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While pavements are currently a significant contributor to the urban heat island effect, modified pavements could play a role in cooling cities. Specifically, the radiative and thermal properties of pavements can be manipulated to alter the timing and magnitude of sensible heat storage and release into the urban airshed. The present study developed and applied a one-dimensional heat transfer model to Phoenix AZ as a case study to explore the potential for modified pavements in a hot desert climate. We explored solar reflective (0.35 albedo) and traditional (0.10 albedo) asphalt pavements. Pavement thermal conductivity and heat storage capacity values were varied across a reasonable range based on existing products. The results from this study show that daytime peak surface temperature of highly conductive (2.4 WK-1m−1) and thermally massive pavements (4.0 MJK-1m−3) is 17.5 °C cooler than less conductive (0.4 WK-1m−1) and thermally light (1.0 MJK-1m−3) pavements. However, at night, the more thermally massive and conductive pavements were as much as 10.8° C warmer than the less conductive and less massive counterpart. Therefore, when the focus is on reducing excess urban heat during the day, it is better to use pavement materials with higher conductivity and thermal storage. However, when the focus is on reducing the nocturnal heat island, it is wise to use lower conductivity and lower thermal storage pavements. Regardless of thermal properties, the use of reflective pavement surfaces will mitigate both the daytime and nocturnal urban heat island effect. We find up to a 10° C reduction in peak daytime surface temperature and a modest reduction of nocturnal temperatures (by up to 1.0° C) when pavement albedo is increased by 0.25. However, reflective pavements result in a higher influx of net radiation for pedestrians walking on these surfaces during the daytime. So, reflective pavement projects should be evaluated for potential adverse impacts on thermal comfort. Nevertheless, depending upon the time of day and the overall solar reflectivity of pedestrian clothing and skin, we argue that the benefits of reduced surface and air temperatures associated with highly reflective paving likely outweigh the adverse effects for pedestrians. However, for regions where daytime thermal comfort is of primary concern, pavements with higher thermal conductivity and thermal storage may perform better than reflective pavements.

The smaller particles that dominate the particle number concentration (PNC) in the ambient air only contribute to a small percentage of particulate matter (PM) mass concentration although present in high particle number concentration. These small particles may be neglected upon assessing the health impacts of the PM. Hence, the knowledge on the particle number concentration size distribution deserves greater attention than the particulate mass concentration. This study investigates the measurement of the particle mass concentrations (PM2.5) and PNC of 0.27 μm

Atmospheric delivery of mercury (Hg) is important to the Upper Great Lakes, and understanding gaseous Hg exchange between surface water and air is critical to predicting the effects of declining me...

The global expansion of harmful cyanobacterial blooms (CyanoHABs) poses an increasing threat to public health. CyanoHABs are characterized by the production of toxic metabolites known as cyanotoxins. Human exposure to cyanotoxins is challenging to forecast, and perhaps the least understood exposure route is via inhalation. While the aerosolization of toxins from marine harmful algal blooms (HABs) has been well documented, the aerosolization of cyanotoxins in freshwater systems remains understudied. In recent years, spray aerosol (SA) produced in the airshed of the Laurentian Great Lakes (United States and Canada) has been characterized, suggesting that freshwater systems may impact atmospheric aerosol loading more than previously understood. Therefore, further investigation regarding the impact of CyanoHABs on human respiratory health is warranted. This review examines current research on the incorporation of cyanobacterial cells and cyanotoxins into SA of aquatic ecosystems which experience HABs. We present an overview of cyanotoxin fate in the environment, biological incorporation into SA, existing data on cyanotoxins in SA, relevant collection methods, and adverse health outcomes associated with cyanotoxin inhalation.

STS scholars offer the atmosphere as an antidote to the homogenizing Anthropocene. They teach us that atmospheres are good to think because they are both diffuse and differential; they reflect the scale of planetary problems without forgetting that those problems manifest unevenly. The atmosphere has, then, become a useful tool for theory work. But it is also being picked up on the ground as a model for grassroots coalition building. This article follows one group we might call an atmospheric coalition, which coalesced to fight a trash incinerator proposed in south Baltimore City. That incinerator would have had a major impact on the local air, particularly due to heavy-metal toxics that land close to their source. But it also would have affected a large regional airshed and released thousands of tons of greenhouse gases. Taking a cue from these multi-scalar impacts, the coalition to stop the incinerator both used the medium of air to trouble insider/outsider dichotomies and valued an uneven distribution of power, letting youth from the frontline community lead. Participants, in other words, built a flexible alliance—and they utilized its flexibility. Sometimes it was advantageous to call the incinerator “everyone’s problem.” Sometimes it was necessary to underscore its differential effects on local people. And sometimes the transience of atmospheric claims worked to transfer jurisdiction over the plant from one group to another. In the process of exploring these maneuvers, I argue that activists used the atmosphere to define a problem-space with pliant parameters of authority and vulnerability.

Evaluation of downscaled meteorological information is crucial to identifying model behaviors that may propagate to end applications such as the simulation of local air quality. This study conducted and assessed yearlong simulations of hourly meteorological conditions over the Terrace–Kitimat Valley of northwestern British Columbia, Canada, at 1-km horizontal gridding for six PBL schemes in the Weather and Forecasting (WRF) Model, version 4.0. In terms of key surface meteorological variables that affect air quality, simulations over land demonstrated better skill for specific humidity and wind direction than for air temperature and wind speed. Spatial differences in modeled atmospheric properties and vertical profiles, especially for moisture content, were used to diagnose the relative capacity of each PBL scheme to represent pollutant dispersion and dilution. Stable conditions at night increased suppression of boundary layer mixing by the nonlocal Yonsei University (YSU) scheme when compared with suppression by the local eddy-diffusion component of the Asymmetric Convective Model, version 2 (ACM2), scheme, resulting in decreased wind speed and ambient temperature but moister air with the YSU scheme. The weakening of mixing by the Mellor–Yamada–Nakanishi–Niino (MYNN3) scheme with inland distance suggested that higher-order, nonlocal transport is sensitive to increasing topographic steepness toward the northern part of the valley. Disparities in mixing strengths among PBL schemes were greater in the summer when conditions were generally less stable with moist, warm air blowing inland than in winter when the valley channels cold, stable air from the interior. Increased convection in daytime led to greater entrainment of air from aloft and a thicker PBL with the YSU scheme than with the ACM2 scheme in summer while increasing countergradient transport in the MYNN3 scheme that reduces dilution.

