Investigating the chemistry and fate of reactive nitrogen (NOy) species in biomass burning smoke using FIREX data

The primary objective of this project is to use laboratory and field data from the planned NOAA FIREX campaign and an advanced smoke plume chemistry model (AER�??s Aerosol Simulation Program, or ASP) to study the chemical transformations and fate of the reactive nitrogen (NOy) species emitted by biomass burning (BB) in the western US. In smoke plumes, the initial NOx and HONO emissions are rapidly converted into other NOy species, including inorganic nitrate, alkyl nitrates (ANs), and peroxy nitrates (PNs, including peroxy acetyl nitrate or PAN). These chemical transformations directly impact the formation of ozone (O3) and the formation of secondary organic aerosol (SOA). At night, NO3 can react with the organic species in the smoke, forming additional SOA, while N2O5 can react to form ClNO2, which produces chlorine atoms that can enhance morning organic oxidation rates.

Plume-scale process models, such as ASP, allow us to examine the chemical transformations of trace gases and aerosols within BB smoke plumes in detail and can be used to develop parameterizations for this plume chemistry in three dimensional air quality models. In this project, we will use ASP and the FIREX data to investigate the chemical transformations of NOy species in BB emissions from wildfires in the western US and how these species impact the formation of O3 and SOA. First, we will use the smog chamber experiments at CIRES and at the USDA Fire Lab to improve the simulation of the rates of formation of various NOy species, as well as O3 and SOA, in ASP. The high level of chemical detail in ASP will allow us to directly compare our model with the hundreds of organic species that will be measured during FIREX.

The improvements made to ASP in the smog chamber studies will improve its ability to investigate the chemical transformations of pollutants in smoke plumes for the FIREX intensive field campaign. For the field study, we will run ASP within a simple Lagrangian parcel model to examine the impact of various fire sources on the NOy, O3, and SOA measurements made by the NOAA WP-3 aircraft, as well as the nighttime observations made by the mobile laboratories. The FIREX observations of the nighttime chemistry of smoke will provide the first examination of the ability of ASP to simulate the nighttime chemistry of BB smoke plumes.

The improved ASP model will then be used to develop a computationally efficient parameterization of the chemical transformation of NOy species from BB, and the associated O3 and SOA formed, in the CMAQ model used in the National Air Quality Forecasting Capability (NAQFC). This parameterization will be used to develop a comprehensive system to forecast the impacts of BB on local air quality and visibility, one of the key goals of FIREX and this FFO.