Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China
Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China
复制标题
中国南方某氮污染城市降水硝酸盐氮氧同位素组成的人为影响
DOI：
10.5194/acp-11-1313-2011
复制
发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Yoh, M.
中科院分区：
文献类型：
--
作者：
Fang, Y. T.;Koba, K.;Yoh, M.
硝酸(HNO(3))或硝酸盐(NO(3)(-))是大气中活性氮氧化物(NO(X)=NO+NO(2))的主要汇。在中国的许多城市，HNO(3)正在成为酸沉降的重要贡献者。测定了2008年和2009年广州市中国南部地区的113个降水样品中NO(3)(-)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地区这座N污染城市大气NO(X)源的空间和季节变化以及NO(3)(-)的形成途径。NO(3)(-)(相对于空气N(2))的增量(15)N值在-4.9到+10.1‰之间，2008年和2009年的平均值分别为+3.9‰和+3.3‰。全年观测到正的增量(15)N值，表明NO(X)排放的人为贡献，特别是燃煤排放。在2008年至2009年期间，观测到了不同的三角洲(15)N-NO(3)(-)的季节模式，这可能反映了与全球金融危机和第16届亚运会紧张筹备有关的不同人类活动。硝酸盐三角洲(18)O值(相对于维也纳标准平均海水)从+33.4到+86.5‰(2008年和2009年的平均值分别为+65.0‰和+67.0‰)，这一范围低于高纬度和极地地区的报告。在我们的研究地点，观察到16%的Delta(18)O值低于预期的最低+55ppm。这可能是由于NO与过氧基反应所致，过氧基可以与O(3)竞争将NO转化为NO(2)，从而将比O(3)低得多的O原子提供给大气中的NO(3)(-)。我们的结果表明，人类活动对大气化学的影响可以通过N污染城市大气NO(3)(-)的N和O同位素组成来记录。
Nitric acid (HNO(3)) or nitrate (NO(3)(-)) is the dominant sink for reactive nitrogen oxides (NO(x) =NO + 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 NO(3)(-) in 113 precipitation samples collected from Guangzhou City in southern China over a twoyear period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NO(x) sources and the NO(3)(-) formation pathways in this Npolluted city in the Pearl River Delta region. The delta(15)N values of NO(3)(-) (versus air N(2)) ranged from -4.9 to +10.1 parts per thousand, and averaged +3.9 parts per thousand in 2008 and +3.3 parts per thousand in 2009. Positive delta(15)N values were observed throughout the year, indicating the anthropogenic contribution of NO(x) emissions, particularly from coal combustion. Different seasonal patterns of delta(15)N-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 delta(18)O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5 parts per thousand (average +65.0 parts per thousand and +67.0 parts per thousand in 2008 and 2009, respectively), a range being lower than those reported for high latitude and polar areas. Sixteen percent of delta(18)O values was observed lower than the expected minimum of +55 parts per thousand 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 delta(18)O 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.