This study investigated the short-term effects of exposure particulate matter (PM10) in Zabol, Iran, from 2013 to 2015. The concentrations of PM10 recorded from 2013 to 2015 were given as the input to the software (AirQ 2.2.3) developed by the World Health Organization (WHO) to estimate the attributed proportion of the health effects and the number of excess cases related to total mortality (TM), cardiovascular mortality (CM), respiratory mortality (RM), hospital admissions due to cardiovascular disease (HACD), and hospital admissions due to respiratory disease (HARD). According to the data, 73 days during 2013–2014 and 144 days during 2014–2015 in Zabol exceeded the National Ambient Air Quality Standards (NAAQS) guideline limits. This finding indicates the impact of the windy period on the ambient air condition of Zabol’s airshed. Moreover, the number of excess cases attributed to TM, CM, RM, HACD, and HARD per 100,000 people was estimated as 182, 96, 18, 94, and 243 individuals during 2013–2014. However, these values increased by about 50% during 2014–2015. This significant level of health effects of PM10 on the residents of Zabol necessitates urgent controlling/management actions to reduce dust storms in this region.

Ozone pollution has been prevalent in the El Paso-Juárez Airshed (EPJA), especially in the past few decades, and it has been on the rise recently. The spatial and temporal distribution of the tropospheric ozone and several key meteorological factors that influence its concentration has not been adequately understood. Therefore, this investigation comprehensively examined 57 high and 48 low ozone episodes occurring in this region during 2013–2019. We found that the interannual ozone concentration in EPJA was strongly affected by anthropogenic emissions. On the other hand, seasonal ozone variations are due to meteorological variables (among them, solar radiation, planetary boundary layer, and winds) in addition to biogenic emission factors. High ozone events are characterized by calm winds, shallow planetary boundary layer (PBL), whereas low ozone events were marked with strong winds, precipitation, and deep PBL. Synoptic and mesoscale wind patterns for these ozone episodes were identified and characterized. Most of the high ozone episodes occurred when an anticyclonic circulation aloft was associated with a 500-mile middle and upper tropospheric high-pressure region over the EPJA. During these events, stable air masses with convective available potential energies (CAPE) values of less than 450 J/kg were found. The importance of surface topography is illustrated by the fact that stations close to the Rio Grande River show a bimodal distribution of wind direction according to the valley axis. High ozone episodes occur with a surface easterly wind that is decoupled from winds above the Franklin mountains.

The direct aerosol-radiative effects in the WRF-Chem model account for scattering/absorption of solar radiation due to aerosols, while aerosol–cloud interactions result in modifying wet scavenging of the ambient concentrations as an indirect aerosol effect. In this study, impact of aerosol on meteorological parameters, PM10 and ozone concentrations are analysed which revealed (i) that a net decrease in shortwave and longwave radiation by direct feedback results in decrease in temperature up to 0.05 K, (ii) that a net increase due to longwave and shortwave radiation when both direct and indirect effects are taken together results in an increase in temperature up to 0.25 K (where the mean of temperature is 33.5 °C and standard deviation 2.13 °C), (iii) a marginal increase in boundary layer height of 50 m with increase in temperature with feedbacks, (iv) overall net increase in radiation by direct and indirect effect together result in an increase in PM10 concentration up to 12 μg m−3 (with PM10 mean as 84.5 μg m−3 and standard deviation 28 μg m−3) and an increase in ozone concentration up to 3 μg m−3 (with ozone mean as 29.65 μg m−3 and standard deviation 5.2 μg m−3) mainly due to net increase in temperature. Furthermore, impact of sensitivity of different aerosol mechanisms on PM10 concentrations was scrutinized for two different mechanisms that revealed underestimation by both of the mechanisms with MOSAIC scheme, showing less fractional bias than MADE/SORGAM. For the dust storm period, MOSAIC scheme simulated higher mass concentrations than MADE/SORGAM scheme and performed well for dust-storm days while closely capturing the peaks of high dust concentrations. This study is one of the first few to demonstrate the impact of both direct and indirect aerosol feedback on local meteorology and air quality using a meteorology–chemistry modelling framework, the WRF-Chem model in a tropical urban airshed in India located in semi-arid climatic zone. It is inferred that semi-arid climatic conditions behave in a vastly different manner than other climatic zones for direct and indirect radiative feedback effects.

Background Previous work has determined an association between proximity to active surface mining in coal producing counties within Central Appalachia and an increased risk of preterm birth (PTB) and low birthweight (LBW); however, the relative importance of specific exposure pathways explaining this association remains poorly understood. Multiple potential exposure pathways to surface mining activities exist during gestation, including inhalation of particulate matter (airshed exposure), or via exposure to impacted surface waters (watershed exposure). Here, we perform a mediation analysis to explore these pathways and the odds of adverse birth outcomes. Methods We obtained birth records acquired through health departments in WV, KY, VA and TN between 1990 and 2015. Surface mine extents for each year were identified through remotely sensed Landsat imagery. Corresponding airsheds were estimated using the HYSPLIT4 atmospheric trajectory model, while watersheds were assigned using United States Geological Survey’s Watershed Boundary Dataset boundaries. We performed logistic regression to determine associations between exposure and the odds of preterm birth, low birthweight, and term low birthweight, and iteratively included within our models: a) the percent of active surface mining landcover within a 5 km buffer of maternal residence; b) the cumulative potential exposure to air pollutants via the airshed experienced at the maternal residence, and; c) the percent of land experiencing surface mining within the watershed of residency. Results Our baseline models found that active surface mining was associated with an increased odds of PTB (1.09, 1.05 – 1.13) and LBW (1.06, 1.02 – 1.11), while controlling for significant predictors. When mediators were added to the base model, the association between active mining and birth outcomes was reduced (PTB: 1.04, 0.99 – 1.09; LBW 1.04, 0.99 – 1.10), while the odds of PTB and LBW increased with airshed exposure (PTB: 1.14, 1.11 – 1.18; LBW: 1.06, 1.03 – 1.10). Conclusions Results were consistent with a hypothesis of mediation via airshed, but suggested mediation via watershed was less likely. These results suggest that air pollution resulting from surface mining activities may be the primary exposure pathway explaining the association between maternal residence proximity to active surface mining and PTB and LBW.

The overall objective of the study was to characterize drayage truck activity and associated emissions in the Paso del Norte region, which is the binational region covering El Paso in Texas and Ciudad Juárez in Mexico. Drayage trucks are a significant source of emissions in the Paso del Norte airshed. The region faces air quality problems and characterizing the unique operational and emission characteristics of drayage vehicles can better support regional air quality planning. In this study, the global positioning system and portable activity measurement system units were fitted to a sample of drayage trucks operating in the El Paso region. The resulting data were analyzed to generate trip-level information on truck activity, along with key parameters, such as speeds, origin, destination, and length. The individual trip information was also used to identify key freight corridors and to estimate emissions associated with drayage activity. The study dataset showed that the Ysleta-Zaragoza International Bridge is the most utilized by the trucks. The facilities visited in the United States tended to be more clustered closer to this bridge, in less urbanized areas, while facilities visited in Mexico tended to be more spread out geographically. Corridor truck volumes and emissions were plotted on maps to visualize emission impacts of drayage trucks, with urbanized areas and areas close to border bridges likely most affected because of higher volumes and emissions. The findings from the study provide an understanding of air quality impacts of drayage trucks in the Paso del Norte airshed.

