Chemical characterization of organic particulate matter from on-road traffic in São Paulo, Brazil
This study reports emission of organic particulate matter by light-duty vehicles (LDVs) and heavy-duty vehicles (HDVs) in the city of São Paulo, Brazil, where vehicles run on three different fuel types: gasoline with 25 % ethanol (called gasohol, E25), hydrated ethanol (E100), and diesel (with 5...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/14397/2016/acp-16-14397-2016.pdf |
| Summary: | This study reports emission of organic particulate matter by light-duty
vehicles (LDVs) and heavy-duty vehicles (HDVs) in the city of São Paulo,
Brazil, where vehicles run on three different fuel types: gasoline with
25 % ethanol (called gasohol, E25), hydrated ethanol (E100), and diesel
(with 5 % biodiesel). The experiments were performed at two tunnels:
Jânio Quadros (TJQ), where 99 % of the vehicles are LDVs, and
RodoAnel Mário Covas (TRA), where up to 30 % of the fleet are HDVs.
Fine particulate matter (PM<sub>2.5</sub>) samples were collected on quartz filters
in May and July 2011 at TJQ and TRA, respectively. The samples were analyzed
by thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS)
and by thermal–optical transmittance (TOT). Emission factors (EFs) for
organic aerosol (OA) and organic carbon (OC) were calculated for the HDV and
the LDV fleet. We found that HDVs emitted more PM<sub>2.5</sub> than LDVs, with OC
EFs of 108 and 523 mg kg<sup>−1</sup> burned fuel for LDVs and HDVs,
respectively. More than 700 ions were identified by TD-PTR-MS and the EF
profiles obtained from HDVs and LDVs exhibited distinct features. Unique
organic tracers for gasoline, biodiesel, and tire wear have been tentatively
identified. nitrogen-containing compounds contributed around 20 % to the
EF values for both types of vehicles, possibly associated with incomplete
fuel burning or fast secondary production. Additionally, 70 and 65 % of
the emitted mass (i.e. the OA) originates from oxygenated compounds from LDVs
and HDVs, respectively.
This may be a consequence of the high oxygen content of the fuel. On the
other hand, additional oxygenation may occur during fuel combustion. The high
fractions of nitrogen- and oxygen-containing compounds show that chemical
processing close to the engine / tailpipe region is an important factor
influencing primary OA emission. The thermal-desorption analysis showed that
HDVs emitted compounds with higher volatility, and with mainly oxygenated and
longer chain hydrocarbons than LDVs. |
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| ISSN: | 1680-7316 1680-7324 |