Black carbon emissions from traffic contribute substantially to air pollution in Nairobi, Kenya

Leonard Kirago; Michael J. Gatari; Örjan Gustafsson; August Andersson
2022 | Commun. Earth Environ. | 3 (74) (1-8)
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Rapid urbanization and population growth drives increased air pollution across Sub-Saharan
Africa with serious implications for human health, yet pollutant sources are poorly constrained. Here, we analyse fine particulate aerosol concentrations and radiocarbon composition of black carbon over a full annual cycle in Nairobi, Kenya. We find that particle
concentrations exceed the World Health Organisation’s recommended safe limit throughout
the year, with little seasonal variability in particle concentration or composition. Organics
(49 ± 7%) and water-soluble inorganic ions, dominated by sulfates (13 ± 5%), constitute the
largest contributors to the particle loadings. Unlike large cities on other continents, the
fraction of black carbon in particles is high (15 ± 4%) suggesting black carbon is a prominent
air pollutant in Nairobi. Radiocarbon-based source quantification indicates that fossil fuel
combustion emissions are a dominant source of black carbon throughout the year (85 ± 3%).
Taken together, this indicates that black carbon emissions from traffic are a key stressor for
air quality in Nairobi.

Black carbon emissions from traffic contribute substantially to air pollution in Nairobi, Kenya

Leonard Kirago; Michael J. Gatari; Örjan Gustafsson; August Andersson
2022 | Commun. Earth Environ.

Rapid urbanization and population growth drives increased air pollution across Sub-Saharan Africa with serious implications for human health, yet pollutant sources are poorly constrained. Here, we analyse fine particulate aerosol concentrations and radiocarbon composition of black carbon over a full annual cycle in Nairobi, Kenya. We find that particle concentrations exceed the World Health Organisation’s recommended safe limit throughout the year, with little seasonal variability in particle concentration or composition. Organics (49 ± 7%) and water-soluble inorganic ions, dominated by sulfates (13 ± 5%), constitute the largest contributors to the particle loadings. Unlike large cities on other continents, the fraction of black carbon in particles is high (15 ± 4%) suggesting black carbon is a prominent air pollutant in Nairobi. Radiocarbon-based source quantification indicates that fossil fuel combustion emissions are a dominant source of black carbon throughout the year (85 ± 3%). Taken together, this indicates that black carbon emissions from traffic are a key stressor for air quality in Nairobi.

Nontarget mass spectrometry and in silico molecular characterization of air pollution from the Indian subcontinent

Papazian, S; D'Agostino, LA; Sadiktsis, I; Froment, J; Bonnefille, B; Sdougkou, K; Xie, HY; Athanassiadis, I; Budhavant, K; Dasari, S; Andersson, A; Gustafsson, O; Martin, JW
2022 | Commun. Earth Environ. | 3 (1)
ambient , brown carbon , chemistry , dark-matter , diversity , evolution , organic aerosol , particulate matter , transport , variability
A combination of high-resolution mass spectrometry and computational molecular characterization techniques can structurally annotate up to 17% of organic compounds in fine particulate matter in highly polluted air sampled in the Maldives. Fine particulate-matter is an important component of air pollution that impacts health and climate, and which delivers anthropogenic contaminants to remote global regions. The complex composition of organic molecules in atmospheric particulates is poorly constrained, but has important implications for understanding pollutant sources, climate-aerosol interactions, and health risks of air pollution exposure. Here, comprehensive nontarget high-resolution mass spectrometry was combined with in silico structural prediction to achieve greater molecular-level insight for fine particulate samples (n = 40) collected at a remote receptor site in the Maldives during January to April 2018. Spectral database matching identified 0.5% of 60,030 molecular features observed, while a conservative computational workflow enabled structural annotation of 17% of organic structures among the remaining molecular dark matter. Compared to clean air from the southern Indian Ocean, molecular structures from highly-polluted regions were dominated by organic nitrogen compounds, many with computed physicochemical properties of high toxicological and climate relevance. We conclude that combining nontarget analysis with computational mass spectrometry can advance molecular-level understanding of the sources and impacts of polluted air.