Bengaluru - capital of the state of Karnataka is the original “Silicon Valley” of India. In this paper, we present a comprehensive snapshot of the state of air quality in Bengaluru, along with an emissions inventory for the pollutants necessary for chemical transport modeling at 0.01° grid resolution (approximately 1-km), for an urban airshed covering 60 × 60 grids (4300 km2). For 2015, emission estimates for the city are 31,300 tons of PM2.5, 67,100 tons of PM10, 5300 tons of SO2, 56,900 tons of NOx, 335,550 tons of CO, and 83,500 tons of NMVOCs. Overall, transport is the key emission source for Bengaluru - vehicle exhaust and on-road dust resuspension account for a combined 56% and 70% of total PM2.5 and PM10 emissions; followed by industries (17.8% including the brick kilns), open waste burning (11.0%), and domestic cooking, heating, and lighting (6.5%), in case of PM2.5. We conducted particulate pollution source apportionment of local and non-local sources, using WRF meteorological model and CAMx chemical transport modeling system. A comparison of range of 24-hr average modeled PM2.5 concentrations (36.5 ± 9.0 μg/m3) and monitored PM2.5 concentrations (32.3 ± 24.2 μg/m3) by month, shows that the model catches the quantitative ranges and qualitative trends. The modeled source contributions highlight the vehicle exhaust (28%) and dust (including on-road resuspended dust and construction activities) (23%), and open waste burning (14%), as the key air pollution sources. Unless there is an aggressive strategy to improve urban planning and public transport options, pollutant emissions under the business as usual scenario are expected to increase at least 50% in 2030 and doubling the urban area with PM2.5 annual averages above the national ambient standard of 40 μg/m3.

Semi-volatile and intermediate-volatility organic compounds (SVOCs and IVOCs) from anthropogenic sources are likely to be important precursors of secondary organic aerosol (SOA) in urban airsheds, yet their treatment in most models is based on limited and obsolete data or completely missing. Additionally, gas-phase oxidation of organic precursors to form SOA is influenced by the presence of nitric oxide (NO), but this influence is poorly constrained in chemical transport models. In this work, we updated the organic aerosol model in the UCD/CIT (University of California at Davis/California Institute of Technology) chemical transport model to include (i) a semi-volatile and reactive treatment of primary organic aerosol (POA), (ii) emissions and SOA formation from IVOCs, (iii) the NOx influence on SOA formation, and (iv) SOA parameterizations for SVOCs and IVOCs that are corrected for vapor wall loss artifacts during chamber experiments. All updates were implemented in the statistical oxidation model (SOM) that simulates the oxidation chemistry, thermodynamics, and gas–particle partitioning of organic aerosol (OA). Model treatment of POA, SVOCs, and IVOCs was based on an interpretation of a comprehensive set of source measurements available up to the year 2016 and resolved broadly by source type. The NOx influence on SOA formation was calculated offline based on measured and modeled VOC:NOx ratios. Finally, the SOA formation from all organic precursors (including SVOCs and IVOCs) was modeled based on recently derived parameterizations that accounted for vapor wall loss artifacts in chamber experiments. The updated model was used to simulate a 2-week summer episode over southern California at a model resolution of 8 km. When combustion-related POA was treated as semi-volatile, modeled POA mass concentrations were reduced by 15 %–40 % in the urban areas in southern California but were still too high when compared against “hydrocarbon-like organic aerosol” factor measurements made at Riverside, CA, during the Study of Organic Aerosols at Riverside (SOAR-1) campaign of 2005. Treating all POA (except that from marine sources) to be semi-volatile, similar to diesel exhaust POA, resulted in a larger reduction in POA mass concentrations and allowed for a better model–measurement comparison at Riverside, but this scenario is unlikely to be realistic since this assumes that POA from sources such as road and construction dust are semi-volatile too. Model predictions suggested that both SVOCs (evaporated POA vapors) and IVOCs did not contribute as much as other anthropogenic precursors (e.g., alkanes, aromatics) to SOA mass concentrations in the urban areas (NOx-dependent. Accounting for the influence of NOx using the VOC:NOx ratios resulted in better predictions of OA mass concentrations in rural/remote environments but still underpredicted OA mass concentrations in urban environments. The updated model's performance against measurements combined with the results from the sensitivity simulations suggests that the OA mass concentrations in southern California are constrained within a factor of 2. Finally, simulations performed for the year 2035 showed that, despite reductions in VOC and NOx emissions in the future, SOA mass concentrations may be higher than in the year 2005, primarily from increased hydroxyl radical (OH) concentrations due to lower ambient NO2 concentrations.

Delhi, with a population of 22 million (1.6% of national total) is one of the most polluted capital cities in the world. Nearly 50% of the published literature in India focus on air pollution in Delhi. However, air pollution impacts are not limited only to the capital city. Yet, there is little information and attempt to quantify these impacts for Tier 1 and 2 cities, even though they account for >30% of India's population. To remedy this vacuum of information, the Air Pollution knowledge Assessments (APnA) city program deliberately focuses on 20 Indian cities, other than Delhi. We established baseline multi-pollutant high-resolution emissions inventory, after collating information from multiple resources detailed in this paper, which was used to estimate spatial concentrations of key pollutants across city's urban airshed using WRF-CAMx chemical transport modeling system. The inventory includes anthropogenic sources, such as transport (road, rail, ship, and aviation), large scale power generation (from coal, diesel, and gas power plants), small scale power generation (from diesel generator sets for household use, commercial use, and agricultural water pumping), small and medium scale industries, dust (road resuspension and construction), domestic (cooking, heating, and lighting), open waste burning, and open fires and non-anthropogenic sources, such as sea salt, dust storms, biogenic, and lightning. The emissions inventory is currently in use for 3-day advance air quality forecasting for public release on an on-going basis. Using meteorological parameters and big data like gridded speed maps from google, the emissions inventory is dynamically updated. The results from this research will be valuable to local and national policy makers - especially the information on source contributions to air pollution.

This study investigates air pollutant concentrations across the international airshed spanning Detroit, Michigan, USA and Windsor, Ontario, Canada. The Geospatial Determinants of Health Outcomes Consortium (GeoDHOC) measured air quality concurrently in Detroit and Windsor using consistent sampling methods and locations during separate, two-week periods in September 2008 and May/June 2009. This paper presents 2009 results and compares them to previously reported 2008 campaign results to assess spatial and temporal variability. A high-density array of 100 passive and 50 active samplers was used to measure nitrogen dioxide (NO2), 26 volatile organic compounds (VOCs), 23 polycyclic aromatic hydrocarbons (PAHs), and three size fractions of particulate matter (PM) in both campaigns. Geospatial and non-spatial tools were used to investigate changes in concentration distributions and site classification into low/medium/high tertiles between the campaigns. During the two-week 2009 campaign, general pollution patterns remained consistent with those observed during 2008. Higher concentrations in Detroit, strong correlations amongst the BTEX group, and consistency of sites falling into the low and high tertiles were observed. Similar spatial patterns for NO2, VOCs, BTEX, and PAHs were also found during both campaigns. Conversely, PM1-2.5 and PM2.5-10 distributions showed greater variability, as did toluene/benzene ratios. Observed differences are attributable to changes in point source emissions associated with changes in localized activities, possibly related to decreased economic and industrial activity in response to the downturn that began in late 2008. Repeated sampling at multiple locations is important to determine spatial and temporal variability in absolute concentrations. However, if the definition of relatively high and low concentrations regions within a well-established urban area is adequate to estimate future air pollutant exposures, a single multi-location campaign may suffice.

