Springtime Nitrogen Oxide-Influenced Chlorine Chemistry in the Coastal Arctic
Springtime Nitrogen Oxide-Influenced Chlorine Chemistry in the Coastal Arctic
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DOI：
10.1021/acs.est.9b01797
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发表时间：
2019-07-16
影响因子：
11.4
通讯作者：
Pratt, Kerri A.
中科院分区：
文献类型：
--
作者：
McNamara, Stephen M.;Raso, Angela R. W.;Pratt, Kerri A.
原子氯（Cl）是一种强大气氧化剂，可以缩短春季北极地区污染物和甲烷的寿命，在那里，分子卤素Cl-2和BrCl是已知的Cl前体。在这里，我们量化了活性氯微量气体的贡献，并提出了据我们所知的ClNO2（另一种Cl前体）、N2O5和HO2NO2在北极的首次观测结果。2016年3月至5月，在阿拉斯加Utqiagvik附近，使用化学电离质谱法测量了高达21ppt的ClNO2、154ppt的Cl-2、27ppt的ClO、71ppt的N2O5、21ppt的BrCl和153ppt的HO2NO2。3月份计算出Cl的主要前体是Cl-2（高达73%），而BrCl在5月份的贡献更大（63%），而总Cl产量较低。ClNO2、N2O5、Cl-2和HO2NO2水平的升高与附近的乌特基亚维克镇和阿拉斯加北坡（普拉德霍湾）油田的污染影响同时发生。我们提出了一种连接NOx与北极氯化学的耦合机制。Cl-2的增强可能是由ClO与NO2反应形成的Cl-(aq)（-）与ClNO2多相反应的结果。除了这种nox增强的氯化学外，在清洁的北极条件下，从积雪光化学生产中观察到Cl-2和BrCl。考虑到预计北极海冰损失将伴随航运和化石燃料开采的增加，这些氮氧化物和氯化学之间的联系以及积雪再循环的作用非常重要。
Atomic chlorine (Cl) is a strong atmospheric oxidant that shortens the lifetimes of pollutants and methane in the springtime Arctic, where the molecular halogens Cl-2 and BrCl are known Cl precursors. Here, we quantify the contributions of reactive chlorine trace gases and present the first observations, to our knowledge, of ClNO2 (another Cl precursor), N2O5, and HO2NO2 in the Arctic. During March - May 2016 near Utqiagvik, Alaska, up to 21 ppt of ClNO2, 154 ppt of Cl-2, 27 ppt of ClO, 71 ppt of N2O5, 21 ppt of BrCl, and 153 ppt of HO2NO2 were measured using chemical ionization mass spectrometry. The main Cl precursor was calculated to be Cl-2 (up to 73%) in March, while BrCl was a greater contributor (63%) in May, when total Cl production was lower. Elevated levels of ClNO2, N2O5, Cl-2, and HO2NO2 coincided with pollution influence from the nearby town of Utqiagvik and the North Slope of Alaska (Prudhoe Bay) Oilfields. We propose a coupled mechanism linking NOx with Arctic chlorine chemistry. Enhanced Cl-2 was likely the result of the multiphase reaction of Cl-(aq)(-) with ClNO2, formed from the reaction of ClO and NO2. In addition to this NOx-enhanced chlorine chemistry, Cl-2 and BrCl were observed under clean Arctic conditions from snowpack photochemical production. These connections between NOx and chlorine chemistry, and the role of snowpack recycling, are important given increasing shipping and fossil fuel extraction predicted to accompany Arctic sea ice loss.