Two systems that are viable for measurement of reactive Hg (RM=gaseous oxidized Hg (GOM) + particulate bound Hg (PBM) include: 1) the Aerohead designed to measure GOM dry deposition; and 2) the University of Nevada, Reno - Reactive Mercury Active System (RMAS) configured to measure RM, GOM, and PBM chemistry and concentrations. Data collected using Aeroheads in Florida were a first step in demonstrating the Tekran speciation system does not adequately measure reactive Hg concentrations.  This was further demonstrated by research associated with the Reno Atmospheric Mercury Intercomparison eXperiment (RAMIX) and confirmed in many other studies. The Tekran system is an automated system designed to measure gaseous elemental Hg, GOM, and PBM, and has been used by researchers for the past ~20 y.

The surface used to measure dry deposition in the Aerohead samplers is a cation exchange membrane (CEM). The CEM is also used in the RMAS to quantify RM concentrations, while nylon membranes are used to determine the chemistry. CEM are digested and analyzed using EPA method 1631. Chemistry of the compounds is determined using thermal desorption analysis of nylon membranes. Concentrations measured with the CEM are 2- to 13-times higher than the Tekran system measurement. Concentrations measured by the CEM have been demonstrated to be accurate using a calibrated dual channel system.

Chemistry determined using the nylon membranes observed in Hawaii, Nevada, Utah, and Maryland agreed with ancillary data and sources defined using HYSPLIT analyses. A polytetrafluoroethylene membrane has been introduced into the RMAS, providing a means of determining GOM and PBM concentrations and chemistry. The Aerohead samplers and RMAS were deployed together in Svalbard, Norway, along with a Tekran system. Using the RMAS together with the Aeroheads and modeling provided a means of estimating dry deposition rates of specific compounds.