Analysis of Data
Using the data provided by the gas chromatograph analysis, the gas fluxes, or the increase of gas over time in the covered containers measured in grams of gas per m2 per day, were calculated for methane, carbon dioxide, and nitrous oxide. This was done both prior to and following the addition of ammonium nitrate. After all water and gas samples were taken, the total biomass of each of the models was measured, and used to calculate the total plant uptake fluxes. Finally, the CH4, CO2, and N2O fluxes were subtracted from the plant uptake fluxes to obtain the overall Global Warming Potential (GWP) in CO2 equivalents of each model.
Note: click on graphs to view in full size.
Figure 1
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Figure 2
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Figure 3
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Figure 4
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Figure 5
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Calculating the Global Warming Potential of Each Wetland Model
Step 1: Calculate the Total Biomass
1) Add the above and belowground plant mass to get the total plant biomass for each wetland model.
Plants belowground + aboveground = g biomass
Step 2: Calculate the CO2 uptake flux of the model
2) Divide this total by 2, because it is assumed that approximately ½ of each plant is carbon.
g biomass/2 = gC
3) Assuming that every atom of carbon in the plants got there by taking up a CO2, multiply the total grams of carbon in each wetland model by
44g/mol CO2
12g/mol C
to find the total CO2 uptake of the model.
gC x 44g/mol CO2
12g/mol C
4) To find the average daily plant uptake flux of each model, divide the total biomass by the number of days of the experiment and by the surface area of the model chamber.
CO2 (uptake) =gCO2/m2/d.
#days x surface area
Step 3: Using the CO2, CH4, N2O, and uptake fluxes, determine the Global Warming Potential (GWP)
5) Multiply the CH4 flux by 25, and the N2O flux by 296. Divide both by 1000 to convert mg units to g.
CH4 flux x 25 N2O flux x 296
1000g
6) Subtract the CO2 and CH4 fluxes from the uptake to get the GWP in CO2 equivalent.
Uptake-CO2 flux-CH4 flux-N2O flux
= GWP in CO2 equivalents
Figure 6
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Note: A positive Global Warming Potential value indicates an atmospheric cooling effect, while a negative GWP is an indicator of atmospheric warming.
Figure 7
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The decrease in nitrate concentrations in the water of each model was measured using a spectrophotometer at 0 minutes and 2 hours following the addition of NH4.NO3.
Figure 8
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