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 (r2 = 0.990) and 12-month outdoor (r2 = 0.996) deployment, yielding sampling rates of 0.158 ± 0.008 m3 day–1 indoors and 0.121 ± 0.005 m3 day–1 outdoors. These sampling rates are close to modeled estimates of 0.166 m3 day–1 indoors and 0.129 m3 day–1 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.