Browsing by Autor "Marco Pandolfi"

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A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(Copernicus Publications, 2018) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Christo Angelov; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki
Abstract. This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(European Organization for Nuclear Research, 2018) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Christo Angelov; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki
This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (sp) and hemispheric backscattering (bsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of sp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, sp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intraannual variability. At mountain sites, higher sp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher sp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low sp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high sp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of sp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of sp are consistent with those reported for PM2:5 and PM10 mass concentrations over similar periods across Europe.
A European aerosol phenomenology-6: Scattering properties of atmospheric aerosolparticles from 28 ACTRIS sites
(2017) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki; Martine Collaud Coen
Abstract. This paper presents the light scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). A large range of ssp was observed across the network. Low ssp values were on average measured in Nordic and Baltic countries and in Western Europe whereas the highest σsp were measured at regional sites in eastern and central Europe. In these regional areas the SAE was also high indicating the predominance of fine-mode particles. On average, the SAE was lower in the Nordic and Baltic, western and southern countries suggesting a lower fraction of fine-mode particle compared to central and eastern Europe. An increasing gradient of ssp was observed when moving from mountain to regional and to urban sites. Conversely, the mass-independent SAE and g parameters did not show the same gradient. At all sites, both SAE and g varied greatly with aerosol particle loading. The lowest values of g were always observed under low ssp indicating a larger contribution from particles in the smaller accumulation mode. Then, g steeply increased with increasing ssp indicating a progressive shift of the particle size distribution toward the larger end of the accumulation mode. Under periods of high particle mass concentrations, the variation of g was less pronounced whereas the SAE increased or decreased suggesting changes mostly in the coarse aerosol particles mode rather than in the fine mode. The station placement seemed to be the main parameter affecting the intra-annual variability. At mountain sites, higher σsp was measured in summer mainly because of the enhanced boundary layer influence. Conversely, less horizontal and vertical dispersion in winter led to higher σsp at all low altitude sites in central and eastern Europe compared to summer. On average, these sites also showed SAE maxima in summer (and correspondingly g minima). Large intra-annual variability of SAE and g was observed also at Nordic and Baltic countries due to seasonal-dependent transport of different air masses to these remote sites. Statistically significant decreasing trends of σsp were observed at 5 out of 13 stations included in trend analyses. The total reductions of ssp were consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
Atmospheric Black Carbon in the metropolitan area of La Paz and El Alto, Bolivia: concentration levels and emission sources
(2024) Valeria Mardoñez-Balderrama; Griša Močnik; Marco Pandolfi; Robin L. Modini; Fernando Velarde; Laura Renzi; Angela Marinoni; Jean‐Luc Jaffrezo; Isabel Moreno; Diego Aliaga
Abstract. Black carbon (BC) is a major component of sub-micron particulate matter (PM) with significant health and climate impacts. Many cities in emerging countries lack comprehensive knowledge about BC emissions and exposure levels. This study investigates BC concentration levels, identify its emission sources, and characterize the optical properties of BC at urban background sites of the two largest high-altitude Bolivian cities: La Paz (LP) (3600 m above sea level) and El Alto (EA) (4050 m a.s.l.) where atmospheric oxygen levels and intense radiation may affect BC production. The study relies on concurrent measurements of equivalent black carbon (eBC), elemental carbon (EC), and refractory black carbon (rBC), and their comparison with analogous data collected at the nearby Global Atmosphere Watch-Chacaltaya station (5240 m a.s.l). The performance of two independent source-apportionment techniques was compared: a bilinear model and a least squares multilinear regression (MLR). Maximum eBC concentrations were observed during the local dry season (LP: eBC=1.5±1.6 μg m-3; EA: 1.9±2.0 μg m-3). While eBC concentrations are lower at the mountain station, daily transport from urban areas is evident. Average mass absorption cross sections of 6.6-8.2 m2 g-1 were found in the urban area at 637 nm. Both source apportionment methods exhibited a reasonable level of agreement in the contribution of biomass burning (BB) to absorption. The MLR method allowed the estimation of the contribution and the source-specific optical properties for multiple sources including open waste burning.
