Articles | Volume 17, issue 18
Research article
28 Sep 2017
Research article |  | 28 Sep 2017

Impacts of large-scale circulation on urban ambient concentrations of gaseous elemental mercury in New York, USA

Huiting Mao, Dolly Hall, Zhuyun Ye, Ying Zhou, Dirk Felton, and Leiming Zhang

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 US East Coast trough in that warm season and was reproduced in 2014 associated with a particularly strong Bermuda High. The US East Coast trough axis index (TAI) and intensity index (TII) were used to characterize the effect of the US East Coast trough on NYC GEM, especially in winter and summer. The intensity and position of the Bermuda High appeared to have a significant impact on GEM in warm seasons. Regional influence on NYC GEM was supported by the GEM–carbon monoxide (CO) correlation with r of 0.17–0.69 (p ∼  0) in most seasons. Simulated regional and local anthropogenic contributions to wintertime NYC anthropogenically induced GEM concentrations were averaged at  ∼  75 % and 25 %, with interannual variation ranging over 67 %–83 % and 17 %–33 %, respectively. 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 buildup and possibly enhancing natural and legacy emissions.

Short summary
Mercury (Hg) is a global pollutant hazardous to human and ecosystem health, and its emission control is imperative. Anthropogenic mercury emissions have been reduced by 78 % in the United States from 1990 to 2014. However, no clearly defined trend was observed in Hg concentrations at urban locations such as the one in this study. This indicates that other factors may have dominated over anthropogenic emission control. The implications of this study could hence be highly policy relevant.
Final-revised paper