Development of a novel on-line flow injection mercury analyzer to determine gaseous elemental mercury over the northern South China Sea

A simple and reliable gaseous elemental mercury analyzer (GEMA) was developed to investigate atmospheric gaseous elemental Hg (GEM) over the northern South China Sea (SCS). This on-line flow injection system couples the main sampling and analytical steps from sample introduction, Au amalgamation/pre-concentration to final detection/data acquisition. This approach provides ease of operation and high analytical performance and is suitable for shipboard use. The analyzer can be fully automated and also be modified to examine other atmospheric Hg species (e.g., reactive gaseous, particulate and methyl-Hg). Here, we present the results of laboratory performance tests and comparison with a traditional manual method, which showed good agreement. The results demonstrate that this approach is accurate and precise. The GEMA allows the reliable GEM determination in ambient air samples (i.e. high recoveries of 107 ± 6%, obtained from 6 spiked gas standards) with a low detection limit of 0.1 ng m−3 for a sample volume of 10 L and an excellent reproducibility (relative standard deviation ≤ 5%, n = 6). Representative field atmospheric GEM data from spring, summer, fall and winter 2003 over the northern SCS are also presented. Seasonal GEM variations with higher GEM (6.9 ± 1.0 ng m−3) in winter and lower in late spring (2.2 ± 0.5) and summer (2.7 ± 0.8) were evident in relation to the East Asian monsoon cycles.