 ng m−3 before fuel switching to 9.1 ng m−3 after regulation, which indicated a crucial improvement due to the implementation of low-sulfur fuels. Ship emissions were proven to be significantly influential both directly and indirectly on the port environment and the coastal areas around Bohai Bay, where the population density reaches over 650 people per square kilometer. The results from this study report the positive impact of fuel switching on the air quality in the study region and indicate a new method for identifying the ship fuel type used by vessels in the area.

A severe fog-haze episode in Beijing-Tianjin-Hebei region: Characteristics, sources and impacts of boundary layer structure

Beijing–Tianjin–Hebei (BTH) region is recognized as one of the most polluted regions in China. In this study, characteristics, synoptic condition, boundary layer structure, and sources of a severe fog–haze episode during the December of 2016 and January of 2017 are investigated. The results show that BTH region is controlled by the uniform pressure field and southwest wind, and the average mass concentrations of PM2.5 in Beijing (BJ), Tianjin (TJ), and Shijiazhuang (SJZ) are 263.5, 192.7, and 296.1 μg/m3, respectively. Besides, the maximum hourly concentration and growth rate of PM2.5 are 578.8 μg/m3 and 13.1 μg/(m3·h), respectively for BJ. According to the wind profiler radar and L–band radar data, the maximum concentration of PM2.5 in two stages basically coincides with the minimum ventilation index (VI) value, and the minimum VI value in stage I and stage II are 5124 m2/s and 4524 m2/s. Moreover, the two stages are accompanied by significant inversion layer in the low levels. Although the maximum temperature inversion (10.8 °C) in stage I is higher that in stage II (8.3 °C) in the boundary layer, the maximum inversion strength in stage II (0.33 °C/hPa) is stronger than that in stage I (0.20 °C/hPa). Besides, weighted potential source contribution function (WPSCF) and conditional probability function analysis(CPF) are applied to investigate the potential source regions of PM2.5, the results show that southern BJ, as well as central and southern Hebei province (HB) are the main potential sources, and CPF values from the wind direction (180°–270°) are all over 0.3.

Oxides of carbon, particulate matters and volatile organic compounds impact on indoor air quality during waterpipe smoking

Air pollutants generated by indoor and outdoor sources adversely affect indoor air quality in many microenvironments. Exposure to indoor air pollutants such as hazardous volatile organic compounds (VOCs), particulate matter with diameters less than 2.5 μm (PM2.5) and 1 μm (PM1), and oxocarbons (e.g. CO and CO2) is of great concern to policy makers and environmental authorities due to their adverse impact on public health. Indoor air pollution from smoking tobacco using a waterpipe has been a worldwide public health challenge due to its toxic, carcinogenic and cardiovascular effects. This study investigates the release of PM2.5, PM1, CO2, CO and 72 VOCs to assess the indoor air quality during waterpipe tobacco smoking in a controlled microenvironment and a public cafe. Particulate matters, CO and CO2 were measured using an OSIRIS instrument, a 3M EVM-7, and a CO2 meter, respectively. The VOCs were sampled using pre-evacuated silicon-coated stainless-steel canisters with a 6-l capacity and analysed by an Agilent gas chromatograph with an Entech cryogen system following the US EPA Compendium Method (TO15). All measured pollutants in the controlled microenvironment showed increasing concentrations during the waterpipe smoking session with PM2.5, PM1, CO2 and total VOC contents reaching 31.4, 26.6, 142 and 38.4%, respectively, above their respective background concentrations. CO showed a build-up rate of 0.6 mg m−3 min−1 in the controlled microenvironment, reaching 16 mg m−3 at the end of the session. In the public waterpipe cafe, the maximum hourly concentrations of PM1, PM2.5, CO and CO2 reached 27 μg m−3, 92 μg m−3, 49.5 mg m−3 and 3244 mg m−3, respectively. These optimum values corresponded to the number of smokers present at the cafe late at night. Overall, the public waterpipe cafe had a higher concentration of pollutants compared with the controlled microenvironment due to the number of waterpipes used in the cafe. These results will provide exciting insight into waterpipe emissions in real-world settings.

