A comparison of PM<sub>2.5</sub>-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)
<p>Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in air, soil, and water and are known to have harmful effects on human health and the environment. The diurnal and nocturnal variations of 17 PAHs in ambient particle-bound PAHs were measured in urban Beijing (China) and Delh...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/14303/2020/acp-20-14303-2020.pdf |
| Summary: | <p>Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in air,
soil, and water and are known to have harmful effects on human health and the
environment. The diurnal and nocturnal variations of 17 PAHs in ambient
particle-bound PAHs were measured in urban Beijing (China) and Delhi (India)
during the summer season using gas-chromatography–quadrupole time-of-flight mass
spectrometry (GC-Q-TOF-MS). The mean concentration of
particles less than 2.5 <span class="inline-formula">µ</span>m (PM<span class="inline-formula"><sub>2.5</sub></span>) observed in Delhi was 3.6 times
higher than in Beijing during the measurement period in both the daytime and
night-time. In Beijing, the mean concentration of the sum of the 17 PAHs
(<span class="inline-formula">∑</span>17 PAHs) was 8.2 <span class="inline-formula">±</span> 5.1 ng m<span class="inline-formula"><sup>−3</sup></span> in daytime, with the
highest contribution from indeno[1,2,3-cd]pyrene (12 %), while at
night-time the total PAHs was 7.2 <span class="inline-formula">±</span> 2.0 ng m<span class="inline-formula"><sup>−3</sup></span>, with the largest
contribution from benzo[b]fluoranthene (14 %). In Delhi, the mean <span class="inline-formula">∑</span>17 PAHs was 13.6 <span class="inline-formula">±</span> 5.9 ng m<span class="inline-formula"><sup>−3</sup></span> in daytime and 22.7 <span class="inline-formula">±</span> 9.4 ng m<span class="inline-formula"><sup>−3</sup></span> at night-time, with the largest contribution from
indeno[1,2,3-cd]pyrene in both the day (17 %) and night (20 %).
Elevated mean concentrations of total PAHs in Delhi observed at night were
attributed to emissions from vehicles and biomass burning and to
meteorological conditions leading to their accumulation from a stable and
low atmospheric boundary layer. Local emission sources were typically
identified as the major contributors to total measured PAHs in both cities.
Major emission sources were characterized based on the contribution from
each class of PAHs, with the four-, five- and six-ring PAHs accounting
<span class="inline-formula">∼</span> 95 % of the total PM<span class="inline-formula"><sub>2.5</sub></span>-bound PAHs mass in both
locations. The high contribution of five-ring PAHs to total PAH concentration
in summer Beijing and Delhi suggests a high contribution from petroleum
combustion. In Delhi, a high contribution from six-ring PAHs was observed at
night, suggesting a potential emission source from the combustion of fuel
and oil in power generators, widely used in Delhi. The lifetime excess lung
cancer risk (LECR) was calculated for Beijing and Delhi, with the highest
estimated risk attributed to Delhi (LECR <span class="inline-formula">=</span> 155 per million people), which is 2.2
times higher than the Beijing risk assessment value (LECR <span class="inline-formula">=</span> 70 per million
people). Finally, we have assessed the emission control policies in each
city and identified those major sectors that could be subject to mitigation
measures.</p> |
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| ISSN: | 1680-7316 1680-7324 |