IntroductionIn 2011 the global mean concentration of atmospheric CO 2 was 391 ppm [1], and the average rate of increase in the concentration of atmospheric CO 2 over the period spanning from 1960 to 2005 of 1.4 ppm yr -1 is therefore considered to be the main driver of climate change [2]. The global mean concentrations of CH 4 and N 2 O in 2011 were 1,803 ppb and 324 ppb, respectively [1]. The significant ability of CH 4 and N 2 O molecules to absorb Pol. J. Environ. Stud. Vol. 25, No. 5 (2016), 2047-2056
AbstractIn order to find out whether streams might be a major source of greenhouse gases to the atmosphere, our investigation sought to determine the total emissions of CH 4 , CO 2 , and N 2 O from the surface water of a small stream. Over a period of a year we used floating chambers to measure gas emissions along the longitudinal profile of Sitka Stream (Czech Republic). Additionally, we measured gas concentrations of surface and interstitial waters. We found that interstitial and surface waters were supersaturated by all monitored gasesespecially by CH 4 -and that the stream is a significant emitter of these greenhouse gases. The concentrations and the emission rates of all three gases were higher in the downstream part than upstream. In the case of CH 4 the majority of total annual emissions (90%) was released from the most downstream section, representing only 1/5 of the stream's total surface area (0.18 km 2 ). The majority of CH 4 and CO 2 emissions were released during warmer periods of the year and the highest N 2 O emissions from Sitka were recorded during summer and winter. The total annual emissions of CH 4 , CO 2 , and N 2 O into the atmosphere from the water's surface were estimated to be 0.6 t, 210 t, and 0.2 t, respectively. After conversion of the greenhouse gas emissions to CO 2 equivalents using a calculation by IPCC, CO 2 accounts for the majority of total annual emissions of greenhouse gases (70.1%), with the second being N 2 O (22.7%), and the last CH 4 (7.2%) for a 100-year time horizon. This work brings worthwhile data of greenhouse gas emissions and concentrations from a small water stream based on seasonal measurements along the longitudinal profile.