Simultaneous aerosol mass spectrometry and chemical ionisation mass spectrometry measurements during a biomass burning event in the UK: insights into nitrate chemistry
Over the past decade, there has been an increasing interest in short-term events that negatively affect air quality such as bonfires and fireworks. High aerosol and gas concentrations generated from public bonfires or fireworks were measured in order to understand the night-time chemical process...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/4093/2018/acp-18-4093-2018.pdf |
| Summary: | Over the past decade, there has been an increasing interest
in short-term events that negatively affect air quality such as bonfires and
fireworks. High aerosol and gas concentrations generated from public
bonfires or fireworks were measured in order to understand the night-time
chemical processes and their atmospheric implications. Nitrogen chemistry was
observed during Bonfire Night with nitrogen containing compounds in both
gas and aerosol phases and further N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub>
concentrations, which depleted early next morning due to photolysis of
NO<sub>3</sub> radicals and ceasing production. Particulate organic oxides of nitrogen
(PONs) concentrations of 2.8 µg m<sup>−3</sup> were estimated using the
<i>m</i> ∕ <i>z</i> 46 : 30 ratios from aerosol mass spectrometer (AMS) measurements,
according to previously published methods. Multilinear engine 2 (ME-2) source apportionment was performed to determine
organic aerosol (OA) concentrations from different sources after modifying the
fragmentation table and it was possible to identify two PON factors
representing primary (pPON_ME2) and secondary (sPON_ME2) contributions. A
slight improvement in the agreement between the source apportionment of the
AMS and a collocated AE-31 Aethalometer was observed after modifying the
prescribed fragmentation in the AMS organic spectrum (the fragmentation
table) to determine PON sources, which resulted in an <i>r</i><sup>2</sup> = 0.894
between biomass burning organic aerosol (BBOA)
and <i>b</i><sub>abs_470wb</sub> compared to an <i>r</i><sup>2</sup> = 0.861
obtained without the modification. Correlations between OA sources and
measurements made using time-of-flight chemical ionisation mass spectrometry
with an iodide adduct ion were performed in order to determine possible gas
tracers to be used in future ME-2 analyses to constrain solutions. During
Bonfire Night, strong correlations (<i>r</i><sup>2</sup>) were observed between BBOA and
methacrylic acid (0.92), acrylic acid (0.90), nitrous acid (0.86), propionic
acid, (0.85) and hydrogen cyanide (0.76). A series of oxygenated species and chlorine
compounds showed good correlations with sPON_ME2 and the low
volatility oxygenated organic aerosol (LVOOA) factor during Bonfire Night and
an event with low pollutant concentrations. Further analysis of pPON_ME2 and
sPON_ME2 was performed in order to determine whether these PON sources
absorb light near the UV region using an Aethalometer. This hypothesis was
tested by doing multilinear regressions between <i>b</i><sub>abs_470wb</sub> and
BBOA, sPON_ME2 and pPON_ME2. Our results suggest that sPON_ME2 does not
absorb light at 470 nm, while pPON_ME2 and LVOOA do absorb light at 470 nm.
This may inform black carbon (BC) source apportionment studies from
Aethalometer measurements, through investigation of the brown carbon
contribution to <i>b</i><sub>abs_470wb</sub>. |
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| ISSN: | 1680-7316 1680-7324 |