A High-Precision Passive Air Sampler for Gaseous Mercury

Passive air samplers (PASs) provide an opportunity to improve the spatial range and resolution of gaseous mercury (Hg) measurements. Here, we propose a sampler design that combines a sulfur-impregnated activated carbon sorbent, a Radiello diffusive barrier, and a protective shield for outdoor deployments. The amount of gaseous Hg taken up by the sampler increased linearly with time for both an 11-week indoor (<i>r</i><sup>2</sup> = 0.990) and 12-month outdoor (<i>r</i><sup>2</sup> = 0.996) deployment, yielding sampling rates of 0.158 ± 0.008 m<sup>3</sup> day<sup>–1</sup> indoors and 0.121 ± 0.005 m<sup>3</sup> day<sup>–1</sup> outdoors. These sampling rates are close to modeled estimates of 0.166 m<sup>3</sup> day<sup>–1</sup> indoors and 0.129 m<sup>3</sup> day<sup>–1</sup> outdoors. Replicate precision is better than for all previous PASs for gaseous Hg, especially during outdoor deployments (2 ± 1.3%). Such precision is essential for discriminating the relatively small concentration variations occurring at background sites. Deployment times for obtaining reliable time-averaged atmospheric gaseous Hg concentrations range from a week to at least one year.