APPLICATION OF ANALYTICAL HIERARCHY PROCESS (AHP) IN EVALUATING MEASURES FOR MITIGATION OF EMISSION IMPACT ON COMMUNITIES NEAR LIGNITE-FIRED POWER PLANT AT MAE MOH, THAILAND

A coal-fired steam power plant, located near an open pit coal mine in Mae Moh, Lampang, a province in the north of Thailand, has been in operation since 1978, with a generating capacity of 2,400 megawatts, and lignite consumption of 40,000 tons/day. A maximum hourly concentration of SO2 of 3,418 .g/m3 was measured and an emission of 150 tons/hour of SO2 from the power plant was estimated. In order to mitigate the impacts of the emission on human health, crops and livestock, several measures have been implemented, such as (1) installation of flue gas desulphurization units (FGD), (2) remote monitoring stations, (3) corporate social responsibility (CSR) programs, and (4) community development fund. Nevertheless, there have still been complaints about the emission from the power plant and resistance to the operation of the plant. The objective of the study is to find out the preferred measures of the people who are directly exposed to the adverse effects of the pollution. A survey was conducted in the area to interview the local villagers for their preferences among the four (4) measures with an inclusion of cessation of the plant as the fifth options. Fifty five (55) respondents who live in the vicinity of the power plant were asked to provide pair-wise comparison of their preferences of the five (5) alternatives based on four (4) different criteria as (A) job opportunity, (B) agricultural concern, (C) health improvement, and (D) public acceptability. Analytical hierarchy process (AHP) was applied to evaluate the results from the survey. The survey results show that health and income are the most important criteria. The community development fund is the most preferred alternative, while cessation of the power plant is the last option.

Analysis of Atmospheric Particulate Matter Pollution Characteristics by LIDAR in Beijing During Spring Festival, 2016

Real-time aerosol extinction retrieved by Micro-pulse LIDAR and concentrations of PM2.5 and PM10 in Beijing were analyzed to investigate the air quality during the Spring Festival. The results showed that fireworks on the New Year's Eve resulted in a sharp increase in particulate matter concentrations in a short time. The maximum concentration of PM2.5 at Guanyuan station was 639.3 μg·m-3, which increased by nearly 30 times in 9 h. The maximum hourly concentration of particulate matter at Dingling and Liulihe suburban stations were significantly higher than that in Guanyuan station, the maximum values were more than 1000 μg·m-3. The particulate matter levels were continuously high on February 10-12 and the concentration of particulate matter at Dingling and Liulihe suburban stations were higher than that at Guanyuan. LIDAR results showed no obvious changes in the extinction coefficient at Dingling on the New Year's Eve. The extinction coefficient at Liulihe was greater than 1 km-1, but the particulate matter pollution was concentrated at altitudes less than 400 m. The extinction coefficient at Chegongzhuang was still higher than 0.4 km-1 at 500 m; however, the duration of pollution was shorter than that of Liulihe. The extinction coefficients at 105 m at all three stations during the New Year's Eve were significantly higher than those at 405 m. There were significant differences in the vertical extinction characteristics of the three sites. The background maximum values of Dingling, Chegongzhuang, and Liulihe were 0.09 km-1, 0.20 km-1, and 0.19 km-1 under 1.0 km, respectively. The maximum extinction coefficients at 00:00 (midnight) were 0.23 km-1, 1.36 km-1, and 1.19 km-1, which were 2.6 times, 6.8 times, and 6.0 times higher than the background value at the same time, respectively. In summary, discharge of fireworks led to a dramatic increase in the extinction coefficient of particulate matter. Temperature inversion and lower wind speeds were the main meteorological factors that contributed to this pollution event.

