Abstract
The evolution, transport characteristics, and potential source regions of PM2.5 and O3 were investigated from 1 January 2015 to 31 December 2020 in the coastal city of Nantong. The annual mean PM2.5 concentration declined obviously over the entire study period, and was 34.7 μg/m3 in 2020. O3 had a relatively smooth decreasing trend, but rebounded greatly during 2017 when the most frequent extreme high-temperature events occurred. Similar trends were observed for PM2.5 and O3 polluted hours. No PM2.5-O3 complex air pollution happened in 2019 and 2020, likely suggesting the preliminary results from the implementation of emission controls. Notable differences in transport pathways and frequencies were observed from the backward trajectory clusters in four seasons in Nantong. Clusters with the largest percentage of polluted PM2.5 and O3 trajectories were transported mostly over short distances rather than long distances. Analysis involving the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) showed that PM2.5 polluted sources were from the adjacent western and northwestern provinces, whereas the influence of eastern marine sources was relatively small. O3 had a greatly different spatial distribution of polluted source regions from PM2.5, mostly covering the North China Plain, the Bohai Sea, and the Yellow Sea.
Highlights
Fine particulate matter (PM2.5) and ozone (O3) are two of the largest contributors to air pollution in the tropospheric atmosphere due to their impact on human health, environmental degradation, vegetation production, and climate change [1,2,3]
Very different evolution characteristics were observed for PM2.5 and O3
Considerable reductions of PM2.5 were observed, pollution control measures did little to O3 due to its complicated nonlinear photochemistry formation, which relied on precursor diagnosis and meteorological conditions
Summary
Fine particulate matter (PM2.5) and ozone (O3) are two of the largest contributors to air pollution in the tropospheric atmosphere due to their impact on human health, environmental degradation, vegetation production, and climate change [1,2,3]. Air pollution might worsen due to regional, long-range transport and unfavorable meteorology conditions, even when local emissions are reduced. Numerous studies have been conducted to explore the evolution and transport characteristics of PM2.5 and O3, as well as the influence of meteorological conditions in eastern China Most of these studies focused on megacities such as Shanghai, Nanjing, and Hangzhou which were severely polluted [15,16,17,18,19,20,21]. The transport pathways and potential source regions of PM2.5 and O3 were identified and synthetically analyzed using the backward trajectory cluster, the potential source contribution function (PSCF), and concentration weighted trajectory (CWT) These results will provide an important basis for exploring efficient strategies to control both PM2.5 and O3 pollution in Nantong
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