Summary: | Nitrogen dioxide (NO<sub>2</sub>) and sulfur dioxide (SO<sub>2</sub>) are important atmospheric trace gases for determining air quality, human health, climate change, and ecological conditions both regionally and globally. In this study, the Ozone Monitoring Instrument (OMI), total column nitrogen dioxide (NO<sub>2</sub>), and sulfur dioxide (SO<sub>2</sub>) were used from 2005 to 2020 to identify pollution hotspots and potential source areas responsible for air pollution in Jiangsu Province. The study investigated the spatiotemporal distribution and variability of NO<sub>2</sub> and SO<sub>2</sub>, the SO<sub>2</sub>/NO<sub>2</sub> ratio, and their trends, and potential source contribution function (PSCF) analysis was performed to identify potential source areas. The spatial distributions showed higher values (>0.60 DU) of annual mean NO<sub>2</sub> and SO<sub>2</sub> for most cities of Jiangsu Province except for Yancheng City (<0.50 DU). The seasonal analyses showed the highest NO<sub>2</sub> and SO<sub>2</sub> in winter, followed by spring, autumn, and summer. Coal-fire-based room heating and stable meteorological conditions during the cold season may cause higher NO<sub>2</sub> and SO<sub>2</sub> in winter. Notably, the occurrence frequency of NO<sub>2</sub> and SO<sub>2</sub> of >1.2 was highest in winter, which varied between 9.14~32.46% for NO<sub>2</sub> and 7.84~21.67% for SO<sub>2</sub>, indicating a high level of pollution across Jiangsu Province. The high SO<sub>2</sub>/NO<sub>2</sub> ratio (>0.60) indicated that industry is the dominant source, with significant annual and seasonal variations. Trends in NO<sub>2</sub> and SO<sub>2</sub> were calculated for 2005–2020, 2006–2010 (when China introduced strict air pollution control policies during the 11th Five Year Plan (FYP)), 2011–2015 (during the 12th FYP), and 2013–2017 (the Action Plan of Air Pollution Prevention and Control (APPC-AC)). Annually, decreasing trends in NO<sub>2</sub> were more prominent during the 12th FYP period (2011–2015: −0.024~−0.052 DU/year) than in the APPC-AC period (2013–2017: −0.007~−0.043 DU/year) and 2005–2020 (−0.002 to −0.012 DU/year). However, no prevention and control policies for NO<sub>2</sub> were included during the 11th FYP period (2006–2010), resulting in an increasing trend in NO<sub>2</sub> (0.015 to 0.031) observed throughout the study area. Furthermore, the implementation of China’s strict air pollution control policies caused a larger decrease in SO<sub>2</sub> (per year) during the 12th FYP period (−0.002~−0.075 DU/year) than in the 11th FYP period (−0.014~−0.071 DU/year), the APPC-AC period (−0.007~−0.043 DU/year), and 2005–2020 (−0.015~−0.032 DU/year). PSCF analysis indicated that the air quality of Jiangsu Province is mainly influenced by local pollution sources.
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