Using National Ambient Air Quality Standards for fine particulate matter to assess regional wildland fire smoke and air quality management

Wildland fire is an important ecological process in the California Sierra Nevada. Personal accounts from pre-20th century describe a much smokier environment than present day. The policy of suppression beginning in the early 20th century and climate change are contributing to increased megafires. We use a single particulate monitoring site at the wildland urban interface to explore impacts from prescribed, managed, and full suppression wildland fires from 2006 to 2015 producing a contextual assessment of smoke impacts over time at the landscape level. Prescribed fire had little effect on local fine particulate matter (PM2.5) air quality with readings typical of similar non-fire times; hourly and daily good to moderate Air Quality Index (AQI) for PM2.5, maximum hourly concentrations 21–103 μg m−3, and mean concentrations between 7.7 and 13.2 μg m−3. Hourly and daily AQI was typically good or moderate during managed fires with 3 h and one day reaching unhealthy while the site remained below National Ambient Air Quality Standards (NAAQS), with maximum hourly concentrations 27–244 μg m−3, and mean concentrations 6.7–11.7 μg m−3. The large high intensity fire in this area created the highest short term impacts (AQI unhealthy for 4 h and very unhealthy for 1 h), 11 unhealthy for sensitive days, and produced the only annual value (43.9 μg m−3) over the NAAQS 98th percentile for PM2.5 (35 μg m−3). Pinehurst remained below the federal standards for PM2.5 when wildland fire in the local area was managed to 7800 ha (8–22% of the historic burn area). Considering air quality impacts from smoke using the NAAQS at a landscape level over time can give land and air managers a metric for broader evaluation of smoke impacts particularly when assessing ecologically beneficial fire. Allowing managers to control the amount and timing of individual wildland fire emissions can help lessen large smoke impacts to public health from a megafire.

Intra-diurnal and daily changes in Didymella ascospore concentrations in the air of an urban site

Didymella species are common plant pathogens affecting mainly cereal crops in countries with temperate climates, and their airborne spores are also a potential human allergen. A 5-y monitoring study was carried out at an urban site in the UK to establish the most likely exposure time in order to alert people sensitised to spores of this genus. Didymella ascospores occurred in air with a bimodal pattern, with peak concentrations occurring at 03:00 and 22:00. The majority of ascospores were observed from 20:30 to 07:30 according to a multivariate regression tree analysis. Similarly, circular tests indicated that the maximum hourly concentrations occurred in the morning hours. The highest ascospore concentrations were observed in very humid conditions occurring after rainfall. The observations taken from an urban site were delayed in relation to the time of ascospore release previously reported from field sites. Thus, there is a high possibility of regional transport of ascospores in the atmosphere from remote sources.

An analysis of the exposure time to very high concentrations of Cladosporium conidia in the air of an urban site

Cladosporium spp. is a ubiquitous mould present both in indoor and outdoor environments and affecting a wide array of substrates. It is considered to be the second most important fungal aeroallergen in countries of temperate climates, after Alternaria species. In order to establish the time of exposure to very high concentrations of Cladosporium conidia by sensitised individuals, a 5-year study was undertaken in the UK in a densely populated area using a volumetric air sampler. Weather data, comprised air temperature, precipitation, relative humidity and wind speed were collected simultaneously. Cladosporium showed a mono-modal pattern with the majority of conidia observed between 09:30 and 19:00 as indicated by descriptive statistics and multivariate regression tree analysis. On the other hand, circular statistics showed that the maximum hourly concentrations were found within 1.5-h window before 09:30. The highest conidia concentrations were observed when dry conditions occurred (40–55%). The maximum temperature associated with peak concentrations was oscillating within the range of 20–25 °C. All findings were confirmed using Kruskal–Wallis, Friedman and sign tests.

