Fossil Fuel Combustion Sources Research Articles

Influence of sources and atmospheric processes on metal solubility in PM2.5 in urban Guangzhou, South China

Water-soluble metals exert a significant influence on human and ecosystem health. In this study, a comprehensive investigation was undertaken to elucidate the solubilities of metals in PM2.5 and potential influencing factors during the dry season of 2019–2020 in urban Guangzhou, South China. The observed average solubility was <20 % for Al, Fe, Sn, and Ti; 20–40 % for V, Cr, Sb, Pb, and Ni; 40–60 % for Ba and Cu; and 60–80 % for Zn, As, Se, Cd, and Mn. Metals (Al, Ti, and Fe) originated from crustal sources (e.g., soil dust) have much lower solubilities than those (Mn, Zn, As, Se, Cd, and Ba) from fossil fuel combustion sources (e.g., traffic emission, coal combustion), suggesting the dominant role the metal sources played on solubility. Enhanced solubilities of Cu, As, Se, Cd, Sn, Sb, and Pb were associated with aerosol acidity, while those of V, Cr, Mn, Ni, Zn, and Ba were linked to organic acid complexation. For the three crustal metals, the solubilities of Al and Ti primarily depended on aerosol acidity, whereas the solubility of Fe depended on both aerosol acidity under pH < 2 conditions and organic acid complexation under pH > 2 conditions. These findings underscore the primary influence of inherent properties of the metals on their solubility and reveal the varying impacts of atmospheric physicochemical processes, with changes in their solubilities being <10 % for Cd, Sn, Sb, and Pb, 10–20 % for Cu, Cr, Mn, Ni, and Ba, and 20–30 % for As, Se, and Zn.

Formation pathways and source apportionments of inorganic nitrogen-containing aerosols in urban environment: Insights from nitrogen and oxygen isotopic compositions in Guangzhou, China

Air quality issues caused by PM2.5-induced persistent extreme haze episodes have become increasingly serious in urban environments in recent years. Secondary water-soluble inorganic sulfate (SO42−), nitrate (NO3−) and ammonium (NH4+) ions are the major components of PM2.5. However, the contributions of inorganic nitrogen species, especially nitrate, to PM2.5 have greatly increased during haze episodes in many cities in China. Therefore, better understanding of their emission sources and formation pathways holds the key to controlling urban PM2.5 pollution more efficiently and effectively. In this study, water-soluble ionic characteristics and isotopic compositions and sources of NH4+ and NO3−, as well as NO3− formation pathways were determined in PM2.5 aerosol samples collected in Guangzhou, China, during 2015–2018. The PM2.5 concentrations varied from 30.5 to 189.8 μg⋅m−3 and their mean values were highest in spring (111.1 μg⋅m−3) and lowest in summer (63.5 μg⋅m−3). The δ15N–NH4+ and δ15N–NO3- values ranged from +4.5 to +20.2‰ and from +4.8 to +14.8‰, respectively, with their mean values being highest in winter (14.0‰ and 9.5‰, respectively) and lowest in summer (10.4‰ and 7.1‰, respectively). The seasonal δ15N variability was mainly attributed to isotopic equilibrium fractionation, and partly due to the changes in NH3 and NOx sources. The average δ18O–NO3- value of 63.0‰, ranging seasonally from +58.6‰ in summer to +68.0‰ in spring, suggests that NO2 +⋅OH pathway played a vital role (70.3–85.9%) in NO3− formation. The Bayesian isotope mixing model results revealed fossil fuel combustion sources as dominant sources of atmospheric NH3 and NOx. This study suggests that more effort should be devoted to reduce NH3 and NOx from combustion-related processes and highlights the importance of δ18O–NO3- analysis for exploring variations of nitrate formation pathways in urban atmospheres.

