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首页> 外文期刊>Atmospheric chemistry and physics >Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China
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Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China

机译：中国南方一个氮污染城市的降水硝酸盐氮，氧同位素组成的人为烙印

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Nitric acid (HNO_3) or nitrate (NO_3) is the dominant sink for reactive nitrogen oxides (NOx Combining double low line NOx + NO_2) in the atmosphere. In many Chinese cities, HNO_3 is becoming a significant contributor to acid deposition. In the present study, we measured nitrogen (N) and oxygen (O) isotopic composition of NO3 in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx SOURCES and the NO _3 formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO_3 (versus air N2) ranged from-4.9 to +10.1, and averaged +3.9 in 2008 and +3.3 in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO_3 were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5 (average +65.0 and +67.0 in 2008 and 2009, respectively), a range being lower than those reported for high latitude and polar areas. Sixteen percent of δ18O values was observed lower than the expected minimum of +55 at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O _3 to convert NO to NO_2, thereby donate O atoms with much lower δ18O value than that of O_3 to atmospheric NO_3. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO_3 in a N-polluted city.
机译：硝酸（HNO_3）或硝酸盐（NO_3）是大气中反应性氮氧化物（NOx结合双低线NOx + NO_2）的主要汇。在许多中国城市，HNO_3成为酸沉积的重要贡献者。在本研究中，我们测量了两年（2008年和2009年）从华南广州市收集的113个降水样品中NO3的氮（N）和氧（O）同位素组成。我们试图更好地了解珠江三角洲这个被N污染的城市中大气NOx来源的空间和季节变化以及NO _3形成途径。 NO_3（相对于空气N2）的δ15N值在-4.9到+10.1之间，2008年的平均值为+3.9，2009年的平均值为+3.3。全年都观测到正的δ15N值，表明人为的NOx排放，特别是煤炭的人为排放燃烧。在2008年至2009年期间，观测到了不同的δ15N-NO_3季节性模式，这可能反映了与全球金融危机和第16届亚运会的紧张准备有关的不同人类活动。硝酸盐δ18O值（相对于维也纳标准平均海水）从+33.4到+86.5（2008年和2009年分别为平均值+65.0和+67.0），范围低于高纬度和极地地区的报告值。在我们的研究地点，观测到δ18O值的百分之十六低于预期的最低值+55。这可能是由于NO与过氧自由基的反应引起的。过氧自由基可与O _3竞争，将NO转化为NO_2，从而将δ18O值比O_3的δ18O值低得多的O原子捐赠给大气NO_3。我们的研究结果突出表明，人类活动对大气化学的影响可以通过N污染城市中大气NO_3的N和O同位素组成来记录。

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