Iron and steel industry emissions and contribution to the air quality in China

To reduce the emissions from the iron and steel industry, China has imposed a series of strengthened emission standards since 2012. An accurate impact of emission reduction on the air quality is critical for evaluating policy efficiency. This study was the first attempt to explore the contribution of emissions from China's iron and steel industry to ambient air quality at national scale, after the implementation of current standards in 2012. First, all emission sources in production processes were estimated at unit level in China's iron and steel industry, covering sulfur dioxide (SO2), nitrogen oxides (NOx) and particulate matter (PM2.5), etc. Second, the corresponding air quality impacts were modeled with the Comprehensive Air Quality Model with extensions (CAMx) model. We find that emission hotspots from China's iron and steel industry, with following aspects. (1) From a spatial perspective, the largest emissions and ambient concentration contributors were mainly concentrated in eastern areas of China, with high crude steel production. (2) Among three main pollutants (i.e., SO2, NOx and PM2.5), SO2 made the largest contribution to ambient concentration in China's iron and steel industry. (3) As for temporal distribution, emission sources presented the greatest contribution to air quality concentration in summer. (4) For policy evaluation, under the current standards in 2012, the contribution of iron and steel industry emissions to air quality decreased by 92.07% and 72.91% for SO2 and PM2.5, respectively. Therefore, these results will be essential to reflecting current emission characteristics and underscoring further opportunities for emission reductions.