Investigate the impact of local iron-steel industrial emission on atmospheric mercury concentration in Yangtze River Delta, China.

Mercury is a global neurotoxic pollutant, which can be globally transported and bioaccumulated in the food chain. Iron-steel production is one of the most significant sources of anthropogenic atmospheric mercury emission, while information on this source is scarce. Hourly gaseous elemental mercury (GEM) and particle bound mercury (PBM) were studied inside (IP) and at the boundary (BP) of a typical iron-steel plant in the Yangtze River Delta (YRD), China from September 2016 to August 2017. The GEM concentrations were 0.97-503.1 and 0.05-112.6 ng/m at the IP and BP sites, respectively, while PBM concentrations were one to four orders of magnitude higher than urban and suburban ambient levels. Several lines of evidences indicated that PBM was mainly originated from the iron-steel manufacturing process, especially from sintering and coke-making processes in this iron-steel plant. However, a combined emission effect contributed to GEM variation. The receptor model of positive matrix factorization (PMF) showed that local direct emissions (coal combustion, industrial activity, vehicle exhaust, and secondary evaporation from polluted soil) contributed 51.3% of the total GEM concentration variation. Potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models clearly showed that air masses moving from areas surrounding YRD had the highest concentrations of atmospheric mercury. These results provided evidence that iron-steel manufacturing emissions have a considerable effect on regional atmospheric mercury concentrations, especially PBM.