To assist in plotting up results, measure the distance from the top of the sediment-water inter­face to each of the ports on the Winogradsky column, with distance to the ports in the sediment as positive and those in the water column negative. Also, measure the distance from the sedi­ment-water interface to the surface of the water and the bottom of the sediments.

2.3. Methane concentration calculation

• From the standards, determine the concentration of methane in ppmv. Use the ideal gas law to determine the number of moles of methane in the 15 ml gas volume:

ppm 15

n_PV_ 106 1000 (1)

RT (0.08205)(293)