| Summary: | Mercury behaves uniquely in the atmosphere due to its volatility and long lifetime. The existing methods for measuring atmospheric mercury are either expensive or labour intensive. The present paper presents a new measurement technique, the diffusive sampler, that is portable, inexpensive, easy to use, and does not need a power supply. The sampler is sufficiently sensitive that it can measure Hg at low ambient levels with an exposure time of 1 to 3 days. The sampler is based on the Radiello diffusive sampler. The sampler is a modified version of the original design, where it was used to collect volatile organic compounds. In the present paper the method is validated under controlled laboratory conditions. The uptake rate of the Radiello diffusive sampler is determined using known concentrations of GEM, and is measured as a function of wind speed, relative humidity and temperature. The Radiello sampler has a detection limit of 0.14 ng m -3 for 1 day of exposure and thus can be used to measure mercury concentrations at the low levels found in ambient air. The Radiello sampler is therefore useful for mapping concentrations close to sources and sinks, in addition to ambient concentrations. For example the sampler can be used to describe the geographical extent of Arctic mercury depletion episodes where GEM is removed and stays close to zero ng m -3 for days, and it can be a powerful tool for mapping gradients around e.g. point sources.
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