Supplementary material to "The impact of biomass burning and aqueous-phase processing on air quality: a multi-year source apportionment study in the Po Valley, Italy"

Abstract. The Po Valley (Italy) is a well-known air quality hotspot characterized by Particulate Matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of the Emilia-Romagna regional project SUPERSITO, the southern Po Valley submicron aerosol chemical composition was characterized by means of High-Resolution Aerosol Mass Spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over four years (from 2011 to 2014) at two different sites (Bologna, BO, urban background and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for an average 45 ± 8 % (ranging 33–58 %) and 46 ± 7 % (ranging 36–50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and at the rural site, respectively. Primary organic aerosol (POA) comprises biomass burning (23 ± 13 % of OA) and fossil fuel (12 ± 7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban/rural concentrations ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 to 38 % of the total OA mass. Secondary organic aerosol (SOA) contribute to OA mass to a much larger extent than POA at both sites throughout the year (69 ± 16 % and 83 ± 16 % at urban and rural, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning ageing products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14–44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. Among the environmental factors controlling the formation of SOA in the Po Valley, the availability of liquid water in the aerosol was shown to play a key role in the cold season. We estimate that organic fraction originating from aqueous reactions of biomass burning products (bb-aqSOA) represents 21 % (14–28 %) and 25 % (14–35 %) of the total OA mass and 44 % (32–56 %) and 61 % (21–100 %) of the SOA mass at the urban and rural sites, respectively.

Download Full-text

The impact of biomass burning and aqueous-phase processing on air quality: a multi-year source apportionment study in the Po Valley, Italy

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-1233-2020 ◽

2020 ◽

Vol 20 (3) ◽

pp. 1233-1254 ◽

Cited By ~ 5

Author(s):

Marco Paglione ◽

Stefania Gilardoni ◽

Matteo Rinaldi ◽

Stefano Decesari ◽

Nicola Zanca ◽

...

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Biomass Burning ◽

Organic Aerosol ◽

Cold Season ◽

Rural Site ◽

Urban Site ◽

Urban Background ◽

Po Valley ◽

Rural Sites

Abstract. The Po Valley (Italy) is a well-known air quality hotspot characterized by particulate matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of Emilia-Romagna regional project “Supersito”, the southern Po Valley submicron aerosol chemical composition was characterized by means of high-resolution aerosol mass spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over 4 years (from 2011 to 2014) at two different sites (Bologna, BO, urban background, and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for averages of 45±8 % (ranging from 33 % to 58 %) and 46±7 % (ranging from 36 % to 50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and rural sites, respectively. Primary organic aerosol (POA) comprises biomass burning (23±13 % of OA) and fossil fuel (12±7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban / rural concentration ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 % to 38 % of the total OA mass. Secondary organic aerosol (SOA) contributes to OA mass to a much larger extent than POA at both sites throughout the year (69±16 % and 83±16 % at the urban and rural sites, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning aging products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14 %–44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. Among the environmental factors controlling the formation of SOA in the Po Valley, the availability of liquid water in the aerosol was shown to play a key role in the cold season. We estimate that the organic fraction originating from aqueous reactions of biomass burning products (“bb-aqSOA”) represents 21 % (14 %–28 %) and 25 % (14 %–35 %) of the total OA mass and 44 % (32 %–56 %) and 61 % (21 %–100 %) of the SOA mass at the urban and rural sites, respectively.

Download Full-text

Supplementary material to "Molecular insights on aging and aqueous phase processing from ambient biomass burning emissions-influenced Po Valley fog and aerosol"

10.5194/acp-2018-301-supplement ◽

2018 ◽

Author(s):

Matthew Brege ◽

Marco Paglione ◽

Stefania Gilardoni ◽

Stefano Decesari ◽

Maria Cristina Facchini ◽

...

