Measurements of non-volatile aerosols with a VTDMA and their correlations with carbonaceous aerosols in Guangzhou, China
Simultaneous measurements of aerosol volatility and carbonaceous matters were conducted at a suburban site in Guangzhou, China, in February and March 2014 using a volatility tandem differential mobility analyzer (VTDMA) and an organic carbon/elemental carbon (OC ∕ EC) analyzer. Low volatility (LV...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/8431/2016/acp-16-8431-2016.pdf |
| Summary: | Simultaneous measurements of aerosol volatility and carbonaceous matters were
conducted at a suburban site in Guangzhou, China, in February and March 2014
using a volatility tandem differential mobility analyzer (VTDMA) and an
organic carbon/elemental carbon (OC ∕ EC) analyzer. Low volatility (LV)
particles, with a volatility shrink factor (VSF) at 300 °C
exceeding 0.9, contributed 5 % of number concentrations of the 40 nm
particles and 11–15 % of the 80–300 nm particles. They were composed of
non-volatile material externally mixed with volatile material, and therefore
did not evaporate significantly at 300 °C. Non-volatile material
mixed internally with the volatile material was referred to as medium
volatility (MV, 0.4 < VSF < 0.9) and high volatility (HV, VSF < 0.4) particles. The MV and HV particles contributed 57–71 % of
number concentration for the particles between 40 and 300 nm in size. The
average EC and OC concentrations measured by the OC ∕ EC analyzer were
3.4 ± 3.0 and 9.0 ± 6.0 µg m<sup>−3</sup>, respectively.
Non-volatile OC evaporating at 475 °C or above, together with EC,
contributed 67 % of the total carbon mass. In spite of the daily maximum
and minimum, the diurnal variations in the volume fractions of the volatile
material, HV, MV and LV residuals were less than 15 % for the 80–300 nm
particles. Back trajectory analysis also suggests that over 90 % of the air
masses influencing the sampling site were well aged as they were transported
at low altitudes (below 1500 m) for over 40 h before arrival. Further
comparison with the diurnal variations in the mass fractions of EC and the
non-volatile OC in PM<sub>2.5</sub> suggests that the non-volatile residuals may be
related to both EC and non-volatile OC in the afternoon, during which the
concentration of aged organics increased. A closure analysis of the total
mass of LV and MV residuals and the mass of EC or the sum of EC and
non-volatile OC was conducted. It suggests that non-volatile OC, in addition
to EC, was one of the components of the non-volatile residuals measured by
the VTDMA in this study. |
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| ISSN: | 1680-7316 1680-7324 |