Mechanisms for log normal concentration distributions in the environment

2021 | Sci Rep | 11 (1)
carbon , contamination , frequency-distributions , metals , model , soil , uncertainty , variability
Log normal-like concentration distributions are ubiquitously observed in the environment. However, the mechanistic origins are not well understood. In this paper, we show that first order exponential kinetics onsets log-normal concentration distributions, under certain assumptions. Given the ubiquity of exponential kinetics, e.g., source and sink processes, this model suggests an explanation for the frequent observation in the environment, and elsewhere. We compare this model to other mechanisms affecting concentration distributions, e.g., source mixing. Finally, we discuss possible implications for data analysis and modelling, e.g., log-normal rates and fluxes.

Wintertime Air Quality in Megacity Dhaka, Bangladesh Strongly Affected by Influx of Black Carbon Aerosols from Regional Biomass Burning

Salam, A; Andersson, A; Jeba, F; Haque, MI; Khan, MDH; Gustafsson, O
2021 | Environ. Sci. Technol. | 55 (18) (12243-12249)
bay , biomass burning , black carbon , chemical characteristics , dual carbon isotope (delta c-13 and delta c-14) , elemental carbon , particulate matter , source apportionment , wintertime air quality
Clean air is a key parameter for a sustainable society, and currently, megacity Dhaka has among the worst air qualities in the world. This results from poorly constrained contributions of a variety of sources from both local emissions and regional influx from the highly polluted Indo-Gangetic Plain, impacting the respiratory health of the 21 million inhabitants in the Greater Dhaka region. An important component of the fine particulate matter (PM2.5) is black carbon (BC) aerosols. In this study, we investigated the combustion sources of BC using a dual carbon isotope (delta C-13 and Delta C-14) in Dhaka during the high-loading winter period of 2013/14 (regular and lockdown/hartal period) in order to guide mitigation policies. On average, BC (13 +/- 6 mu g m(-3)) contributed about 9% of the PM2.5 (145 +/- 79 mu g m(-3)) loadings. The relative contribution from biomass combustion under regular conditions was 44 +/- 1% (with the rest from fossil combustion), while during periods of politically motivated large-scale lockdown of business and traffic, the biomass burning contribution increased to 63 +/- 1%. To reduce the severe health impact of BC and other aerosol pollution in Dhaka, mitigation should therefore target regional-scale biomass/agricultural burning in addition to local traffic.

Observed and Modeled Black Carbon Deposition and Sources in the Western Russian Arctic 1800-2014

Ruppel, MM; Eckhardt, S; Pesonen, A; Mizohata, K; Oinonen, MJ; Stohl, A; Andersson, A; Jones, V; Manninen, S; Gustafsson, O
2021 | Environ. Sci. Technol. | 55 (8) (4368-4377)
aerosols , biomass burning emissions , elemental carbon , ice-core record , reactive gases , snow
Black carbon (BC) particles contribute to climate warming by heating the atmosphere and reducing the albedo of snow/ice surfaces. The available Arctic BC deposition records are restricted to the Atlantic and North American sectors, for which previous studies suggest considerable spatial differences in trends. Here, we present first long-term BC deposition and radiocarbon-based source apportionment data from Russia using four lake sediment records from western Arctic Russia, a region influenced by BC emissions from oil and gas production. The records consistently indicate increasing BC fluxes between 1800 and 2014. The radiocarbon analyses suggest mainly (similar to 70%) biomass sources for BC with fossil fuel contributions peaking around 1960-1990. Backward calculations with the atmospheric transport model FLEXPART show emission source areas and indicate that modeled BC deposition between 1900 and 1999 is largely driven by emission trends. Comparison of observed and modeled data suggests the need to update anthropogenic BC emission inventories for Russia, as these seem to underestimate Russian BC emissions and since 1980s potentially inaccurately portray their trend. Additionally, the observations may indicate underestimation of wildfire emissions in inventories. Reliable information on BC deposition trends and sources is essential for design of efficient and effective policies to limit climate warming.