Atmospheric black carbon in the metropolitan area of La Paz and El Alto, Bolivia: concentration levels and emission sources
(Copernicus Publications, 2024) Valeria Mardoñez-Balderrama; Griša Močnik; Marco Pandolfi; Robin L. Modini; Fernando Velarde; Laura Renzi; Angela Marinoni; Jean‐Luc Jaffrezo; Isabel Moreno; Diego Aliaga
Abstract. Black carbon (BC) is a major component of submicron particulate matter (PM), with significant health and climate impacts. Many cities in emerging countries lack comprehensive knowledge about BC emissions and exposure levels. This study investigates BC concentration levels, identifies its emission sources, and characterizes the optical properties of BC at urban background sites of the two largest high-altitude Bolivian cities: La Paz (LP) (3600 m above sea level) and El Alto (EA) (4050 m a.s.l.), where atmospheric oxygen levels and intense radiation may affect BC production. The study relies on concurrent measurements of equivalent black carbon (eBC), elemental carbon (EC), and refractory black carbon (rBC) and their comparison with analogous data collected at the nearby Chacaltaya Global Atmosphere Watch Station (5240 m a.s.l). The performance of two independent source apportionment techniques was compared: a bilinear model and a least-squares multilinear regression (MLR). Maximum eBC concentrations were observed during the local dry season (LP: eBC = 1.5 ± 1.6 µg m−3; EA: 1.9±2.0 µg m−3). While eBC concentrations are lower at the mountain station, daily transport from urban areas is evident. Average mass absorption cross sections of 6.6–8.2 m2 g−1 were found in the urban area at 637 nm. Both source apportionment methods exhibited a reasonable level of agreement in the contribution of biomass burning (BB) to absorption. The MLR method allowed the estimation of the contribution and the source-specific optical properties for multiple sources, including open waste burning.
Biomass burning and urban emission impacts in the Andes Cordillera region based on in situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.)
(Copernicus Publications, 2019) Aurélien Chauvigné; Diego Aliaga; Karine Sellegri; Nadège Montoux; Radovan Krejčí; Griša Močnik; Isabel Moreno; Thomas Müller; Marco Pandolfi; Fernando Velarde
Abstract. This study documents and analyses a 4-year continuous record of aerosol optical properties measured at the Global Atmosphere Watch (GAW) station of Chacaltaya (CHC; 5240 m a.s.l.), in Bolivia. Records of particle light scattering and particle light absorption coefficients are used to investigate how the high Andean Cordillera is affected by both long-range transport and by the fast-growing agglomeration of La Paz–El Alto, located approximately 20 km away and 1.5 km below the sampling site. The extended multi-year record allows us to study the properties of aerosol particles for different air mass types, during wet and dry seasons, also covering periods when the site was affected by biomass burning in the Bolivian lowlands and the Amazon Basin. The absorption, scattering, and extinction coefficients (median annual values of 0.74, 12.14, and 12.96 Mm−1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94, and 8.68 Mm−1 respectively) and higher values during the dry season (0.80, 11.23, and 14.51 Mm−1 respectively). The record is driven by variability at both seasonal and diurnal scales. At a diurnal scale, all records of intensive and extensive aerosol properties show a pronounced variation (daytime maximum, night-time minimum), as a result of the dynamic and convective effects. The particle light absorption, scattering, and extinction coefficients are on average 1.94, 1.49, and 1.55 times higher respectively in the turbulent thermally driven conditions than the more stable conditions, due to more efficient transport from the boundary layer. Retrieved intensive optical properties are significantly different from one season to the other, reflecting the changing aerosol emission sources of aerosol at a larger scale. Using the wavelength dependence of aerosol particle optical properties, we discriminated between contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass burning and urban transport or industries) emissions according to seasons and local circulation. The main sources influencing measurements at CHC are from the urban area of La Paz–El Alto in the Altiplano and from regional biomass burning in the Amazon Basin. Results show a 28 % to 80 % increase in the extinction coefficients during the biomass burning season with respect to the dry season, which is observed in both tropospheric dynamic conditions. From this analysis, long-term observations at CHC provide the first direct evidence of the impact of biomass burning emissions of the Amazon Basin and urban emissions from the La Paz area on atmospheric optical properties at a remote site all the way to the free troposphere.
Biomass-burning and urban emission impacts in the Andes Cordillera region based on in-situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.)
