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 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 (PM 1 -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.Published by Copernicus Publications on behalf of the European Geosciences Union. 1234M. Paglione et al.: Impact of biomass burning and aqueous-phase processing on air quality 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.

Global Importance of Hydroxymethanesulfonate in Ambient Particulate Matter: Implications for Air Quality

“…For our analysis, we extracted the material on one quarter of each of the filters in 20 mL milli‐Q water and sonicated this for 30 min at 25°C. Observations in Italy come from Bologna and from San Pietro Capofiume, located in the Po Valley (Paglione et al, 2020). Samples from Bologna were collected on 4–15 February and 7–18 October 2013, and on 3–21 February 2014.…”

“…A reanalysis of AMS observations in Beijing and new IC measurements have also suggested the likely presence of HMS there in winter (Ma et al, 2020;Song et al, 2019). HMS has also recently been detected in field campaigns in the Po Valley, Italy (Gilardoni et al, 2016;Paglione et al, 2020), and previously in the United Kingdom, Germany, Japan, and the United States (Dall'Osto et al, 2009;Dixon & Aasen, 1999;Lee et al, 2003;Scheinhardt et al, 2014;Suzuki et al, 2001;Whiteaker & Prather, 2003).…”

“…Recent work suggests that AMS can in fact provide insight into the HMS contribution to PM if attention is paid to matrix effects and ion balance (Song et al, 2019). Other recent work has shown a high correlation between HMS identified by nuclear magnetic resonance spectroscopy (NMR) and certain oxygenated organic aerosol components identified by positive matrix factorization analysis of organic aerosol mass spectra and interpreted as SOA formed via aqueous phase processes (Gilardoni et al, 2016; Paglione et al, 2020). HMS has also been detected via electrospray ionization‐tandem and via single particle mass spectrometry, but matrix effects can impede efforts at quantification (Chapman et al, 1990; Dovrou et al, 2019; Froyd et al, 2010; Lee et al, 2003; Neubauer et al, 1996; Whiteaker & Prather, 2003).…”

The impact of stay-home policies during Coronavirus-19 pandemic on the chemical and toxicological characteristics of ambient PM2.5 in the metropolitan area of Milan, Italy

“…Although the strict lockdown policies and in turn curtailed traffic decreased the ambient PM 2.5 levels in this area with respect to the pre-pandemic period ( Collivignarelli et al, 2020 ), the contribution of domestic biomass burning emissions to total PM 2.5 may have surged due to the stay-home strategies ( Sicard et al, 2020 ). Previous studies have documented the extensive domestic biomass burning (for residential heating purposes) as a major source of pollution, elevating the PM 2.5 mass concentration in the area during the colder periods of the year ( Paglione et al, 2020 ; Ricciardelli et al, 2017 ; Tositti et al, 2014 ). In particular, the recently published study by Hakimzadeh et al (2020) attributed a dominant fraction of PM 2.5 oxidative potential in the Lombardy area to the domestic biomass burning emissions.…”

Differentiation of the Athens Fine PM Profile during Economic Recession (March of 2008 Versus March of 2013): Impact of Changes in Anthropogenic Emissions and the Associated Health Effect

“…In Europe, atmospheric pollution is responsible for more than 400,000 premature deaths a year, with the largest share to the exposure of fine particulate matter (PM 2.5 , PM 1 ) [1]. Fine particles have increased potential health risk being compared to the one of coarse particles, for many reasons: (i) they penetrate deeper in the lung (ii) they can penetrate more readily into indoor environments (iii) they have longer periods of suspension (iv) they may be transported over long distances (v) they carry higher concentrations of toxic compounds and (vi) they can absorb larger amounts of semi-volatile compounds [2].…”