palimmn_lessonplan.doc

# Slowly open the stopcock gas will bubble out place

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Slowly open the stopcock. Gas will bubble out. Place the glass collection bottle over the stream of bubbles, to fill the bottle by displacing water inside. Keep the collection bottle underwater and upside down and seal it with a rubber stopper. Make the analogy with what happens in a lake: Ask the students to imagine an underground plumbing network under the lake. In some places, the underground pipes have holes, or seeps, where methane comes from. The methane gas comes out of these seeps as bubbles. The goal is to find a seep, and capture the gas that comes out of it with a bubble trap. With the gas that students collect, the PALIMMN research group will run analyses to determine the CH4 content of the sample. It will be used to determine how much methane is released from the bubbling seep that the students sampled. The concentration in methane seeps is usually over 60%. 4) Collect methane from bubble traps on a lake (1h 15 minimum) Use the document “How to collect methane from Bubble Traps” This can be done in winter or in summer (either from a small boat or from the shore with good boots). This step requires going to the lake twice. Teachers may want to practice before taking students out on the lake. It is good safety procedure to work in teams of at least two people on ice or water. 4

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Identify a methane seep and set up the bubble trap. Please note the coordinates with a GPS (if possible), the day and time at which you start collecting gas. You might be able to set only 1 or 2 traps. Ask the students to explain the procedure of collecting methane from the trap. Make sure they know the most important points: do not pull the trap out of the water when you proceed; do not handle the trap by the bottle or stopcock (they are very fragile); gently manipulate the plastic skirt to make the methane bubbles come into the top of the plastic bottle where the stopcock is; insert the collection bottle into the stopcock outlet; gently open the stopcock to let the methane come into the collection bottle; keep the bottle as it is (in the water, upside down, move it as little as possible) and close it (under water); label the seep references (number, date) on the bottle with a sharpie. Depending on the strength of the methane seep, gas will accumulate in a matter of minutes or weeks. If you are measuring a strong seep, then while you are waiting for gas to accumulate in your trap take some time to walk along the lake and find places where you can see methane bubbles in the ice in order to later conduct ice-bubble survey transects (step 5, see below). Look for methane bubbles by walking on the lake, shoveling away the snow every so often. Look for areas with clear black ice. Methane seeps will occur as beautiful clusters of bubbles trapped in lake ice. The common pattern is to find more methane bubbles close to the lake shores than in the lake center. When you decide where you will set the transects for your students, leave a marker in place. Wait until you students are with you to shovel snow, and conduct a methane ice bubble survey.

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