In Chhattisgarh, Raipur-Durg-Bhilai (RDB) tri-city area hosts the new administrative capital of the state, interconnected by an expressway forming the industrial corridor and is one of the largest steel manufacturing hubs in India. Between 1998 and 2016, the satellite and global model data derived concentrations show a 50% increase in the overall PM2.5 pollution in the region. The average PM10 concentration measured at commercial, industrial, and residential monitoring stations is 125 ± 52 µg m–3 in 2015. None of the stations currently measure PM2.5. The annual average PM10 concentrations in 2011 is 175 ± 110 µg m–3, which translates to 28% improvement in 5 years. A multiple pollutant emissions inventory was established for this urban airshed (extending 60 km × 30 km), with annual estimates of 41,500 tons of PM2.5, 59,650 tons of PM10, 7,600 tons of SO2, 67,000 tons of NOx, 163,300 tons of CO, 118,150 tons of NMVOCs, and 3.1 million tons of CO2 for 2015, and further projected to 2030 under business as usual conditions. The ambient source contributions were calculated using WRF-CAMx chemical transport modeling system, highlighting the heavy industries (mostly steel) (23%), followed by transport (including on road dust) (29%), domestic cooking and heating (12%), open waste burning (6%), as the key air pollution sources in the urban area. The city has an estimated 26% of the ambient annual PM2.5 pollution originating outside the urban airshed - this contribution is mostly coming from the coal-fired power plants, large (metal and non-metal processing) industries, and brick kilns located outside the urban airshed and seasonal open biomass fires.

The Arve river valley airshed in the French Alps experiences particularly severe air pollution during wintertime stable atmospheric conditions associated with persistent cold-air pools. PM10 data recorded in the region indicate that the urbanised area of the central basin-shape section of the valley is generally the most polluted, with a harmful impact on the health of inhabitants. In the present work, we examine the air pollution transport potential of the Arve river valley airshed using results from high-resolution numerical simulations of a cold-air pool documented as part of the Passy-2015 field campaign. Passive tracers were used to model PM10 with emissions provided by a detailed inventory developed by the local air-quality agency. The observed differential in PM10 levels between valley sections was well captured by the numerical model and could not be explained solely by the differential in emissions. The stagnation, recirculation and ventilation potential of the airshed was evaluated spatially and temporally using integral quantities. The analysis indicated that the central basin-shape section of the valley is poorly ventilated and hence air pollution there would originate mostly from local emission sources. This stagnation zone appears to be almost decoupled from the rest of the airshed. The airshed was decomposed in separate valley sections so as to quantify the fate of the pollutants emitted within each section. Air pollution apportioned according to the contribution of emissions from the different valley sections shows that indeed the central basin-shape section is dominated by local sources. The situation was found more complex in the valley sections further downstream, where the contribution from the sum of the non-local sources can be as large as that from local sources. This study allows to identify the origin of the strong pollution in the Arve river valley, through the link between the local topography, emission sources and pollutant transport.

Biomass burning smoke is often a significant source of airborne fine particles in regional areas where air quality monitoring is scarce. Emerging sensor technology provides opportunities to monitor air quality on a much larger geographical scale with much finer spatial resolution. It can also engage communities in the conversation around local pollution sources. The SMoke Observation Gadget (SMOG), a unit with a Plantower dust sensor PMS3003, was designed as part of a school-based Science, Technology, Engineering and Mathematics (STEM) project looking at smoke impacts in regional areas of Victoria, Australia. A smoke-specific calibration curve between the SMOG units and a standard regulatory instrument was developed using an hourly data set collected during a peat fire. The calibration curve was applied to the SMOG units during all field-based validation measurements at several locations and during different seasons. The results showed strong associations between individual SMOG units for PM2.5 concentrations (r2 = 0.93–0.99) and good accuracy (mean absolute error (MAE) &lt, 2 μg m−3). Correlations of the SMOG units to reference instruments also demonstrated strong associations (r2 = 0.87–95) and good accuracy (MAE of 2.5–3.0 μg m−3). The PM2.5 concentrations tracked by the SMOG units had a similar response time as those measured by collocated reference instruments. Overall, the study has shown that the SMOG units provide relevant information about ambient PM2.5 concentrations in an airshed impacted predominantly by biomass burning, provided that an adequate adjustment factor is applied.

M (Environmental Management), North-West University, Potchefstroom Campus In response to deteriorating air quality, South Africa, as many countries have, implemented national programmes that aim to manage and regulate ambient air quality and air pollution. Air Quality Management Plans (AQMPs) are clear outlines of measures and resources needed to achieve air quality objectives in a given geographical area and require efforts by government, business, industry, NGOs and the public. The success of the AQMPs depends primarily on the support of all stakeholders. The Vaal Triangle Air Shed Priority Area (VTAPA) was declared in 2006 as an area which exceeds ambient air quality standards or may cause adverse air quality impacts in the area. This research study focused on the VTAPA with the aim of evaluating the quality of the first and second-generation air quality management plan for the Vaal Triangle Air-shed Priority area. The first objective of this study included developing a review package that can be used to assess the quality of AQMPs in South Africa by adopting and modifying the Lee and Colley package. The second objective was to apply the developed review package to evaluate the quality of the VTAPA AQMP systematically. The extent to which the AQMP met the expected outcomes of the review package defined the quality of the AQMP report. Both the first and second-generation draft AQMPs were considered to be of good quality. The first-generation AQMP was found to be of better quality than that of the second-generation draft. Funding mechanisms need to be investigated to assist in the implementation of intervention strategies in the AQMP as both the first and second-generation draft AQMPs were found to be lacking in terms of potential to secure funds. Though the second-generation draft AQMP was found to be of lesser quality, the source apportionment study for identification of all sources as well as a better-outlined air quality management system was found to be good improvements to the AQMP. Masters