Integrated studies of a regional ozone pollution synthetically affected by subtropical high and typhoon system in the Yangtze River Delta region, China

Abstract. Severe high ozone (O3) episodes usually have close relations to synoptic systems. A regional continuous O3 pollution episode was detected over the Yangtze River Delta (YRD) region in China during 7–12 August 2013, in which the O3 concentrations in more than half of the cities exceeded the national air quality standard. The maximum hourly concentration of O3 reached 167.1 ppb. By means of the observational analysis and the numerical simulation, the characteristics and the essential impact factors of the typical regional O3 pollution are comprehensively investigated. The observational analysis shows that the atmospheric subsidence dominated by the western Pacific subtropical high plays a crucial role in the formation of high-level O3. The favorable weather conditions, such as extremely high temperature, low relative humidity and weak wind speed, caused by the abnormally strong subtropical high are responsible for the trapping and the chemical production of O3 in the boundary layer. In addition, when the YRD cities are at the front of Typhoon Utor, the periphery circulation of typhoon system can enhance the downward airflows and cause worse air quality. However, when the typhoon system weakens the subtropical high, the prevailing southeasterly surface wind leads to the mitigation of the O3 pollution. The integrated process rate (IPR) analysis incorporated in the Community Multi-scale Air Quality (CMAQ) model is applied to further illustrate the combined influence of subtropical high and typhoon system in this O3 episode. The results show that the vertical diffusion (VDIF) and the gas-phase chemistry (CHEM) are two major contributors to O3 formation. During the episode, the contributions of VDIF and CHEM to O3 maintain the high values over the YRD region. On 10–12 August, the cities close to the sea are apparently affected by the typhoon system, with the contribution of VDIF increasing to 28.45 ppb h−1 in Shanghai and 19.76 ppb h−1 in Hangzhou. In contrast, the cities far away from the sea can hardly be affected by the periphery circulation of typhoon system. When the typhoon system significantly weakens the subtropical high, the contribution values of all individual processes decrease to a low level in all YRD cities. These results provide an insight for the O3 pollution synthetically impacted by the western Pacific subtropical high and the tropical cyclone system.

Air Quality at Devils Postpile National Monument, Sierra Nevada Mountains, California, USA

Ambient concentrations of O_3, PM_(2.5), NH_3, NO, NO_2, HNO_3, SO_2 and VOCs were measured at Devils Postpile National Monument (DEPO) during the summer seasons of 2013 and 2014. The measurements were impacted by the Aspen and Rim Fires in 2013, and the French and King Fires in 2014. While O_3 concentrations were not discernibly perturbed by the fire events, the 70 ppb threshold (8-hour average) corresponding to both the current California Ambient Air Quality Standard (CAAQS) and the new National Ambient Air Quality Standard (NAAQS) was exceeded on five days during 2013, and on 16 days during 2014. The older NAAQS of 75 ppb (8-hour average) was exceeded once in 2013, and six times in 2014. Exceedances of the CAAQS or NAAQS occurred when background sources of O_3 were augmented by regional-scale transport, at higher altitudes, of polluted air masses that had passed through the San Joaquin Valley before arriving at the DEPO site. The 2013 Aspen Fire elevated PM_(2.5) to a maximum hourly concentration of 214 μg m^(-3) and a maximum 24 h mean of 92.7 μg m^(-3), and resulted in 13 exceedances of the 35 μg m^(-3) (24 h average) NAAQS for PM_(2.5). The 2013 Rim Fire increased PM_(2.5) to a maximum hourly concentration of 132 μg m^(-3) and a maximum 24 h mean of 69.6 μg m^(-3), and resulted in two exceedances of the 24 h NAAQS. Concentrations of NH_3 increased during all fires, as did those of NO_2 during the Aspen and Rim Fires. Concentrations of benzene increased substantially during the French Fire.

Measurement of fine particulate matter water-soluble inorganic species and precursor gases in the Alberta Oil Sands Region using an improved semicontinuous monitor