Urgency of controlling agricultural nitrogen sources to alleviate summertime air pollution in the North China Plain

Agricultural nitrogen sources (ANS) have played an increasingly important role in the air quality since ANS emission controls are much weaker than those for fossil fuel combustion sources due to the increasing food demand. However, ANS emissions are highly uncertain due to stochastic agricultural management activities and limited field measurements, and impacts of ANS on the air quality remain elusive. In the study, the WRF-Chem model has been used to investigate ANS shares in near surface air pollutant concentrations during a growing season in the North China Plain (NCP), with ANS emissions constrained by satellite retrievals. Soil NOX and agricultural NH3 emissions are about 36% and 92% of their total emissions during the growing season. Sensitivity studies demonstrate that ANS count 16.9 μg m−3 (9.9%) of the mean maximum daily average 8-h ozone concentrations (MDA8 [O3]) and 8.9 μg m−3 (31.7%) of fine particulate matter concentrations ([PM2.5]) on average in the NCP. Additionally, the contributions of ANS to MDA8 [O3] and [PM2.5] increase with the deterioration of air pollution in cities. A 50% emission reduction in ANS decreases MDA8 [O3] ([PM2.5]) from 4.2% to 8.4% (from 19.7% to 31.9%) when the air quality changes from being lightly to heavily polluted in terms of MDA8 [O3] (hourly [PM2.5]). Without fossil fuel combustion emissions, the simulated average MDA8 [O3] and [PM2.5] are 111.7 and 8.2 μg m−3 in cities of the NCP, respectively, exceeding the new standards from the World Health Organization. Our study highlights important contributions of ANS to air quality and the urgency of ANS emission abatement for air pollution alleviation during summertime in the NCP.

Seasonal Variation in Chemical Composition of Total Suspended Particles During the COVID-19 Pandemic in the Source Area of Urumqi River, Tianshan, China

The research of atmospheric aerosol in mountain glacier areas has attracted more and more people’s attention. For the first time, a field observation study of total suspended particles (TSPs) for four seasons from September 2019 to August 2020 was carried out at the Tianshan Glaciological Station in the source area of Urumqi River, East Tianshan Mountains, China. The TSPs presented typical seasonal characteristics of high in autumn and low in winter, with the annual average value of 181 ± 170 μg m−3. Concentrations of Ca2+, SO42−, NO3−, Cl−, NH4+ and K+, OC, EC were elevated in autumn. The influence of stationary source emissions was stronger than mobile sources, which was explained by the average ratio of NO3−/SO42− (0.31 ± 0.17). The concentration of secondary organic carbon (SOC) was higher in summer and autumn, especially in summer, indicating that secondary formation processes of organic aerosols were frequent in summer. Impact of fossil fuel combustion sources were evident over the Glaciers, corroborated by the diagnostic mass ratios of OC/EC (0–21.4, 3.38) and K+/EC (0–0.31, 0.08). The factor analysis illustrated that aerosols were mainly affected by rock salt, dust, coal combustion, and automobile exhaust. The local sources made significant contributions to TSPs in the source of Urumqi River by the results of Results of Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and potential source contribution function (PSCF).

Detailed Carbon Isotope Study of PM2.5 Aerosols at Urban Background, Suburban Background and Regional Background Sites in Hungary

The aim of this study was to estimate and refine the potential sources of carbon in the atmospheric PM2.5 fraction aerosol at three sampling sites in Hungary. Quantification of total, organic and elemental carbon (TC, OC and EC, respectively), as well as radiocarbon (14C) and stable carbon isotope analyses were performed on exposed filters collected at an urban background site, a suburban background site of the capital of Hungary, Budapest from October 2017 to July 2018. Results were also collected from the rural regional background site of K-puszta. Compared to TC concentrations from other regions of Europe, the ratio of the lowest and highest values at all sites in Hungary are lower than these European locations, probably due to the specific meteorological conditions prevailing in the Carpathian Basin over the observation period. The concentration of OC was constantly higher than that of EC and a seasonal variation with higher values in the heating period (October–March) and lower values in the non-heating vegetation period (April–September) could be observed for both EC and OC fractions. Using 14C, the seasonal mean fraction of contemporary carbon (fC) within the TC varied between 0.50 and 0.78 at the sites, suggesting that modern sources were remarkable during the year, regardless of the heating or vegetation period. At the two urban sites, assuming constant industrial emission during the year, the fossil fuel combustion sources were responsible for the seasonal variation of EC, while modern carbon emissions from biomass-burning and biogenic sources influenced the OC concentration. The higher EC/TC ratios at these sites were associated with lower fC and δ13C values, which can be explained by soot emission from transportation. The notably high EC/TC ratios in the spring were likely caused by the reduced concentration of OC instead of increased EC concentrations. This could probably be caused by the ending of winter biomass burning, which emits a huge amount of OC into the atmosphere. On the contrary, the rural K-puszta site showed some differences relative to the sites in Budapest. No correlation could be revealed between the EC/TC ratio, fC and δ13C results, suggesting that the structure of sources was very stagnant and balanced in each season. In autumn, however, some less depleted values were observed, and agricultural corn-stalk burning after harvesting in the southern and eastern directions from Hungary can be suggested as the main source.

