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| Simultaneous Determination of Denitrification and Anaerobic Ammonium Oxidation in River Sediments Using Membrane Inlet Mass Spectrometry |
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| KeyWord:Taihu Lake region；membrane inlet mass spectrometry；15N isotope pairing technique；sediment；denitrification；anammox |
| Author Name | Affiliation | | ZHAO Yong-qiang | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China；University of Chinese Academy of Sciences, Beijing 100049, China | | XIA Yong-qiu | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China | | LI Bo-lun | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China；University of Chinese Academy of Sciences, Beijing 100049, China | | YAN Xiao-yuan | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China |
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| Abstract: |
| We used membrane inlet mass spectrometry（MIMS） and 15N isotope pairing technique（15N IPT） to simultaneously measure denitrification and anammox in river sediments of Taihu Lake region. Homogenized sediment slurries were incubated with 15N-labeled NO-3 and NH+4 amendments to determine the potential rates of denitrification and anammox. Production of 29N2 and 30N2 in slurries was determined using MIMS. Laboratory experiments showed that using MIMS to determinate the production rates of 29N2 and 30N2 was appropriate, and the measured values for river sediments of Taihu Lake region were similar to those reported in other freshwater systems. The potential rates of denitrification and total N removal in the sediments ranged from（18.5±2.8）~（133.2±27.1）μmol N·m-2·h-1 and （30.0±2.4）~（161.1±30.4）μmol N·m-2·h-1, respectively, and were significantly higher in the northwest than in the southwest part of the Taihu Lake region. The contribution of denitrification to the total N2 production was（61.3±4.5）%~（83.2±2.1）%. Potential anammox rates varied from（10.4±2.3）~（28.0±4.4）μmol N·m-2·h-1, and N removal by anammox accounted for（16.9±2.1）%~（38.7±4.5）% of the total N2 production. The spatial variation of the percentages of anammox to total N2 production was opposite to that of potential denitrification. The contents of nitrate and dissolved organic carbon in sediments were probably the main factors controlling denitrification and anammox. This study shows good applicability of MIMS in combination with 15N IPT in simultaneous determination of denitrification and anammox rates in aquatic systems. Advantages of this method include：reduced analytical errors by avoiding complicated gas extraction steps, no need of sample preparation, rapid measurement, and small sample size. Our results indicate that potential rates of N removal in sediments show spatial variation and denitrification is responsible for N removal but anammox should not be ignored. |
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