Understanding the regional background ozone using multiple methods: A
case study in northern China
Abstract
Uprising ground-level ozone (O3) and its regional
pollution in eastern China are attracting more attention. On top of
local precursor emissions and photochemistry, background ozone and
long-range transport also contribute significantly to O3
concentrations. To quantify the regional O3 background
concentrations and its yearly and seasonal variations, multiple methods,
including the principal component analysis (PCA) and the Texas
Commission on Environmental Quality (TCEQ) method, were applied for a
case study in Shandong (SD) province in North China, where serious
O3 pollution occurred frequently yet the background
contributions have not been well quantified. Results derived from
multiple methods show an overall consistent trend with 2018-2020
averaged regional background O3 (MDA8) of 88.9
μg/m3, accounting for 79.4% of total
O3 in the region. From 2018-2020, the changes of
regional MDA8 O3 estimated by Methods 1, 2, 3, and 4 are
-3.8 μg/m3,1.6 μg/m3, -5.2
μg/m3 and 0.9 μg/m3, respectively.
Clear seasonal variations in the regional background O3
are observed, showing a pattern of summer > spring
> autumn > winter. In addition, the regional
ozone contribution at coastal cities was larger than that for inland
cities whereas local O3 formation gradually increased
from coastal areas to inland areas. The sea-land wind contribution to
O3 in the eastern coastal cities in summer was around
2.1% at the three-year average level, while the local photochemistry to
O3 in the inland cities was about 29.7% during ozone
season. Local photochemical contribution to O3 in inland
cities during ozone pollution episodes can reach up to 55.8%.
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