Online Chemical Characterization and Sources of Submicron Aerosol in the Major Mediterranean Port City of Piraeus, Greece

Port cities are affected by a wide array of emissions, including those from the shipping, road transport, and residential sectors; therefore, the characterization and apportionment of such sources in a high temporal resolution is crucial. This study presents measurements of fine aerosol chemical composition in Piraeus, one of the largest European ports, during two monthly periods (winter vs. summer) in 2018–2019, using online instrumentation (Aerosol Chemical Speciation Monitor—ACSM, 7-λ aethalometer). PMF source apportionment was performed on the ACSM mass spectra to quantify organic aerosol (OA) components, while equivalent black carbon (BC) was decomposed to its fossil fuel combustion and biomass burning (BB) fractions. The combined traffic, shipping and, especially, residential emissions led to considerably elevated submicron aerosol levels (22.8 μg m−3) in winter, which frequently became episodic late at night under stagnant conditions. Carbonaceous compounds comprised the major portion of this submicron aerosol in winter, with mean OA and BC contributions of 61% (13.9 μg m−3) and 16% (3.7 μg m−3), respectively. The contribution of BB to BC concentrations was considerable and spatially uniform. OA related to BB emissions (fresh and processed) and hydrocarbon-like OA (from vehicular traffic and port-related fossil fuel emissions including shipping) accounted for 37% and 30% of OA, respectively. In summer, the average PM1 concentration was significantly lower (14.8 μg m−3) and less variable, especially for the components associated with secondary aerosols (such as OA and sulfate). The effect of the port sector was evident in summer and maintained BC concentrations at high levels (2.8 μg m−3), despite the absence of BB and improved atmospheric dispersion. Oxygenated components yielded over 70% of OA in summer, with the more oxidized secondary component of regional origin being dominant (41%) despite the intensity of local sources, in the Piraeus environment. In general, with respect to local sources that can be the target of mitigation policies, this work highlights the importance of port-related activities but also reveals the extensive wintertime impact of residential wood burning. While a separation of the BB source is feasible, more research is needed on how to disentangle the short-term effects of different fossil-fuel combustion sources.

Cropland nitrogen dioxide emissions and effects on the ozone pollution in the North China plain

Soil nitrogen dioxide (NOX = NO2 + NO) emissions have been measured and estimated to be the second most significant contributor to the NOX burden following the fossil fuel combustion source globally. NOX emissions from croplands are subject to being underestimated or overlooked in air pollution simulations of regional atmospheric chemistry models. With constraints of ground and space observations of NO2, the WRF-Chem model is used to investigate the cropland NOX emission and its contribution to the near-surface ozone (O3) pollution in North China Plain (NCP) during a growing season as a case study. Model simulations have revealed that the cropland NOX emissions are underestimated by around 80% without constraints of satellite measured NO2 column densities. The biogenic NOX source is estimated to account for half of the anthropogenic NOX emissions in the NCP during the growing season. Additionally, the cropland NOX source contributes around 5.0% of the maximum daily average 8h O3 concentration and 27.7% of NO2 concentration in the NCP. Our results suggest the agriculture NOX emission exerts non-negligible impacts on the summertime air quality and needs to be considered when designing emission abatement strategies.

Molecular characterization and spatial distribution of dicarboxylic acids and related compounds in fresh snow in China