The Lake Michigan Ozone Study 2017 (LMOS 2017) in May and June 2017 enabled study of transport, emissions, and chemical evolution related to ozone air pollution in the Lake Michigan airshed. Two highly instrumented ground sampling sites were part of a wider sampling strategy of aircraft, shipborne, and ground-based mobile sampling. The Zion, Illinois site (on the coast of Lake Michigan, 67 km north of Chicago) was selected to sample higher NOx air parcels having undergone less photochemical processing. The Sheboygan, Wisconsin site (on the coast of Lake Michigan, 211 km north of Chicago) was selected due to its favorable location for observation of photochemically aged plumes during ozone episodes involving southerly winds with lake breeze. The study encountered elevated ozone during three multiday periods. Daytime ozone episode concentrations at Zion were 60 ppb for ozone, 3.8 ppb for NOx, 1.2 ppb for nitric acid, and 8.2 µg/m3 for fine particulate matter. At Sheboygan daytime ozone episode concentrations were 60 ppb for ozone, 2.5 ppb for NOx, and 2.9 ppb for NOy. To facilitate informed use of the LMOS 2017 data repository, we here present comprehensive site description, including airmass influences during high ozone periods of the campaign, overview of meteorological and pollutant measurements, analysis of continuous emission monitor data from nearby large point sources, and characterization of local source impacts from vehicle traffic, large point sources, and rail. Consistent with previous field campaigns and the conceptual model of ozone episodes in the area, trajectories from the southwest, south, and lake breeze trajectories (south or southeast) were overrepresented during pollution episodes. Local source impacts from vehicle traffic, large point sources, and rail were assessed and found to represent less than about 15% of typical concentrations measured. Implications for model-observation comparison and design of future field campaigns are discussed. Implication StatementThe Lake Michigan Ozone Study 2017 (LMOS 2017) was conducted along the western shore of Lake Michigan, and involved two well-instrumented coastal ground sites (Zion, IL, and Sheboygan, WI). LMOS 2017 data is publicly available, and this paper provides detailed site characterization and measurement summary to enable informed use of repository data. Minor local source impacts were detected but were largely confined to nighttime conditions of less interest for ozone episode analysis and modeling. The role of these sites in the wider field campaign and their detailed description facilitates future campaign planning, informed data repository use, and model-observation comparison. Implication Statement The Lake Michigan Ozone Study 2017 (LMOS 2017) was conducted along the western shore of Lake Michigan, and involved two well-instrumented coastal ground sites (Zion, IL, and Sheboygan, WI). LMOS 2017 data is publicly available, and this paper provides detailed site characterization and measurement summary to enable informed use of repository data. Minor local source impacts were detected but were largely confined to nighttime conditions of less interest for ozone episode analysis and modeling. The role of these sites in the wider field campaign and their detailed description facilitates future campaign planning, informed data repository use, and model-observation comparison.

In response to deteriorating air quality, South Africa implemented national programmes that aim to manage and regulate ambient air quality and air pollution. Air Quality Management Plans (AQMPs) are clear outlines of measures and resources needed to achieve air quality objectives in a given geographical area and require support from government, business, industry, non-governmental organisations (NGOs) and the public. The success of the AQMPs depends primarily on the support of all stakeholders and the quality of the management plan. The Vaal Triangle Airshed Priority Area (VTAPA) was declared in 2006 as an area where ambient air quality standards are exceeded or may cause adverse air quality impacts. This research study focused on the VTAPA to evaluate the quality of the first and second-generation AQMPs for the VTAPA. Quality evaluation includes an analysis of procedures, processes, methods and documents. Effectiveness refers to the results of individual activities; therefore, the extent to which the AQMP met the expected outcomes of the review package defined the quality of the AQMP report. Both the first and draft second-generation AQMPs were considered to be of good quality. The first-generation AQMP was found to be of better quality than that of the draft second-generation AQMP. Funding mechanisms need to be investigated to assist in implementing intervention strategies in the AQMP as both the first and draft second-generation AQMPs were found to lack the potential to secure funds. Though the draft second-generation AQMP was found to be of lesser quality, the source apportionment study for identification of all sources as well as a better-outlined air quality management system was found to be good improvements to the AQMP.

This study investigated the contribution of anthropogenic emission of benzene from petroleum refineries to the Nigerian’s ambient air quality with the view of understanding the impact of petroleum production facilities on host airshed. The Activities of the four existing and 22 proposed petroleum refineries in Nigeria were obtained from the Department of Petroleum Resources and these were combined with emission factors of different units at the refineries to estimate benzene emissions. No-control-measure option (worst case scenario) was assumed because of lack of information on control efficiency of the refineries. The study revealed that two of the existing refineries in one of the oil-producing cities in Nigeria released a total of 10.01 × 1011 tons/year of benzene into the ambient air of the city, apart from additional 2.35 × 1013 tons/year anticipated to be released from three of the proposed refineries into the ambient air of the same host community. If operated at full capacity, the estimated benzene emission from the four existing refineries stood at 5.50 × 1013 tons/year while the 22 proposed refineries have the capacity of releasing additional 16.73 × 1013 ton/year. On the overall, the contribution of benzene from refineries on yearly basis to Nigerian airshed was estimated to be 22.24 × 1013 tons. These concentrations if not checked could lead to devastating environmental issues. Some mitigating measures were suggested to control and subsequently abate benzene emission from these refineries.

India’s capital, New Delhi, has notoriously poor air quality. While the overall cost of emission reduction is miniscule compared with the overall health and economic benefits, policymakers have been unsuccessful due to resistance from specific stakeholders. We measure the economic impact on the four states within the Delhi airshed across eight emission reduction scenarios for four major sectors of the economy—i.e., construction, transportation, agriculture, and power. The findings suggest that a transition from coal to RE coupled with transport electrification benefits all four states and the nation. Policies that attempt to reduce emissions—e.g., Happy Seeders for agriculture and emission control systems for coal power plants—without any subsidy from the government lead to adverse impacts across most metrics.

Significance Water vapor emitted from anthropogenic combustion for winter heating in northern China may exacerbate air pollution. This hypothesis is of considerable scientific and environmental interest. We conducted a multiyear sampling campaign of air vapor isotope compositions and associated atmospheric data from the city of Xi’an, located in an enclosed basin in northwestern China. We found that the fraction of combustion-derived water vapor increases with increasing relative humidity and with the concentration of particulate matter with an aerodynamic diameter less than 2.5 μm in polluted conditions based on field observation, isotopic analysis, and numerical simulation. Our results demonstrated that combustion-derived water is nontrivial when considering energy policy for improving air quality., Anthropogenic combustion-derived water (CDW) may accumulate in an airshed due to stagnant air, which may further enhance the formation of secondary aerosols and worsen air quality. Here we collected three-winter-season, hourly resolution, water-vapor stable H and O isotope compositions together with atmospheric physical and chemical data from the city of Xi’an, located in the Guanzhong Basin (GZB) in northwestern China, to elucidate the role of CDW in particulate pollution. Based on our experimentally determined water vapor isotope composition of the CDW for individual and weighted fuels in the basin, we found that CDW constitutes 6.2% of the atmospheric moisture on average and its fraction is positively correlated with [PM2.5] (concentration of particulate matter with an aerodynamic diameter less than 2.5 μm) as well as relative humidity during the periods of rising [PM2.5]. Our modeling results showed that CDW added additional average 4.6 μg m−3 PM2.5 during severely polluted conditions in the GZB, which corresponded to an average 5.1% of local anthropogenic [PM2.5] (average at ∼91.0 μg m−3). Our result is consistent with the proposed positive feedback between the relative humidity and a moisture sensitive air-pollution condition, alerting to the nontrivial role of CDW when considering change of energy structure such as a massive coal-to-gas switch in household heating in winter.

