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[Hypobromite oxidation combined with hydroxylamine hydrochloride reduction method for analyzing ammonium nitrogen isotope in atmospheric samples.]

Authors :
Xiang YK
Cao F
Yang XY
Zhai XY
Zhang YL
Source :
Ying yong sheng tai xue bao = The journal of applied ecology [Ying Yong Sheng Tai Xue Bao] 2019 Jun; Vol. 30 (6), pp. 1847-1853.
Publication Year :
2019

Abstract

Ammonium salts, including ammonium nitrate, ammonium sulfate and ammonium hydrogen sulfate, are the main components of secondary inorganic aerosols and play an important role in the formation of haze events. The sources and transformation processes of atmospheric ammonium have received more and more attention. In this study, we modified the previous stable isotope analysis technique by improving the injection volume and adding a pH adjustment step, which gave a rapid and accurate measurement of ammonium nitrogen isotope ratio in atmospheric aerosol samples. Firstly, we added alkaline hypobromite to the extracted solution of the atmospheric aerosol filter samples (0.25 μg·mL <superscript>-1</superscript> ammonium nitrogen in 4 mL) to oxidize ammonium (NH <subscript>4</subscript> <superscript>+</superscript> ) to nitrite (NO <subscript>2</subscript> <superscript>-</superscript> ). Then, after adjusting the pH, nitrite (NO <subscript>2</subscript> <superscript>-</superscript> ) was reduced to nitrous oxide (N <subscript>2</subscript> O) by hydroxylamine hydrochloride under pH <0.3. Finally, nitrous oxide (N <subscript>2</subscript> O) was analyzed by Precon-GasBench-IRMS system to measure ammonium nitrogen isotope ratio. Our approach required low amount of NH <subscript>4</subscript> <superscript>+</superscript> and avoided the use of highly toxic and explosive reagents. Meanwhile, the precision of our method could reach as high as 0.2‰ (n=10). This method could increase the NH <subscript>4</subscript> <superscript>+</superscript> reduction efficiency to 100% at a condition of pH <0.3 and satisfy the demands of precision and accuracy for determination of ammonium nitrogen isotope in atmospheric aerosol samples. This method would help us better understand the sources, evolutions, chemical and deposition processes of atmospheric ammonium.

Details

Language :
Chinese
ISSN :
1001-9332
Volume :
30
Issue :
6
Database :
MEDLINE
Journal :
Ying yong sheng tai xue bao = The journal of applied ecology
Publication Type :
Academic Journal
Accession number :
31257755
Full Text :
https://doi.org/10.13287/j.1001-9332.201906.011