The COVID-19 outbreak provides a
“controlled experiment”
to investigate the response of aerosol pollution to the reduction
of anthropogenic activities. Here we explore the chemical characteristics,
variations, and emission sources of organic aerosol (OA) based on
the observation of air pollutants and combination of aerosol mass
spectrometer (AMS) and positive matrix factorization (PMF) analysis
in Beijing in early 2020. By eliminating the impacts of atmospheric
boundary layer and the Spring Festival, we found that the lockdown
effectively reduced cooking-related OA (COA) but influenced fossil
fuel combustion OA (FFOA) very little. In contrast, both secondary
OA (SOA) and O3 formation was enhanced significantly after
lockdown: less-oxidized oxygenated OA (LO-OOA, 37% in OA) was probably
an aged product from fossil fuel and biomass burning emission with
aqueous chemistry being an important formation pathway, while more-oxidized
oxygenated OA (MO-OOA, 41% in OA) was affected by regional transport
of air pollutants and related with both aqueous and photochemical
processes. Combining FFOA and LO-OOA, more than 50% of OA pollution
was attributed to combustion activities during the whole observation
period. Our findings highlight that fossil fuel/biomass combustion
are still the largest sources of OA pollution, and only controlling
traffic and cooking emissions cannot efficiently eliminate the heavy
air pollution in winter Beijing.
China
has been promoting one of the world’s largest campaigns
for clean heating renovation since 2017. Here, we present an integrated
cost–benefit analysis in a major prefecture-level city by combining
a large-scale household energy survey and PM2.5 exposure
measurement, high-resolution chemical transport simulation, and health
impact assessment. We find that the completed renovation decreases
the share of solid fuels in the heating energy mix from 96 to 6% and
achieves a concomitant reduction of cooking solid-fuel use by 70%.
The completed renovation decreases the ambient PM2.5 concentration
in Linfen by 0.5–5 μg m–3 (2.4 μg
m–3 on average) and decreases the integrated PM2.5 exposure by 4.2 (3.5–5.0) μg m–3. The renovation is estimated to avoid 162 (125–225) and 328
(254–457) premature deaths annually based on two health impact assessment methods. The ratios
of monetized health benefits to cost are 1.51 (0.73–2.59) and
3.06 (1.49–5.23) based on the above two methods. The benefit-to-cost
ratio is projected to remain high if the renovation is further expanded.
More polluted and less wealthy households enjoy larger health benefits
but also experience a higher expense increase, suggesting that a more
carefully designed subsidy policy is needed to protect low-income
households.
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