(2019) Chauvigné Aurélien; Diego Aliaga; Marcos Andrade; Patrick Ginot; Radovan Krejčí; Griša Močnik; Nadège Montoux; Isabel Moreno; Thomas Müller; Marco Pandolfi
Abstract. We present the variability of aerosol particle optical properties measured at the global Atmosphere Watch (GAW) station Chacaltaya (5240 m a.s.l.). The in-situ mountain site is ideally located to study regional impacts of the densely populated urban area of La Paz/El Alto, and the intensive activity in the Amazonian basin. Four year measurements allow to study aerosol particle properties for distinct atmospheric conditions as stable and turbulent layers, different airmass origins, as well as for wet and dry seasons, including biomass-burning influenced periods. The absorption, scattering and extinction coefficients (median annual values of 0.74, 12.14 and 12.96 Mm−1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94 and 8.68 Mm−1 respectively) and higher values during the dry season (0.80, 11.23 and 14.51 Mm−1 respectively). These parameters also show a pronounced diurnal variation (maximum during daytime, minimum during night-time, as a result of the dynamic and convective effects of leading to lower atmospheric layers reaching the site during daytime. Retrieved intensive optical properties are significantly different from one season to the other, showing the influence of different sources of aerosols according to the season. Both intensive and extensive optical properties of aerosols were found to be different among the different atmospheric layers. The particle light absorption, scattering and extinction coefficients are in average 1.94, 1.49 and 1.55 times higher, respectively, in the turbulent layer compared to the stable layer. We observe that the difference is highest during the wet season and lowest during the dry season. Using wavelength dependence of aerosol particle optical properties, we discriminated contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass-burning and urban transport or industries) emissions according to seasons and tropospheric layers. The main sources influencing measurements at CHC are arising from the urban area of La Paz/El Alto, and regional biomass-burning from the Amazonian basin. Results show a 28 % to 80 % increase of the extinction coefficients during the biomass-burning season with respect to the dry season, which is observed in both tropospheric layers. From this analyse, long-term observations at CHC provides the first direct evidence of the impact of emissions in the Amazonian basin on atmospheric optical properties far away from their sources, all the way to the stable layer.
Comment on acp-2022-780
(2023) Valeria MardoÃ±ez; Marco Pandolfi; Lucille Joanna S. Borlaza; Jean‐Luc Jaffrezo; AndrÃ©s Alastuey; Jean‐Luc Besombes; Isabel Moreno; Noemí Pérez; GriÅ¡a MoÄ nik; Patrick Ginot
Abstract. La Paz and El Alto are two fast-growing high-altitude Bolivian cities forming the second largest metropolitan area in the country, located between 3200 and 4050 m a.s.l. Together they host a growing population of around 1.8 million people. The air quality in this conurbation is strongly influenced by urbanization. However, there are no comprehensive studies that have assessed the sources of air pollution and their impacts on health. Despite being neighboring cities, the drastic change in altitude and topography between La Paz and El Alto together with different socio-economic activities lead to different sources, dynamics and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The US-EPA Positive Matrix Factorization (PMF v.5.0) receptor model was then applied for source apportionment of PM10. This is the first source apportionment study in South America that incorporates a large set of organic markers (such as levoglucosan, polycyclic aromatic hydrocarbons – PAH, hopanes and alkanes) together with inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), together responsible for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively, and dust contributing 20 % and 32 % to the total. Secondary aerosols contributed 22 % (24 %) in La Paz (El Alto). Agriculture-related smoke from biomass burning originated in the Bolivian lowlands and neighboring countries contributed to 8 % (7 %) of the total PM10 mass annually. This contribution increased to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Finally, it was possible to identify a profile related to open waste burning occurring between the months of May and August. Despite the fact that this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, compounds potentially hazardous to health. Our analysis resulted in the identification of two specific traffic-related sources. In addition, we also identified a lubricant source (not frequently identified) and a non-exhaust emissions source. This study shows that PM10 concentrations in La Paz and El Alto region are mostly impacted by a limited number of local sources. In conclusion, dust, traffic emissions, open waste burning and biomass burning are the main sources to target in order to improve air quality in both cities.