Low molecular weight organic compounds are ubiquitous in the atmosphere. However, knowledge on their concentrations and molecular distribution in fresh snow remains limited. Here, twelve fresh snow samples collected at eight sites in China were investigated for dicarboxylic acids and related compounds (DCRCs) including oxocarboxylic acids and α-dicarbonyls. Dissolved organic carbon (DOC) concentrations in the snow samples ranged from 0.99 to 14.6 mg C L−1. Concentrations of total dicarboxylic acids were from 225 to 1970 μg L−1 (av. 650 μg L−1), while oxoacids (28.3–173, av. 68.1 μg L−1) and dicarbonyls (12.6–69.2, av. 31.3 μg L−1) were less abundant, accounting for 4.6–8.5% (6.2%), 0.45–1.4% (0.73%), and 0.12–0.88% (0.46%) of DOC, respectively. Molecular patterns of dicarboxylic acids are characterized by a predominance of oxalic acid (C2) (95.0–1030, av. 310 μg L−1), followed by phthalic (Ph) (9.69–244, av. 69.9 μg L−1) or succinic (C4) (23.8–163, av. 63.7 μg L−1) acid. Higher concentrations of Ph in snow from Beijing and Tianjin than other urban and rural regions suggest significant emissions from vehicular exhausts and other fossil fuel combustion sources in megacities. C2 constituted 40–54% of total diacids, corresponding to 1.5–2.6% of snow DOC. The total measured DCRCs represent 5.5–10% of snow DOC, which suggests that there are large amounts of unknown organics requiring further investigations. The spatial distributions of diacids exhibited higher loadings in megacities than rural and island sites. Molecular distributions of diacids indicated that the photochemical modification was restrained under the weak solar radiation during the snow events, while anthropogenic primary sources had a more significant influence in megacities than rural areas and islands.

Atmospheric black carbon in urban and traffic areas in Shanghai: Temporal variations, source characteristics, and population exposure

Black carbon (BC) measurements were performed at Pudong (PD) urban supersite and Gonghexin (GH) roadside station from December 1, 2017 to August 10, 2020 to investigate the variations, source characteristics, and population exposure levels of BC in traffic and urban areas in Shanghai, China. The BC median concentration at GH was more than two-fold that at PD. Absorption Ångström exponent (AAE) values were 1.27 ± 0.17 and 1.31 ± 0.17 at PD and GH, respectively, suggesting the dominance of liquid fossil fuel combustion sources (i.e., traffic exhaust) at these stations. The higher BC and AAE values in winter at PD indicated the relatively increasing contribution of solid fuels (i.e., biomass burning) to BC concentration in urban Shanghai. The diurnal variation in BC showed similar twin-peak patterns at PD and GH, implying that traffic emission mainly contributed to ambient BC concentration in urban Shanghai. The estimated daily intakes (EDIs) of BC were generally higher in males than in females at both PD and GH. The highest BC EDIs at PD were found in age subgroups 1–<2 and 2–<3 years. In contrast, the BC EDIs at GH were observed in age subgroups 6–<9, 12–<15, and 15–<18 years, which were higher than those determined at PD, indicating that more attention must be paid to BC exposure of the population in these age subgroups. These results provide scientific insights into variations, source characteristics, and population exposure levels of BC in urban and traffic areas and could help in the development of BC control strategies in Shanghai.

Respiratory Emergency Department Visit Associations with Exposures to Fine Particulate Matter Mass, Constituents, and Sources in Dhaka, Bangladesh Air Pollution.

Rationale: To date, there is no published local epidemiological evidence documenting the respiratory health effects of source-specific air pollution in South Asia, where particulate matter ⩽2.5 μm in aerodynamic diameter (PM2.5) composition is different from past studies. Differences include more biomass and residue crop-burning emissions, which may have differing health implications. Objectives: We assessed PM2.5 associations with respiratory emergency department (ED) visits in a biomass-burning-dominated high-pollution region and evaluated their variability by pollution source and composition. Methods: Time-series regression modeling was applied to daily ED visits from January 2014 through December 2017. Air pollutant effect sizes were estimated after addressing long-term trends and seasonality, day of week, holidays, relative humidity, ambient temperature, and the effect modification by season, age, and sex. Results: PM2.5 yielded a significant association with increased respiratory ED visits (0.84%; 95% confidence interval, 0.33-1.35%) per 10-μg/m3 increase. The PM2.5 health effect size varied with season, the highest being during monsoon season, when fossil-fuel combustion sources dominated exposures. Results from a source-specific health effect analysis were also consistent with fossil-fuel PM2.5 having a larger effect size per 10 μg/m3 than PM2.5 from other sources (fossil-fuel PM2.5: 2.79% [0.33-5.31%], biomass-burning PM2.5: 1.27% [0-2.54%], and other PM2.5: 0.95% [0.06-1.85%]). Age-specific associations varied, with children and older adults being disproportionately affected by the air pollution, especially by the combustion-related particles. Conclusions: This study provided novel and important evidence that respiratory health in Dhaka is significantly affected by particle air pollution, with a greater health impact by fossil-fuel combustion-derived PM2.5.