Source quantification of South Asian black carbon aerosols with isotopes and modeling

Sanjeev Dasari; August Andersson; Andreas Stohl; Nikolaos Evangeliou; Srinivas Bikkina; Henry Holmstrand; Krishnakant Budhavant; Abdus Salam; Örjan Gustafsson;
2020 | Environ. Sci. Technol.
black carbon
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Seasonal source variability of carbonaceous aerosols at the Rwanda Climate Observatory

Andersson A; Kirillova EN; Decesari S; DeWitt L; Gasore J; Potter KE; Prinn RG; Rupakheti M; de Dieu Ndikubwimana J; Nkusi J; Safari B
2020 | Atmos. Chem. Phys. | 20 (4561-4573)

Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost

Wild, B.; Andersson, A.; Bröder, L.; Vonk, J.; Hugelius, G.; McClelland, J.W.; Song, W.; Raymond, P.A.; Gustafsson, Ö.
2019 | Proc. Natl. Acad. Sci. U.S.A. | 116 (21) (10280-10285)

Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling

P. Winiger; T. E. Barrett; R. J. Sheesley; L. Huang; S. Sharma; L. A. Barrie; K. E. Yttri; N. Evangeliou; S. Eckhardt; A. Stohl; Z. Klimont; C. Heyes; I. P. Semiletov; O. V. Dudarev; A. Charkin; N. Shakhova; H. Holmstrand; A. Andersson; Ö. Gustafsson
2019 | Sci. Adv. | 5 (2)

Photochemical degradation affects the light absorption of water-soluble brown carbon in the South Asian outflow

Sanjeev Dasari; August Andersson; Srinivas Bikkina; Henry Holmstrand; Krishnakant Budhavant; Sreedharan Satheesh; Eija Asmi; Jutta Kesti; John Backman; Abdus Salam; Deewan Singh Bisht; Suresh Tiwari; Zahid Hameed; Örjan Gustafsson;
2019 | Sci. Adv. | 5, no. 1, eaau8066
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Light-absorbing organic aerosols, known as brown carbon (BrC), counteract the overall cooling effect of aerosols on Earth’s climate. The spatial and temporal dynamics of their light-absorbing properties are poorly constrained and unaccounted for in climate models, because of limited ambient observations. We combine carbon isotope forensics (δ13C) with measurements of light absorption in a conceptual aging model to constrain the loss of light absorptivity (i.e., bleaching) of water-soluble BrC (WS-BrC) aerosols in one of the world’s largest BrC emission regions—South Asia. On this regional scale, we find that atmospheric photochemical oxidation reduces the light absorption of WS-BrC by ~84% during transport over 6000 km in the Indo-Gangetic Plain, with an ambient first-order bleaching rate of 0.20 ± 0.05 day−1 during over-ocean transit across Bay of Bengal to an Indian Ocean receptor site. This study facilitates dynamic parameterization of WS-BrC absorption properties, thereby constraining BrC climate impact over South Asia.

Quantifying degradative loss of terrigenous organic carbon in surface sediments across the Laptev and East Siberian Sea

Lisa Bröder; August Andersson; Tommaso Tesi; Igor Semiletov; Örjan Gustafsson
2019 | Global Biogeochem Cycles | 33 (85-99)

Contact information

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Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Toxicological Chemistry)

Mailing address:
Department of Environmental Science
Stockholm University
106 91 Stockholm

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Stella Papadopoulou
Science Communicator
Phone +46 (0)8 674 70 11
stella.papadopoulou@aces.su.se