Keyword(s):

Aqueous Phase ◽

Biomass Burning ◽

Po Valley ◽

Supplementary Material

Download Full-text

Development of PM<sub>2.5</sub> source impact spatial fields using a hybrid source apportionment air quality model

Geoscientific Model Development ◽

10.5194/gmd-8-2153-2015 ◽

2015 ◽

Vol 8 (7) ◽

pp. 2153-2165 ◽

Cited By ~ 26

Author(s):

C. E. Ivey ◽

H. A. Holmes ◽

Y. T. Hu ◽

J. A. Mulholland ◽

A. G. Russell

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Large Scale ◽

Major Ions ◽

Current Knowledge ◽

Direct Method ◽

Hybrid Approach ◽

Sensitivity Analyses ◽

Adjustment Factors ◽

The Impact

Abstract. An integral part of air quality management is knowledge of the impact of pollutant sources on ambient concentrations of particulate matter (PM). There is also a growing desire to directly use source impact estimates in health studies; however, source impacts cannot be directly measured. Several limitations are inherent in most source apportionment methods motivating the development of a novel hybrid approach that is used to estimate source impacts by combining the capabilities of receptor models (RMs) and chemical transport models (CTMs). The hybrid CTM–RM method calculates adjustment factors to refine the CTM-estimated impact of sources at monitoring sites using pollutant species observations and the results of CTM sensitivity analyses, though it does not directly generate spatial source impact fields. The CTM used here is the Community Multiscale Air Quality (CMAQ) model, and the RM approach is based on the chemical mass balance (CMB) model. This work presents a method that utilizes kriging to spatially interpolate source-specific impact adjustment factors to generate revised CTM source impact fields from the CTM–RM method results, and is applied for January 2004 over the continental United States. The kriging step is evaluated using data withholding and by comparing results to data from alternative networks. Data withholding also provides an estimate of method uncertainty. Directly applied (hybrid, HYB) and spatially interpolated (spatial hybrid, SH) hybrid adjustment factors at withheld observation sites had a correlation coefficient of 0.89, a linear regression slope of 0.83 ± 0.02, and an intercept of 0.14 ± 0.02. Refined source contributions reflect current knowledge of PM emissions (e.g., significant differences in biomass burning impact fields). Concentrations of 19 species and total PM2.5 mass were reconstructed for withheld observation sites using HYB and SH adjustment factors. The mean concentrations of total PM2.5 at withheld observation sites were 11.7 (± 8.3), 16.3 (± 11), 8.59 (± 4.7), and 9.2 (± 5.7) μg m−3 for the observations, CTM, HYB, and SH predictions, respectively. Correlations improved for concentrations of major ions, including nitrate (CMAQ–DDM (decoupled direct method): 0.404, SH: 0.449), ammonium (CMAQ–DDM: 0.454, SH: 0.492), and sulfate (CMAQ–DDM: 0.706, SH: 0.730). Errors in simulated concentrations of metals were reduced considerably: 295 % (CMAQ–DDM) to 139 % (SH) for vanadium; and 1340 % (CMAQ–DDM) to 326 % (SH) for manganese. Errors in simulated concentrations of some metals are expected to remain given the uncertainties in source profiles. Species concentrations were reconstructed using SH results, and the error relative to observed concentrations was greatly reduced as compared to CTM-simulated concentrations. Results demonstrate that the hybrid method along with a spatial extension can be used for large-scale, spatially resolved source apportionment studies where observational data are spatially and temporally limited.

Download Full-text

Sources of organic aerosols in Europe: a modeling study using CAMx with modified volatility basis set scheme

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15247-2019 ◽

2019 ◽

Vol 19 (24) ◽

pp. 15247-15270 ◽

Cited By ~ 3

Author(s):

Jianhui Jiang ◽

Sebnem Aksoyoglu ◽

Imad El-Haddad ◽

Giancarlo Ciarelli ◽

Hugo A. C. Denier van der Gon ◽

...

