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AN EXAMINATION OF METHODS FOR THE MEASUREMENTS OF REACTIVE GASEOUS MERCURY IN THE ATMOSPHERE. (R825245)
Citation:
Sheu, G. AND R. P. Mason. AN EXAMINATION OF METHODS FOR THE MEASUREMENTS OF REACTIVE GASEOUS MERCURY IN THE ATMOSPHERE. (R825245). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 35:1209-1216, (2000).
Description:
Reactive gaseous Hg (RGHg), usually assumed to be HgCl2, may
dominate the total Hg depositional flux due to its higher surface reactivity and
water solubility. Three methods are currently used for RGHg sampling:
multi-stage filter packs, refluxing mist chambers, and KCl-coated denuders, but
none of these methods are considered standard. Field comparisons were performed
at Chesapeake Biological Laboratory (CBL) to test if these methods could give
comparable results. Mist chambers and denuders were operated continuously for 24
h in some cases to observe the diurnal variation. All methods demonstrated the
dynamic fluctuation of atmospheric RGHg, ranging from a few picograms per cubic
meter to more than 500 pg/m3. These methods also reported similar
temporal RGHg trends. At low RGHg levels, the denuder tended to report higher
values of RGHg relative to the filter pack, while mist chamber values were
generally in agreement with the filter pack. Discrepancy among methods was more
significant under higher RGHg levels. Considering the uncertainties associated
with these methods, our data suggest that these methods did produce comparable
results. The 24-h continuous measurements showed that RGHg was usually
undetectable at night. However, our data also suggest factors in addition to
photochemistry, such as movement and mixing of air masses, are influencing the
distribution of RGHg at CBL.