Stephanie L. Mora Garcia

The investigation of the atmospheric chemical reactions in polluted environments is a well-studied area of atmospheric chemistry with the areas that have been historically targeted for investigation being those in big cities with heavy influence of anthropogenic pollution from small vehicle transportation and industrial emissions. These studies have informed about the increase in nitrogen and sulfur oxides, particulate matter, volatile organic compounds, heavy metals, and much more pollutants in urban environments. A major finding is that the increase in certain types of pollutants, and therefore certain atmospheric chemistry reactions is dependent on the pollution sources. This leads to the question: how is local atmospheric chemistry changed in areas that are used as logistic hubs, which are large geographic areas used as central points for the sorting, distribution, and transportation of goods. In the Inland Empire, which consists of San Bernardino and Riverside Counties, there are 4000+ warehouses that each operate numerous heavy diesel trucks, making it a logistics hub. This is an environmental justice issue as the local air quality is negatively affected by the operation of logistic hubs. Direct emission of pollution products produced by heavy diesel trucks are harmful to human health on their own; moreover, the reactions of diesel exhaust particulate matter with atmospheric constituents has not been extensively studied.  The research group will investigate the reactions of diesel exhaust particulate matter with oxides of nitrogen to investigate the possible reintroduction of reactive nitrogen oxides into the atmosphere.

Diesel exhaust particulate matter (DEPM) refers to the conglomerate carbonaceous particles that are formed from the exhaust of diesel operating vehicles and deposit on surfaces or stay airborne depending on size and phase. In logistic hubs, DEPM is present at higher concentrations making its reactions with atmospheric constituents significant. A class of important reactions is that of oxides of nitrogen with DEPM because research has found that the photolysis of oxides of nitrogen in the presence of organic compounds can lead to the reintroduction of oxides of nitrogen into the atmosphere after thought to have been at the end of its cycle by deposition. The lab will conduct laboratory studies of these heterogenous reactions of oxides of nitrogen with molecular models of DEPM to elucidate the atmospheric reactions in areas impacted by heavy diesel traffic in the hopes to better understand the change in air quality brought on by the increase in warehouses in disadvantaged communities.

Specialized analytical instruments and methods must be employed to study atmospheric chemistry as the conditions are important to consider. In the atmosphere, there are gases and liquids and solids, in the form of aerosols, all at trace level concentrations, from ppt to low ppb. Therefore, we need instruments that can probe not only such low concentrations of analytes but also the appropriate state – atmospheric chemical reactions are often heterogenous reactions meaning that the reactants are in different phases. To investigate the atmospheric chemistry questions proposed in the research lab, specialized analytical methods with be developed.