Applying a new method for direct collection, volume quantification and determination of N2 emission from water

The emission of N-2 is important to remove excess N from lakes, ponds, and wetlands. To investigate the gas emission from water, Gao et al. (2013) developed a new method using a bubble trap device to collect gas samples from waters. However, the determination accuracy of sampling volume and gas component concentration was still debatable. In this study, the method was optimized for in situ sampling, accurate volume measurement and direct injection to a gas chromatograph for the analysis of N-2 and other gases. By the optimized new method, the recovery rate for N-2 was 100.28% on average; the mean coefficient of determination (R-2) was 0.9997; the limit of detection was 0.02%. We further assessed the effects of the new method, bottle full of water, vs. vacuum bag and vacuum vial methods, on variations of N-2 concentration as influenced by sample storage times of 1, 2, 3, 5, and 7 days at constant temperature of 15 degrees C, using indices of averaged relative peak area (%) in comparison with the averaged relative peak area of each method at 0 day. The indices of the bottle full of water method were the lowest (99.5%-108.5%) compared to the indices of vacuum bag and vacuum vial methods (119%-217%). Meanwhile, the gas chromatograph determination of other gas components (O-2, CH4, and N2O) was also accurate. The new method was an alternative way to investigate N-2 released from various kinds of aquatic ecosystems. (C) 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.