Highly time-resolved aerosol measurements and analysis are necessary for a proper aerosol characterization in many polluted regions, because aerosol concentrations in polluted environments can change over time scales of minutes. However, many urban measuring sites have measuring devices that provide time resolved average aerosol concentrations over a day or two at best. Light-scattering properties of mineral dust and soot particles in the El Paso-Ju&aacute, rez Airshed were analyzed with an improved methodology, using the T-matrix, a maximum likelihood estimator (MLE), and data from both an acoustic extinctiometer and a laser particle counter. The hourly inter-comparisons of the scattering coefficients&rsquo, results between the model and those obtained using the instruments at a wavelength of 0.87 &mu, m show good agreement. This methodology has been applied in the El Paso-Ju&aacute, rez Airshed successfully, and it could be used in other cities where mineral dust and soot are major components of the aerosol concentrations.

Anthropogenic atmospheric emission and subsequent deposition of sulfur (S) has been linked to disrupted watershed biogeochemical processes through soil and surface water acidification. We investigated watershed-scale impacts of acidic deposition on tributary concentrations and watershed exports of major nutrients and ions for the Kitimat River Watershed, British Columbia. Since the 1950s, the Kitimat watershed had an aluminum smelting facility with substantial emissions at the river estuary. Emissions load the airshed overlying the watershed and potentially impact western tributaries leaving eastern tributaries available as reference. We assessed concentrations and export of key compounds in three reference and six potentially impacted tributaries and watersheds in 2015 and 2016. Sulfate (SO4), fluoride (F), nitrate (NO3), and chloride (Cl) were significantly higher in impacted tributaries. F concentrations exceeded the Canadian Council of Ministers of the Environment guideline for aquatic life in 83% of samples collected from impacted streams. Watershed export and associated uncertainty were determined by bootstrapped flow-stratified Beale’s unbiased estimator. Impact of emissions on watershed export was modeled in a Bayesian approach to include variance in the export estimate to inform the uncertainty of model parameters. Export of SO4 and Ca increased significantly within 16 km and 8 km, respectively, toward the smelter emissions. The corresponding impacted area for SO4 and Ca was approximately 100 km2 and 45 km2, respectively. SO4 export is likely due to direct impacts of S deposition, with excess S being flushed from the watersheds. Ca export patterns likely result from indirect impacts of S deposition on soil chemistry and flushing of Ca. These impacts may contribute to effects within tributaries on benthic stream communities and regionally important juvenile Pacific salmon.

Se presenta el análisis preliminar de cuencas atmosféricas con origen en el Valle de Sogamoso, Boyacá, Colombia, mediante la modelación del comportamiento de las parcelas de aire como herramienta para la planificación territorial. El estudio de caso se sitúa en uno de los corredores industriales de mayor emisión de contaminantes en Colombia, por tanto, es importante conocer el comportamiento de las variables meteorológicas, la topografía de la zona y la dinámica atmosférica que allí se desarrolla como consecuencia de relacionar las dos variables, para lograr la conformación y delimitación de la cuenca atmosférica. Se calculó por medio del modelo HYSPLIT, las trayectorias de parcelas de aire hacia adelante durante los meses de febrero y abril, estableciendo las temporadas secas y húmedas del año 2015. Se observó la circulación de parcelas de aire provenientes del Valle, hacia territorios que han presentado altos índices en contaminación atmosférica para el contaminante PM10 y se evidenció la relación de las variables meteorológicas y topográficas para delimitar la cuenca. Se proponen criterios para la planificación y ordenamiento territorial desde el enfoque de cuencas atmosféricas como unidad de gestión regional y apoyo a los sistemas de monitoreo de calidad del aire, con el fin de establecer una variable ambiental como eje principal para la toma de decisiones territoriales.

The quality of air breathed in South Africa is of great concern, especially in industrialised regions where PM2.5 concentrations are high. Long term exposure to PM2.5 is associated with serious adverse health impacts. Traditionally, PM2.5 is monitored by a network of ground-based instruments. However, the coverage of monitoring networks in South Africa is not dense enough to fully capture the spatial variability of PM2.5 concentrations. This study explored whether satellite remote sensing could offer a viable alternative to ground-based monitoring. Using an eight-year record (2009 to 2016) of satellite retrievals (MODIS, MISR and SeaWIFS) for PM2.5 concentrations, spatial variations and temporal trends for PM2.5 are evaluated for the Vaal Triangle Airshed Priority Area (VTAPA). Results are compared to corresponding measurements from the VTAPA surface monitoring stations. High PM2.5 concentrations were clustered around the centre and towards the south-west of the VTAPA over the highly industrialised cities of Vanderbijlpark and Sasolburg. Satellite retrievals tended to overestimate PM2.5 concentrations. Overall, there was a poor spatial agreement between satellite-retrieved PM2.5 estimates and ground-level PM2.5 measurements. Root mean square error values ranged from 6 to 11 µg/m3 and from -0.89 to 0.32 for the correlation coefficient. For satellite remote sensing to be effectively exploited for air quality assessments in the VTAPA and elsewhere, further research to improve the precision and accuracy of satellite-retrieved PM2.5 is required.

This study investigated the status of air quality at Olushosun, Abule Egba, and Solous dumpsite in Lagos, Nigeria. The parameters examined are total suspended particulates (TSP), CO, NO2, SO2, and odour. The Landfill Gas Emissions Model (LandGEM) was used to estimate the potential landfill gas emissions from the dumpsites. Sulphur dioxide (SO2) was not detected at Olushosun and Abule Egba dumpsites. At Solous, the measured concentration is about 21-folds of the 1-h limit with 24-h concentration of 0.09 ppm which is about ninefolds of the FMENV’s set limit. The measured concentrations of NO2 are about 1.3-folds of the set limit at all the locations in Olushosun and Abule Egba but between 2.5 and 5.0-folds at Solous. In Olushosun, the measured 1-h CO concentrations range between 8.0 and 40 ppm, at Abule Egba and Solous, the range is 10.0–44.0 ppm and 1.0–179.0 ppm, respectively. At Olushosun, the 1-h TSP concentration is about 2.5-folds of the 1-h limit but 3.2-folds and 2.8-folds of the same limit at both Abule Egba and Solous, respectively. The odour levels from the three dumpsites are significantly high ranging between 4 and 5 on the “intensity by word” scale of 5. The measured air quality parameters concentrations signify a badly impaired airshed and can be classified as having poor air quality which calls for urgent attention. The methane potential using the LandGem tool is estimated to be between 4.04 × 102 and 4.97 × 104 ton/year which is equivalent to about 6.06 × 105 to 7.45 × 107 m3/year. This can be used to generate about 0.4–49 MW of electricity if efficiently captured.

In the another chapter of this volume, we have presented the details on the air quality of a highly industrialized suburb of the kind that occurs in all major cities of India—as also of most developing countries. The air quality was monitored by us round the year with a network of 11 sampling stations. We now present studies on the modeling of the air quality of the area, the forecasting carried out thereafter, and its implications.

