Identification of NO2 and SO2 Pollution Hotspots and Sources in Jiangsu Province of China

Nitrogen dioxide (NO2) and sulfur dioxide (SO2) 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 (NO2), and sulfur dioxide (SO2) 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 NO2 and SO2, the SO2/NO2 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 NO2 and SO2 for most cities of Jiangsu Province except for Yancheng City (<0.50 DU). The seasonal analyses showed the highest NO2 and SO2 in winter, followed by spring, autumn, and summer. Coal-fire-based room heating and stable meteorological conditions during the cold season may cause higher NO2 and SO2 in winter. Notably, the occurrence frequency of NO2 and SO2 of >1.2 was highest in winter, which varied between 9.14 similar to 32.46% for NO2 and 7.84 similar to 21.67% for SO2, indicating a high level of pollution across Jiangsu Province. The high SO2/NO2 ratio (>0.60) indicated that industry is the dominant source, with significant annual and seasonal variations. Trends in NO2 and SO2 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 NO2 were more prominent during the 12th FYP period (2011-2015: -0.024 similar to-0.052 DU/year) than in the APPC-AC period (2013-2017: -0.007 similar to-0.043 DU/year) and 2005-2020 (-0.002 to -0.012 DU/year). However, no prevention and control policies for NO2 were included during the 11th FYP period (2006-2010), resulting in an increasing trend in NO2 (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 SO2 (per year) during the 12th FYP period (-0.002 similar to-0.075 DU/year) than in the 11th FYP period (-0.014 similar to-0.071 DU/year), the APPC-AC period (-0.007 similar to-0.043 DU/year), and 2005-2020 (-0.015 similar to-0.032 DU/year). PSCF analysis indicated that the air quality of Jiangsu Province is mainly influenced by local pollution sources.

Automated summary

The study analyzed the spatial distribution and variability of NO2 and SO2 in Jiangsu Province, identifying industry as the dominant pollution source with high levels of pollution, especially in winter. Trends showed decreasing levels of NO2 during strict air pollution control policy periods. Industry was found to be a significant contributor to air pollution in Jiangsu Province.