Highly-resolved spatial-temporal variations of air pollutants from Chinese industrial boilers

Industrial boilers are a significant anthropogenic source of air pollutant emissions. In this study, a county-based atmospheric emission inventory of particulate matter (PM), PM₁₀, PM_2.5, SO₂, NOx, organic carbon (OC) and elemental carbon (EC) from industrial boilers over mainland China in 2017 was developed for the first time, based on county-level activity data from ~61,000 coal-fired industrial boilers (CFIBs), ~44,000 biomass-fired industrial boilers (BFIBs), ~71,000 gas-fired industrial boilers (GFIBs) and ~9300 oil-fired industrial boilers (OFIBs), updated emission factors (EFs) and air pollution control device (APCD) efficiencies. The total national PM, PM_2.5, PM₁₀, SO₂, NOx, OC and EC emissions from industrial boilers in 2017 were estimated to be 1,240, 347, 761, 1,648, 1,340, 13.1 and 15.8 kilotons (kt), respectively. Intensive air pollutant emissions from industrial boilers of more than 1000 kg/km² were predominantly in north-eastern, northern and eastern China. CFIBs contributed the most (77.6-94.0 %) to air pollutant emissions because of their high air pollutant EFs and the large amounts of coal consumed. BFIBs were the second-highest contributor to national air pollutant emissions, with the contribution of BFIBs to PM_2.5, OC and EC emissions in central and southern China reaching up to 42.1 %, 61.7 % and 45.5 %, respectively. There were seasonal peaks in monthly air pollutant emissions in heating regions. The overall uncertainty realting to the new emission inventory was estimated as -25.9 %-22.7 %. Significant air pollutant emission reductions were obtained from 2017 to 2030, and by 2030 the PM, PM₁₀, PM_2.5, SO₂ and NOx emissions were forecast to decrease by 40.1-84.0 %, 41.6-84.3 %, 44.5-75.2 %, 44.5-75.2 % and 19.5-46.8 % compared to 2017, respectively, under four proposed scenarios. The results of this study showed that differentiated industrial boiler management measures should be developed according to the actual emission characteristics. This work developed a county-based atmospheric emission inventory of PM, PM₁₀, PM_2.5, SO₂, NOx, OC and EC from Chinese industrial boilers in 2017 for the first time.