A study is presented which is specific to a highly industrialized suburb of Chennai, India, but is illustrative of similar regions that are present in most large cities of India as also in other developing countries. The study area covered by us consists of a large-scale petroleum refinery and several downstream petrochemical industries situated cheek-by-jowl in a cluster called the Manali Industrial Complex. Its airshed was continuously monitored with the help of eleven ambient air quality monitoring stations, set on the basis of the wind roses of the study area in different seasons. The findings have been discussed in terms of the compatibility of the airshed with the ambient air quality standard set by India’s Central Pollution Control Board.

Indo-Gangetic Plain (IGP) in the Indian sub-continent faces massive aerosol loading, for which it is regarded as a global air pollution hotspot. This study examined the spatial variation in columnar aerosol loading (2001–2019) over the eastern state of Bihar and its 38 administrative districts affected by transboundary transport and local emissions. In the current study, aerosol optical depth (AOD0.55μm) retrieved at 1 × 1 Km2 resolution by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor using the Multi-Angle Implementation of Atmospheric Correction algorithm (MCD19A2, Collection 6) was analyzed. A significant increase in AOD from 0.49 to 0.68, with an inter-annual variability of 12.0%, was observed. The highest seasonal aerosol loading of the range 0.51–0.75 was observed during the post-monsoon (OND) and winter (JF) seasons due to long-range transport of pollutants from upper and central IGP regions and aerosols emitted locally, which further was aggravated by poor metrological conditions. AOD was not found to vary significantly with the land use pattern (e.g., urban, rural, and background), implying the substantial influence of regional transport. A significant increase in the annual AOD trend (0.0106 year−1) and seasonal trends (0.0072–0.0182 year−1) was observed for the analysis period. Districts located along the Ganga river stretch exhibited the highest annual AOD rate with an overall percentage increase of 40–50%. Low to moderate model performance (R2:0.25–0.65; MAPE: 15.2–26.7%) was exhibited by Auto-Regressive Integrated Moving Average (ARIMA) time series model over the study area for the successive two years (2020 and 2021), emphasizing the districts with a potential for high aerosol loading that requires immediate addressing under Business as usual (BAU) scenarios. The overall study augments policymakers with decision-making support to instigate air quality measures at the state epicenters. The study also recommends inter-state coordination to develop an integrated airshed management approach for holistic improvement in state air quality.

Wind-blown dust is an important source of trace metals, nutrients, and biological material to montane ecosystems. Mountain ranges in northern Utah are located downwind of multiple dust sources including the Great Basin Desert and the Wasatch Front urban area, providing an opportunity to investigate regional-scale differences in dust deposition chemistry and bacterial composition. We sampled discrete dust layers from snowpack across multiple locations in the Wasatch and Uinta Mountains (Utah) and the Snake Range (Nevada) during spring 2014 and 2015. Dust chemistry was unique in each airshed, suggesting that spatial variability and local sources were more important than temporal variability for the sampling period. The central Wasatch dust contained the highest concentrations of playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Cu, Pb, Se) compared with lowest concentrations of these elements in the northern Wasatch, which is further from playa and anthropogenic sources. Sequential extractions indicate that the majority of Ca, Sr, and Cd is potentially available for transport during snowmelt while other elements are relatively immobile. Central Wasatch dust was more reactive to acetic acid than northern Wasatch dust for most elements, including REE + Y. Sr isotopes (87Sr/86Sr ratios) were also unique to each sampling area, with the most radiogenic values in the central Wasatch. Similar to dust chemistry, bacterial communities in dusty snow reflected geographically localized dust events. In the central Wasatch, 69% of bacterial species were unique, suggesting that the airshed received the most diverse dust inputs from a combination of playa and anthropogenic sources. Gram-positive Actinobacteria and Firmicutes were common in snow but specific bacterial families distinguished airsheds (e.g., Bacillaceae, Geodermatophilaceae, Nakamurellaceae). Our results demonstrate that evaluating dust chemistry and bacteria in snow on a regional scale may more clearly link dust sources to the entrainment of pollutants and seeding of bacteria species to montane systems.

SAPRC16 is an interim update to the SAPRC series of chemical mechanisms that includes updated rate constants, a revised representation of radical chemistry, and a new speciation lumping scheme to better develop predictions of SOA precursors. In this study, the ability of the SAPRC16 chemical mechanism to simulate regional ozone episodes is tested in seven (7) major cities across the United States. The UCD-CIT 3-dimensional (3D) airshed model was configured with both SAPRC11 (base mechanism) and SAPRC16 (updated mechanism). Concentrations of ozone, hydroxyl radical (OH) and hydroperoxyl (HO2) radical predicted with both mechanisms were compared to measured values. It was generally observed that SAPRC16 predicts slightly lower ozone concentrations than SAPRC11 in NOx rich urban centers. A box model analysis shows that the SAPRC16 mechanism quenches ozone production earlier than SAPRC11 as NOx concentrations increase (yielding decreasing VOC/NOx ratios). This could be caused by more detailed HO2+RO2 reactions and RO2 isomerization reactions in SAPRC16 that compete with the HO2+NO reaction. Predictions from SAPRC11 are in better agreement with the measurements in the western United States, however SAPRC16 outperforms SAPRC11 in some eastern and southern U.S. cities. These results may also be strongly influenced by the accuracy of emissions inventories in each region. Differences in ozone concentrations predicted by SAPRC16 and SAPRC11 increased as emissions decreased suggesting that the two mechanisms will predict different outcomes from future emissions control programs. In general, the SAPRC11 mechanisms slightly over-predicts OH concentration while under-predicting HO2 radical concentration and the SAPRC16 mechanism slightly under predicts OH and under predicts HO2, sometimes by large amounts. The reasons for this behavior are unknown at this time. These features will influence the secondary organic aerosol (SOA) predictions from each mechanism since the branching between high NOx and low NOx regimes depends on calculated HO2 concentrations. Further analysis of the HO2+RO2 reactions and RO2 isomerization reactions and the reasons for the lower HO2 predictions in the updated SAPRC16 chemical mechanism should be carried out before widespread adoption of the new mechanism.

