Sensitivities of NO<sub>x</sub> transformation and the effects on surface ozone and nitrate

Abstract

As precursors for tropospheric ozone and nitrate aerosols, Nitrogen oxides (NO_x) in present atmosphere and its transformation in responding to emission and climate perturbations are studied by CAM-Chem model and air quality measurements including National Emission Inventory (NEI), Clean Air Status and Trends Network (CASTNET) and Environmental Protection Agency Air Quality System (EPA AQS). It is found that not only the surface ozone formation but also the nitrate formation is associated with the relative emissions of NO_x and volatile organic compounds (VOC). Due to the availability of VOC and associated NO_x titration, ozone productions in industrial regions increase in warmer conditions and slightly decrease against NO_x emission increase, which is converse to the response in farming region. The decrease or small increase in ozone concentrations over industrial regions result in the responded nitrate increasing rate staying above the increasing rate of NO_x emissions. It is indicated that ozone concentration change is more directly affected by changes in climate and precursor emissions, while nitrate concentration change is also affected by local ozone production types and their seasonal transfer. The sensitivity to temperature perturbations shows that warmer climate accelerates the decomposition of odd nitrogen (NO_y) during the night. As a result, the transformation rate of NO_x to nitrate decreases. Examinations on the historical emission and air quality records on typical pollution areas further confirm the conclusion drawn from modeling experiments

A statistical modeling framework for projecting future ambient ozone and its health impact due to climate change

“…Moreover, the statistical model developed for projection is specific to both the study location and the chosen reference period. The complex relationship between precursors, other chemicals, and meteorology for ozone production is likely to vary across region and time (Lei and Wang 2014). …”

Chemical Compositions, Sources, and Intra‐Regional Transportation of Submicron Particles Between North China Plain and Twain‐Hu Basin of Central China in Winter

“…The highest two values of O 3 were found in two rural sites, HA (45.1 ± 23.2 μg m −3 ) and SX (41.7 ± 25.6 μg m −3 ), which could be explained by the titration effect (Lei & Wang, 2014). The increase in NO x emission could lead to a higher O 3 titration by NO and result in a decrease of O 3 in urban sites.…”

Extensive spatio-temporal analyses of surface ozone and related meteorological variables in South Korea for 1999–2010

“…In the model experiments by Lin et al (2008), both averaged O 3 concentration and frequencies of high-O 3 episodes in the future were predicted to increase over the United States and East Asia. Based on climate-chemistry model experiments, Lei and Wang (2013) also have shown that O 3 production increases in warmer conditions in industrial regions over the United States.…”