Impacts of Large-Scale Circulation on Urban Ambient Concentrations of Gaseous Elemental Mercury in New York, USA
Huiting Mao1, Dolly Hall2, Zhuyun Ye1, Ying Zhou1, Dirk Felton3, and Leiming Zhang41Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210 2Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742 3Bureau of Air Quality Surveillance, Division of Air Resources, New York State Department of Environmental Conservation, Albany, NY 12233 4Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto, M3H 5T4, Canada
Received: 27 Feb 2017 – Accepted for review: 21 Mar 2017 – Discussion started: 29 Mar 2017
Abstract. The impact of large-scale circulation on urban gaseous elemental mercury (GEM) was investigated through analysis of 2008–2015 measurement data from an urban site in New York City (NYC), New York, USA. Distinct annual cycles were observed in 2009–2010 with mixing ratios in warm seasons (i.e. spring–summer) 10–20 ppqv (~ 10 %–25 %) higher than in cool seasons (i.e. fall–winter). This annual cycle was disrupted in 2011 by an anomalously strong influence of the North American trough in that warm season and was reproduced in 2014 with annual amplitude enhanced up to ~ 70 ppqv associated with a particularly strong Bermuda High. North American trough axis index (TAI) and intensity index (TII) were used to characterize the effect of the North American trough on NYC GEM especially in winter and summer. The intensity and position of the Bermuda High had a significant impact on GEM in warm seasons supported by a strong correlation (r reaching 0.96, p < 0.05) of GEM with Bermuda High intensity indices in summer. Regional influence on NYC GEM was supported by the GEM-carbon monoxide (CO) correlation with r of 0.24–0.66 (p ~ 0) in most seasons and larger r in summers. Interannual variations were found in simulated regional and local anthropogenic contributions, averaged at ~ 75 % (67 %–83 %) and 25 % (17 %–33 %), respectively, to wintertime NYC anthropogenically induced GEM concentrations. Results from this study suggest the possibility that the increasingly strong Bermuda High over the past decades could dominate over anthropogenic mercury emission control in affecting ambient concentrations of mercury via regional build-up and possibly enhancing natural and legacy emissions.
Mao, H., Hall, D., Ye, Z., Zhou, Y., Felton, D., and Zhang, L.: Impacts of Large-Scale Circulation on Urban Ambient Concentrations of Gaseous Elemental Mercury in New York, USA, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-176, in review, 2017.