Long-term exposure to low-level air pollution and incidence of asthma: the ELAPSE project.

Long-term exposure to ambient air pollution has been linked to childhood-onset asthma, although evidence is still insufficient. Within the multicentre project Effects of Low-Level Air Pollution: A Study in Europe (ELAPSE), we examined the associations of long-term exposures to particulate matter with a diameter <2.5 µm (PM2.5), nitrogen dioxide (NO2) and black carbon (BC) with asthma incidence in adults. We pooled data from three cohorts in Denmark and Sweden with information on asthma hospital diagnoses. The average concentrations of air pollutants in 2010 were modelled by hybrid land-use regression models at participants' baseline residential addresses. Associations of air pollution exposures with asthma incidence were explored with Cox proportional hazard models, adjusting for potential confounders. Of 98 326 participants, 1965 developed asthma during a mean follow-up of 16.6 years. We observed associations in fully adjusted models with hazard ratios of 1.22 (95% CI 1.04-1.43) per 5 μg·m-3 for PM2.5, 1.17 (95% CI 1.10-1.25) per 10 µg·m-3 for NO2 and 1.15 (95% CI 1.08-1.23) per 0.5×10-5 m-1 for BC. Hazard ratios were larger in cohort subsets with exposure levels below the European Union and US limit values and possibly World Health Organization guidelines for PM2.5 and NO2. NO2 and BC estimates remained unchanged in two-pollutant models with PM2.5, whereas PM2.5 estimates were attenuated to unity. The concentration-response curves showed no evidence of a threshold. Long-term exposure to air pollution, especially from fossil fuel combustion sources such as motorised traffic, was associated with adult-onset asthma, even at levels below the current limit values.

Mineral dust and fossil fuel combustion dominate sources of aerosol sulfate in urban Peru identified by sulfur stable isotopes and water-soluble ions

High sulfur emissions in the Central Andes have in the past been attributed to active volcanoes and numerous copper smelting facilities in the region. This study evaluates the contribution of these sources on Arequipa, Peru through an evaluation of aerosol sulfate δ34S values and water-soluble ions (WSI). The anthropogenic and natural sources of particulate pollution were determined by aerosol filter sampling from four different locations (urban, suburban, industrial, and rural) providing a view of the spatial variability of aerosols within the city. Sulfate (avg. 2.97 μm/m3) is the most abundant ion species in the aerosols sampled contributing on average 20% of the molar mass. Ion composition profiles between sampling sites are very similar indicating common sources and high contributions of mobilized local surface salt to the aerosols in this desert region. The regional atmospheric chemistry model (RACM) 0-D run for the area confirms that emissions from fuel combustion sources alone cannot account for the high concentrations of sulfate observed. A combination of the RACM results, WSI data, and a Bayesian δ34S isotope mixing model determined that the majority of aerosol sulfates in the area are from mineral dust adding to fossil fuel combustion sources. Mineral dust entrainment in the region is likely elevated by the close proximity of open-pit mining and unpaved roads near the city. Marine organic aerosols and smelting located along the Pacific contribute little to Arequipa's aerosol sulfate concentration. While the influence of volcanic sulfate (9% on average) is low, overall natural sulfate (dust, volcanic, and DMS) accounts for 43% of the aerosol sulfate. Therefore, even though the local environment creates high sulfate background levels, a reduction of sulfate aerosol pollution would be possible if fossil fuel emissions were reduced.

Traffic-related air pollution reduction at UK schools during the Covid-19 lockdown.

Elevated urban Nitrogen Dioxide (NO2) is a consequence of road traffic and other fossil-fuel combustion sources, and the road transport sector provides a significant contribution to UK NO2 emissions. The inhalation of traffic-related air pollution, including NO2, can cause a range of problems to human health. Due to their developing organs, children are particularly susceptible to the negative effects of air pollution inhalation. Accordingly, schools and associated travel behaviours present an important area of study for the reduction of child exposure to these harmful pollutants.COVID-19 reached the UK in late January 2020. On the 23rd of March that year, the UK government announced a nationwide stay-at-home order, or lockdown, banning all non-essential travel and contact with people outside of their own homes. The lockdown was accompanied by the closure of schools, public facilities, amenities, businesses and places of worship.The current study aims to assess the significance of nationwide NO2 reductions at schools in England as a consequence of the lockdown in order to highlight the benefits of associated behavioural changes within the context of schools in England and potential child exposure. NO2 data were collected from all AURN (Automatic Urban and Rural Network) monitoring sites within 500 m of nurseries, primary schools, secondary schools and colleges in England. A significant reduction of mean NO2 concentrations was observed in the first month of the UK lockdown at background (−35.13%) and traffic (−40.82%) sites.Whilst lockdown restrictions are undoubtedly unsustainable, the study results demonstrate the possible reductions of NO2 at schools in England and potential reductions of child exposure that are achievable when public behaviours shift towards active travel, work from home policies and generally lower use of polluting vehicles.

