| Abstract
| - Reactive gaseous Hg (RGHg), usually assumed to beHgCl2, may dominate the total Hg depositional flux due toits higher surface reactivity and water solubility. Threemethods are currently used for RGHg sampling: multi-stage filter packs, refluxing mist chambers, and KCl-coateddenuders, but none of these methods are consideredstandard. Field comparisons were performed at ChesapeakeBiological Laboratory (CBL) to test if these methodscould give comparable results. Mist chambers and denuderswere operated continuously for 24 h in some cases toobserve the diurnal variation. All methods demonstratedthe dynamic fluctuation of atmospheric RGHg, ranging froma few picograms per cubic meter to more than 500 pg/m3. These methods also reported similar temporal RGHgtrends. At low RGHg levels, the denuder tended to reporthigher values of RGHg relative to the filter pack, whilemist chamber values were generally in agreement with thefilter pack. Discrepancy among methods was moresignificant under higher RGHg levels. Considering theuncertainties associated with these methods, our datasuggest that these methods did produce comparable results.The 24-h continuous measurements showed that RGHgwas usually undetectable at night. However, our data alsosuggest factors in addition to photochemistry, such asmovement and mixing of air masses, are influencing thedistribution of RGHg at CBL.
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