Nitrate photolysis in ice and snow: A critical review of its multiphase chemistry

摘要

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 similar to 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.