Long-term Measurements of Carbonaceous Aerosol at Cape Hedo, Okinawa, Japan: Effects of Changes in Emissions in East Asia

ABSTRACT We investigated the changes in the carbonaceous-aerosol sources and their effects on the long-term elemental carbon (EC) and organic carbon (OC) concentration trends at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, during the period 2004–2013. We obtained the EC and OC concentrations by conducting semi-real-time measurements using a carbon monitor, and performing an offline thermal/optical filter analysis according to the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. The annual average concentration of the EC remained constant between 2004 and 2013, but that of the OC decreased at a rate of 0.11 µg C m–3 y–1 (α > 0.05). The secondary OC (SOC)/OC ratio showed an increasing trend from 2004 till 2011, which may have been caused by a reduction in primary emissions of OC and compositional changes in the organic compounds originating in China, from which air pollutants were frequently transported during spring and winter. Although the EC concentration did not change appreciably in either season, the OC concentration decreased at rates of 0.10 µg C m–3 y–1 and 0.11 µg C m–3 y–1 during spring and winter, respectively. We estimated the contributions from the various sources of carbonaceous aerosol, viz., biomass burning, fossil-fuel combustion, and air-pollutant transport from China, based on the OC/EC ratio, which decreased from 5.7 to 2.4 in terms of the annual average. The growing share from fossil-fuel combustion is responsible for the decline in biofuel-burning OC emissions transported from China to CHAAMS.

Long-term exposure to low-level air pollution and incidence of asthma: the ELAPSE project

Long-term exposure to ambient air pollution has been linked to childhood-onset asthma, while evidence is still insufficient. Within the multicentre project "Effects of Low-Level Air Pollution: A Study in Europe" (ELAPSE), we examined the associations of long-term exposures to particulate matter with diameter<2.5 µm (PM2.5), nitrogen dioxide (NO2), and black carbon (BC) with asthma incidence in adults. We pooled data from three cohorts in Denmark and Sweden with information on asthma hospital diagnoses. The average concentrations of air pollutants in 2010 were modelled by hybrid land use regression models at participants' baseline residential addresses. Associations of air pollution exposures with asthma incidence were explored with Cox proportional hazard models, adjusting for potential confounders. Of 98 326 participants, 1965 developed asthma during a 16.6 years mean follow-up. We observed associations in fully adjusted models with hazard ratios and 95% confidence intervals of 1.22 (1.04-1.43) per 5 μg·m-3 for PM2.5, 1.17 (1.10-1.25) per 10 µg·m-3 for NO2, and 1.15 (1.08-1.23) per 0.5 10-5 m-1 for BC. Hazard ratios were larger in cohort subsets with exposure levels below the EU and US limit values and possibly WHO guidelines for PM2.5 and NO2. NO2 and BC estimates remained unchanged in two-pollutant models with PM2.5, whereas PM2.5 estimates were attenuated to unity. The concentration response curves showed no evidence of a threshold. Long-term exposure to air pollution, especially from fossil fuel combustion sources such as motorised traffic, was associated with adult-onset asthma, even at levels below the current limit values.

The Impact of Fossil-Fuels and Biomass Combustion on Outdoor PM2.5 Mass Associations with Respiratory Emergency Department Visits in Dhaka, Bangladesh

