Statistical exploration of gaseous elemental mercury (GEM) measured at Cape Point from 2007 to 2011

Abstract

Abstract. The authors evaluated continuous high-resolution gaseous elemental mercury (GEM) data from the Cape Point Global Atmosphere Watch (CPT GAW) station with different statistical analysis techniques. GEM data were evaluated by cluster analysis and the results indicated that two clusters, separated at 0.904 ng m −3 , existed. The air mass history for the two-cluster solution was investigated by means of back-trajectory analysis. The air mass back-trajectory net result showed lower GEM concentrations originating from the sparsely populated semi-arid interior of South Africa and the marine environment, whereas higher GEM concentrations originated predominately along the coast of South Africa that most likely coincide with trade routes and industrial activities in urban areas along the coast. Considering the net result from the air mass back-trajectories, it is evident that not all low GEM concentrations are from marine origin, and similarly, not all high GEM concentrations have a terrestrial origin. Equations were developed by means of multi-linear regression (MLR) analysis that allowed for the estimation and/or prediction of atmospheric GEM concentrations from other atmospheric parameters measured at the CPT GAW station. These equations also provided some insight into the relation and interaction of GEM with other atmospheric parameters. Both measured and MLR calculated data confirm a decline in GEM concentrations at CPT GAW over the period evaluated.

Atmospheric mercury in the Southern Hemisphere – Part 2: Source apportionment analysis at Cape Point station, South Africa

“…CO mixing ratios for "Atlantic" and "Eastern Ocean" lie in the middle with varying order. The highest annual average and median CH4 mixing ratios were observed in air masses attributed almost always to "Local" or "Continental" (averages "Local" in 2007, 2008, 2011, 2014, 2016and "Continental" in 2009, 2010, 2012, 2016medians "Local" in 2007, 2010, and 2014-2016and "Continental" in 2008, 2009, and 2011. Mixing ratios "Eastern Ocean" were mostly the lowest (averages in 2007, 2009-2012, 2015; medians in 2007, 2009 -2011, 2015) or second lowest (averages in 2008 and 2013; medians in 2008, 2012, 2016).…”

Spatial, temporal and source contribution assessments of black carbon over the northern interior of South Africa

“…is situated approximately 100 km west of Johannesburg on the property of a commercial farmer. It is representative of a regional background site but is also affected by aged plumes from major source regions in South Africa Venter et al, 2016). A detailed description of the Welgegund measurement station and related source regions was relatively recently presented by Beukes et al (2013a, b).…”

“…Several authors have previously applied similar methods for various atmospheric species (e.g. Awang et al, 2015;Du Preez et al, 2015;Venter et al, 2015).…”

Monsoon-facilitated characteristics and transport of atmospheric mercury at a high-altitude background site in southwestern China

“…2, and the mean TGM concentration over the sampling period was 2.09 ± 0.63 ng m −3 with a higher level (2.22 ng m −3 ) during the ISM period than that during the non-ISM period (1.99 ng m −3 ) ( Table 1). The TGM mean concentration at ALS was slightly higher than that of the global background (1.5-1.7 ng m −3 in the Northern Hemisphere and 1.1-1.3 ng m −3 in the Southern Hemisphere) (Lindberg et al, 2007;Slemr et al, 2015;Venter et al, 2015), and higher than those (1.58 to 1.93 ng m −3 ) observed in some remote areas in northern America and Europe (Kim et al, 2005;Sprovieri et al, 2010). Compared to the background concentrations observed at the Shangri-La Baseline Observatory in the Yunnan province (2.55 ± 0.73 ng m −3 ; Zhang et al, 2015), at Mt.…”