Urban heat island effect has been assessed using weather research and forecasting model (WRF v3.5) focusing on air temperature and surface skin temperature in the sub-tropical urban Indian megacity of Delhi. Impact of urbanization-related changes in land use/land cover (LULC) on model outputs has been analyzed. Four simulations have been carried out with different types of LULC data viz. (1) USGS, (2) MODIS, (3) user-modified USGS and (4) user-modified land use data coupled with urban canopy model (UCM) for incorporation of canopy features. Heat island intensities have been estimated based on these simulations and subsequently compared with those derived from in situ and satellite observations. There is a significant improvement in model performance with modification of LULC and inclusion of UCM. Overall, RMSEs for near surface temperature improved from 6.3 to 3.9 °C and index of agreement for mean urban heat island intensities (UHI) improved from 0.4 to 0.7 with modified land use coupled with UCM. In general, model is able to capture the magnitude of UHI as well as high UHI zones well. A simple method of bias correction in model has been applied to improve model results for further application. The study highlights the importance of appropriate and updated the representation of land use–land cover and urban canopies for improving predictive capabilities of the mesoscale models. Urban heat island has been known to have effect on human thermal comfort. In the present study, Heat Index, a commonly used indicator of thermal comfort, is assessed spatially using WRF-UCM derived results. Urban areas were found to have higher Heat Index than non-urban areas by a difference of about 1.5–2 °C. Further, it was found that urban canopy effect leads to rise in thermal discomfort by increasing Heat Index. There is an increase in Heat Index of about 2.0–2.5 °C at dense built-up stations. Decrease in thermal comfort causes a significant impact on energy demand. Hence, analysis of urban heat island effect vis-a-vis thermal comfort provides useful information with regard to impact on human comfort and welfare.

Reactions between ammonia (NH3) and organic compounds containing carbonyl functional groups in aerosol particles can form organic products that are less basic than NH3 and are thus unable to neutralize efficiently nitric and sulfuric acids. In this exploratory study, the University of California, Irvine - California Institute of Technology (UCI-CIT) model is used to investigate the potential air quality impacts of including of the chemical uptake of NH3 by secondary organic aerosols (SOA) in a regional airshed model. A surface reaction of NH3 with SOA is implemented into the model to determine the impact of this process on NH3 and PM2.5 concentrations in the South Coast Air Basin of California (SoCAB). Air quality simulations are conducted using uptake coefficients ranging from 10−5 to 10−2 to explore the sensitivity of changes in NH3 and PM2.5 concentrations to the magnitude of the uptake coefficient. Results indicate that the chemical uptake of NH3 by SOA can potentially deplete gaseous NH3 concentrations, causing indirect reductions in the amount of ammonium nitrate and ammonium sulfate in particulate matter. The magnitude of the impact on NH3 and PM2.5 concentrations exhibits a strong but non-linear dependence on the value of the uptake coefficient, with evidence for small but notable impacts on air quality even with the lowest assumed uptake coefficient of 10−5.

Air quality offsets in South Africa are intended to counterbalance the harm caused by atmospheric emissions and deliver a net ambient air quality benefit in the affected airshed. In practice, they are implemented as a condition of leniency from compliance with the Minimum Emission Standards, and they focus on converting solid fuel burning households in low-income communities to cleaner forms of energy. Air quality offsets are not supported by all stakeholders, with non-governmental organisations in particular voicing vociferous objections. To date, there have only been very limited analyses of the ethical dimensions of air quality offsets. In this paper, air quality offsets and the Minimum Emission Standards are examined and compared from the perspective of three notions of environmental justice: distributive justice, which focuses on the distribution of environmental burdens and benefits; procedural justice, which considers inclusion and exclusion in decision- and policy-making processes; and justice as recognition, which focuses on the cultural and institutional processes that determine recognition, misrecognition and non-recognition of various groups. It is found that air quality offsets should guide action which promotes distributive justice because they are focussed on reducing polluting emissions in vulnerable, low-income communities that are exposed to the highest levels of ambient pollution. From a procedural justice perspective, South Africa’s legislative processes provide for involving most stakeholders in decision-making processes. Air quality offset initiatives should be evaluated once they have been implemented at scale to determine whether they have indeed aided in redressing injustices. Assessment criteria could include whether the air quality-related health risk of vulnerable communities has been reduced, whether community members have participated in the design and implementation of interventions, and whether marginalised members of the community have benefitted from the interventions.

Ambient air pollution has important impacts on a variety of environmental issues, particularly on human health and ecosystem processes. A key tool for understanding the impacts of atmospheric pollution is through the long term measurement of the ambient concentrations of criteria atmospheric pollutants. Monitoring of ambient pollution concentrations has been conducted in the National Air Quality Priority areas since 2009. During this time period, significant changes in the management of air pollution have occurred, including the adoption of the ambient air quality standards, and the implementation of section 21 emission standards. This paper examines the long term evolution of ambient concentrations for PM, SO2 in the Vaal Triangle Airshed Priority Area 2007-2017 and Highveld Priority Area. These trends will be evaluated against the implementation of management interventions and highlight the variation in the measured concentrations and emerging areas of concern.

Results of a methodological study on the use of Positive Matrix Factorization (PMF) with smaller datasets are being reported in this work. This study is based on 29 PM10 and 33 PM2.5 samples from a receptor in a rural setup in Apulia (Southern Italy). Running PMF on the two size fractions separately resulted in the model not functioning correctly. We therefore, augmented the size of the dataset by aggregating the PM10 and PM2.5 data. The 5-factor solution obtained for the aggregated data was fairly rotationally stable, and was further refined by the rotational tools included in USEPA PMF version 5. These refinements include the imposition of constraints on the solution, based on our knowledge of the chemical composition of the aerosol sources affecting the receptor. Additionally, the uncertainties associated with this solution were fully characterised using the improved error estimation techniques in this version of PMF. Five factors in all, were isolated by PMF: ammonium sulfate, marine aerosol, mixed carbonaceous aerosol, crustal/Saharan dust and total traffic. The results obtained by PMF were further tested inter alia, by comparing them to those obtained by two other receptor modelling techniques: Constrained Weighted Non-negative Matrix Factorization (CW – NMF) and Chemical Mass Balance (CMB). The results of these tests suggest that the solution obtained by PMF, is valid, indicating that for this particular airshed PMF managed to extract most of the information about the aerosol sources affecting the receptor – even from a dataset with a limited number of samples.

Particulate nitrate ( p NO 3 - ) is an important component of secondary aerosols in urban areas. Therefore, it is critical to explore its formation mechanism to assist with the planning of haze abatement strategies. Here we report vertical measurements of NOx and O3 by in situ instruments on a movable carriage on a tower during a winter heavy-haze episode (18 to 20 December 2016) in urban Beijing, China. Based on the box model simulation at different heights, we found that p NO 3 - formation via N2O5 heterogeneous uptake was negligible at ground level due to N2O5 concentrations of near zero controlled by high NO emissions and NO concentration. In contrast, the contribution from N2O5 uptake was large at high altitudes (e.g., > 150 m), which was supported by the lower total oxidant ( NO2 + O3 ) level at high altitudes than at ground level. Modeling results show the specific case that the nighttime integrated production of p NO 3 - for the high-altitude air mass above urban Beijing was estimated to be 50 µ g m −3 and enhanced the surface-layer p NO 3 - the next morning by 28 µ g m −3 through vertical mixing. Sensitivity tests suggested that the nocturnal NOx loss by NO3 – N2O5 chemistry was maximized once the N2O5 uptake coefficient was over 2 × 10 −3 on polluted days with Sa at 3000 µ m 2 cm −3 in wintertime. The case study provided a chance to highlight the fact that p NO 3 - formation via N2O5 heterogeneous hydrolysis may be an important source of particulate nitrate in the urban airshed during wintertime.