Comment on egusphere-2024-770
(2024) Valeria Mardoñez-Balderrama; Griša Močnik; Marco Pandolfi; Robin L. Modini; Fernando Velarde; Laura Renzi; Angela Marinoni; Jean‐Luc Jaffrezo; Isabel Moreno; Diego Aliaga
Abstract. Black carbon (BC) is a major component of sub-micron particulate matter (PM) with significant health and climate impacts. Many cities in emerging countries lack comprehensive knowledge about BC emissions and exposure levels. This study investigates BC concentration levels, identify its emission sources, and characterize the optical properties of BC at urban background sites of the two largest high-altitude Bolivian cities: La Paz (LP) (3600 m above sea level) and El Alto (EA) (4050 m a.s.l.) where atmospheric oxygen levels and intense radiation may affect BC production. The study relies on concurrent measurements of equivalent black carbon (eBC), elemental carbon (EC), and refractory black carbon (rBC), and their comparison with analogous data collected at the nearby Global Atmosphere Watch-Chacaltaya station (5240 m a.s.l). The performance of two independent source-apportionment techniques was compared: a bilinear model and a least squares multilinear regression (MLR). Maximum eBC concentrations were observed during the local dry season (LP: eBC=1.5±1.6 μg m-3; EA: 1.9±2.0 μg m-3). While eBC concentrations are lower at the mountain station, daily transport from urban areas is evident. Average mass absorption cross sections of 6.6-8.2 m2 g-1 were found in the urban area at 637 nm. Both source apportionment methods exhibited a reasonable level of agreement in the contribution of biomass burning (BB) to absorption. The MLR method allowed the estimation of the contribution and the source-specific optical properties for multiple sources including open waste burning.
Source apportionment study on particulate air pollution in two high-altitude Bolivian cities: La Paz and El Alto
(Copernicus Publications, 2023) Valeria Mardóñez; Marco Pandolfi; Lucille Joanna S. Borlaza; Jean‐Luc Jaffrezo; Andrés Alástuey; Jean‐Luc Besombes; Isabel Moreno; Noemí Pérez; Griša Močnik; Patrick Ginot
Abstract. La Paz and El Alto are two fast-growing, high-altitude Bolivian cities forming the second-largest metropolitan area in the country. Located between 3200 and 4050 m a.s.l. (above sea level), these cities are home to a burgeoning population of approximately 1.8 million residents. The air quality in this conurbation is heavily influenced by urbanization; however, there are no comprehensive studies evaluating the sources of air pollution and their health impacts. Despite their proximity, the substantial variation in altitude, topography, and socioeconomic activities between La Paz and El Alto result in distinct sources, dynamics, and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The United States Environmental Protection Agency (U.S. EPA) Positive Matrix Factorization (PMF v.5.0) receptor model was employed for the source apportionment of PM10. This is one of the first source apportionment studies in South America that incorporates an extensive suite of organic markers, including levoglucosan, polycyclic aromatic hydrocarbons (PAHs), hopanes, and alkanes, alongside inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from the following two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), accountable for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively; and dust, which contributed 20 % and 32 % to the total PM mass. Secondary aerosols accounted for 22 % (24 %) in La Paz (El Alto). Agricultural smoke resulting from biomass burning in the Bolivian lowlands and neighboring countries contributed to 9 % (8 %) of the total PM10 mass annually, increasing to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Additionally, a profile associated with open waste burning occurring from May to August was identified. Although this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, which are compounds potentially hazardous to human health. Our analysis additionally resolved two different traffic-related factors, a lubricant source (not frequently identified), and a non-exhaust emissions source. Overall, this study demonstrates that PM10 concentrations in La Paz and El Alto region are predominantly influenced by a limited number of local sources. In conclusion, to improve air quality in both cities, efforts should primarily focus on addressing dust, traffic emissions, open waste burning, and biomass burning.
Source apportionment study on particulate air pollution in two high-altitude Bolivian cities: La Paz and El Alto
(2022) Valeria Mardóñez; Marco Pandolfi; Lucille Joanna S. Borlaza; Jean‐Luc Jaffrezo; Andrés Alástuey; Jean‐Luc Besombes; Isabel Moreno; Noemí Pérez; Griša Močnik; Patrick Ginot
Abstract. La Paz and El Alto are two fast-growing high-altitude Bolivian cities forming the second largest metropolitan area in the country, located between 3200 and 4050 m a.s.l. Together they host a growing population of around 1.8 million people. The air quality in this conurbation is strongly influenced by urbanization. However, there are no comprehensive studies that have assessed the sources of air pollution and their impacts on health. Despite being neighboring cities, the drastic change in altitude and topography between La Paz and El Alto together with different socio-economic activities lead to different sources, dynamics and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The US-EPA Positive Matrix Factorization (PMF v.5.0) receptor model was then applied for source apportionment of PM10. This is the first source apportionment study in South America that incorporates a large set of organic markers (such as levoglucosan, polycyclic aromatic hydrocarbons – PAH, hopanes and alkanes) together with inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), together responsible for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively, and dust contributing 20 % and 32 % to the total. Secondary aerosols contributed 22 % (24 %) in La Paz (El Alto). Agriculture-related smoke from biomass burning originated in the Bolivian lowlands and neighboring countries contributed to 8 % (7 %) of the total PM10 mass annually. This contribution increased to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Finally, it was possible to identify a profile related to open waste burning occurring between the months of May and August. Despite the fact that this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, compounds potentially hazardous to health. Our analysis resulted in the identification of two specific traffic-related sources. In addition, we also identified a lubricant source (not frequently identified) and a non-exhaust emissions source. This study shows that PM10 concentrations in La Paz and El Alto region are mostly impacted by a limited number of local sources. In conclusion, dust, traffic emissions, open waste burning and biomass burning are the main sources to target in order to improve air quality in both cities.
