An application of passive samplers to understand atmospheric mercury concentration and dry deposition spatial distributions.

Two modified passive samplers were evaluated at multiple field locations. The sampling rate (SR) of the modified polyurethane foam (PUF)-disk passive sampler for total gaseous mercury (TGM) using gold-coated quartz fiber filters (GcQFF) and gaseous oxidized mercury (GOM) using ion-exchange membranes (IEM) were 6.4 ± 1.4 and 15.3 ± 0.3 m(3) day(-1), respectively. The relative percent difference between TGM and GOM concentrations measured by a Tekran system and the passive samplers averaged 19 ± 14 and 13 ± 12% and ranged between 4-44 and 1.5-41%, respectively. The GcQFF and IEM substrates were also evaluated as collection media for surrogate surface dry deposition measurements. Mercury (Hg) concentration and dry deposition gradients were observed using these samplers at an urban/industrial site and compared to a rural/remote site. The Hg dry deposition rates measured by the surrogate surfaces were always higher than those calculated by a widely used inferential modeling method (1.3-50 fold). The Hg dry deposition measured at urban and suburban sites were comparable to those calculated from model. However, they were very different at a rural site, probably due to the low concentrations. Both methods are relatively low cost and will aid in understanding spatial distributions of Hg ambient air concentrations and dry deposition.