Novel Tracer Method To Measure Isotopic Labeled Gas-Phase Nitrous Acid (HO15NO) in Biogeochemical Studies

详细信息    查看全文

• 作者：Dianming Wu ; Christopher J. Kampf ; Ulrich P枚schl ; Robert Oswald ; Junfang Cui ; Michael Ermel ; Chunsheng Hu ; Ivonne Trebs ; Matthias S枚rgel
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：July 15, 2014
• 年：2014
• 卷：48
• 期：14
• 页码：8021-8027
• 全文大小：311K
• ISSN：1520-5851

文摘

Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to 60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography鈥搈ass spectrometry (LC-MS) to measure the ¹⁵N relative exceedance, 蠄(¹⁵N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of 蠄(¹⁵N) = 0.2鈥?.5, the relative standard deviation of 蠄(¹⁵N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO¹⁵NO emissions from soil in a dynamic chamber with and without spiking ¹⁵N labeled urea. The identification of HO¹⁵NO from soil with ¹⁵N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO₂^{鈥?/sup> as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO₂鈥?/sup> in the hydrosphere.}