Walter, K.M., Zimov S.A., Chanton, J.D., Verbyla, D., & F. S. Chapin III. 2006 "Methane Bubbling from Siberian Thaw Lakes as a Positive Feedback to Climate Warming", Nature 443, 71-75
Drill a hole at the highest point on the bottom of the two-liter bottle. Note: the hole should be slightly smaller than the outer diameter of the plastic tubing.
Insert the plastic tubbing into the hole. It should extent into the bottle only as far as needed to stay put ( < 1cm ).
Glue around the tubing to secure it to the bottle and around the stopcock to secure it to the tubing to prevent leaks. This portion of the assembly should be watertight and airtight. Let it dry for 48 hours.
Cut a 1 meter diameter circle in the plastic sheet. Mark a hole in the middle of the circle. As marked, cut a very small hole, smaller than the mouth of the bottle.
Cut holes approximately 1 cm from the edge of the plastic sheet, every 20 cm.
Cut a piece of steel cable, 1 meter in length. Weave the cable through the holes in the plastic sheet to form a loop.
Overlap the end of the cable by several inches, and secure with black tape.
Put the mouth of the bottle through the hole. Secure with tape. Be sure to wrap tape tightly. This portion of assembly should be watertight and airtight.
Cut three 0.75 meter pieces of string. Tie them to the steel cable at semi-equidistant points along the loop.
Pull the strings together so that the hoop shape is maintained, but there is a minimum of slack. Tie all three strings in a knot. Tie a second knot about 5 cm below the first.
Cut another piece of string and tie it to the weight. Tie the weight between the first and second knot that hangs down from the steel cable hoop.
Complete! You can now use your bubble trap to collect methane from a lake, either in winter or in summer, over a strong emitting seep.