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Biomass Burning ◽

Agricultural Waste ◽

Organic Aerosols ◽

Basis Set ◽

Anthropogenic Sources ◽

Wood Burning ◽

Gasoline Vehicles

Abstract. Source apportionment of organic aerosols (OAs) is of great importance to better understand the health impact and climate effects of particulate matter air pollution. Air quality models are used as potential tools to identify OA components and sources at high spatial and temporal resolution; however, they generally underestimate OA concentrations, and comparisons of their outputs with an extended set of measurements are still rare due to the lack of long-term experimental data. In this study, we addressed such challenges at the European level. Using the regional Comprehensive Air Quality Model with Extensions (CAMx) and a volatility basis set (VBS) scheme which was optimized based on recent chamber experiments with wood burning and diesel vehicle emissions, and which contains more source-specific sets compared to previous studies, we calculated the contribution of OA components and defined their sources over a whole-year period (2011). We modeled separately the primary and secondary OA contributions from old and new diesel and gasoline vehicles, biomass burning (mostly residential wood burning and agricultural waste burning excluding wildfires), other anthropogenic sources (mainly shipping, industry and energy production) and biogenic sources. An important feature of this study is that we evaluated the model results with measurements over a longer period than in previous studies, which strengthens our confidence in our modeled source apportionment results. Comparison against positive matrix factorization (PMF) analyses of aerosol mass spectrometric measurements at nine European sites suggested that the modified VBS scheme improved the model performance for total OA as well as the OA components, including hydrocarbon-like (HOA), biomass burning (BBOA) and oxygenated components (OOA). By using the modified VBS scheme, the mean bias of OOA was reduced from −1.3 to −0.4 µg m−3 corresponding to a reduction of mean fractional bias from −45 % to −20 %. The winter OOA simulation, which was largely underestimated in previous studies, was improved by 29 % to 42 % among the evaluated sites compared to the default parameterization. Wood burning was the dominant OA source in winter (61 %), while biogenic emissions contributed ∼ 55 % to OA during summer in Europe on average. In both seasons, other anthropogenic sources comprised the second largest component (9 % in winter and 19 % in summer as domain average), while the average contributions of diesel and gasoline vehicles were rather small (∼ 5 %) except for the metropolitan areas where the highest contribution reached 31 %. The results indicate the need to improve the emission inventory to include currently missing and highly uncertain local emissions, as well as further improvement of VBS parameterization for winter biomass burning. Although this study focused on Europe, it can be applied in any other part of the globe. This study highlights the ability of long-term measurements and source apportionment modeling to validate and improve emission inventories, and identify sources not yet properly included in existing inventories.

Download Full-text

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 2: Long-term impact on air quality

10.5194/acp-2019-128 ◽

2019 ◽

Author(s):

Henri Diémoz ◽

Gian Paolo Gobbi ◽

Tiziana Magri ◽

Giordano Pession ◽

Sara Pittavino ◽

...

Keyword(s):

Air Quality ◽

Chemical Composition ◽

Weather Prediction ◽

Urban Site ◽

Aerosol Layer ◽

Aerosol Transport ◽

Po Valley ◽

Aerosol Mass Concentration ◽

The Impact ◽

Aerosol Properties

Abstract. This work evaluates the impact of trans-regional aerosol transport from the polluted Po basin on particulate matter levels (PM10) and physico-chemical characteristics in the northwestern Alps. To this purpose, we exploited a multi-sensor, multiplatform database over a 3-years period (2015–2017) accompanied by a series of numerical simulations. The experimental setup included operational (24/7) vertically-resolved aerosol profiles by an Automated LiDAR-Ceilometer (ALC), verticallyintegrated aerosol properties by a sun/sky photometer, and surface measurements of aerosol mass concentration, size distribution and chemical composition. This experimental set of observations was then complemented by modelling tools, including Numerical Weather Prediction (NWP), Trajectory Statistical (TSM) and Chemical Transport (CTM) models, plus Positive Matrix Factorisation (PMF) on both the PM10 chemical speciation analyses and size distributions. In a first companion study (Diémoz et al., 2019), we showed and discussed through detailed case studies the 4-D phenomenology of recurrent episodes of aerosol transport from the polluted Po basin to the northwestern Italian Alps, and particularly to the Aosta Valley. Here we draw more general and statistically significant conclusions on the frequency of occurrence of this phenomenon, and on the quantitative impact of this regular, wind-driven, aerosol-rich atmospheric tide on PM10 air quality levels in this alpine environment. Combining vertically-resolved ALC measurements with wind information, we found that an advected aerosol layer is observed at the receptor site (Aosta) in 93 % of days characterized by easterly winds (thermally-driven winds from the plain or synoptic circulation regimes), and that the longer the time spent by air masses over the Po plain the higher this probability. On a seasonal basis, frequency of advected aerosol layers from the Po basin maximises in summer (70 % of the days classified using the ALC profiles) and minimises in winter and spring (57 % of the classified days). Duration of these advection events ranges from few hours up to several days, while aerosol layer thickness ranges from 500 up to 4000 m. This phenomenon was found to largely impact both surface levels and column-integrated aerosol properties, with PM10 and AOD values respectively increasing up to a factor of 3.5 and 4 in dates under the Po Valley influence. Similar variations in PM10 values observed at different stations within the Aosta Valley also indicated the phenomenon to act at the regional scale and to be related to non-local emissions. Pollution transport events were also shown to modify the mean chemical composition and typical size of particles in the target region. In fact, increase in secondary species, and mainly nitrate- and sulfate-rich components, were found to be effective proxies of the advections, with the transported aerosol responsible for at least 25 % of the PM10 measured in the urban site of Aosta, and adding up to over 50 μg m−3 during specific episodes, thus exceeding alone the EU established daily limit. This percentage is expected to be higher in the rural, pristine areas on the northwestern Alps, where chemical data were not available and trans-boundary contribution to PM10 might thus exceed the local one. Advected aerosols were also found to be on average finer, more light-scattering and more hygroscopic than the locally-produced ones. From a modelling point of view, our CTM simulations performed over a full year showed that the model is able to reproduce the phenomenon but underestimates its impact on PM10 levels. As a sensitivity test, we employed the ALC-derived identification of aerosol advections to re-weight the emissions from outside the boundaries of the regional domain in order to match the observed PM10 field. This simplified exercise indicated that an increase of such external emissions by a factor of 4 in the model would reduce the PM10 mean bias forecasts error (MBE) from −10 μg m−3 to less than 2 μg m−3, the normalised mean standard deviation (NMSD) from over −50 % to less than −10 % and would halve the model PM10 maximum deviations.

