The invention relates to an in-situ monitoring method for the flux of
methane gas on a water-gas interface, which comprises the following steps of: 1) arranging a circular gasbag at the open of a tank with an open bottom, connecting the gasbag to an anchor through a
rope, and filling gas in the gasbag; 2) throwing the anchor to an
observation point, and after the tank is stabilized, connecting gas in the tank with a
methane concentration measurement instrument through a gas tube; 3) starting the
methane concentration measurement instrument, measuring and recording the
methane gas concentration X1 on the water-gas interface, and recording the measurement time t1; 4) measuring and recording a
water level h in the tank in the step 1) and an actual height H of the tank; 5) after the sampling is finished, measuring and recording the
methane gas concentration X2, the temperature T2 and the
gas pressure P2 on the water-gas interface, and recording the measurement time t2; and 6) calculating the flux of the
methane gas between the water and the air by utilizing the methane
gas concentration X1 and X2, the time t1 and t2, the
water level h in the tank, the actual height H of the tank, the temperature T2 and the
gas pressure P2 recorded in the steps 3), 4) and 5). The in-situ monitoring method is suitable for monitoring the flux of the methane gas between the water which takes
paddy field,
wetland, marshland, lake surface, river, sea,
sewage and the like as an underlying surface and the air.