Historical Changes in Seasonal Aerosol Acidity in the Po Valley (Italy) as Inferred from Fog Water and Aerosol Measurements

Abstract. While numerous studies have demonstrated the association between outdoor exposure to atmospheric particulate matter (PM) and adverse health effects, the actual chemical species responsible for PM toxicological properties remain a subject of investigation. We provide here reactive oxygen species (ROS) activity data for PM samples collected at a rural site in the Po Valley, Italy, during the fog season (i.e., November–March). We show that the intrinsic ROS activity of Po Valley PM, which is mainly composed of biomass burning and secondary aerosols, is comparable to that of traffic-related particles in urban areas. The airborne concentration of PM components responsible for the ROS activity decreases in fog conditions, when water-soluble species are scavenged within the droplets. Due to this partitioning effect of fog, the measured ROS activity of fog water was contributed mainly by water-soluble organic carbon (WSOC) and secondary inorganic ions rather than by transition metals. We found that the intrinsic ROS activity of fog droplets is even greater (> 2.5 times) than that of the PM on which droplets are formed, indicating that redox-active compounds are not only scavenged from the particulate phase, but are also produced within the droplets. Therefore, even if fog formation exerts a scavenging effect on PM mass and redox-active compounds, the aqueous-phase formation of reactive secondary organic compounds can eventually enhance ROS activity of PM when fog evaporates. These findings, based on a case study during a field campaign in November 2015, indicate that a significant portion of airborne toxicity in the Po Valley is largely produced by environmental conditions (fog formation and fog processing) and not simply by the emission and transport of pollutants.

Download Full-text

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

10.5194/acp-2018-301 ◽

2018 ◽

Author(s):

Matthew Brege ◽

Marco Paglione ◽

Stefania Gilardoni ◽

Stefano Decesari ◽

Maria Cristina Facchini ◽

...

Keyword(s):

Mass Spectrometry ◽

Organic Matter ◽

Biomass Burning ◽

Nmr Analysis ◽

Fog Water ◽

Po Valley ◽

Two Samples ◽

Atmospheric Organic Matter ◽

Ft Icr Ms ◽

Ft Icr

Abstract. Atmospheric organic matter is a complex mixture of thousands of individual organic compounds originating from a combination of primary emissions and secondary processes. To study the influence of regional biomass burning emissions and secondary processes, ambient samples of fog and aerosol were collected in the Po Valley (Italy) during the 2013 Supersito field campaign. After the extent of fresh vs. aged biomass burning influence was estimated from proton nuclear magnetic resonance (1H-NMR) and high resolution time of flight aerosol mass spectrometry (HR-TOF-AMS) observations, two samples of fog water and two samples of PM1 aerosol were selected for ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Over 4300 distinct molecular formulas were assigned to electrospray ionization FT-ICR MS anions and were sorted into four elemental groups (CHO, CHNO, CHOS and CHNOS) and 64 subclasses. Molecular weight distributions indicated that the water-soluble organic matter was largely non-polymeric without clearly repeating units, although some evidence of dimerization was observed for C10 compounds and especially for C8–9 CHNO species in the aged aerosol. The selected samples had an atypically large frequency of molecular formulas containing nitrogen and sulfur (not evident in the NMR composition) attributed to multifunctional organonitrates and organosulfates. While higher numbers of organonitrates were observed in aerosol (dry or deliquesced particles), higher numbers of organosulfates were mostly found in fog water and so chemical reactions promoted by liquid water must be postulated for their formation. Consistent with the observation of an enhanced aromatic proton signature in the 1H-NMR analysis, the average molecular formula double bond equivalents and carbon numbers were higher in the fresh biomass burning influenced samples, whereas the average O : C and H : C values from FT-ICR MS were higher in the samples with an aged influence (O : C > 0.6 and H : C > 1.2). The aged fog had a large set of unique highly oxygenated CHO fragments in HR-TOF-AMS mass spectra, which reflects an enrichment of carboxylic acids and other compounds carrying acyl groups as highlighted by the NMR analysis. Fog compositions were more SOA-like than aerosols as indicated by the observed similarity between the aged aerosol and fresh fog, implying that fog nuclei must be somewhat aged. Overall, functionalization with nitrate and sulfate moieties in addition to aqueous oxidation trigger an increase in the molecular complexity in this environment, which is apparent in the FT-ICR MS results. This study demonstrates the significance of the aqueous phase to transform the molecular chemistry of atmospheric organic matter and contribute to secondary organic aerosol.