Introduction: Developed world studies report associations between particle air pollution and increased risk of emergency department (ED) visits for respiratory diseases, but few were conducted in the south Asia region, where PM2.5 composition is different. Differences are from greater biomass and residue crop-burning, which may have differing health impacts from past PM2.5 studies. Despite that fact, an “equal toxicity” assumption has been made in most global PM2.5 effect estimates. We evaluated this assumption in Dhaka.Methods: The acute effects of PM2.5 and source component’s on 38,233 respiratory ED visits during 2014-2017 were assessed using time-series modeling, adjusted for temporal trend, day of week, holidays, relative humidity, and temperature. Daily counts of respiratory ED visits were obtained from National Institute of Chest Diseases and Hospital. Analyses were conducted to test for seasonal effect modification by including dummy variables for monsoon vs. non-monsoon seasons.Results: PM2.5 yielded statistically significant association with increased respiratory ED visits [Excess Risk, ER=0.88%, 95%CI: 0.37%, 1.39%] per 10 μg/m3 increase. The effect of PM2.5 air pollution per 10 µg/m3 varies with season, with the highest during monsoon season [2.84%, 95%CI: 0.74, 4.91] vs. non-monsoon season [0.77%, 95%CI: 0.23%, 1.31%], suggesting that the effect size per unit mass is much larger when fossil-fuel combustion sources dominated exposures, with effect per unit mass declining when crop-burning and dust sources dominated exposures. A source-specific health effect analysis model using elemental source tracers provided consistent results, with fossil-fuel PM2.5 having a larger ER per 10 μg/m3 than biomass-combustion PM2.5.Conclusion: This study found that the respiratory health in Dhaka is significantly affected by particle air pollution, with greater impact by fossil-fuel PM2.5. This disparity in health impact by PM2.5 source origin should be considered in PM2.5 risk assessment, PM2.5 mitigation measure prioritization, and clinical advice.

Characterizing Light-absorbing Aerosols in a Low-income Settlement in South Africa

Light-absorbing aerosols, particularly black carbon (BC), have significant impacts on human health and the climate. They are also the least-studied fraction of atmospheric particles, particularly in residential areas of southern Africa. The optical characteristics of ground-based light-absorbing aerosols from Kwadela Township in South Africa are investigated in this study. Daily averaged ambient PM25 highest levels were 51.39 µg m–3 and 32.18 µg m–3, whereas hourly averages peaked at 61.31 µg m–3 and 34.69 µg m–3 during winter and summer, respectively. Levels of daily averaged light-absorbing aerosols were 2.9 times higher (1.89 ± 0.5 µg m–3) in winter 2014 than in summer 2015 (0.66 ± 0.2 µg m–3). In both seasons, hourly averaged levels showed bimodal diurnal cycles, which correlated with the PM2.5 diurnal patterns that indicated distinct peaks in the morning and evening. These diurnal cycle peak periods corresponded with the times of increased solid domestic fuel usage, road traffic, and also shallower boundary layer. On average, light-absorbing aerosols contributed a larger proportion of total ambient PM2.5 levels in winter (6.5 ± 1.0%) than in summer (3.4 ± 1.0%). The winter average Absorption Ångstrӧm exponent AAE(370/880 nm) (1.7± 0.5), indicated the dominance of brown carbon (BrC) from biofuel/biomass burning and/or low-quality coal combustion emissions. In summer, the average AAE(370/950 nm) (1.3 ± 0.7), suggested the presence of BC and BrC in the mornings and evenings possibly from fossil fuel combustion sources. At midday and at night in summer, the AAE was close to 1, suggesting more BC contributions from sources such as diesel emissions during this time. A combination of BC and BrC particulates dominated on 50% and 5% of the summer days, respectively, whereas fresh BC were only measured in summer days (23%). Residential solid-fuel and/biomass combustion are important sources of light-absorbing aerosols in this study region, with concomitant human health and environmental impacts.

Chemical characterization of wintertime aerosols over the Arabian Sea: Impact of marine sources and long-range transport