Download Full-text

Are contributions of emissions to ozone a matter of scale? – a study using MECO(n) (MESSy v2.50)

Geoscientific Model Development ◽

10.5194/gmd-13-363-2020 ◽

2020 ◽

Vol 13 (1) ◽

pp. 363-383 ◽

Cited By ~ 1

Author(s):

Mariano Mertens ◽

Astrid Kerkweg ◽

Volker Grewe ◽

Patrick Jöckel ◽

Robert Sausen

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Emission Inventory ◽

Climate Model ◽

Stratospheric Ozone ◽

Model Resolution ◽

Regional Models ◽

Continental Scale ◽

The Impact ◽

Apportionment Methods

Abstract. Anthropogenic and natural emissions influence the tropospheric ozone budget, thereby affecting air quality and climate. To study the influence of different emission sources on the ozone budget, often source apportionment studies with a tagged tracer approach are performed. Studies investigating air quality issues usually rely on regional models with a fine spatial resolution, while studies focusing on climate-related questions often use coarsely resolved global models. It is well known that simulated ozone mixing ratios depend on the resolution of the model and the resolution of the emission inventory. Whether the contributions simulated using source apportionment approaches also depend on the model resolution, however, is still unclear. Therefore, this study attempts for the first time to analyse the impact of the model, the model resolution, and the emission inventory resolution on simulated ozone contributions using a diagnostic tagging method. The differences in the ozone contributions caused by these factors are compared with differences that arise from the usage of different emission inventories. To do so, we apply the MECO(n) (MESSy-fied ECHAM and COSMO models nested n times) model system which couples online a global chemistry-climate model with a regional chemistry-climate model equipped with a tagging scheme for source apportionment. The results of the global model (at 300 km horizontal resolution) are compared with the results of the regional model at 50 km (Europe) and 12 km (Germany) resolutions. Besides model-specific differences and biases that are discussed in detail, our results have important implications for other modelling studies and modellers applying source apportionment methods. First, contributions from anthropogenic emissions averaged over the continental scale are quite robust with respect to the model, model resolution, and emission inventory resolution. Second, differences on the regional scale caused by different models and model resolutions can be quite large, and regional models are indispensable for source apportionment studies on the subcontinental scale. Third, contributions from stratospheric ozone transported to the surface differ strongly between the models, mainly caused by differences in the efficiency of the vertical mixing. As stratospheric ozone plays an important role for ground level ozone, but the models show large differences in the amount of downward transported ozone, source apportionment methods should account for this source explicitly to better understand inter-model differences.

Download Full-text

When smoke comes to town: The impact of biomass burning smoke on air quality

Atmospheric Environment ◽

10.1016/j.atmosenv.2015.03.050 ◽

2015 ◽

Vol 121 ◽

pp. 13-21 ◽

Cited By ~ 19

Author(s):

Melita Keywood ◽

Martin Cope ◽

C.P. Mick Meyer ◽

Yoshi Iinuma ◽

Kathryn Emmerson

Keyword(s):

Air Quality ◽

Biomass Burning ◽

The Impact

Download Full-text

Source Apportionment of Fine Organic Particulate Matter (PM2.5) in Central Addis Ababa, Ethiopia

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph182111608 ◽

2021 ◽

Vol 18 (21) ◽

pp. 11608

Author(s):

Worku Tefera ◽

Abera Kumie ◽

Kiros Berhane ◽

Frank Gilliland ◽

Alexandra Lai ◽

...