The ambient ion monitor–ion chromatography (AIM-IC) system, which provides hourly measurements of the main chemical components of PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm) and its precursor gases, was evaluated and deployed from May to July 2011 and April to December 2013 in the Athabasca Oil Sands Region (AOSR) of northeastern Alberta, Canada. The collection efficiencies for the gas-phase SO2 and HNO3 using the cellulose membrane were 96% and 100%, respectively, and the collection efficiency of NH3 using the nylon membrane was 100%. The AIM-IC was compared with a collocated annular denuder sampling system (ADSS) and a Federal Reference Method (FRM) Partisol PM2.5 sampler. The correlation coefficients of SO42− concentrations between the AIM-IC and ADSS and between the AIM-IC and the Partisol PM2.5 sampler were 0.98 and 0.95, respectively. The comparisons also showed no statistically significant difference between the measurement sets, suggesting that the AIM-IC measurements of the PM2.5 chemical composition are comparable to the ADSS and Partisol PM2.5 methods. NH3 concentration in the summer (mean ± standard deviation, 1.9 ± 0.7 µg m−3) was higher than in the winter (1.3 ± 0.9 µg m−3). HNO3 and NO3− concentrations were generally low in the AOSR, and especially in the winter months. NH4+ (0.94 ± 0.96 µg m−3) and SO42− (0.58 ± 0.93 µg m−3) were the major ionic species of PM2.5. Direct SO2 emissions from oil sands processing operations influenced ambient particulate NH4+ and SO42− values, with hourly concentrations of NH4+ and SO42− measured downwind (~30 km away from the stack) at 10 and 28 µg m−3. During the regional forest fire event in 2011, high concentrations of NO3−, NH4+, HNO3, NH3, and PM2.5 were observed and the corresponding maximum hourly concentrations were 31, 15, 9.6, 89, and >450 (the upper limit of PM2.5 measurement) µg m−3, suggesting the formation of NH4NO3.Implications: The AOSR in Canada is one of the most scrutinized industrial regions in the developed world due to the extent of oil extraction activities. Because of this, it is important to accurately assess the effect of these operations on regional air quality. In this study, we compare a new analytical approach, AIM-IC, with more standard analytical approaches to understand how local anthropogenic and nonanthropogenic sources (e.g., forest fires) impact regional air quality. With this approach, we also better characterize PM2.5 composition and its precursor gases to understand secondary aerosol formation mechanisms and to better identify possible control techniques if needed.

Enhanced formation of fine particulate nitrate at a rural site on the North China Plain in summer: The important roles of ammonia and ozone

Severe PM2.5 pollution was observed frequently on the North China Plain, and nitrate contributed a large fraction of the elevated PM2.5 concentrations. To obtain a comprehensive understanding of the formation pathways of these fine particulate nitrate and the key factors that affect these pathways, field measurements of fine particulate nitrate and related air pollutants were made at a rural site on the North China Plain in the summer of 2013. Extremely high concentrations of fine particulate nitrate were frequently observed at night and in the early morning. The maximum hourly concentration of fine particulate nitrate reached 87.2 μg m−3. This concentration accounted for 29.9% of the PM2.5. The very high NH3 concentration in the early morning significantly accelerated the formation of fine particulate nitrate, as indicated by the concurrent appearance of NH3 and NO3− concentration peaks and a rising neutralization ratio (the equivalent ratio of NH4+ to the sum of SO42− and NO3−). On a number of other episode days, strong photochemical activity during daytime led to high concentrations of O3 at night. The fast secondary formation of fine particulate nitrate was mainly attributed to the hydrolysis of N2O5, which was produced from O3 and NO2. Considering the important roles of NH3 and O3 in fine particulate nitrate formation, we suggest the control of NH3 emissions and photochemical pollution to address the high levels of fine particulate nitrate and the severe PM2.5 pollution on the North China Plain.

