Abstract Nitrate, a member of the oxidized nitrogen family (NOy), is one of the primary species involved in the nitrogen cycle and thus plays a key role in ecosystem processes, globally. It exists as nitrate salts and as nitric acid (HNO3) in both aerosols and the gas phase. It is formed from the NO3 radical/N2O5 or directly from the oxidation of NO2 and is lost by photolysis, OH oxidation, and deposition. In regions covered with snow/ice it has a significant impact on air quality, atmospheric oxidizing capacity, greenhouse gas concentrations, and paleoclimate/isotopic data. Snow/ice environments can, at seasonal maximum, comprise ∼30% of Earth's surface area while 10% is covered with ice/snow found at the polar cryosphere. Nitrate makes up 75–100% of the nitrogen budget deposited from the atmosphere and measured at the Arctic and Antarctica. Its concentrations in Greenland ice have risen by a factor of 2–3, reflecting the long-ranged transport of increased anthropogenic NOx (NO + NO2) emissions. The polar cryosphere is an active medium for the movement of traces gases, such as nitrate, between the snowpack/sea-ice and overlying atmosphere. Field, laboratory, and modeling efforts have quantitatively shown that the exchange of trace species between the snowpack and the air above is governed by photochemistry in combination with air moving gases between these two matrices. Polar tropospheric chemistry and dynamics immensely impact processes governing chemical composition, isotopic signatures, oxidizing capacity, and thus regional climate. This study presents a comprehensive review of laboratory and modeling efforts – contextualized by field measurements – that have elucidated physicochemical processes governing nitrate photochemistry and its impact on the polar snowpack. Specifically, after an Introduction to nitrate photochemistry in ice, we discuss the: 1) initial Arctic field measurements that sparked interest in ice photolysis in the polar regions; 2) suite of follow-up field studies that catalyzed laboratory and snow-chamber investigations that gave deeper understanding of the effects of snow/ice – air trace gas exchange due to nitrate photochemistry; 3) complementary laboratory, snow-chamber investigations; and 4) a detailed review of recent nitrate ice photolysis laboratory experiments and the potential impact of utilizing laboratory and computational models to study the role of nitrate in the nitrogen cycle.

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冰雪中的硝酸盐光解：对其多相化学的批判性回顾

摘要 硝酸盐是氧化氮家族 (NOy) 的成员，是参与氮循环的主要物种之一，因此在全球生态系统过程中起着关键作用。它以硝酸盐和硝酸 (HNO3) 的形式存在于气溶胶和气相中。它由 NO3 自由基/N2O5 或直接由 NO2 氧化形成，并通过光解、OH ​​氧化和沉积而损失。在被雪/冰覆盖的地区，它对空气质量、大气氧化能力、温室气体浓度和古气候/同位素数据有重大影响。在季节性最大值时，雪/冰环境可以占地球表面积的约 30%，而 10% 被极地冰冻圈发现的冰/雪覆盖。硝酸盐占大气中沉积并在北极和南极洲测量的氮预算的 75-100%。它在格陵兰冰中的浓度增加了 2-3 倍，反映了人为 NOx (NO + NO2) 排放量增加的远距离迁移。极地冰冻圈是微量气体（例如硝酸盐）在积雪/海冰和上覆大气之间移动的活跃介质。现场、实验室和建模工作已经定量地表明，积雪和上方空气之间痕量物质的交换受光化学以及这两个矩阵之间的空气移动气体的控制。极地对流层化学和动力学对控制化学成分、同位素特征、氧化能力以及区域气候的过程产生巨大影响。这项研究对实验室和建模工作进行了全面回顾——以现场测量为背景——阐明了控制硝酸盐光化学的物理化学过程及其对极地积雪的影响。具体来说，在介绍了冰中硝酸盐光化学之后，我们讨论了：1) 最初的北极场测量引发了对极地地区冰光解​​的兴趣；2) 一系列后续实地研究，催化实验室和雪室调查，更深入地了解雪/冰 - 由于硝酸盐光化学引起的空气痕量气体交换的影响；3) 补充实验室、雪室调查；