Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...

The surveys also found significant methane emissions from the slopes of each landfill cell,
especially from the bioreactor cell of Site #1, and the control cell of Site #2. In fact, total
methane emissions from the slopes of each cell surveyed during the campaign were more
significant than emissions from the top of the landfill cells when considering the much larger
surface areas of the slopes compared to the tops of the cells.
Overall, total methane emissions from the bioreactor cell of Site #1 were much greater than
emissions from the control cell of Site #1, as expected. However, total methane emissions from
the bioreactor cell of Site #2 were significantly lower than emissions from the control cell of Site
#2. This may be due to the fact that leachate had not been injected into the bioreactor cell at the
site in several months due to excessive rainfall. Another factor that may have contributed to the
relatively lower emissions from the bioreactor cell of Site #2 was the presence of a fresh soil
cover that had been added to the surface of the cell prior to the measurement campaign. Using
the data presented in Table 4-1, the calculated total site methane emissions was 5,300 kg/day
from Site #1 and 5,600 kg/day for Site #2.
For each of the two sites, Summa® canister samples were collected at the gas header pipe
upstream of any gas treatment. The header pipe samples were analyzed to provide data on gas
composition (methane and carbon dioxide), NMOC, and trace organic constituents including
HAPs, H2S, and volatile organic compounds (VOC). Data were also obtained on mercury in the
header pipe gas. Data were collected using header pipe gas measurements for total, elemental
and organo-mercury (including methyl- and dimethyl-mercury). Table 4-2 presents a summary
of the mercury results for both sites from sampling occurring in February and October 2007.
Table 4-2. Average Concentrations of Total, Dimethyl, Monomethyl, and Elemental
Mercury Measured at Each Site 1
Compound
Total Mercury-
February 2007
Total Mercury-
October 2007
Average
Concentration
(ng/m 3 )
Site #1 Site #2
Range
(ng/m 3 )
Average
Concentrati
on (ng/m 3 )
Range
(ng/m 3 )
5,022 4,958 to 5,148 43 36 to 47
24,495 21,689 to 25,770 270 109 to 526
2
Dimethyl Mercury 1.91 1.22 to 2.65 5.66 0.69 to 9.19
Monomethyl
Mercury
11.8 11.1 to 12.4 0.16 0.06 to 0.31
Elemental Mercury 3,266 3,094 to 3,445 47 22 to 64
1 Total mercury measurements were repeated in the field sampling occurring in October 2007. Organo-mercury and
elemental mercury analysis was not repeated. Although there were no observed differences in sampling between
field campaigns, there was a difference in analytical methods for total mercury analysis. This is explained in the text
supporting this table.
2 Spike recoveries for the dimethyl mercury samples were significantly lower than the QAPP acceptance criteria.
During the February 2007 field campaign, total mercury concentrations in the landfill gas at Site
#1 ranged from 5,000to 5,200 ng/m 3 with an average of 5,000 ng/m 3 for all of the samples. Spike
4-2