Sources of particulate air pollution in two high-altitude Bolivian cities: La Paz and El Alto
(2022) Valeria Mardóñez; Gaëlle Uzu; Marcos Andrade; Lucille Joanna S. Borlaza; Marco Pandolfi; Samuël Weber; Isabel Moreno; Jean‐Luc Jaffrezo; Jean‐Luc Besombes; Andrés Alástuey
&lt;p&gt;La Paz and El Alto are two high-altitude (above 3000 m.a.s.l) Bolivian cities that form part of one of the largest metropolitan areas in the country with a population of around 1.8 million people. Air quality in this conurbation is strongly influenced by both regional and local anthropogenic and natural pollution sources that have not yet been studied in this region. Moreover, despite being contiguous cities, the drastic change in altitude and topography between them leads to different production, dynamics and transport of particulate matter (PM). The need for a characterization of the pollutant sources in these sites lies not only in the importance of regulating the emissions to protect public health, but also in the observed significant impact that these pollutant sources could have on the surrounding Bolivian glaciers. PM&lt;sub&gt;10&lt;/sub&gt; was collected onto 24-h filters at two background stations located in La Paz and El Alto between April 2016 and June 2017. The US-EPA Positive Matrix Factorization (PMF v.5.0) receptor model was applied for apportioning the sources that affect air quality in the two cities. This is the first source apportionment study in South America that incorporates a large set of organic markers (such as levoglucosan, PAH's, Hopanes and Alkanes) together with inorganic species. The multisite PMF allowed to resolve 11 main sources. The largest annual contribution to PM&lt;sub&gt;10&lt;/sub&gt; came from 2 major sources: The ensemble of vehicular emissions, responsible for 30.3% of the measured mass (gasoline-like-powered vehicles: 16.0%; diesel-like-powered vehicles: 7.8%; non-exhaust emissions: 3.8%; Lubricant oil: 2.7%) and Mineral Dust contributing 29.7% to the total PM&lt;sub&gt;10&lt;/sub&gt; mass. Other 21.9% was attributed to factors associated to secondary aerosols (NO&lt;sub&gt;3&lt;/sub&gt;-rich: 6.6%; SO&lt;sub&gt;4&lt;/sub&gt;-rich: 9.8%; MSA-rich: 5.5%). Agriculture-related smoke from biomass burning originated in the lowlands in the country and neighbouring countries contributed to 7.6% of the total PM&lt;sub&gt;10&lt;/sub&gt; mass annually, this contribution doubled at the end of the biomass burning season. Primary biogenic emissions, on their side, were responsible for 6.3% of the measured PM&lt;sub&gt;10&lt;/sub&gt; mass. Finally, it was possible to identify a profile related to open waste burning happening between the months of May and August. Despite the fact that this source contributed with only 4.6% to the total PM&lt;sub&gt;10&lt;/sub&gt; mass, it constitutes the second-largest source of PAHs, compounds potentially hazardous for health. Running a multisite-PMF at these two high altitude sites, not only provided more robustness to the model, but also led to the dissociation of the found traffic profile into two separate vehicular sources, one for diesel and one for gasoline-powered vehicles. This study demonstrates that PM&lt;sub&gt;10&lt;/sub&gt; concentrations in this Bolivian region are mostly impacted by a limited number of local sources, which is different to what is observed in many European urban areas. We conclude that traffic emissions and biomass burning are the main sources to target in order to improve air quality in both cities. Our results highlight the need for dedicated studies of air pollution in high altitude regions of South America and can serve as the start of such investigations.&lt;/p&gt;