Two-year monitoring of gaseous elementary mercury in a typical iron-steel plant in Yangtze River Delta, China: Characterization and estimation of its dynamic oxidation

A two-year gaseous elementary mercury (GEM) measurement was implemented at an iron-steel plant in Yangtze River Delta, China, which provided an excellent opportunity to investigate their dynamic cycling. The hourly GEM concentrations ranged between 0.78 and 113.8 ng m(-3), with a mean value of 3.83 +/- 2.53 ng m(-3). Temporally, seasonal GEM contents decreased as winter approximate to spring > summer > autumn, while diurnal cycling was observed with a steady decrease at 14:00-17:00. GEM variations were found to be related to source emissions, meteorology and regional transportation. Three major oxidants (O-3, Br center dot and OH center dot radicals) were used to evaluate GEM oxidation in the daytime, and the estimated GEM depletion rate was 70.8 +/- 52.5 molecule cm(-3) s(-1) (0.09 +/- 0.06 ng m(-3) h(-1)). The GEM oxidized by Br center dot radicals accounted for 83.4% of the total GEM oxidation rate, followed by O-3 (13.8%). The estimated atmospheric lifetime of GEM was 22.9 to 345.2 days, which implies a major contribution of Br radicals to the GEM sink. These findings highlight the ability of iron-steel industry emissions and in-situ oxidation to affect daily local GEM cycling significantly. (C) 2018 Elsevier B.V. All rights reserved.