Environmental pollution in Mongolia: Effects across the lifespan

Mongolia has undergone rapid urbanization and significant economic expansion since 1991, when the country emerged from Soviet domination. It is a vast country mostly comprising open steppe, desert and mountain ranges and in the open country is one of the cleanest places on earth. However, Ulaanbaatar, the capital city lies on a high altitude plateau in a bowl surrounded by mountains, which in the winter months is subject to atmospheric inversion. The population of Ulaanbaatar is just over 1 million, about 40% of whom live in apartment homes, while the remaining 60% still live in the traditional nomadic round felt tents called Gers or houses in surrounding ger areas. Because of the extremely cold temperatures in the winter months (−40 °F is a common daily low), heating is a major issue. Most Gers and houses in ger areas in Ulaanbaatar are heated by burning coal in traditional Ger stoves, which are actually designed to burn Yak dung or wood out on the Steppe. Air pollution has recently become a very serious public health problem in Ulaanbaatar with ground level air pollution, measured in terms of particulate matter (PM), >200 times WHO safety guidelines. Measurements carried out in Ulaanbaatar from November 17 to 28 have shown a maximum daily concentration of 600 µg/m3 (PM10) and 350 µg/m3 (PM2.5) with maximum hourly concentrations exceeding 1300 (PM2.5) and 2500 (PM10) µg/m3. These levels vastly exceed the Mongolian target average daily concentrations of 50 (PM2.5) and 100 (PM10) µg/m3. We measured markedly (3-fold) elevated ambient and expired carbon monoxide (CO) levels in Mongolian school children in the summer months in Ulaanbaatar, compared to school children studied in a rural Aimag on the open steppe (Dashdendev et al., 2011). Importantly the lung function of the children on the steppe was significantly better than those living in Ulaanbaatar. So we concluded that the level of urban air pollution in the capital city is clearly having an adverse impact on the pulmonary health of urban Mongolian children. Since the Ger stove is not needed for heating in the summer months, we speculated that the summer pollution relates more to vehicular emissions. Vehicular traffic has increased dramatically throughout Mongolia, but particularly in Ulaanbaatar over the last decade. Many of these privately owned vehicles are second hand models that lack catalytic converters. We speculate that this level of urban pollution in winter and summer is adversely affecting the pulmonary as well as other aspects of health of the Mongolian population across the lifespan. However, because >50% of the Mongolian population is under 25 years of age, the impact will disproportionately fall upon children and young women of child bearing age. Similar patterns of adverse health risk such as asthma, obesity and autism in proximity to freeways and major roads have previously been well documented by us and our colleagues in Los Angeles, CA. In this issue of Environmental Research, collaborating public health researchers from Taiwan and Mongolia correlated SO2 and NO2 levels in Ulaanbaatar with land use patterns. They conclude that SO2 and NO2 concentrations are very high in Ulaanbaatar, especially in the winter, and that this can be explained by several land use variables, including proximity to the Ger areas, the city center, the main roads, and the city power plants, which lie upwind. These findings are a productive step towards identifying sources of air pollutants that can be targeted for regulatory interventions. There is therefore clearly an urgent need for environmental health research and implementation of an air pollution reduction program in Mongolia. This need has been increasingly recognized in recent years in position papers by the Mongolian Government and the Mongolian scientific community, wherein the respiratory environmental health cost of pollution has been conservatively estimated as 4% of GDP. Some preliminary successes in policy implementation were funded by the Millennium Challenge Account for the distribution of 20,000 modern, efficient heating and cooking stoves for Gers. This is a step in the right direction, however, much more remains to be done to understand the dimensions of the pollution problem in Ulaanbaatar and to abate vehicular, industrial and domestic pollution levels back to the pristine steppe it once was.

The relative impacts of distributed and centralized generation of electricity on local air quality in the South Coast Air Basin of California

This paper examines the air quality impact of using distributed generation (DG) to satisfy future growth in power demand in the South Coast Air Basin of Los Angeles, relative to the impact when the demand is met by expanding current central generation (CG) capacity. The impact of decreasing boiler emissions by capturing the waste heat from DGs is not examined. The air quality impacts of these two alternate scenarios are quantified in terms of hourly maximum ground-level and annually averaged primary NOx concentrations, which are estimated using AERMOD. This study focuses on the impact of primary emissions at source–receptor distances of tens of kilometers. We find that the shift to DGs has the potential for decreasing maximum hourly impacts of power generation in the vicinity of the DGs. The maximum hourly concentration is reduced from 25 to 6ppb if DGs rather than CGs are used to generate power. However, the annually averaged concentrations are likely to be higher than for the scenario in which existing CGs are used to satisfy power demand growth. Future DG penetration will add an annual average of 0.1ppb to the current basin average, 20ppb, while expanding existing CGs will add 0.05ppb.