Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
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ecoveries for the total mercury samples were 98.2 percent. Total mercury concentrations in the<br />
landfill gas at Site #2 ranged <strong>from</strong> 36 to 47 ng/m 3 with an average of 43 ng/m 3 for all of the<br />
samples. Spike recoveries for the total mercury samples were not performed at Site #2.<br />
During the October 2007 field campaign, total mercury concentrations in the landfill gas at Site<br />
#1 ranged <strong>from</strong> 21,700 to 25,800 ng/m 3 with an average of 24,500 ng/m 3 for all of the samples.<br />
Spike recoveries for the total mercury samples were 102 percent. Total mercury concentrations<br />
in the landfill gas at Site #2 ranged <strong>from</strong> 109 to 526 ng/m 3 with an average of 352 ng/m 3 for all of<br />
the samples.<br />
There is almost 5 times difference in the total mercury results for Site 1 between the February<br />
and October sampling dates (5,022 in February versus 25,400 ng/m 3 in October). For site 2, the<br />
difference in total mercury results between February and October is about 6 times higher (43<br />
versus 270 ng/m 3 ). The collection technique and equipment were the same during both sampling<br />
campaigns. Spike recoveries for total mercury during both sampling periods were acceptable and<br />
showed no degradation or loss of mercury.<br />
There was a difference in the analytical method that was used to evaluate the samples between<br />
February and the October 2007. The February matrix spike analysis was performed by adding a<br />
known amount of mercury to the sample after sampling and leaching (i.e., Method 1631). This<br />
post-leaching type of spiking does not assess any potential losses of mercury <strong>from</strong> sampling,<br />
matrix interferences, or the wet leaching procedure.<br />
To account for potential mercury losses <strong>from</strong> sampling or matrix interferences, EPA developed<br />
EPA Method 30B, “Determination of Mercury <strong>from</strong> Coal-Fired Combustion Sources using<br />
Carbon Sorbent Traps”. This method requires additional replicates and QA/QC that helps to<br />
account for any potential losses of mercury <strong>from</strong> sampling and matrix interferences. Method<br />
30B is being used for power plants and other mercury sources to demonstrate performance of<br />
mercury continuous emission monitors. Therefore, in the October 2007 field sampling<br />
campaign, the thermal decomposition mercury analysis technique. Sampling included a prespiked<br />
iodated carbon tube traps spiked with elemental mercury and were used to assess matrix<br />
recovery at Site #1. Results for the thermal decomposition mercury analysis matrix spike<br />
recovery were 102%. The results for total mercury analysis <strong>from</strong> the October sampling are<br />
thought to be more reliable because of the additional QA/QC requirements to account for<br />
mercury loss during sampling and analysis.<br />
Dimethyl mercury concentrations in the landfill gas at Site #1 ranged <strong>from</strong> 1.22 to 2.65 ng/m 3<br />
with an average of 1.91 ng/m 3 . Dimethyl mercury concentrations in the landfill gas at Site #2<br />
ranged <strong>from</strong> 0.69 to 9.19 ng/m 3 with an average of 5.66 ng/m 3 . Spike recoveries for the dimethyl<br />
mercury traps were 13.9 percent for Site #1 and 1.9 percent for Site #2. Un-sampled spike traps<br />
had recoveries <strong>from</strong> 87.4 to 89.9 percent with an average of 88.7 percent. Recoveries for the<br />
spiked/sampled traps were significantly lower than the acceptance criteria of 50 to 150 percent<br />
established in the project QAPP. This is possibly due to the presence of an unknown interfering<br />
compound either destroying or masking the detection of the dimethyl mercury. For this reason,<br />
all of the dimethyl mercury results <strong>from</strong> this campaign must be labeled as suspect. Oversampling<br />
was performed by the ARCADIS personnel performing the sampling. Sampling was<br />
performed at approximated 10 times the necessary volume to collect a valid sample.<br />
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