Download Full-text

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-13197-2018 ◽

2018 ◽

Vol 18 (17) ◽

pp. 13197-13214 ◽

Cited By ~ 12

Author(s):

Matthew Brege ◽

Marco Paglione ◽

Stefania Gilardoni ◽

Stefano Decesari ◽

Maria Cristina Facchini ◽

...

Keyword(s):

Mass Spectrometry ◽

Biomass Burning ◽

Organic Aerosol ◽

Molecular Formula ◽

Nmr Analysis ◽

Fog Water ◽

Po Valley ◽

Two Samples ◽

Ft Icr Ms ◽

Ft Icr

Abstract. To study the influence of regional biomass burning emissions and secondary processes, ambient samples of fog and aerosol were collected in the Po Valley (Italy) during the 2013 Supersito field campaign. After the extent of fresh vs. aged biomass burning influence was estimated from proton nuclear magnetic resonance (1H NMR) and high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), two samples of fog water and two samples of PM1 aerosol were selected for ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Molecular compositions indicated that the water-soluble organic matter was largely non-polymeric without clearly repeating units. The selected samples had an atypically large frequency of molecular formulas containing nitrogen and sulfur (not evident in the NMR composition) attributed to multifunctional organonitrates and organosulfates. Higher numbers of organonitrates were observed in aerosol, and higher numbers of organosulfates were observed in fog water. Consistent with the observation of an enhanced aromatic proton signature in the 1H-NMR analysis, the average molecular formula double-bond equivalents and carbon numbers were higher in the fresh biomass-burning-influenced samples. The average O : C and H : C values from FT-ICR MS were higher in the samples with an aged influence (O : C = 0.50–0.58, and H : C = 1.31–1.37) compared to those with fresh influence (O : C = 0.43–0.48, and H : C = 1.13–1.30). The aged fog had a large set of unique highly oxygenated CHO fragments in the HR-ToF-AMS, which reflects an enrichment of carboxylic acids and other compounds carrying acyl groups, highlighted by the NMR analysis. Fog compositions were more oxidized and SOA (secondary organic aerosol)-like than aerosols as indicated by their NMR measured acyl-to-alkoxyl ratios and the observed molecular formula similarity between the aged aerosol and fresh fog, implying that fog nuclei must be somewhat aged. Overall, functionalization with nitrate and sulfate moieties, in addition to aqueous oxidation, triggers an increase in the molecular complexity in this environment, which is apparent in the FT-ICR MS results. This study demonstrates the significance of the aqueous phase in transforming the molecular chemistry of atmospheric organic matter and contributing to secondary organic aerosol.

Download Full-text

Hybrid multiple-site mass closure and source apportionment of PM2.5 and aerosol acidity at major cities in the Po Valley

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.135287 ◽

2020 ◽

Vol 704 ◽

pp. 135287 ◽

Cited By ~ 8

Author(s):

Mauro Masiol ◽

Stefania Squizzato ◽

Gianni Formenton ◽

Md Badiuzzaman Khan ◽

Philip K. Hopke ◽

...

Keyword(s):

Source Apportionment ◽

Multiple Site ◽

Mass Closure ◽

Po Valley ◽

Aerosol Acidity

Download Full-text

Reconstructing Elemental Carbon Long-Term Trend in the Po Valley (Italy) from Fog Water Samples

Atmosphere ◽

10.3390/atmos11060580 ◽

2020 ◽

Vol 11 (6) ◽

pp. 580

Author(s):

Stefania Gilardoni ◽

Leone Tarozzi ◽

Silvia Sandrini ◽

Pierina Ielpo ◽

Daniele Contini ◽

...

