2 research outputs found
Radiocarbon-Based Source Apportionment of Carbonaceous Aerosols at a Regional Background Site on Hainan Island, South China
To assign fossil
and nonfossil contributions to carbonaceous particles,
radiocarbon (<sup>14</sup>C) measurements were performed on organic
carbon (OC), elemental carbon (EC), and water-insoluble OC (WINSOC)
of aerosol samples from a regional background site in South China
under different seasonal conditions. The average contributions of
fossil sources to EC, OC and WINSOC were 38 Ā± 11%, 19 Ā±
10%, and 17 Ā± 10%, respectively, indicating generally a dominance
of nonfossil emissions. A higher contribution from fossil sources
to EC (ā¼51%) and OC (ā¼30%) was observed for air-masses
transported from Southeast China in fall, associated with large fossil-fuel
combustion and vehicle emissions in highly urbanized regions of China.
In contrast, an increase of the nonfossil contribution by 5ā10%
was observed during the periods with enhanced open biomass-burning
activities in Southeast Asia or Southeast China. A modified EC tracer
method was used to estimate the secondary organic carbon from fossil
emissions by determining <sup>14</sup>C-derived fossil WINSOC and
fossil EC. This approach indicates a dominating secondary component
(70 Ā± 7%) of fossil OC. Furthermore, contributions of biogenic
and biomass-burning emissions to contemporary OC were estimated to
be 56 Ā± 16% and 44 Ā± 14%, respectively
Contribution of Nitrated Phenols to Wood Burning Brown Carbon Light Absorption in Detling, United Kingdom during Winter Time
We
show for the first time quantitative online measurements of
five nitrated phenol (NP) compounds in ambient air (nitrophenol C<sub>6</sub>H<sub>5</sub>NO<sub>3</sub>, methylnitrophenol C<sub>7</sub>H<sub>7</sub>NO<sub>3</sub>, nitrocatechol C<sub>6</sub>H<sub>5</sub>NO<sub>4</sub>, methylnitrocatechol C<sub>7</sub>H<sub>7</sub>NO<sub>4</sub>, and dinitrophenol C<sub>6</sub>H<sub>4</sub>N<sub>2</sub>O<sub>5</sub>) measured with a micro-orifice volatilization impactor
(MOVI) high-resolution chemical ionization mass spectrometer in Detling,
United Kingdom during JanuaryāFebruary, 2012. NPs absorb radiation
in the near-ultraviolet (UV) range of the electromagnetic spectrum
and thus are potential components of poorly characterized light-absorbing
organic matter (ābrown carbonā) which can affect the
climate and air quality. Total NP concentrations varied between less
than 1 and 98 ng m<sup>ā3</sup>, with a mean value of 20 ng
m<sup>ā3</sup>. We conclude that NPs measured in Detling have
a significant contribution from biomass burning with an estimated
emission factor of 0.2 ng (ppb CO)<sup>ā1</sup>. Particle light
absorption measurements by a seven-wavelength aethalometer in the
near-UV (370 nm) and literature values of molecular absorption cross
sections are used to estimate the contribution of NP to wood burning
brown carbon UV light absorption. We show that these five NPs are
potentially important contributors to absorption at 370 nm measured
by an aethalometer and account for 4 Ā± 2% of UV light absorption
by brown carbon. They can thus affect atmospheric radiative transfer
and photochemistry and with that climate and air quality