Abstract We examined here the compositional characteristics of total suspended particulate (TSP) samples collected along the east coast of the Arabian Sea during a winter cruise (SS379: 6–24 December 2018) to understand the extent of influence of air pollutants from terrestrial sources. The TSP samples (N = 17) were analyzed for water-soluble inorganic species (WSIS), elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC). Backward air mass trajectories and satellite-based fire counts revealed an influence of long-range transport of biomass burning emissions in the Indo-Gangetic Plain and southern India. Anthropogenic (82–97%) SO42− is the most abundant WSIS followed by Na+ and/or NH4+. Ambient EC loadings (0.5–2.4 μg m−3) and OC/EC ratios (2.5–10.5) are higher than usually expected for fossil-fuel combustion sources. Low mass ratios of NO3−/non-sea-salt SO42− (0.08–0.49), as well as high ratios of nss-K+/EC (0.14–1.18) and WSOC/OC (0.30–0.74), highlight the significance of coal combustion and biomass burning emissions in the regional influx of air pollutants to the Arabian Sea. The multiple linear regression analysis has indicated strong correlations among sea salt components (Na+, Cl− and Mg2+), carbonaceous components (OC, EC and WSOC), and anthropogenic WSIS (NH4+ and SO42−). Furthermore, we used minimum R-squared technique based primary OC/EC ratio in the EC-tracer method to estimate the contribution of secondary organic carbon (SOC) to OC (7–61%) and TSP mass (0.7–11%). Overall, the composition of TSP is characterized by 21 ± 10% of particulate organic matter, 2.3 ± 1.1% of EC, 21 ± 9% of anthropogenic WSIS and 43 ± 15% of unidentified fraction including dust. This study has implications for understanding the evolving nature of secondary inorganic and organic aerosols in the continental outflows.

Assessing the PM2.5 impact of biomass combustion in megacity Dhaka, Bangladesh

In Dhaka, Bangladesh, fine particulate matter (PM2.5) air pollution shows strong seasonal trends, with significantly higher mean concentrations during winter than during the monsoon (winter = 178.1 μg/m3 vs. monsoon = 30.2 μg/m3). Large-scale open burning of post-harvest agricultural waste across the Indo-Gangetic Plain is a major source of PM2.5 air pollution in northern India during the non-monsoon period. This study evaluates the extent to which the seasonal differences in PM2.5 pollution concentrations in Dhaka are accounted for by biomass-burning vs. fossil-fuel combustion sources. To assess this, an index was developed based on elemental potassium (K) as a marker for biomass particulate matter, after adjusting for soil-associated K contributions. Alternatively, particulate sulfur was employed as a tracer index for fossil-fuel combustion PM2.5. By simultaneously regressing total PM2.5 on S and adjusted K, the PM2.5 mass for each day was apportioned into: 1) fossil-fuels combustion associated PM2.5; 2) biomass-burning associated PM2.5; and, 3) all other PM2.5. The results indicated that fossil-fuel combustion contributed 21.6% (19.5 μg/m3), while biomass contributed 40.2% (36.3 μg/m3) of overall average PM2.5 from September 2013 to December 2017. However, the mean source contributions varied by season: PM2.5 in Dhaka during the monsoon season was dominated by fossil-fuels sources (44.3%), whereas PM2.5 mass was dominated by biomass-burning (41.4%) during the remainder of the year. The contribution to PM2.5 and each of its source components by transport of pollution into Dhaka during non-monsoon time was also evaluated by: 1) Conditional bivariate (CBPF) and pollution rose plots; 2) Concentration weighted trajectories (CWT), and; 3) NASA satellite photos to identify aerosol loading and fire locations on high pollution days. The collective evidence indicates that, while the air pollution in Dhaka is contributed to by both local and transboundary sources, the highest pollution days were dominated by biomass-related PM2.5, during periods of crop-burning in the Indo-Gangetic Plain.

Assessment of Ambient Air Toxics and Wood Smoke Pollution among Communities in Sacramento County.

Ambient air monitoring and phone survey data were collected in three environmental justice (EJ) and three non-EJ communities in Sacramento County during winter 2016–2017 to understand the differences in air toxics and in wood smoke pollution among communities. Concentrations of six hazardous air pollutants (HAPs) and black carbon (BC) from fossil fuel (BCff) were significantly higher at EJ communities versus non-EJ communities. BC from wood burning (BCwb) was significantly higher at non-EJ communities. Correlation analysis indicated that the six HAPs were predominantly from fossil fuel combustion sources, not from wood burning. The HAPs were moderately variable across sites (coefficient of divergence (COD) range of 0.07 for carbon tetrachloride to 0.28 for m- and p-xylenes), while BCff and BCwb were highly variable (COD values of 0.46 and 0.50). The BCwb was well correlated with levoglucosan (R2 of 0.68 to 0.95), indicating that BCwb was a robust indicator for wood burning. At the two permanent monitoring sites, wood burning comprised 29–39% of the fine particulate matter (PM2.5) on nights when PM2.5 concentrations were forecasted to be high. Phone survey data were consistent with study measurements; the only significant difference in the survey results among communities were that non-EJ residents burn with indoor devices more often than EJ residents.