Keyword(s):

Air Quality ◽

Water Samples ◽

Atmospheric Aerosol ◽

Elemental Carbon ◽

Winter Season ◽

Reduction Rate ◽

Anthropogenic Sources ◽

Fog Water ◽

Po Valley

Elemental carbon (EC), a ubiquitous component of fine atmospheric aerosol derived from incomplete combustion, is an important player for both climate change and air quality deterioration. Several policy measures have been implemented over the last decades to reduce EC emissions from anthropogenic sources, but still, long-term EC measurements to verify the efficacy of such measurements are limited. In this study, we analyze the concentration of EC suspended in fog water samples, collected over the period 1997–2016 in a rural background site of the southern Po Valley. The comparison between EC in fog water and EC atmospheric aerosol concentration measured since 2012 allowed us to reconstruct EC atmospheric concentration from fog water chemical composition dating back to 1997. The results agree with the EC atmospheric observations performed at the European Monitoring and Evaluation Program (EMEP) station of Ispra in the northern part of the Po Valley since 2002, and confirm that the Po Valley is a pollution hotspot, not only in urban areas, but also in rural locations. The reconstructed trend over the period 1997–2016 indicates that EC concentration during the winter season has decreased on average by 4% per year, in agreement with the emission reduction rate, confirming the effectiveness of air quality measures implemented during the past 20 years.

Download Full-text

Seasonal trend of fog water chemical composition in the Po Valley

Environmental Pollution ◽

10.1016/0269-7491(92)90059-j ◽

1992 ◽

Vol 75 (1) ◽

pp. 75-80 ◽

Cited By ~ 17

Author(s):

Sandro Fuzzi ◽

Maria Cristina Facchini ◽

Giordano Orsi ◽

Donatella Ferri

Keyword(s):

Chemical Composition ◽

Seasonal Trend ◽

Fog Water ◽

Po Valley ◽

Water Chemical Composition

Download Full-text

Chemistry of carbonyl compounds in Po Valley fog water

The Science of The Total Environment ◽

10.1016/0048-9697(90)90289-7 ◽

1990 ◽

Vol 91 ◽

pp. 79-86 ◽

Cited By ~ 13

Author(s):

Maria Cristina Facchini ◽

John Lind ◽

Giordano Orsi ◽

Sandro Fuzzi

Keyword(s):

Carbonyl Compounds ◽

Fog Water ◽

Po Valley

Download Full-text

Enhanced toxicity of aerosol in fog conditions in the Po Valley, Italy

10.5194/acp-2017-118 ◽

2017 ◽

Author(s):

Stefano Decesari ◽

Mohammad H. Sowlat ◽

Sina Hasheminassab ◽

Silvia Sandrini ◽

Stefania Gilardoni ◽

...

Keyword(s):

Urban Areas ◽

Water Soluble ◽

Atmospheric Particulate Matter ◽

Rural Site ◽

Activity Data ◽

Active Compounds ◽

Fog Water ◽

Po Valley ◽

Redox Active ◽

Airborne Concentration

Abstract. While numerous studies have demonstrated the association between outdoor exposure to atmospheric particulate matter (PM) and adverse health effects, the actual chemical species responsible for PM toxicological properties remain a subject of investigation. We provide here reactive oxygen species (ROS) activity data for PM samples collected at a rural site in the Po Valley, Italy, during the fog season (i.e., November–March). We show that the intrinsic ROS activity of Po Valley PM, which is mainly composed of biomass burning and secondary aerosols, is comparable to that of traffic-related particles in urban areas. The airborne concentration of PM components responsible for the ROS activity decreases in fog conditions, when water-soluble species are scavenged within the droplets. Thanks to this partitioning effect of fog, the measured ROS activity of fog water was contributed mainly by water-soluble organic carbon (WSOC) and secondary inorganic ions rather than by transition metals. We found that the intrinsic ROS activity of fog droplets is even greater (> 2.5 times) than that of the PM on which droplets are formed, indicating that redox-active compounds are not only scavenged from the particulate phase, but are also produced within the droplets. Therefore, even if fog formation exerts a scavenging effect on PM mass and redox-active compounds, the aqueous-phase formation of reactive secondary organic compounds can eventually enhance ROS activity of PM when fog evaporates. These findings, based on a case study during a field campaign in November 2015, indicate that a significant portion of airborne toxicity in the Po Valley is largely produced by environmental conditions (fog formation and fog processing) and not simply by the emission and transport of pollutants.

Download Full-text