Keyword(s):

Air Pollution ◽

Particulate Matter ◽

Source Apportionment ◽

Biomass Burning ◽

Addis Ababa ◽

Atmospheric Particulate Matter ◽

Motor Vehicles ◽

Soil Dust ◽

Rain Season ◽

The Impact

The development of infrastructure, a rapidly increasing population, and urbanization has resulted in increasing air pollution levels in the African city of Addis Ababa. Prior investigations into air pollution have not yet sufficiently addressed the sources of atmospheric particulate matter. This study aims to identify the major sources of fine particulate matter (PM2.5) and its seasonal contribution in Addis Ababa, Ethiopia. Twenty-four-hour average PM2.5 mass samples were collected every 6th day, from November 2015 through November 2016. Chemical species were measured in samples and source apportionment was conducted using a chemical mass balance (CMB) receptor model that uses particle-phase organic tracer concentrations to estimate source contributions to PM2.5 organic carbon (OC) and the overall PM2.5 mass. Vehicular sources (28%), biomass burning (18.3%), plus soil dust (17.4%) comprise about two-thirds of the PM2.5 mass, followed by sulfate (6.5%). The sources of air pollution vary seasonally, particularly during the main wet season (June–September) and short rain season (February–April): From motor vehicles, (31.0 ± 2.6%) vs. (24.7 ± 1.2%); biomass burning, (21.5 ± 5%) vs. (14 ± 2%); and soil dust, (11 ± 6.4%) vs. (22.7 ± 8.4%), respectively, are amongst the three principal sources of ambient PM2.5 mass in the city. We suggest policy measures focusing on transportation, cleaner fuel or energy, waste management, and increasing awareness on the impact of air pollution on the public’s health.

Download Full-text

Numerical analysis of the impact of agricultural emissions on PM<sub>2.5</sub> in China using a high-resolution ammonia emissions inventory

10.5194/acp-2019-1128 ◽

2020 ◽

Author(s):

Xiao Han ◽

Lingyun Zhu ◽

Mingxu Liu ◽

Yu Song ◽

Meigen Zhang

Keyword(s):

Air Quality ◽

High Resolution ◽

Source Apportionment ◽

Mass Concentration ◽

Atmospheric Modeling ◽

Central China ◽

High Mass ◽

Emissions Inventory ◽

Aerosol Mass Concentration ◽

The Impact

Abstract. China is one of the largest agricultural countries in the world. The NH3 emissions from agricultural activities in China significantly affect regional air quality and horizontal visibility. To reliably estimate the influence of NH3 on agriculture, a high-resolution agricultural NH3 emissions inventory, compiled with a 1 km × 1 km horizontal resolution, was applied to calculate the NH3 mass burden in China. The key emission factors of this inventory were enhanced by considering the results of many native experiments, and the activity data of spatial and temporal information were updated using statistical data from 2015. Fertilizer and husbandry, as well as farmland ecosystems, livestock waste, crop residue burning, fuel wood combustion, and other NH3 emission sources were included in the inventory. Furthermore, a source apportionment tool, ISAM (Integrated Source Apportionment Method), coupled with the air quality modeling system RAMS-CMAQ (Regional Atmospheric Modeling System and Community Multiscale Air Quality), was applied to capture the contribution of NH3 emitted from total agriculture (Tagr) in China. The aerosol mass concentration in 2015 was simulated, and the results showed that a high mass concentration of NH3, which exceeded 10 μg m−3, appeared mainly in the North China Plain (NCP), Central China (CNC), the Yangtz River Delta (YRD), and the Sichan Basin (SCB), and the annual average contribution of Tagr NH3 to PM2.5 mass burden in China was 14–18 %. Specific to the PM2.5 components, Tagr NH3 provided a major contribution to ammonium formation (87.6 %) but a tiny contribution to sulfate (2.2 %). In addition, several brute-force sensitivity tests were conducted to estimate the impact of Tagr NH3 emissions reduction on the PM2.5 mass burden. Compared with the results of ISAM, it was found that even though the Tagr NH3 only contributed 10.1 % of nitrate under current emissions scenarios, the reduction of nitrate could reach 98.8 % upon removal of the Tagr NH3 emissions. The main reason for this deviation could be that the NH3 contribution to nitrate is small under rich NH3 conditions and large in poor NH3 environments. Thus, the influence of NH3 on nitrate formation could be enhanced with the decrease of ambient NH3 mass concentration.

Download Full-text